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The Effects of Microlearning: A Scoping Review

• Research Article
• Published: 26 January 2022
• Volume 70 , pages 363–395, ( 2022 )

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• Ai-dung Taylor 1 &
• Woei Hung   ORCID: orcid.org/0000-0001-9998-3163 2  

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Microlearning has gained popularity in both the training industry and professional studies disciplines over the last several years. While substantial information exists in industry articles and commentaries on the definition of microlearning—along with how to create, develop, and implement it—a closer look at the existing research is important. Further study is needed to understand how to inform instructional design professionals of current trends and the effects of microlearning training on the enhancement of learner performance in both workplace and academic settings. Thus, this scoping review aims to examine the literature and identify noticeable trends, patterns, and evidence of how microlearning has been used and implemented in both academic learning and industry training settings.

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Andriotis, N. (2018b). What is microlearning: A complete guide for beginners . eLearning industry. Retrieved December 10, 2018, from https://elearningindustry.com/what-is-microlearning-benefits-best-practices

Andriotis, N. (2018a). Zooming in: Microlearning examples in the corporate world . eLearning industry. Retrieved September 10, 2018, from https://elearningindustry.com/microlearning-examples-in-corporate-world

Arksey, H., & O’Malley, L. (2005). Scoping studies: Towards a methodological frame work. International Journal of Social Research Methodology, 8 (1), 19–32. https://doi.org/10.1080/1364557032000119616

Article   Google Scholar  

BasuMallick, C. (2018). How micro learning is transforming workforce efficiency. HR Technologist. Retrieved August 14, 2018, from https://www.hrtechnologist.com/articles/learning-development/how-micro-learning-is-transforming-workforce-efficiency/

Bradbury, N. A. (2016). Attention span during lectures: 8 seconds, 10 minutes, or more? Advances in Physiology Education, 40 (4), 509–513. https://doi.org/10.1152/advan.00109.2016

Branzetti, J. B., Adedipe, A. A., Gittinger, M. J., Rosenman, E. D., Brolliar, S., Chipman, A. K., Grand, J. A., & Fernandez, R. (2017). Randomised controlled trial to assess the effect of a Just-in-Time training on procedural performance: A proof-of-concept study to address procedural skill decay. BMJ Quality & Safety, 26 (11), 881–891. https://doi.org/10.1136/bmjqs-2017-006656

Cheng, Y.-T., Liu, D. R., & Wang, V. J. (2017). Teaching splinting techniques using a just-in-time training instructional video. Pediatric Emergency Care . https://journals.lww.com/pec-online/Fulltext/2017/03000/Teaching_Splinting_Techniques_Using_a_Just_in_Time.5.aspx . Accessed 25 March 2020.

Chuang, Y., & Tsao, C. (2012). Enhancing nursing students’ medication knowledge: The effect of learning materials delivered by short message service. Computers & Education, 31 , 168–175.

Google Scholar  

Chung, C.-J., Hwang, G.-J., & Lai, C.-L. (2019). A review of experimental mobile learning research in 2010–2016 based on the activity theory framework. Computers & Education, 129 , 1–13. https://doi.org/10.1016/j.compedu.2018.10.010

Davis, B. G. (1993). Tools for Teaching . Jossey-Bass.

De Gagne, J. C., Park, H. K., Hall, K., Woodward, A., Yamane, S., & Kim, S. S. (2019). Microlearning in health professions education: Scoping review. JMIR Medical Education, 5 (2), e13997. https://doi.org/10.2196/13997

Gagné, R. M., & Briggs, L. J. (1979). Principles of instructional design (2nd ed.). Rinehart & Winston.

Genota, L. (2018). Why “Generation Z” learners prefer YouTube lessons. Education week. Retrieved September 12, 2018, from https://web-s-ebscohost-com.ezproxy.library.und.edu/ehost/delivery?sid=436a4eba-6c5d-435a-95a9-0d6a6fc635ac%40redis&vid=2&ReturnUrl=https%3a%2f%2fweb.s.ebscohost.com%2fehost%2fdetail%2fdetail%3fvid%3d1%26sid%3d436a4eba-6c5d-435a-95a9-0d6a6fc635ac%2540redis%26bdata%3dJnNpdGU9ZWhvc3QtbGl2ZSZzY29wZT1zaXRl

Ghosh, S. (2016). 8 Tips for creating effective microlearning courses . Training industry. Retrieved August 4, 2016, from https://trainingindustry.com/articles/content-development/8-tips-for-creating-effective-microlearning-courses/

Giurgiu, L., & Bălcescu, N. (2017). Microlearning an evolving eLearning trend. Scientific Bulletin . https://doi.org/10.1515/bsaft-2017-0003

Göschlberger, B., & Bruck, P. (2017). Gamification in mobile and workplace integrated microlearning. iiWAS’17 . https://doi.org/10.1145/3151759.3151795

Gross, B., Rusin, L., Kiesewetter, J., Zottmann, J. M., Fischer, M. R., Prückner, S., & Zech, A. (2019). Microlearning for patient safety: Crew resource management training in 15-minutes. PLoS ONE, 14 (3), e0213178. https://doi.org/10.1371/journal.pone.0213178

Gutenberg Technology. (2019). Is microlearning the future of learner training? Gutenberg technology. Retrieved March 26, 2019, from https://blog.gutenberg-technology.com/en/is-microlearning-the-future-of-learner-training

Gutierrez, K. (2018). Numbers don’t lie: Why microlearning is better for your learners (and You too) . SH!FT disruptive eLearning. Retrieved September 27, 2018, from https://www.shiftelearning.com/blog/numbers-dont-lie-why-bite-sized-learning-is-better-for-your-learners-and-you-too

Han, Y., Faulkner, M., Fritz, H., Fadoju, D., Muir, A., Abowd, G., Head, L., & Arriaga, R. (2015). A Pilot Randomized trial of text-messaging for symptom awareness and diabetes knowledge in adolescents with type 1 diabetes. Journal of Pediatric Nursing, 30 , 850–861. https://doi.org/10.1016/j.pedn.2015.02.002

Hartley, J., & Davies, I. K. (1978). Note taking: A critical review. Program Learning & Educational Technology, 15 , 207–224.

Hassinger-Das, B., Dore, R. A., Aloisi, K., Hossain, M., Pearce, M., & Paterra, M. (2020). Children’s reality status judgments of digital media: implications for a COVID-19 world and beyond. Frontiers in Psychology, 11 , 570068. https://doi.org/10.3389/fpsyg.2020.570068

Hesse, A., Ospina, P., Wieland, M., Yepes, F. A. L., Nguyen, B., & Heuwieser, W. (2019). Short communication: Microlearning courses are effective at increasing the feelings of confidence and accuracy in the work of dairy personnel. Journal of Dairy Science, 102 (10), 9505–9511. https://doi.org/10.3168/jds.2018-15927

Hogle, P. (2018). Let moments of learning need guide when to use microlearning . Learning solutions magazine. Retrieved September 10, 2018, from https://learningsolutionsmag.com/articles/let-moments-of-learning-need-guide-when-to-use-microlearning

Hug, T. (2021). Sound pedagogy practices for designing and implementing microlearning objects. In T. Hug (Ed.), Microlearning in the digital age: The design and delivery of learning in snippets (pp. 33–57). Routledge.

Chapter   Google Scholar  

Kulhavy, R. W., Schwartz, N. H., & Peterson, S. (1986). Working memory: The encoding process. In G. D. Phye & T. Andre (Eds.), Cognitive classroom learning: Understanding, thinking, and problem solving (pp. 115–140). Academic.

Levac, D., Colquhoun, H., & O’Brien, K. (2010). Scoping studies: Advancing the methodology. Implementation Science . https://doi.org/10.1186/1748-5908-5-69

Mcintosh, M., Konzelmann, J., Smith, J., Kalynych, C., Wears, R., Schneider, H., Wylie, T., Kaminski, A., & Joseph, M. (2009). Stabilization and treatment of dental avulsions and fractures by emergency physicians using just-in-time training. Annals of Emergency Medicine, 54 , 585–592. https://doi.org/10.1016/j.annemergmed.2009.06.510

McKeachie, W. J., & Sviinicki, M. (2006). McKeachie’s teaching tips: Strategies, research, and theory for college and university teachers . Hougton-Mifflin.

Oesch, T. (2017). What’s In a Name? The story of microlearning . Training industry. Retrieved November 17, 2017, from https://trainingindustry.com/articles/content-development/whats-in-a-name-the-story-of-microlearning/

Orwoll, B., Diane, S., Henry, D., Tsang, L., Chu, K., Meer, C., Hartman, K., & Roy-Burman, A. (2017). Gamification and microlearning for engagement with quality improvement (GAMEQI): A bundled digital intervention for the prevention of central line-associated bloodstream infection. American Journal of Medical Quality, 33 (1), 21–29.

Pandey, A. (2019). Microlearning trends to adopt in 2019 . eLearning industry. Retrieved March 12, 2019, from https://elearningindustry.com/microlearning-trends-in-2019-adopt

Pascual, K. J., Vlasova, E., Lockett, K., Richardson, J., & Yochelson, M. (2018). Evaluating the impact of personalized stroke management toolkits on patient experience and stroke recovery. Journal of Patient Experience, 5 (4), 244–249.

Sanal, A. (2019). Microlearning in 2019: Top 8 reasons to adopt in workplace . XL Pro Corporate E-Learning. Retrieved January 22, 2019, from https://playxlpro.com/microlearning-in-2019-top-8-reasons-to-adopt-in-workplace/

Sawarynski, K., & Baxa, D. (2019). Utilization of an online module bank for a research training curriculum: Development, implementation, evolution, evaluation, and lessons learned. Medical Education Online, 24 (1), 1611297. https://doi.org/10.1080/10872981.2019.1611297

Seidel, T. (2018). Microlearning is more than a buzzword . Association for talent development. Retrieved June 27, 2018, from https://www.td.org/insights/microlearning-is-more-than-a-buzzword

Selko, A. (2019). Is micro learning a better way to train our workforce? . Industry week. Retrieved July 8, 2019, from https://www.industryweek.com/talent/article/22027877/is-micro-learning-a-better-way-to-train-our-workforce

Sichani, M., Mobarakeh, S., & Omid, A. (2018). The effect of distance learning via SMS on academic achievement and satisfaction of medical students. Journal of Education and Health Promotion . https://doi.org/10.4103/jehp.jehp_116_16

Simons, L., Foerster, F., Bruck, P., Motiwalla, L., & Jonker, C. (2015). Microlearning mApp raises health competence: Hybrid service design. Health Technology, 5 , 35–43. https://doi.org/10.1007/s12553-015-0095-1

Smith, N. (2016). Why microlearning is a great workforce training strategy . Training industry. Retrieved November 2, 2016, from https://trainingindustry.com/articles/content-development/why-microlearning-is-a-great-workforce-training-strategy/

Sweller, J. (1988). Cognitive load during problem solving: Effects on learning. Cognitive Science, 12 , 257–285.

Torgerson, C., & Iannone, S. (2019). 4 Strategies for creating microlearning that works . Learning Solutions Magazine. Retrieved August 12, 2019, from https://learningsolutionsmag.com/articles/4-strategies-for-creating-microlearning-that-works

Van den Eynde, J., Crauwels, A., Demaerel, P. G., Van Eycken, L., Bullens, D., Schrijvers, R., & Toelen, J. (2019). YouTube videos as a source of information about immunology for medical students: Cross-sectional study. JMIR Medical Education, 5 (1), e12605. https://doi.org/10.2196/12605

Watmough, N. (2019). Make micro-learning work for you . Training journal. Retrieved September 24, 2019, from https://www.trainingjournal.com/articles/opinion/make-micro-learning-work-you

Wilkie, B. J. (2013). An assessment of a just-in-time training intervention in a manufacturing organization . The University of Southern Mississippi.

Yoo, J., Han, M., Jamena, G., Pei, P., Baldocchi, H., Menard, E., Diane, S., Oishi, P., & Nguyen, T. (2018). Cloud-based implementation of new frontline clinical workflows: Standardizing practice at scale to improve patient safety. Iproceedings, 4 (2), e11776. https://doi.org/10.2196/11776

Zambito, V. (2018). The brain science of microlearning: Why it works . Training industry. Retrieved January 17, 2018, from https://trainingindustry.com/articles/content-development/the-brain-science-of-microlearning-why-it-works/

Zhang, J., & West, R. E. (2020). Designing microlearning instruction for professional development through a competency based approach. TechTrends, 64 (2), 310–318. https://doi.org/10.1007/s11528-019-00449-4

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Taylor, Ad., Hung, W. The Effects of Microlearning: A Scoping Review. Education Tech Research Dev 70 , 363–395 (2022). https://doi.org/10.1007/s11423-022-10084-1

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Accepted : 13 January 2022

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Issue Date : April 2022

DOI : https://doi.org/10.1007/s11423-022-10084-1

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Title: tensorflow lite micro: embedded machine learning on tinyml systems.

Abstract: Deep learning inference on embedded devices is a burgeoning field with myriad applications because tiny embedded devices are omnipresent. But we must overcome major challenges before we can benefit from this opportunity. Embedded processors are severely resource constrained. Their nearest mobile counterparts exhibit at least a 100 -- 1,000x difference in compute capability, memory availability, and power consumption. As a result, the machine-learning (ML) models and associated ML inference framework must not only execute efficiently but also operate in a few kilobytes of memory. Also, the embedded devices' ecosystem is heavily fragmented. To maximize efficiency, system vendors often omit many features that commonly appear in mainstream systems, including dynamic memory allocation and virtual memory, that allow for cross-platform interoperability. The hardware comes in many flavors (e.g., instruction-set architecture and FPU support, or lack thereof). We introduce TensorFlow Lite Micro (TF Micro), an open-source ML inference framework for running deep-learning models on embedded systems. TF Micro tackles the efficiency requirements imposed by embedded-system resource constraints and the fragmentation challenges that make cross-platform interoperability nearly impossible. The framework adopts a unique interpreter-based approach that provides flexibility while overcoming these challenges. This paper explains the design decisions behind TF Micro and describes its implementation details. Also, we present an evaluation to demonstrate its low resource requirement and minimal run-time performance overhead.

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The role of micro, small and medium enterprises (MSMEs) to the sustainable development of sub-Saharan Africa and its challenges: a systematic review of evidence from Ethiopia

• Ebrahim Endris   ORCID: orcid.org/0000-0002-9048-2351 1 &
• Andualem Kassegn 1  

Journal of Innovation and Entrepreneurship volume  11 , Article number:  20 ( 2022 ) Cite this article

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Micro, small and medium-sized enterprises (MSMEs) have a potential impact on achieving many of the sustainable development goals much greater than their size. This review aimed to investigate existing literature on the contribution of MSMEs to the sustainable development of Ethiopia and its challenges. The review provides a comprehensive and systematic summary of evidence and provides future research directions. A systematic review methodology was adopted through reviewing the available literature comprehensively including research articles, policy documents, and reports over the period 2011–2021 from ScienceDirect, Google Scholar, ECONBIZ, IJSTOR, EBSCO, Web of Science, and Scopus databases. A search on these databases and grey literature returned 1270 articles; 87 papers were included in this review following screening of aticles using pre-determined criteria. The paper found that MSMEs significantly contributed to the sustainable development goals of Ethiopia through creating employment, alleviating poverty, and improving their living standards. However, the review has identified access to finance, access to electricity, and trade regulation are the major constraints for the development of the sector. The review outlines key policy implications to develop a comprehensive policy that alleviates the existing challenges of the sector and calls for further MSMEs impact evaluation research.

Introduction

Growth in the working age population is expected to be even more rapid, increasing by 265.8% in Africa and by 306.6% in sub-Saharan Africa, compared to 28.3% globally (Bhorat & Oosthuizen, 2020 ). Consequently, unemployment is a colossal problem in sub-Saharan Africa (Dey, 2012 ). Entrepreneurship can be a cure for Africa’s problems such as unemployment, inequality, low productivity, disconnect from global value chains, etc. (Devine & Kiggundu, 2016 ). The General Assembly adopted resolution 71/221 recognizes the important contribution entrepreneurship to sustainable development by creating jobs, driving economic growth and innovation, improving social conditions, and addressing social and environmental challenges (UN, 2018 ). Hence, investment in entrepreneurial ventures can contribute immensely to economic growth and job creation (Arko-Achemfuor, 2017 ) and thus jobs provide income, which improves living standards and consumption possibilities (IFC, 2013 ). Micro, small and medium-sized enterprises (MSMEs) are a major source of growth, innovation and jobs and their potential impact on achieving many of the sustainable development goals is much greater than their size (ITC, 2019 ). Therefore, there is a great interest of young people to start a business and many of them are willing to undertake risks and challenges of entrepreneurship (Papulová & Papula, 2015 ).

Sustainable development goals (SDGs) in Africa emphasize on labor-intensive sectors (SDG 8.2), increase small-scale enterprises’ access to affordable credit in support of decent job creation and entrepreneurship (SDG 8.3 and 9.3) (Brixiová et al., 2020 ). The informal sector (nonfarm) has been a growing source of employment for a large section of the African youth, but also for older workers trying to seize entrepreneurial opportunities. Its contribution to GDP and poverty reduction has been substantial, and it has become a major point of entry into the labor market (AFDB, 2019 ). Small and medium-sized enterprises (SMEs) make crucial contributions to job creation and income generation. The promotion of SMEs has been a key area of intervention in recent years in view of the major employment challenges (ILO, 2015 ). For that reason, the employment share of the self-employed in low-income countries is almost five times (54%) the share in high-income countries (11%), and the employment share of micro-enterprises (2–9 employees) also much higher (ILO, 2019b ). Small and medium enterprises have embraced technological innovations in creating new opportunities as well as expanding their businesses. In particular, high mobile phone penetration has brought opportunities to SMEs in rural and urban areas of Africa (Amankwah-Amoah et al., 2018 ).

Ethiopia most important development priorities were job creation for the increasing supply of labor force which contributed in reducing poverty (NPC, 2016 ; WBG, 2018 ). Hence, the implementation of the micro and small enterprises (MSEs) development strategies given undue role to achieve these objectives (NPC, 2016 ). The revised MSE strategy focus on enhancing the competitiveness of MSEs, ensuring continued rural development through sustainable growth of MSEs, and making the subsector a foundation for industrial development (FMSEDA, 2011 ). During Growth and Transformation Plan (GTP) I implementation period (2010/2011–2014/2015), construction sector was largest over other sector which accounts about 36.2%, followed by services with 20.8%, trade with 15.2%, manufacturing with 14.7% and urban agriculture accounts 13.1% employment through MSEs (EEA, 2015 ).

Establishment of MSEs strategy by itself cannot alleviate the problems facing MSEs and improve the development of the sectors (Hunegnaw, 2019 ). The ability of the firm to operate for longer time depends up on a proper tradeoff between management of investment in long-term and short-term funds (Dinku, 2013 ). The more rapid growth of small firms in Ethiopia is offset by a very high rate of firm failures (Page & Söderbom, 2015 ), this risk of business failure is high during the first 2–4 years of business operation (Woldehanna et al., 2018 ). Given the implication of MSMEs to the national development goals and it is a key development policy, there is little evidence that explore its role and prevailing challenges in a broader context. Hence, this review article aimed to provide an exploratory insight on the contribution of MSMEs in achieving sustainable development of Ethiopia and identify the prevailing challenges. The review contributes to the existing literature by providing evidence for these specific questions. (1) What is the role of MSMEs in attaining sustainable development goals of sub-Saharan Africa specifically Ethiopia? (2) What are the challenges hindering the development MSMEs in the country? This literature review identifies the specific research gaps uniquely relevant for future researches and policy direction for the development of the sector.

Review methodology

The review adopted a systematic literature review method, which offers an explicit, trustworthy, and reproducible method to minimize bias, thus providing more reliable findings for the evaluation and interpretation of previous research relevant to a particular field (Sniazhko & Muralidharan, 2019 ). The review based on extensive overview of relevant literature (research articles, policy documents, and reports) following a systematic review approach utilizing PRISMA guidelines (Liberati et al., 2009 ).

Literature search

The review retrieved from international databases using keywords identified. The literature search was conducted in ScienceDirect, ECONBIZ, IJSTOR, Google Scholar, EBSCO, Web of Science and Scopus databases that provides large collection of articles. The literature search was done using the following keywords: ((“micro enterprise” OR “small enterprise” OR “enterprise” OR “sustainable development”) AND “Ethiopia” OR “Africa”) in the citation information, keywords and abstracts. Moreover, we conducted a snowball search by examining the reference lists of included studies to include additional relevant studies that might have been missed for a variety of reasons. In addition, national university research repository used to search relevant thesis and dissertation to obtain a comprehensive set of evidence. The review used secondary data extracted from international organization databases such as World Bank, IFC, ILO, and NBE to support the review with empirical evidences. These databases are recognized as the key sources for retrieving relevant, up-to-date articles in socio-economic field, and are commonly used by other scholars to conduct systematic review (Sniazhko & Muralidharan, 2019 ). The preliminary searches within the databases using the abovementioned keywords identified 1270 records.

Study identification and the screening and selection process

The two fundamental components in a systematic literature review are (i) deciding on the inclusion and exclusion criteria of studies, and (ii) assessing the quality of the studies to be included (Čablová et al., 2017 ). The preliminary extensive list of identified articles was narrowed down to specifically relevant literature through inclusion and exclusion criteria. The articles retrieved from online database searches and different sources were collected in to Endnote Library. The articles identified in stage one was examined thoroughly to exclude the duplicated articles of the same titles that were available in multiple search databases. For the initial search, we set three inclusion criteria: (1) any literature that include at least one of key terms or words (2) literature written in English language, and (3) conducted over the last 10 years (2011–2021). In addition, filter criteria were applied to reduce the number of articles based on (1) articles published before 2011, (2) editorial comments, book reviews, and review articles, and (3) any literature out of the scope of this review were excluded. Then, repetitive articles, and articles not related to the subject using the inclusion criteria were excluded. By applying these inclusion and exclusion criterions, the search generated 210 records.

Our search identified 1270 retrieved records, which were reduced to 960 after removing duplicates. Two of the researchers (E.E and A.K.) who used the above criteria to determine paper eligibility to be included in the study, reviewed titles and abstracts independently. From theses, 210 articles were identified eligible for full-text review after screening title and abstracts for final inclusion. There are 123 articles excluded because no empirical evidence relevant for this review. Any disagreements regarding the exclusion of an article were resolved through a discussion among the authors, through multiple round reading when necessary to achieve consensus. The details of procedures presented in the PRISMA flow diagram (Fig.  1 ), and 87 studies finally reviewed comprehensively in an attempt to identify the findings within the articles. The findings in the articles synthesized qualitatively to provide answers for review questions.

Study selection process (PISMA flow diagram)

Results and discussion

Implication of msmes towards sub-saharan africa sustainable development.

Entrepreneurial activity is crucial to the achievement of multiple SDGs, including SDG 1: “End poverty in all its forms everywhere”; SDG 8: “Promote inclusive and sustainable economic growth, employment and decent work for all”; SDG 10: “Reduce inequality within and among countries” (Bosma et al., 2020 ). The United Nations’ SDG 8 sets out a global consensus that business enterprises should aim for sustained, inclusive, and sustainable economic growth and also ensure decent work and living environments for all (Lin & Koh, 2019 ). Small and medium-sized enterprises play a key role in job creation, providing two-thirds of all formal jobs in developing countries and 80% in low-income countries. The sustained success of SMEs depends on local conditions, such as public services, good corporate law and access to finance (EDFI, 2016 ). In addition, MSEs provides a substantial collective contribution to the national economy (White, 2018 ), contribute more than 50% of most African GDP and an average of 60% of employment (Muiruri, 2017 ). It employs the vast majority of any local labor force and has an integral role in any sustainable growth trajectory and it is ‘the missing link’ for inclusive growth (ITC, 2018 ). Although African SMEs generate about 80% of new jobs, they also account for most lost jobs (ILO, 2019a ). Micro enterprises in Ethiopia account the greatest share of employment from developing countries (IFC, 2013 ).

Investing in SMEs can contribute to 60% of the targets established in the SDGs and about $1 trillion additional SME investment help developing countries reach the SDGs. Small and medium enterprise contribute to 83% of SDG 8 (Promote sustained, inclusive and sustainable economic growth, full and productive employment and decent work for all) targets, and 88% of SDG 9 (Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation) targets (ITC, 2019 ). Hence, financial stability in sub-Saharan Africa enhances entrepreneurial development which improve economic growth and accelerated achievement of SDGs (Babajide et al., 2020 ). There is a large concentration of enterprises in sub-Saharan Africa, 44 million MSMEs, of which 97% are micro-enterprises, of which the largest share (37 million MSMEs) accounted by Nigeria enterprise (IFC, 2017 ).

Even though, the contribution of MSEs to total employment and gross job flows were underestimated (Li & Rama, 2015 ), it contributed to economic growth through their operational activities, via job creation in Nigeria economy (Matthew et al., 2020 ) and micro-enterprises alone account for a staggering 97% of manufacturing sector employment in Ethiopia (Li & Rama, 2015 ). Entrepreneurship and new venture creation in South Africa emphasize on employment opportunities for MSMEs employees, and the social dimensions of poverty reduction approaches are broader than these economic imperatives (Rambe & Mosweunyane, 2017 ). Small-scale enterprises employment has absorbed over 49% of the increase in the labor force in five countries of sub-Saharan Africa (Botswana, Kenya, Malawi, Swaziland and Zimbabwe). Similarly, about 80% of employment growth in Tanzania accounted by informal enterprises (Diao et al., 2018 ).

Problems in the development of enterprise in sub-Saharan Africa

Entrepreneurial activity in low-income countries dominated by individuals who are forced into starting their own business due to a lack of employment and typically not highly productive (Doran et al., 2018 ). The main challenges constrained SMEs contribution to local economic development of developing countries are lack of finance, lack of business skills, poor market access, and lack of operating space (Gebreyesus & Adewale, 2015 ). The contribution of MSMEs to sustainable development is constrained by unfavorable business environments, inadequate access to finance and high levels of informality (ITC, 2019 ). The challenges such as lack of access to finance, weak entrepreneurial attitudes, government policies, regulations and practices for entrepreneurs, and training are main constraints to SME development in sub-Saharan Africa (Achtenhagen & Brundin, 2016 ; Herrington & Coduras, 2019 ; IFC, 2011 ). Due to this, the core focus of the owner of MSMEs are personal financial survival rather than on growing and developing the business, which affected the success of small businesses. In these circumstances, profit made in the business is often spent on personal expenses rather than being reinvested into the business (IFC, 2020b ).

Accessing finance for entrepreneurship development in Africa is still continuing and new challenges to MSMEs (Atiase et al., 2017 ; Beck & Cull, 2014 ). Access to credit currently fails to support entrepreneurship development in Africa (Atiase et al., 2017 ; Wang, 2016 ), and SMEs have limited access to finance even though banks have sufficient liquidity (Brixiová et al., 2020 ). Most financial institutions undermine smaller enterprises and instead focus on big businesses that can provide the required collateral for their loans (Atiase et al., 2017 ). Difficulty to obtain formal credit were due to small capital of MSEs below critical collateral value (lack tangible assets as collateral) (Jin & Zhang, 2019 ), high risk premiums, and higher transaction cost to banks, as SMEs loan size are generally small (Quartey et al., 2017 ). Sub-Saharan Africa have low financial inclusion index (Ofori-Abebrese et al., 2020 ). Hence, access to finance remains the largest obstacle for SMEs in the region and 75% of enterprises were financed by internal funds and other 10% used traditional banking loans (Leke & Signé, 2020 ). For example, 79% of informal businesses have never obtained loan, and only 21% utilized bank loan in South Africa. From this, only 19% of formal businesses used a bank loan to start their business (IFC, 2020b ). In Tanzania, only 30% of MSMEs had access to financial services (Ishengoma, 2018 ). A large number of enterprises in sub-Saharan Africa are occasional enterprises that function for a limited period of the year. For instance, lack of profitability and a lack of finance the most important reasons for enterprise exit in Uganda (Nagler & Naudé, 2016 ). Furthermore, lack of finance and harsh business environment tends to constrain the growth of MSMEs in Uganda (Lakuma et al., 2019 ), access to finance is still a hurdle to MSMEs establishment in Lesotho (Khoase & Govender, 2013 ), and access to both debt and equity markets also affected micro-enterprises in South Africa (Fatoki, 2017 ).

The limitation of finance has an inhibiting effect on the growth of African firms (Fowowe, 2017 ). For example, financially constrained firms have 6.6% lower marginal revenue product of capital relative to unconstrained firms. Moreover, constrained firms are also more inefficient and less productive relative to unconstrained firms in sub-Saharan Africa. Constrained firms are 15% less efficient due to borrowing constraints compared to unconstrained firms (Amos & Zanhouo, 2019 ). For instance, SME access to bank finance can further increase the contribution of SMEs to the Ghanaian economy and increase their chances of survival and success through exports (Abor et al., 2014 ).

The low performances in sub-Saharan Africa attributed exclusively to factors outside firms, such as poor infrastructure and unfavorable governance (Mano et al., 2012 ). The risks faced by entrepreneurs in Nigeria SMEs arose from the increasing complexity and sophistication of the industrial sector and increasing macroeconomic instability (Ejembi & Ogiji, 2017 ). The operational environment of SMEs strongly indicate that their productivity is constrained by lack of adequate infrastructure as well as inefficient institutions in Nigeria (Effiom & Edet, 2020 ). The lack of business infrastructure hampers MSMEs’ ability to scale and grow in South African, lack of equipment as the second largest challenge at startup (IFC, 2020b ), and limited awareness of government program (Fatoki, 2017 ). The results further indicate that the majority of MSMEs had no access to public infrastructure, i.e., only 16% and 28% of MSMEs had access to electricity from the national grid and water from the public or municipal sources, respectively (Ishengoma, 2018 ).

The impact of COVID-19 on sub-Saharan Africa MSMEs

COVID-19 lockdowns and social distancing measures influenced the MSMEs operation. Finding from study carried out in 132 countries revealed that two-thirds of micro and small firms reported that COVID-19 has affected their business operations and one-fifth of SMEs confirmed they face risks of closing down permanently within 3 months (ITC, 2020 ). The COVID-19 outbreak has posed great challenges for the survival and growth of SMEs (Guo et al., 2020 ). The upheaval caused by the spread of COVID-19 have a devastating effect on small businesses. Moreover, the economic fallout from this pandemic get worse for small businesses and their employees (Liguori & Pittz, 2020 ). The feature of MSMEs such as more labor-intensive activity hurt during COVID-19 lockdowns, limited reserves and lack of collateral for new credit lines are key factors which make SMES highly vulnerable to the impact of COVID-19 pandemic (COMESA, 2020 ).

The study on 367 agri-food MSMEs from 17 low and middle income countries revealed that 94.3% of firm’s operations had been impacted by the pandemic, primarily through decreased sales as well as lower access to inputs and financing amid limited financial reserves. Moreover, 84% firms reported changing their production volume as a result of the pandemic; of these, about 13% reported stopping production and about 82% reported decreasing production (Nordhagen et al., 2021 ). The pandemic has severely affected about 37 million microenterprise and 28,000 SMEs due their lack of adequate cash buffers and access to finance. About 25 million micro-enterprises operating in tourism, hospitality, entertainment, and trade had to close or face significantly reduced operating hours (IFC, 2020a ). Therefore, COVID-19 is a substantial threat to the attainment of SDGs 1, 2, 3 and 8 in Nigeria (Ogisi & Begho, 2021 ). The pandemic severely hurt financial health of MSMEs in sub-Saharan Africa via reduced profit, turnover decrease, and liquidity crunch. The percentage of MSMEs that suffered due to the pandemic is presented (Table 1 ) for some countries for which data were obtained.

Role of MSMEs development in Ethiopia

Micro and small enterprise development is the primary strategy of GTP II to expand employment and reducing poverty particularly focusing on women and youths (NPC, 2016 ). The government of Ethiopia proposed MSEs as means of creating employment to millions of youths and achieving sustainable development goals. Hence, there is policy support leads SMEs generating more employment compare to large firms (Ashenafi, 2014 ). Therefore, the contribution of MSEs to employment creation is much higher (99%) than that of medium and large enterprises (1%) (Abera et al., 2019 ). A sizable number of people are employed in small-scale tourism enterprises with a decent average monthly income that can improve their living standard in Hawassa City (Tamene & Wondirad, 2019 ). Similarly, MSEs program had led to positive outcomes on the income and livelihood of beneficiaries in Bahir Dar City (Melese, 2017 ). With respect to sector contribution, manufacturing and construction enterprise ranked first and second, respectively, in creating job opportunities for job seekers in Kolfe-Keranio Sub-City, Addis Ababa (Tafa, 2019 ). Manufacturing and urban agriculture sector provide huge contribution in reducing food insecurity of operators in Mecha district (Yimesgen, 2019 ).

The conceptual framework on the role MSMEs towards SDGs is presented in Fig.  2 . The framework showed that MSMEs has positive implication in meeting SDG 1, 2, 5, 8, 9, and 12 (Bosma et al., 2020 ; ITC, 2019 ; Lin & Koh, 2019 ).

Framework on MSMEs contribution to sustainable development. Source: own sketch based on literature review

Employment in micro-enterprises leveled as high in terms of its extent of importance to poverty reduction (Kidane et al., 2015 ). It have played a positive role in women’s livelihood by creating employment opportunity for those who are in need of job and with low level of income, empowered them socially and economically (Admasu, 2016 ; Menda, 2015 ). In addition, entrepreneurs have created job opportunities to others while also contributing to local economy and communities through income tax payment. It provides annual average of minimum 5–7 and maximum 17–23 employment opportunities in the last 5 years. The annual average income of the enterprises was at the minimum ranging between 30,000–50,000 Birr and maximum ranging between 141,001–200,000 Birr (Hiluf, 2018 ). The distribution of MSEs established and number of employment opportunities in the enterprise varying across years. Based on Fig.  3 , the number of enterprise and employment in MSEs was largest in 2014/2015.

Number of enterprise and employment created in Ethiopia. Source: authors calculation from NBE (2020)

Challenges of MSME in Ethiopia

Financing msmes in ethiopia.

Access to finance improve the survival rates, productivity and competence of MSEs. These enterprises in Debre-Markos town obtained from microfinance, Iqub , Idir , own capital and relatives than large banks (Tadesse, 2014 ). The main sources of initial capital for MSE’s are microfinance institution followed by bank and own capital (Alemu, 2018 ). Insufficient credit services for youth is a challenge in implementing rural youth economic development (Abdi, 2019 ). Financial institutions’ reluctance to give credit to young SMEs due to fear that firms may be defaulter (Nega & Hussein, 2016 ). The revolving funds of 10 billion birr for MSEs (FDRE, 2017 ) were not enough to ease financial challenges of the sector. The existence of inadequate loan size, borrowing cost and collateral requirement (Goshim & Tefera, 2018 ; Sissay, 2016 ; Tadesse, 2014 ), and high rate matching fund and liquidity problem for matching fund (Abeiy, 2017 ; Amentie et al., 2016 ; Sissay, 2016 ) constrained MSEs access to finance in Ethiopia. Moreover, loan duration affects MSEs access to finance from formal financial institutions (Petros, 2017 ; Tadesse, 2014 ). The business firms’ obstacle in Ethiopia (Fig.  4 ) showed that finance and electricity were the first and second major challenges in Ethiopia. As depicted in Fig.  5 , finance is a major barrier and high loan rejection rate for MSEs than medium enterprises.

Financial challenges across enterprise size. Source: Author calculation from World Bank enterprise survey (2015)

Financial challenges across enterprise size. Source: author calculation from IFC database (2019)

Micro and small enterprises (MSEs) needs business knowledge, skills and entrepreneurial orientation to profitably operate their business consistently in the existing business dynamics (Ghebremichael & Kassahun, 2014 ; Tarekegn et al., 2018 ). However, there are personal factor such as lack of business vision, risk averse of members, personal business exposure aggravate MSEs members dropout (Daba & Atnafu, 2016 ). The impact of aspiration to expand existing business and starting additional new business on growth of the MSEs is much higher for small enterprise compared to microenterprise (Amha, 2015 ).

Barriers against the development of MSMEs in Ethiopia

The existence of favorable working environment like government played a key role in the growth and development of MSEs (Hailu, 2016 ; Yimesgen, 2019 ). This support service program on average increased Dire Dawa MSEs monthly sales by 28%, employement by 42%, and capital asset formation by 60% (Eshetu et al., 2013 ). However, these supports are not sufficient for the development of micro and small enterprise (Hailu, 2016 ). In addtion, lack of training to start their own venture (Tewolde & Feleke, 2017 ), lack of awareness about the contribution and accessibility of consultancy service are the major problem of enterprises (Kidane et al., 2015 ). The ease of obtaining licenses to SMEs in Ethiopia was  better relative to sub-Saharan Africa region (Table 2 ).

Micro and small enterprises were formally registered when they start operation in Ethiopia. The challenge of informal competitor lower in Ethiopia than sub-Saharan Africa and its effect decrease as firms grow from small to large enterprises (Fig.  6 ). This is due to large firms have the capacity to compete at large scale than small enterprise. Informal firms are also more credit constrained compared to formal firms (Aga & Reilly, 2011 ).

Informality of small and medium enterprise. Source: author calculation from World Bank Enterprise database (2020)

Micro and small enterprise access to sufficient premises in proper location increases enterprises financial performance (Ababiya, 2018 ). Poor infrastructure (Abeiy, 2017 ; Kinati et al., 2015 ) would cause more than 25% worktime loss daily due to power interruption (Cherkos et al., 2018 ) and business location identified as significant factors that hinder the growth of enterprises (Batisa, 2019 ). Power outages affected firms’ productivity, and the overall total cost due to outage increased by approximately 15% of firm’s aggregate cost (Abdisa, 2018 ). The cost of power outages for MSMEs in Addis Ababa is substantial, and a reduction of one power outage corresponds to a tariff increase of 16% (Carlsson et al., 2018 ). The location of enterprise effect on business performance raises two different arguments. Empirical evidences showed that MSEs desire to established in the center of town for attracting large customers even though rent in the downtown is high (Yimesgen, 2019 ). The second argument showed that MSEs that operate out of town have better performance. This is because MSEs have easy access for input and potential for business expansion (Kebeu, 2014 ). Entrepreneurial opportunities were increasing in Ethiopia, as presented in Fig.  7 over the 5 years. The score of ease of doing business increased over the last 5 years. However, the score of getting credit is stagnant which indicates access to finance were the long existing challenge of MSMEs development in Ethiopia.

Performance of doing business in Ethiopia. Source: author calculation from World Bank Enterprise database (2020)

The presence of market linkage enables MSEs to supply their produce and acquire inputs in the commercial value chain, which create jobs and improve efficiency of enterprises. However, the existing vertical linkage between MSEs and large enterprises are very limited, and limited access to raw materials (Mechalu, 2017 ; Mohammed & Beshir, 2019 ) and high cost of raw materials are major challenges of MSEs (Seifu, 2017 ). The absence of market linkage identified the critical problems of enterprises (Daba & Amanu, 2019 ; Dabi, 2017 ). Furthermore, there are weak institutional and sectoral linkages (Abera et al., 2019 ). As a result, informal linkages have a significant role to access market (Hadis & Ali, 2018 ).

Micro, small and medium-sized enterprises (MSMEs) has been a key area of intervention to sustainable development specifically in growing youth population of sub-Saharan Africa. Given the implication of MSMEs in national development goals and it is a key development policy, there is little evidence particularly at broader context. Hence, this review article presents a systematic review of studies on the contribution of MSMEs in achieving sustainable development of Ethiopia and identifies the prevailing challenges. The paper has also demonstrated that MSMEs has myriad role in economy growth, poverty reduction, industrialization and livelihood as a whole. Micro enterprises in Ethiopia account the greatest share of employment from developing countries. Investing in small and medium-sized enterprises (SMEs) can contribute in some measure to 60% of the targets established in the SDGs. Manufacturing sector of Ethiopia micro-enterprises account for a staggering 97% of employment, 80% of employment growth in Tanzania accounted largely by informal enterprises. The review pointed that employment in micro-enterprises leveled as high in terms of its extent of importance to poverty reduction, empowered women socially, economically, and contributing to local economy and communities through income tax payment in Ethiopia.

The review revealed that lack of access to finance, poor infrastructure, and entrepreneurial attitudes are main challenges facing MSMEs in sub-Saharan Africa. Access to finance remains the largest obstacle for enterprises in the region. The problems became severe in time of crisis such as COVID-19 that lead two-thirds of micro and small firms in crisis and one-fifth of SMEs face risks of closing down permanently. The existence of inadequate loan size, borrowing cost and collateral requirement constrained MSEs in getting access to finance thereby the development of micro and small enterprise in Ethiopia. In addition, poor infrastructures are the main constraint that lead MSMEs to high worktime loss, reduce productivity, and increased cost of enterprise production.

Recommendations and future research directions

Based on the review of studies, key implications for policy and future research include:

It is essential to unlock entrepreneurship potential through integrated multi-sectoral and sustainable approach. Policy measures should prioritize inclusive financing schemes to vulnerable and marginalized entrepreneurs and enterprises that support business recovery during the crisis, and development of MSMEs.

In addition, strong intervention to infrastructure development particularly electricity supply, working premise that increase ease of doing business and sustainable development of the country.

Furthermore, this review calls for further research that focus on areas not given sufficient research attention such as the impact of MSMEs in achieving SDG 1 (No poverty), SDG 2 (Zero hunger), SDG 9 (Industrialization), SDG 12 (Responsible consumption and production). Future research needs to address ways to overcome the challenges hindering MSMEs’ development.

Availability of data and materials

Not applicable.

Abbreviations

Ethiopia Economic Association

Federal Micro and Small Enterprises Development Agency

Growth and Transformation Plan

Micro and small enterprises

Micro, small and medium enterprises

National Bank of Ethiopia

National Plan Commission of Ethiopia

Sustainable development goals

Small and medium enterprises

Ababiya, A. (2018). Financial performance of agricultural enterprises and their determinant factors in Hadiya Zone, Ethiopia. European Journal of Business and Management, 10 (19), 25–34.

Google Scholar  

Abdi, B. (2019). Challenges and prospects of rural youth economic empowerment. The case of Dire Teyara of Harari Regional State, Ethiopia . Ethiopian Civil Service University.

Abdisa, L. T. (2018). Power outages, economic cost, and firm performance: Evidence from Ethiopia. Utilities Policy, 53 , 111–120. https://doi.org/10.1016/j.jup.2018.06.009

Article   Google Scholar  

Abeiy, A. (2017). Factors affecting performance of micro and small enterprises in Addis Ababa. The case of Addis Ketema Sub City Administration (City Government of Addis Ababa) . Addis Ababa University.

Abera, H., Vermaack, C., Gebrekirstos, K., Minwuyelet, L., Tsegay, M., Hagos, N., & Gidey, Y. (2019). Contributions of micro, small and medium enterprises (MSMEs) to income generation, employment and GDP: Case study Ethiopia. Journal of Sustainable Development, 12 (3), 46–81. https://doi.org/10.5539/jsd.v12n3p46

Abor, J. Y., Agbloyor, E. K., & Kuipo, R. (2014). Bank finance and export activities of small and medium enterprises. Review of Development Finance, 4 (2), 97–103. https://doi.org/10.1016/j.rdf.2014.05.004

Achtenhagen, L., & Brundin, E. (2016). Entrepreneurship and SME management across Africa context, challenges, cases . Springer Science.

Admasu, A. (2016). The role of small and micro enterprises on the livelihood of poor women entrepreneurs in urban locality of Addis Ababa: The case of Woreda 8 of Yeka Sub-City . Addis Ababa University.

AFDB. (2019). Creating decent jobs strategies, policies, and instruments: Policy research document 2 . African Development Bank.

Aga, G. A., & Reilly, B. (2011). Access to credit and informality among micro and small enterprises in Ethiopia. International Review of Applied Economics, 25 (3), 313–329. https://doi.org/10.1080/02692171.2010.498417

Alemu, O. (2018). Determinants of loan repayment of micro and small enterprises in Jimma Town, Ethiopia. Global Journal of Management and Business Research B Economics and Commerce, 18 (4), 47–66.

Amankwah-Amoah, J., Osabutey, E. L. C., & Egbetokun, A. (2018). Contemporary challenges and opportunities of doing business in Africa: The emerging roles and effects of technologies. Technological Forecasting and Social Change, 131 , 171–174. https://doi.org/10.1016/j.techfore.2018.01.003

Amentie, C., Negash, E., & Kumera, L. (2016). Barriers to growth of medium and small enterprises in developing country: Case study Ethiopia. Journal of Entrepreneurship & Organization Management, 5 (3), 1–4. https://doi.org/10.4172/2169-026X.1000190

Amha, W. (2015). Growth of youth-owned MSEs in Ethiopia: Characteristics, determinants and challenges. Ethiopian Journal of Economics, 24 (2), 93–128.

Amos, S., & Zanhouo, D. A. K. (2019). Financial constraints, firm productivity and cross-country income differences: Evidence from sub-Sahara Africa. Borsa Istanbul Review, 19 (4), 357–371. https://doi.org/10.1016/j.bir.2019.07.004

Arko-Achemfuor, A. (2017). Financing small, medium and micro-enterprises (SMMEs) in rural South Africa: An exploratory study of stokvels in the nailed Local Municipality, North West Province. Journal of Sociology and Social Anthropology, 3 (2), 127–133. https://doi.org/10.1080/09766634.2012.11885572

Ashenafi, B. (2014). The impact of subsidy on the growth of small and medium enterprises (SMEs). Journal of Economics and Sustainable Development, 5 (3), 178–188.

Atiase, V. Y., Mahmood, S., Wang, Y., & Botchie, D. (2017). Developing entrepreneurship in Africa: Investigating critical resource challenges. Journal of Small Business and Enterprise Development, 25 (4), 644–666. https://doi.org/10.1108/JSBED-03-2017-0084

Babajide, A., Lawal, A., Asaleye, A., Okafor, T., & Osuma, G. (2020). Financial stability and entrepreneurship development in sub-Sahara Africa: Implications for sustainable development goals. Cogent Social Sciences, 6 (1), 1–17. https://doi.org/10.1080/23311886.2020.1798330

Batisa, S. (2019). Determinants of youth based micro and small enterprises growth in Dawro Zone: A case of Mareka Wereda. International Journal of Research in Business Studies and Management, 6 (12), 27–37.

Beck, T., & Cull, R. (2014). SME finance in Africa. Journal of African Economies, 23 (5), 583–613. https://doi.org/10.1093/jae/eju016

Bhorat, H., & Oosthuizen, M. (2020). Jobs, economic growth, and capacity development for youth in Africa (Working Paper Series N° 336, Issue). African Development Bank.

Bosma, N., Hill, S., Ionescu-Somers, A., Donna Kelley, J. L., & Tarnawa, A. (2020). Global Entrepreneurship Monitor 2019/2020 global report . Global Entrepreneurship Research Association.

Brixiová, Z., Kangoye, T., & Yogo, T. U. (2020). Access to finance among small and medium-sized enterprises and job creation in Africa. Structural Change and Economic Dynamics, 55 , 177–189. https://doi.org/10.1016/j.strueco.2020.08.008

Čablová, L., Pates, R., Miovský, M., & Noel, J. (2017). How to write a systematic review article and meta-analysis. In T. F. Babor, K. Stenius, R. Pates, M. Miovský, J. O’Reilly, & P. Candon (Eds.), Publishing addiction science: A guide for the perplexed (pp. 173–189). Ubiquity Press. https://doi.org/10.5334/bbd.i

Chapter   Google Scholar  

Carlsson, F., Demeke, E., Martinsson, P., & Tesemma, T. (2018). Cost of power outages for manufacturing firms in Ethiopia: A stated preference study . University of Gothenburg.

Cherkos, T., Zegeye, M., Tilahun, S., & Avvari, M. (2018). Examining significant factors in micro and small enterprises performance: Case study in Amhara region, Ethiopia. Journal of Industrial Engineering International, 14 (2), 227–239. https://doi.org/10.1007/s40092-017-0221-y

COMESA. (2020). Economic impact of covid-19 on micro, small and medium enterprises (MSMEs) in Africa and policy options for mitigation . Common Market for Eastern and Southern Africa.

Daba, A., & Atnafu, M. (2016). Analysis of the main cause for the entrepreneurs drop out in micro and small enterprises: Evidences from Nekemte Town, Eastern Wollega Zone, Oromia Regional State, Ethiopia. International Journal of Economics & Management Sciences, 5 (6), 1–16. https://doi.org/10.4172/2162-6359.1000376

Daba, B., & Amanu, K. (2019). The roles of micro and small enterprises in empowering women: The case of Jimma Town, Ethiopia. International Journal of Multicultural and Multireligious Understanding, 6 (2), 190–202. https://doi.org/10.18415/ijmmu.v6i2.69766

Dabi, N. (2017). Performance of micro and small-scale enterprises: The case of Adama, Oromia. World Journal of Economic and Finance, 3 (1), 046–051.

Devine, R. A., & Kiggundu, M. N. (2016). Entrepreneurship in Africa: Identifying the frontier of impactful research. Africa Journal of Management, 2 (3), 349–380. https://doi.org/10.1080/23322373.2016.1206802

Dey, P. (2012). Rapid incubation model for the development of micro and small enterprises in Sub-Saharan Africa. Global Journal of Management and Business Research, 12 (10), 78–85.

Diao, X., Kweka, J., & McMillan, M. (2018). Small firms, structural change and labor productivity growth in Africa: Evidence from Tanzania. World Development, 105 , 400–415. https://doi.org/10.1016/j.worlddev.2017.12.016

Dinku, T. (2013). Impact of working capital management on profitability of micro and small enterprises in Ethiopia: The case of Bahir Dar City Administration. International Journal of Accounting and Taxation, 1 (1), 15–24.

Doran, J., McCarthy, N., & O’Connor, M. (2018). The role of entrepreneurship in stimulating economic growth in developed and developing countries. Cogent Economics & Finance, 6 (1), 1–14. https://doi.org/10.1080/23322039.2018.1442093

EDFI. (2016). Investing to create jobs, boost growth and fight poverty . Association of the European Development Finance Institutions.

EEA. (2015). Small and Micro Enterprises (SMEs) development in Ethiopia: Policies, performances, constraints and prospects (EEA Research Brief, Issue). Ethiopia Economic Association.

Effiom, L., & Edet, S. E. (2020). Financial innovation and the performance of small and medium scale enterprises in Nigeria. Journal of Small Business & Entrepreneurship . https://doi.org/10.1080/08276331.2020.1779559

Ejembi, S. A., & Ogiji, P. (2017). A comparative analysis of risks and returns of running small/medium micro enterprises in North Central Nigeria. Journal of Social Sciences, 15 (1), 7–15. https://doi.org/10.1080/09718923.2007.11892556

Eshetu, T., Ketema, M., & Kassa, B. (2013). Economic impact of support service program on micro and small enterprises: The case of Dire Dawa Administration, Ethiopia. Agris on-Line Papers in Economics and Informatics, 5 , 21–29.

Fatoki, O. (2017). Enhancing access to external finance for new micro-enterprises in South Africa. Journal of Economics, 5 (1), 1–6. https://doi.org/10.1080/09765239.2014.11884978

FDRE. (2017). Ethiopian youth revolving fund establishment proclamation .

FMSEDA. (2011). Micro and small enterprise development strategy, provision framework and methods of implementation .

Fowowe, B. (2017). Access to finance and firm performance: Evidence from African countries. Review of Development Finance, 7 (1), 6–17. https://doi.org/10.1016/j.rdf.2017.01.006

Gebreyesus, G., & Adewale, A. (2015). An assessment of the roles of small and medium enterprises (SMEs) in the Local Economic Development (LED) in South Africa. Journal of Economics, 6 (3), 280–290. https://doi.org/10.1080/09765239.2015.11917617

Ghebremichael, A., & Kassahun, T. (2014). Entrepreneurial orientation as growth predictor of small enterprises: Evidence from Tigray Regional State of Ethiopia. Developing Country Studies, 4 (11), 133–143.

Goshim, A., & Tefera, Y. (2018). Role of financial institution on the growth of small and medium enterprises: The case in North Shewa Zone, Amhara Region, Ethiopia. Journal of Investment and Management, 7 (5), 143–150. https://doi.org/10.11648/j.jim.20180705.12

Guo, H., Yang, Z., Huang, R., & Guo, A. (2020). The digitalization and public crisis responses of small and medium enterprises: Implications from a COVID-19 survey. Frontiers of Business Research in China, 14 (1), 19. https://doi.org/10.1186/s11782-020-00087-1

Hadis, S., & Ali, Y. (2018). Micro and small enterprises in Ethiopia; Linkages and implications: Evidence from Kombolcha Town. International Journal of Political Science and Development, 6 (1), 16–26. https://doi.org/10.14662/IJPSD2018.001

Hailu, D. (2016). Effects of government support on performance of micro and small enterprises in Ambo Town . Haramaya: Haramaya University.

Herrington, M., & Coduras, A. (2019). The national entrepreneurship framework conditions in sub-Saharan Africa: a comparative study of GEM data/National Expert Surveys for South Africa, Angola, Mozambique and Madagascar. Journal of Global Entrepreneurship Research, 9 (1), 60. https://doi.org/10.1186/s40497-019-0183-1

Hiluf, N. (2018). Socio-economic roles and challenges of micro and small enterprises in Addis Ababa: The case of Arada Sub-City . Deberberhan University.

Hunegnaw, G. (2019). Policy framework of small and micro enterprises and its role on the development of the sector in Bahir Dar City, Ethiopia. Public Policy and Administration Research, 9 (4), 1–8. https://doi.org/10.7176/PPAR

IFC. (2011). Strengthening access to finance for women-owned SMEs in developing countries . International Finance Corporation.

IFC. (2013). Assessing private sector contributions to job creation and poverty reduction . International Finance Corporation.

IFC. (2017). MSME finance gap: Assessment of the shortfalls and opportunities in financing micro, small and medium enterprises in emerging markets . International Finance Corporation.

IFC. (2020a). Covid-19 rapid assessment: Impact on the nigerian private sector and perspectives on accelerating the recovery . Supplement to the Country Private Sector Diagnostic on Nigeria .

IFC. (2020b). The MSME Voice: GROWING SOUTH AFRICA’S SMALL BUSINESS SECTOR .

ILO. (2015). Small and medium-sized enterprises and decent and productive employment creation (Report IV, Issue).

ILO. (2019a). Enabling environment for sustainable enterprises in Sierra Leone . International Labour Organization.

ILO. (2019b). Global evidence on the contribution to employment by the self-employed, micro-enterprises and SMEs . International Labour Organization.

Ishengoma, E. K. (2018). Entrepreneur ATTRIBUTES and formalization of micro, small and medium enterprises in Tanzania. Journal of African Business, 19 (4), 491–511. https://doi.org/10.1080/15228916.2018.1472480

ITC. (2018). Promoting SME competitiveness in Africa: Data for de-risking investment . International Trade Centre.

ITC. (2019). SME competitiveness outlook 2019: Big money for small business—Financing the sustainable development goals . International Trade Centre.

ITC. (2020). Impact of COVID-19 lockdown on economies, small businesses . International Trade Centre, Geneva.

Jin, Y., & Zhang, S. (2019). Credit rationing in small and micro enterprises: A theoretical analysis. Sustainability, 11 (5), 1330. https://doi.org/10.3390/su11051330

Kebeu, H. (2014). Entrepreneurial success as a function of human capital and psychological factors among micro and small enterprises operators: A psychological perspective study. International Journal of Social Sciences and Entrepreneurship, 1 (12), 352–367.

Khoase, R. G., & Govender, K. K. (2013). Enhancing small, medium and micro enterprise development: Exploring selective interventions by the Lesotho government. Development Southern Africa, 30 (4–05), 596–615. https://doi.org/10.1080/0376835x.2013.834814

Kidane, M., Mulugeta, D., Adera, A., Yimmam, Y., & Molla, T. (2015). Microenterprises targeting youth group to socioeconomic development: The case of Addis Ababa, Ethiopia. International Journal of Business and Economics Research, 4 (3), 144–156. https://doi.org/10.11648/j.ijber.20150403.17

Kinati, B., Asmera, T., & Minalu, T. (2015). Factors affecting developments of micro and small enterprises (Case of Mettu, Hurumu, Bedelle and Gore Towns of Ilu Aba Bora Administrative Zone). International Journal of Scientific and Research Publications, 5 (1), 1–10.

Lakuma, C. P., Marty, R., & Muhumuza, F. (2019). Financial inclusion and micro, small, and medium enterprises (MSMEs) growth in Uganda. Journal of Innovation and Entrepreneurship, 8 (15), 1–20. https://doi.org/10.1186/s13731-019-0110-2

Leke, A., & Signé, L. (2020). Spotlighting opportunities for business in Africa and strategies to succeed in the world’s next big growth market .

Li, Y., & Rama, M. N. (2015). Firm dynamics, productivity growth, and job creation in developing countries: The role of micro- and small enterprises. The World Bank Research Observer, 30 (1), 3–37. https://doi.org/10.1093/wbro/lkv002

Liberati, A., Altman, D. G., Tetzlaff, J., Mulrow, C., Gøtzsche, P. C., Ioannidis, J. P. A., Clarke, M., Devereaux, P. J., Kleijnen, J., & Moher, D. (2009). The PRiSMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: Explanation and elaboration. British Medical Journal . https://doi.org/10.1136/bmj.b2700

Liguori, E. W., & Pittz, T. G. (2020). Strategies for small business: Surviving and thriving in the era of COVID-19. Journal of the International Council for Small Business, 1 (2), 106–110. https://doi.org/10.1080/26437015.2020.1779538

Lin, R.-T., & Koh, D. (2019). Small and medium enterprises: Barriers and drivers of managing environmental and occupational health risks. In Encyclopedia of environmental health (pp. 682–692). https://doi.org/10.1016/b978-0-12-409548-9.11347-8 .

Mano, Y., Iddrisu, A., Yoshino, Y., & Sonobe, T. (2012). How can micro and small enterprises in Sub-Saharan Africa become more productive? The impacts of experimental basic managerial training. World Development, 40 (3), 458–468. https://doi.org/10.1016/j.worlddev.2011.09.013

Matthew, O., Ufua, D. E., Osabohien, R., Olawande, T., Edafe, D., & O. (2020). Addressing unemployment challenge through micro and small enterprises (MSEs): Evidence from Nigeria. Problems and Perspectives in Management, 18 (2), 79–89. https://doi.org/10.21511/ppm.18(2).2020.08

Mechalu, A. (2017). Marketing challenges of micro and small enterprises (MSEs) in Bishoftu Town . Addis Ababa University.

Melese, B. (2017). Micro and small enterprises as an anti-poverty and employment generation strategy in Bahir Dar City, North-Western Ethiopia. Poverty & Public Policy, 9 (3), 258–275.

Menda, S. (2015). Role of micro and small scale business enterprises in urban poverty alleviation; A case study on Cobblestone paving Sector in Addis Ababa city . Addis Ababa University.

Mohammed, S., & Beshir, H. (2019). Determinants of business linkage between medium-small and large business enterprises in manufacturing sector: The Case of Kombolcha City. Journal of Economics and Sustainable Development, 10 (3), 74–92. https://doi.org/10.7176/JESD

Muiruri, S. (2017). African small and medium enterprises (SMES) contributions, challenges and solutions. European Journal of Research and Reflection in Management Sciences, 5 (1), 36–48.

Nagler, P., & Naudé, W. (2016). Non-farm entrepreneurship in rural sub-Saharan Africa: New empirical evidence. Food Policy . https://doi.org/10.1016/j.foodpol.2016.09.019

Nega, F., & Hussein, E. (2016). Small and medium enterprise access to finance in Ethiopia: Synthesis of demand and supply . Addis Ababa, Ethiopia.

Nordhagen, S., Igbeka, U., Rowlands, H., Shine, R. S., Heneghan, E., & Tench, J. (2021). COVID-19 and small enterprises in the food supply chain: Early impacts and implications for longer-term food system resilience in low- and middle-income countries. World Development . https://doi.org/10.1016/j.worlddev.2021.105405

NPC. (2016). Growth and Transformation Plan II (GTP II) (2015/16–2019/20), Volume I: Main text . Federal Democratic Republic of Ethiopia.

Ofori-Abebrese, G., Baidoo, S. T., Essiam, E., & McMillan, D. (2020). Estimating the effects of financial inclusion on welfare in sub-Saharan Africa. Cogent Business & Management, 7 (1), 1839164. https://doi.org/10.1080/23311975.2020.1839164

Ogisi, O. R. D., & Begho, T. (2021). Covid 19: Ramifications for progress towards the sustainable development goals (SDGs) in Nigeria. International Review of Applied Economics, 35 (2), 256–268. https://doi.org/10.1080/02692171.2020.1864302

Page, J., & Söderbom, M. (2015). Is small beautiful? Small enterprise, aid and employment in Africa. African Development Review, 27 (S1), 44–55.

Papulová, Z., & Papula, J. (2015). Entrepreneurship in the eyes of the young generation. Procedia Economics and Finance, 34 , 514–520. https://doi.org/10.1016/S2212-5671(15)01662-7

Petros, G. (2017). Factors affecting micro and small enterprises in accessing credit facilities: A study in Hadeya Zone, Hosanna Town Southern Ethiopia. International Journal of African and Asian Studies, 39 , 39–53.

Quartey, P., Turkson, E., Abor, J. Y., & Iddrisu, A. M. (2017). Financing the growth of SMEs in Africa: What are the contraints to SME financing within ECOWAS? Review of Development Finance, 7 (1), 18–28. https://doi.org/10.1016/j.rdf.2017.03.001

Rambe, P., & Mosweunyane, L. (2017). A poverty-reduction oriented perspective to small business development in South Africa: A human capabilities approach. African Journal of Science, Technology, Innovation and Development . https://doi.org/10.1080/20421338.2017.1322749

Seifu, D. (2017). Prospects and challenges of Micro and Small Scale Enterprises (MSEs): A study on Shashemene City, Ethiopia. International Journal for Research in Business, Management and Accounting, 3 (8), 1–15.

Sissay, F. (2016). The influence of micro finance institution on the development and performance of micro and small business enterprises in Addis Ababa (Ethiopia) . Indira Gandhi National Open University.

Sniazhko, S., & Muralidharan, E. (2019). Uncertainty in decision-making: A review of the international business literature. Cogent Business & Management, 6 (1), 1650692. https://doi.org/10.1080/23311975.2019.1650692

Tadesse, B. (2014). Access to finance for micro and small enterprises in Debre Markos Town Ethiopia. Global Journal of Current Research, 2 (2), 36–46.

Tafa, T. (2019). The contribution of group-based micro and small enterprises in employment creation and income generation: Evidence from Woreda Fourteen of Kolfe Keranio Sub-City, Addis Ababa, Ethiopia. International Journal of African and Asian Studies, 55 , 8–19. https://doi.org/10.7176/JAAS/55-02

Tamene, K., & Wondirad, A. (2019). Economic impacts of tourism on small-scale tourism enterprises (SSTEs) in Hawassa City, Southern Ethiopia. International Journal of Tourism Sciences, 19 (1), 38–55. https://doi.org/10.1080/15980634.2019.1592951

Tarekegn, M., Tesfaw, D., & Ebre, S. (2018). Entrepreneurial capabilities of micro and small-scale enterprises (MSEs): Evidence from South Wollo Zone, Ethiopia. Abyssinia Journal of Business and Social Sciences, 3 (1), 10–21. https://doi.org/10.20372/ajbs.2018.3.1.182

Tewolde, A., & Feleke, C. (2017). Challenges and prospects of entrepreneurship development and job creation for youth unemployed: Evidence from Addis Ababa and Dire Dawa city administrations, Ethiopia. Journal of Innovation and Entrepreneurship, 6 (11), 1–22. https://doi.org/10.1186/s13731-017-0070-3

UN. (2018). Entrepreneurship for sustainable development: Report of the Secretary-General . United Nations.

Wang, Y. (2016). What are the biggest obstacles to growth of SMEs in developing countries?—An empirical evidence from an enterprise survey. Borsa Istanbul Review, 16 (3), 167–176. https://doi.org/10.1016/j.bir.2016.06.001

WBG. (2018). FY 2018 Ethiopia Country Opinion Survey Report (Public Opinion Research Group, Issue).

White, S. (2018). Creating better business environments for micro and small enterprises’, Technical Report . Donor Committee for Enterprise Development.

Woldehanna, T., Amha, W., & Yonis, M. B. (2018). Correlates of business survival: Empirical evidence on youth-owned micro and small enterprises in Urban Ethiopia. IZA Journal of Development and Migration, 8 (14), 1–26. https://doi.org/10.1186/s40176-018-0122-x

Yimesgen, Y. (2019). The growth determinants of micro and small enterprises and its linkages with food security: The case of Mecha district Amhara Region, Ethiopia. African Journal of Business Management, 13 (4), 138–146. https://doi.org/10.5897/AJBM2018.8697

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Ebrahim Endris is lecturer and researcher in the Department of Agricultural Economics at Woldia University, Ethiopia. He received his M.Sc and B.Sc from Haramaya University. Andualem Kassegn is lecturer and researcher in the Department of Agricultural Economics at Woldia University, Ethiopia. He has M.Sc in Agricultural Economics from Wollo University and BA in Economics from Mekelle University.

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Endris, E., Kassegn, A. The role of micro, small and medium enterprises (MSMEs) to the sustainable development of sub-Saharan Africa and its challenges: a systematic review of evidence from Ethiopia. J Innov Entrep 11 , 20 (2022). https://doi.org/10.1186/s13731-022-00221-8

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Microalgae: A Promising Source of Valuable Bioproducts

Vyacheslav dolganyuk.

1 Institute of Living Systems, Immanuel Kant Baltic Federal University, A. Nevskogo Street 14, 236016 Kaliningrad, Russia; ur.liam@fv_kunaglod (V.D.); ur.liam@airad-aninotna (D.B.); [email protected] (O.B.); moc.liamg@93eztakd (D.K.); ur.liam@98_80_devs (N.P.); ur.liam@psa-sats (S.S.)

Daria Belova

Olga babich.

2 Laboratory of Biocatalysis, Kemerovo State University, Krasnaya Street 6, 650043 Kemerovo, Russia; [email protected]

Alexander Prosekov

Svetlana ivanova.

3 Natural Nutraceutical Biotesting Laboratory, Kemerovo State University, Krasnaya Street 6, 650043 Kemerovo, Russia

4 Department of General Mathematics and Informatics, Kemerovo State University, Krasnaya Street 6, 650043 Kemerovo, Russia

Dmitry Katserov

Nikolai patyukov, stanislav sukhikh.

Microalgae are a group of autotrophic microorganisms that live in marine, freshwater and soil ecosystems and produce organic substances in the process of photosynthesis. Due to their high metabolic flexibility, adaptation to various cultivation conditions as well as the possibility of rapid growth, the number of studies on their use as a source of biologically valuable products is growing rapidly. Currently, integrated technologies for the cultivation of microalgae aiming to isolate various biologically active substances from biomass to increase the profitability of algae production are being sought. To implement this kind of development, the high productivity of industrial cultivation systems must be accompanied by the ability to control the biosynthesis of biologically valuable compounds in conditions of intensive culture growth. The review considers the main factors (temperature, pH, component composition, etc.) that affect the biomass growth process and the biologically active substance synthesis in microalgae. The advantages and disadvantages of existing cultivation methods are outlined. An analysis of various methods for the isolation and overproduction of the main biologically active substances of microalgae (proteins, lipids, polysaccharides, pigments and vitamins) is presented and new technologies and approaches aimed at using microalgae as promising ingredients in value-added products are considered.

1. Introduction

Recently, the issues of microalgae cultivation have been of increasing interest among researchers due to their ability to synthesize various biologically active substances, the rapid growth of biomass and the ability to adjust their biochemical composition depending on cultivation conditions. Microalgae are marine or freshwater microorganisms consisting of a single eukaryotic cell. These are unicellular flora representatives with huge potential for application in various branches of science and technology [ 1 ]. Previously, cyanobacteria, which later became considered bacteria, were also classified as blue-green algae. Currently, there are many types of eukaryotic unicellular microorganisms. Their diversity can be compared with the diversity of insects [ 1 , 2 ]. Unlike heterotrophic microorganisms, which require various organic compounds for growth, unicellular photosynthetic organisms produce biomass from completely oxidized inorganic substances and mineral elements due to the light energy converted during photosynthesis. Furthermore, microalgae biomass production technologies do not pollute the environment, use carbon dioxide while generating oxygen, consume a relatively small amount of water and may occupy land unsuitable for cultivation of agricultural crops [ 2 ].

At present, two main areas of use of microalgae can be distinguished: the production of biomass as a biologically active additive, and the cultivation of microalgae for the subsequent isolation of biologically active substances from biomass.

Microalgae are rich in nutrients and biologically active substances, such as proteins, polysaccharides, lipids, polyunsaturated fatty acids, vitamins, pigments, phycobiliproteins, enzymes, etc. Biologically active substances from microalgae are capable of exhibiting antioxidant, antibacterial, antiviral, antitumor, regenerative, antihypertensive, neuroprotective and immunostimulating effects [ 3 ]. These compounds are in demand in pharmacology, medicine, cosmetology, the chemical industry, fish farming, the energy industry, agriculture in the production of feed and functional foods [ 4 ].

Microalgae are less studied than seaweeds, but their advantages are associated with rapid growth, high photosynthetic efficiency and the possibility of cultivation under production conditions. In addition, the biodiversity of microalgae will increase the number of different sources of biologically active substances, such as polysaccharides, lipids, proteins and pigments.

Currently, integrated technologies for the cultivation of microalgae aiming to isolate various biologically active substances from biomass to increase the profitability of algae production are being sought. The purpose of this review is to analyze recent works (less than 10 years) aimed at isolating biologically valuable substances from microalgae and assessing their biological activity. This review aims to assess the potential of microalgae as a raw-material basis for biologically valuable substances of various activity spectra.

2. Factors Affecting Biomass Production

The level of biomass accumulation and productivity of biologically active substances is an important indicator of the effectiveness of the microalgae strain. These parameters are influenced by many conditions, including the composition of the culture medium, temperature, pH, growth phase, method of harvesting and illumination [ 5 ].

The optimum growth temperature for the most commonly used microalgae, such as Chlorella, Chlamydomonas, Botryococcus, Scenedesmus, Neochloris, Haematococcus and Nannochloropsis , is in the range of 15–35 °C depending on the strain [ 6 ]. It has been shown that some microalgae strains have high stress resistance at high temperatures. For example, strains of Asterarcys quadricellulare and Chlorella sorokiniana , isolated from soil near a steel mill, not only grow at 43 °C, but are also resistant to high concentrations of CO 2 and NO [ 7 ]. It is known that the use of thermotolerant microorganisms can significantly reduce the growth of incidental microflora. In addition, the use of such strains allows cultivation under natural conditions. The effect of technological parameters of the microalgae cultivation process (temperature, duration, stirring) on biomass production is presented in Table 1 , Table 2 and Table 3 .

The influence of temperature on the growth of various microalgae (table reconstructed using data from Varshney et al. [ 7 ]).

The influence of cultivation time on the growth of various microalgae (table reconstructed using data from Qiu et al. [ 8 ]).

The influence of culture stirring on the growth of various microalgae (table reconstructed using data from Varshney et al. [ 7 ]).

The recommended cultivation temperature for maximum biomass yield of various types of microalgae is a temperature ranging from 27 °C to 30 °C. With increasing cultivation temperature to 35 °C, the biomass yield decreases sharply.

A significant accumulation of biomass was observed by the 14th day of cultivation of all the studied microalgae.

The growth of microalgae biomass under stationary conditions is slowed down compared to cultivation with stirring (50–100 rpm).

The hydrogen potential (pH) is of great importance in the cultivation of microalgae, as it determines the solubility of minerals and carbon dioxide in the medium, in addition to the direct effect on the microalgae themselves [ 8 ]. The pH of the culture medium can be influenced by such factors as composition and buffer capacity, the amount of dissolved carbon dioxide, temperature and metabolic activity of the cells. Different types of microalgae have different levels of tolerance to the pH of the culture medium, which may affect their growth rate. For some microalgae, the optimal pH ranges from 6 to 8. In a number of cases, a steady increase in the microalgae biomass is observed at extremely low pH values, as, for example, for Chlorella protothecoides var. acidicola isolated from the surface of the microbial mat and having a growth optimum at pH 2.5 and 30 °C [ 9 ]. The use of buffer solutions reduces pH fluctuations in cultures, however, for large-scale cultivation systems, the use of buffers increases the cost of production, making it impossible. One way to control pH changes is to aerate cultures by pumping atmospheric air (0.03% CO 2 ) or CO 2 -enriched air through the medium, since carbon dioxide, when dissolved, reduces the pH of the medium [ 10 ]. The effect of pH on the biomass yield of various types of microalgae is presented in Table 4 . The optimal pH indicator is in a range from 6 to 8, however, when the biomass of the microalgae Chlorella vulgaris is produced, a decrease in pH to 4 leads to the greatest yield.

The influence of pH on the growth of various microalgae (table reconstructed using data from Varshney et al. [ 7 ]).

Combining the given data, the recommended values of technological parameters for growing microalgae are presented in Table 5 .

Optimal conditions for growing microalgae biomass (table reconstructed using data from Nancucheo and Johnson [ 9 ]).

The salinity of the solution is another factor affecting the growth and development of microalgae. Some types of microalgae are very limited in terms of salinity, especially those found in freshwater. In general, microalgae can be divided according to salinity resistance into oligogaline when they can develop only in water with low salinity (maximum salinity 0.5–5.0 g/L), mesogaline—develop in media with moderately saltwater with a salinity of 5–18 g/L and polyhaline—develop in saltwater with a salinity of 18–30 g/L [ 11 ].

An ideal culture medium for microalgae should contain inorganic elements such as nitrogen (N) and phosphorus (P), which can vary depending on the cultivated species. After carbon, which is approximately 50% of the fraction of elements in the biomass of microalgae, nitrogen takes second place, with a concentration of 1% to 14% in the dry mass. It can be absorbed in inorganic forms of NO 3 , NO 2 , NO and NH 4 and in some cases as N 2 or in an organic form via urea or amino acids. The decrease in nitrogen concentration during cultivation leads to the predominant synthesis of lipids and polysaccharides. The phosphorus concentration in the dry biomass of microalgae can be from 0.05% to 3.3% [ 12 ]. In natural environments, as well as in wastewater, phosphorus is present in various forms, such as orthophosphate, polyphosphate, pyrophosphate and metaphosphate. In addition, there are various types of agricultural fertilizers that can be used to saturate the microalgae cultivation environment with phosphorus, such as phosphates and superphosphates derived from phosphorites. For adequate growth of microalgae, the medium must contain other nutrients—trace elements. The main trace elements are Mg, S, Ca, Na, Cl, Fe, Zn, Cu, Mo, Mn, B and Co, with an emphasis on Mg, S and Fe [ 13 ].

Nutrient limitation has a direct impact on the synthesis of biologically active substances, biomass growth and photosynthesis processes in microalgae [ 14 ]. High illumination and limitation of nutrients (nitrogen or phosphorus) lead to an increase in the size of the lipid fraction and stimulate the accumulation of triacylglycerols. In low light conditions, mainly polar lipids (phospholipids and glycolipids) accumulate, which are structurally and functionally associated with cell membranes. Cell growth is reduced under such conditions. However, there are exceptions, for example, diatoms, in which the lipid content in the long phases does not respond to nitrogen starvation [ 15 ].

Stress caused by nutrient deficiency also leads to the formation of free radicals in the cell and a change in antioxidant content. Primary carotenoids (chlorophylls, β-carotenoids, violaxanthin and voheriaxanthin) are synthesized under normal favorable microalgae growth conditions, especially in Eustigmatophyceae strains . However, secondary carotenoids are produced under stress caused by nitrogen deficiency, synthesized from primary carotenoids and accumulating outside the chloroplast after the cell growth phase [ 16 ]. Under intense exposure to light, microalgae are photo-damaged, and some become pale green and decrease in size, which indicates a decrease in the density of chlorophyll and affects cell development [ 17 ]. Furthermore, with excess light, violaxanthin is converted to zeaxanthin by removing epoxides using the anthraxanthin monoepoxycarotinoid. Zeaxanthin is epoxidized in low light conditions, and nitrogen deficiency contributes to the accumulation of astaxanthin pigment in some microalgae, such as Haemotococcus pluvialis [ 15 ].

During autotrophic growth, microalgae carry out oxygen photosynthesis and fix carbon dioxide. One part of fixed carbon is used to maintain cells and growth, while the other part is stored in several forms, depending on different types of microalgae. Microalgae require 1.8 to 2.0 kg of CO 2 to produce 1 kg of biomass. Given this stoichiometric ratio, the amount of CO 2 present in the air (0.03%) is not enough for high culture productivity. Thus, in order to increase the efficiency of photosynthesis, media with microalgae cultures should be supplemented with carbon, either in the form of salts, such as bicarbonate, or by introducing CO 2 -enriched air. A study by Dúran et al. [ 18 ] demonstrated that when the air was supplied (600 mL/min) to the photobioreactor, microalgae showed optimal growth with a CO 2 content of up to 20% in the supplied air. This makes it possible to use CO 2 from industrial combustion, generating on average 5.0% of CO 2 , in microalgae cultivation. This approach combines an inexpensive carbon source for microalgae and reduces CO 2 emissions. The supply of CO 2 to microalgae cultures can increase biomass productivity, however, a decrease in pH due to an increase in the availability of CO 2 in the aqueous phase may impede the growth of certain types of microalgae [ 19 ].

The optimal conditions for the growth of microalgae depend on the light intensity, wavelength and photoperiod to which the cells are exposed during cultivation [ 20 ].

Light intensity is directly related to the photochemical phase of photosynthesis, when light is absorbed through chlorophyll molecules, the synthesis of adenosine triphosphate (ATP) and the photolysis of water. In general, photosynthesis can be defined as a process in which light energy synthesizes polysaccharides and oxygen from carbon dioxide and water [ 21 ]. Light intensity is one of the important aspects of growing microalgae and requires special attention. The amount of light received by cultured cells is directly related to carbon, which will be fixed, affecting the growth rate of cultures [ 22 ]. The light source can be either artificial or natural (sunlight), the latter being the most cost-effective due to its availability. Photosynthesis in microalgae increases with increasing light intensity until it reaches a maximum speed at the saturation point [ 23 ]. Above the saturation point, excess light leads to a phenomenon called photoinhibition, which is determined by the change and possible inactivation of photosystem II (PSII), affecting electron transport in the chain of reduction reactions from NADP + to NADPH. Photoinhibition and photosynthesis can be classified as moderate or intense, which determines whether this inhibition is dynamic or chronic [ 24 ]. The light intensity does not affect its accessibility in the depths of the plant environment. In other words, even if the light intensity is high enough to cause inhibition of photosynthesis, the light may not reach the shaded cells, which affects the efficiency of biomass production. Therefore, to supplement natural light or even for cultures under artificial lighting, it is recommended that LEDs be placed inside the medium to improve photon delivery and distribution.

Photosynthetically active radiation, useful for microalgae, is in the range from 400 to 700 nm from light radiation, which corresponds to 50% of solar radiation and intensity from 800 to 1000 W/m 2 [ 25 ]. This is confirmed by the results of Fu et al. [ 26 ], who demonstrated that Dunaliella salina shows the highest biomass and carotenoid productivity (β-carotene and lutein) when 75% of red light (wavelength about 700 nm) and 25% of blue light (wavelength about 400 nm) are used together, compared with the only red light.

There are light/dark (L/D) cycles in the microalgae growth tanks provided by the medium stirring system. These cycles affect the efficiency of photosynthesis conversion and biomass productivity in microalgae. It was also found that the efficiency of photosynthesis in Chlamydomonas reinhardtii improved when L/D cycles of less than 20 s were applied, with an increase in the growth rate of up to 40% [ 27 ].

Using the example of various types of marine and freshwater microalgae, it was shown that the duration of the photoperiod affects the intensity of photosynthesis, productivity, cell division rate and carbon dioxide consumption. Almost always, the listed indicators for various light and dark modes were higher than for continuous illumination. However, at present, there is no consensus on the mechanisms that explain the increase in productivity under the influence of the photoperiod [ 28 ].

There are several hypotheses in the literature that explain the phenomenon of an increase in the growth rate of lower phototrophs in the presence of a photoperiod. For example, under continuous illumination, some products of photosynthesis that inhibit it may accumulate in the cells, the outflow of which occurs in the dark period. Furthermore, in the presence of a photoperiod, the activity of ribulose-1,5-bisphosphate carboxylase may increase, which may be due to the regulation of carbon consumption mechanisms. It can be assumed that when limiting the growth of microalgae culture by CO 2 concentration, the increase in productivity is due to an increase in carbon concentration during the dark period due to the dark respiration of the cells. Additionally, if there is a dark period in the daily cycle, a change in the biochemical composition of algae occurs, in particular, the respiratory consumption of reserve compounds, which, in turn, can lead to a decrease in respiration rate [ 29 ].

An effective stirring of the culture medium is important for obtaining high cell concentrations. Stirring maintains cells in suspension, eliminates thermal separation, distributes nutrients and increases gas exchange efficiency. Stirring can reduce the degree of self-darkening and the likelihood of photoinhibition by uniformly distributing light among all microalgae cells [ 30 ]. In addition, stirring is also responsible for the possibility of CO 2 capture from the atmosphere and facilitates the transfer of biosynthesized O 2 from the liquid phase to the gaseous one, which stimulates photosynthesis in microalgae culture [ 31 ]. The connection between stirring and illumination becomes more obvious when the culture has a high concentration of cells, since under this condition the light is blocked by cells of the surface region and the light intensity decreases sharply with the depth of the culture [ 32 ]. In a study by Sánchez et al. [ 33 ], it can be noted that in cultivation systems with stirring blades, the daily growth of the microalgae culture Isochrysis galbana was two times higher compared to a system without stirring (8.8 × 10 5 and 4.0 × 10 5 cells/mL).

The growth rate of photosynthetic microorganisms increases with increasing turbulence caused by stirring, but above the optimum level of turbulence, this growth decreases sharply due to damage to the cells. Many photosynthetic microorganisms have a fragile cell wall; some are mobile or threadlike and may be subject to physical exertion. Thus, it is desirable that the stirring is carried out with the lowest possible hydrodynamic stress.

3. Methods of Microalgae Cultivation

The conditions for the cultivation of microalgae can be divided into three main methods: photoautotrophic, heterotrophic and mixotrophic. Photoautotrophic is the most commonly used cultivation method. Microalgae use light (usually solar) as an energy source and inorganic carbon (e.g., carbon dioxide) as a carbon source to generate chemical energy. With heterotrophic cultivation, microalgae can grow not only under photoautotrophic conditions, but also use organic carbon in the absence of light. Owing to the ability to grow in the dark, microalgae growing during heterotrophic cultivation are much less demanding on the ratio of surface area to volume than autotrophic cultivation [ 34 ].

Mixotrophic cultivation is a generalized two-stage mode in which microalgae have a high initial content of organic carbon, but are induced for assotrophic assimilation of CO 2 due to depletion of organic substances and oxygen production through photosynthesis [ 35 , 36 ]. During mixotrophic cultivation, microalgae grow under optimal autotrophic and heterotrophic conditions, combining the advantages of both cultivation modes [ 37 ]. Under such conditions, acetyl-CoA is produced and maintained both by fixing CO 2 and extracellular organic carbon, which indicates a decrease in photoinhibition. Mixotrophic cultures are often observed in ecological water bodies, where they are supported by both chemical, physical and organic activity of biota. Venkata Mohan et al. [ 38 ] presents in detail metabolic schemes for each cultivation mode.

The design and operation of an algae cultivation system play a decisive role in both the productivity of photosynthesis and economic efficiency. The design of the cultivation system should have a short path of light, the optimal volume of liquid for appropriate stirring and scattering of light. Working with large volumes of fluid requires high hydrostatic pressure and higher energy consumption for proper stirring [ 39 ]. Various large-scale cultivation systems have been developed for the large-scale production of microalgae. They usually work under photoautotrophic conditions and can be divided into two main groups: open or closed cultivation systems. Ninety percent of microalgae biomass production worldwide is through open cultivation systems. Open systems usually use open shallow ponds made of aligned raceways (2–10 m wide and 15–30 cm in depth) in the form of simple loops or meandering systems where turbulence is provided by rotating impellers [ 40 ]. These reactors are easily expandable, and investment and operating costs are relatively small. The main disadvantages of open cultivation systems are the complexity of process control, as well as the inability to organize a continuous cultivation process. High susceptibility to contamination by other microalgae and microorganisms, dependence on weather conditions (light, temperature) and daily temperature fluctuations make the open pond system unsuitable for large-scale culture [ 35 , 41 , 42 ].

Closed photobioreactors were designed to overcome the aforementioned disadvantages of open pond systems, resulting in a series of reactor designs that increased surface-to-volume ratio and system reliability [ 32 , 43 ]. Closed systems allow continuous operation and offer higher biomass productivity and quality, as well as higher photosynthesis efficiency. Liquid evaporation is minimized through the use of a closed system. However, such systems are difficult to scale due to their complex organization and reduction of light penetration with increasing cell concentration and the removal of oxygen generated during photorespiration is a serious problem. Closed photobioreactors are certainly more expensive than open systems [ 44 ].

There are bubble-airlift, bubble-column, tubular and panel photobioreactors. Mostly in pilot tubular photobioreactors, microalgae grow at a depth of illumination of 3–6 cm, where light penetration is less than 50%. Panel photobioreactors are the simplest solution for laboratory-scale microalgae cultivation. Of all these types of photobioreactors, they have a maximum illuminated surface and allow achieving high cell densities. However, during their operation, it is necessary to maintain a balance of illumination to prevent photoinhibition. The main achievements in the field of closed photobioreactors have been considered by Wang et al [ 45 ].

Currently, several basic technologies for the production of microalgae biomass are being developed in Russia and abroad, which include cultivation: (a) in open waters; (b) in greenhouse ponds; (c) in closed photobioreactors. Genomic and biochemical technologies are used for microalgae cultivation. In the framework of this work, the effect of all three types of the described methods for the cultivation of microalgae was studied [ 46 ]. The characteristics of the possible methods of microalgae cultivation under various conditions are presented in Table 6 .

Characteristics of possible methods for microalgae cultivation.

The production of microalgae remains an expensive process, and therefore efforts are being made to develop more efficient photobioreactors, as well as to optimize their control and modeling in order to maximize biomass yield and reduce production costs [ 46 ]. Each of the considered methods has both advantages and disadvantages, however, the heterotrophic method is the most preferred method for the cell biomass accumulation.

4. Microalgae Proteins Extraction Methods

The total protein content in biomass depends on the type of microalgae and varies from 30% to 70% of dry weight [ 47 ]. It has been reported that some microalgae contain soluble proteins in their cytoplasm. In addition, chloroplast microalgae contain soluble protein, central pyrenoid and phytobiliproteins, although some microalgae, such as Arthrospira plantesis , Chlamydomonas reinhardtii and Neochloris cohaerens instead have thylakoid sacs surrounding the peripheral part of the cytoplasm associated with phycobilisomes [ 48 ].

The amino acid composition of microalgae proteins is quite diverse and is not inferior in biological value to animal proteins [ 49 ]. The amino acid profile of Arthrospira platensis includes leucine, valine, isoleucine, phenylalanine, methionine, cysteine and tyrosine. The Porphyridium cruentum , Haematococcus pluvialis and Nannochloropsis gaditana microalgae proteins contain aspartic acid, threonine, serine, glutamic acid, glycine, alanine, cysteine and valine. In diatom microalgae, the main amino acids are serine, alanine, arginine, leucine, glycine, aspartate and threonine. In Chlorella vulgaris , Botryococcus braunii and Scenedesmus obliquus the essential amino acids cysteine and arginine account for about 44.7% of the total amino acid profile [ 50 , 51 ].

Vernèsa et al. [ 52 ] suggested a new method for the extraction of proteins from Arthrospira platensis , based on the combined effect of three parameters: pressure, temperature and ultrasound. Using the developed method, the authors were able to increase the protein yield by 229% compared with the usual method of ultrasonic treatment. It is assumed that the combined effect of pressure, temperature and ultrasound better destroys cells and intensifies the mass transfer process compared to using only ultrasound. Acoustic cavitation acted on Arthrospira platensis filaments through various mechanisms, such as fragmentation, sonoporation and destruction. These phenomena contributed to more efficient extraction of proteins from Arthrospira platensis .

Xie et al. [ 53 ] studied the effect of the concentration of nitrates in the nutrient medium on the accumulation of protein in microalgae Chlorella vulgaris . The authors were able to increase the protein content to 44.3% under optimized cultivation conditions.

Many methods of concentrating and isolating proteins from microalgae are difficult to scale. The three-phase separation method has attracted the interest of many researchers due to its quick, simple and scalable use for the concentration, isolation and deactivation of proteins from crude samples. Waghmare et al. [ 54 ] studied the effect of various parameters on the three-phase separation method to optimize the process of protein isolation from Chlorella pyrenoidosa . Also, Chia et al. [ 55 ] presented the extraction of protein from the microalgae Chlorella vulgaris by the method of three-phase separation with ultrasonic treatment. As a result of using additional ultrasonic processing, the authors were able to obtain an increased protein yield in a shorter period of time. Three-phase ultrasound separation is believed to be a more efficient method for extracting biomolecules from microalgae.

Safi et al. [ 47 ] analyzed the effectiveness of aqueous extraction of proteins from five microalgae ( Haematococcus pluvialis, Nannochloropsis oculata, Chlorella vulgaris, Porphyridium cruentum, Arthrospira platensis ) using various methods of cell destruction. It was found that the highest yield of protein occurs after the destruction of cells under high pressure using water extraction, followed by chemical, ultrasonic and mechanical treatments. Lupatini et al. [ 56 ] presented a method for extracting proteins and polysaccharides from Spirulina platensis biomass using the ultrasonic treatment and mechanical stirring under alkaline conditions. Under optimized extraction conditions, when treated with ultrasound for 33–40 min and stirring for 40–55 min, the protein yield was 75.76% and polysaccharides yield was 41.52%. Safi et al. [ 57 ] presented mild bioprocessing of the microalga Nannochloropsis gaditana to obtain a water-soluble protein fraction free of chlorophyll. To destroy the cells, homogenization under pressure or enzymatic hydrolysis was used, followed by ultrafiltration/diafiltration. Kose et al. [ 58 ] obtained protein hydrolysates from the microalgae Chlorella vulgaris, Chlorella cyanobacterium and Spirulina platensis and evaluated their digestibility in in vitro experiments. The studied hydrolysates showed rather high digestibility values and low cytotoxicity.

Nee et al. [ 59 ] evaluated the effect of various types of solvents (methanol, ethanol, 1-propanol and water) on the yield of proteins from the cell wall of microalgae. It was found that water is the most effective extractant of microalgae proteins compared to other solvents.

Data analysis ( Table 7 ) reveals the prospects for the use of combined approaches (for example, simultaneous flocculation and filtration) for the isolation of proteins from the biomass of cells of all types of microalgae.

Advantages and disadvantages of various methods for protein isolation from microalgae biomass (table built using combined data from previous studies [ 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ]).

5. Microalgae Lipids

Microalgae can produce various types of lipids: triacylglycerols, phospholipids, glycolipids or phytosterols, which contain fatty acids ranging from C12 to C24, often with mono- and poly-unsaturated fatty acids C16 and C18. The lipid content in microalgae varies from 20% to 50% of dry weight. These lipids can be used for energy storage, as energy substrates, as structural components of the cell membrane and for metabolic processes (signal transduction, transcriptional and translational control, intercellular interactions, secretion and transfer of vesicles) [ 60 ]. The number of lipids and the presence or position of double bonds in the carbon chain may vary depending on the type of microalgae and cultivation conditions. Optimal conditions can facilitate the conversion of fatty acids to glycerol-based membrane lipids, while adverse conditions can increase the synthesis of neutral lipids, such as triacylglycerols. Typically, many microalgae contain polyunsaturated fatty acids (PUFAs) such as arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. The main saturated fatty acid is palmitic [ 5 ]. The importance of lipids derived from algae lies in their commercial value as an alternative source for obtaining functional food products from their PUFAs, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as their precursor α-linolenic acid [ 60 ]. Most microalgae with high omega-3 content are marine species, for example, Schizochytrium sp. and Nannochloropsis sp. However, freshwater species, for example, Desmodesmus sp., have also been investigated as a source of omega-3 long-chain PUFA, EPA and DHA acids [ 61 , 62 ]. It was found that freshwater microalgae species produce biomass with a lower amount of PUFA.

Since the human body is not able to produce some essential fatty acids, they must be obtained from food or using various food additives, often obtained from fish and fish oil. However, due to the increased interest in the modern world for vegetarian and vegan diets, microalgae can become an alternative source of these nutritional supplements. In addition, many types of fatty fish contain traces of heavy metals that can adversely affect health and cause neurotoxic effects. Depending on the cultivation conditions and the composition of the nutrient medium, the profile of fatty acids may vary for the same types of microalgae. For example, Scharff et al. [ 63 ] evaluated the effect of the photoperiod on the biochemical profile of microalgae Chlorella vulgaris and Scendesmus obliquus and found that longer photoperiods (24:0, 22:2, 20:4) can reduce the synthesis of α-linolenic acid and cause the synthesis of linoleic acid, which is more distinctly observed for C. vulgaris than S. obliquus . On the other hand, Chandra et al. [ 64 ] established that the content of both linoleic and α-linolenic acids increases together with an increase in light intensity, which is a continuous lighting condition for an optimal photoperiod. Choi et al. [ 65 ] studied the dependence of biomass productivity and total fatty acid content in microalgae on various lighting conditions (continuous light, light-dark cycle, continuous darkness and continuous darkness with additional flashing light). The analysis found that the use of flashing light significantly increased the growth rate of Chlorella vulgaris and the concentration of fatty acids in the biomass. Carpio et al. [ 66 ] estimated the lipid content and profile in the biomass of the microalgae Chlorella vulgaris Beij at various concentrations of Fe and CO 2 . It was found that the most intensive growth of biomass (460.0 ± 10 mg/L of dry biomass) was observed at a concentration of Fe (4.8 × 10 −5 mol Fe/L) with 2% CO 2 . While the total lipid content (27.0 ± 0.8%) was maximum at a concentration of Fe (2.4 × 10 −5 mol Fe/L) and 2% CO 2 . Thus, we can conclude that the concentration of iron and other elements also affects the total lipid content, which can significantly affect the profile of fatty acids [ 67 ]. Abd El Baky et al. [ 68 ] studied production, lipid accumulation, and the profile of fatty acids in the microalgae Dunaliella salina . By varying the CO 2 aeration from 0.01% to 12.0%, a 20-fold increase in the lipid content in Dunaliella salina was obtained. Ramirez-Lopez et al. [ 69 ] suggested a new culture medium stimulating the growth of biomass and lipid accumulation for the microalga Chlorella vulgaris . In the process of optimizing the component composition of the medium, the contents of sodium nitrate, ammonium bicarbonate, heptahydrate of magnesium sulfate, potassium dihydrogen phosphate, dipotassium phosphate and diammonium phosphate were varied. Using a new culture medium, it was possible to increase biomass productivity by 40% and an 85% lipid concentration. The concentration of some components of the nutrient media was reduced to 50%. Josephine et al. [ 70 ] studied the influence of growth factors and the optimization of the collection time of Chlorella vulgaris to increase lipid production. An exogenous supplement called the chlorella growth factor (CGF) significantly increased biomass and lipid levels, which determined its potential as a biomass growth promoter in large-scale production. It was found that nitrogen starvation favored the synthesis of more unsaturated fatty acids than saturated ones.

Cultivation of Chlorella vulgaris in the presence of sodium selenite and chromium (III) chloride yielded a biologically active lipid complex, including selenium and chromium [ 71 ]. The authors evaluated the effect of the obtained complex on the energy metabolism of rats subjected to experimentally induced diabetes mellitus. It was found that in rats, the selenium-chrome-lipid complex from the Chlorella improved energy metabolism. The authors concluded that this complex in comparison with inorganic forms of chromium and selenium has potential for regulating energy metabolism in people with diabetes. It was found that the energy metabolism of rats increased when using a biologically active lipid isolated from the microalgae biomass.

Anthony et al. [ 72 ] presented a column chromatography technique for sequential isolation of several biologically active substances from the Chlorella vulgaris biomass (a nucleotide-peptide complex enriched with vitamins, minerals and polysaccharides, lipids and carotenoids). The proposed method [ 70 ] allowed to obtain an increased yield of lipids (18%) and lutein (9%) without foreign impurities of chlorophyll. The highest lipid content was noted in microcultures of microalgae Haematococcus pluvialis, Scenedesmus obliquus and Chlorella vulgaris . The amount of lipids in these microalgae cultures is 19.61 ± 0.58%, 17.13 ± 0.51% and 16.24 ± 0.48%, respectively. The fat content in the Neochloris cohaerens cell culture was 6.61 ± 0.19%, which is 1.35 times higher than the lipid content in the dry biomass of Chlamydomonas reinhardtii microalgae (4.90 ± 0.14%), but less than in the microbial cell culture of Botryococcus braunii and Nannochloropsis gaditana (7.23 ± 0.21% and 7.84 ± 0.13%, respectively). Further study of the microbial lipid profile of microorganisms Chlorella vulgaris, Botryococcus braunii, Neochloris cohaerens, Chlamydomonas reinhardtii and Nannochloropsis gaditana was carried out using gas chromatography. A reagent for transesterification of triglycerides of fatty acids was preliminarily prepared. The studied samples of microalgae ( Chlorella vulgaris, Botryococcus braunii, Neochloris cohaerens, Chlamydomonas reinhardtii and Nannochloropsis gaditana ) were characterized by a diverse fatty acid composition ( Table 8 ). It was found that the fatty acid composition of the studied microcultures is represented by high-molecular-weight polyunsaturated fatty acids.

The results of the study of the fatty acid composition of the microalgae lipid fraction (% of total lipids; table built using combined data from previous studies [ 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 ]).

* C14:0—myristic acid; C14:1—myristooleic acid; C15:0—pentadecanoic acid; C16:0—palmitic acid; C16:1—palmitoleic acid; C16:2—hexadecadienoic acid; C16:3—hexadecatrienic acid; C17:0—heptadecanoic acid; C17:1—cis-10-Heptadecenoic acid; C18:0—stearic acid; C18:1—oleic acid; C18:2—linoleic acid; C18:3—linolenic acid; C20:0—arachinic acid; C22:0—behenic acid; C22:5—docosapentaenoic acid; C22:6—docosahexaenoic acid; C24:0—lignoceric acid; C24:1—nervonic acid.

6. Microalgae Polysaccharides

It has been reported that polysaccharides of the microalgae Chlorella sorokiniana can induce the secretion of interleukin 12 (IL12), which activates natural killer cells (NKs) and leads to the differentiation of T helper cells into Th1 cells. This effect is important in antiviral and antitumor therapies [ 73 ].

Song et al. [ 74 ] selected parameters for the extraction and purification of the polysaccharide from the Arctic strain of Chlorella sp. to evaluate its antioxidant activity. Under optimized conditions, the polysaccharide yield was 9.62 ± 0.11% of dry weight. After its purification, three fractions were obtained: PI, P-II and P-III. The highest antioxidant activity was shown by the P-IIa fraction. Structural analysis showed that P-IIa is a spiran group heteropolysaccharide consisting mainly of rhamnose, arabinose, glucose and galactose.

Liu et al. [ 75 ] presented a method for producing a new type of polysaccharide from the microalga Arthrospira platensis . Microalgae were cultured under conditions of nitrogen deficiency in open industrial reservoirs. The maximum productivity of biomass and polysaccharides was 27.5 g/m 2 ·day and 26.2 g/m 2 ·day, respectively. The polysaccharide was extracted with hot water by homogenization under pressure, and purification was carried out by flocculation.

El-Ahmady El-Naggar et al. [ 76 ] extracted and identified water-soluble polysaccharides from the microalga Chlorella vulgaris in order to use them as plant growth stimulants.

Liu et al. [ 77 ] isolated a water-soluble polysaccharide from Haematococcus pluvialis using a DEAE-52 anion exchange column and Sephacryl S400 chromatography. The resulting polysaccharide showed immunomodulatory activity.

Gaignard et al. [ 78 ] investigated 166 species of marine microalgae and cyanobacteria in order to identify strains producing original exopolysaccharides. Forty-five strains with the desired characteristics were isolated. Eight new genera of microalgae producing exopolysaccharides, including polymers with a very original composition, were discovered.

In the course of the studies, it was found that the microalgae cultures of Botryococcus braunii and Haematococcus pluvialis , in comparison with other microalgae cells, are characterized by a high content of carbohydrates: 27.36 ± 0.76% and 21.95 ± 0.74%, respectively. The mass fraction of carbohydrates in the biomass of microalgae Scenedesmus obliquus reaches a value of 13.69 ± 0.34, and the carbohydrate content in the biomass of microalgae Nannochloropsis gaditana is 15.34 ± 0.51. Microalgae Chlamydomonas reinhardtii, Neochloris cohaerens and Chlorella vulgaris synthesize carbohydrates in the amount of 12.48 ± 0.34%, 12.58 ± 0.34% and 12.23 ± 0.33%, respectively.

7. Microalgae Pigments and Vitamins

Microalgae contain various types of pigments: carotenoids (orange color), xanthophylls (yellowish tint), phycobilins (red or blue color) and chlorophylls (green color). The content of carotenoids and chlorophyll in microalgae is usually higher than in some plants [ 79 ].

Carotenoids can be stored in oil droplets, in the stroma of the chloroplast or the cytosol, depending on the type of microalgae. Carotenoids in microalgae are usually present in low concentrations (0.5% μg −1 dry weight), although in some Chlorophyta they can reach up to 10% μg −1 dry weight when cultivated under adverse conditions, as is the case for Dunaliella salina [ 80 ]. Carotenoids play an important role in oxygen photosynthesis, as a direct quencher of reactive oxygen species, as well as in the thermal dissipation of excess energy in the photosynthetic apparatus. Microalgae carotenoids can also be used as antioxidant molecules that can quench free radicals, thereby protecting cells and tissues from oxidative damage, including preventing oxidative spoilage of food products. The main carotenoids of microalgae are β-carotene, lycopene, astaxanthin, zeaxanthin, violaxanthin and lutein. Among them, β-carotene, lutein and astaxanthin are the most studied [ 81 ].

Phycobilins (phycocyanin and phycoerythrin) are found in the stroma of the chloroplasts Cyanobacteria, Rhodophyta, Glucophyta and some cryptomonads. They are highly soluble in water and are widely used in the food industry as dyes and in molecular biology as fluorescent markers [ 79 ].

Chlorophylls are fat-soluble green pigments that are actively involved in the process of photosynthesis [ 82 ]. The chlorophyll content in microalgae varies from 0.5% to 1.0% of dry weight, mainly chlorophyll a, however, some microalgae, for example, Dinophyta also contain chlorophyll b and c [ 81 ].

Microalgae also represent a valuable source of vitamins: A, B1, B2, B6, B12, C, E, biotin, folic acid, pantothenic acid, etc. For example, Isochrysis galbana is an important source of vitamins A and E, folic acid, nicotinic acid, pantothenic acid, biotin, thiamine, riboflavin, pyridoxine, cobalamin, chlorophyll (a and c), fucoxanthin and diadinoxanthin, while Euglena gracilis antioxidant can produce vitamins such as β-carotene and vitamins C and E [ 80 ].

Vitamin B12 refers to water-soluble vitamins and is synthesized in animal products, but absent in plant ones. Vitamin B12 deficiency is common in people following a vegan or vegetarian diet. Some types of microalgae may contain or synthesize vitamin B12, for example, Chlorella sp. and Pleurochrysis carterae . However, it is not always in bioavailable form and further studies are needed to identify potential sources of vitamin B12 among microalgae [ 83 ].

Vitamin E is synthesized in many microalgae, for example, Dunaliella tertiolecta, Tetraselmis suecica, Nannochloropsis oculata, Chaetoceros calcitrans and Porphyridium cruentum . A number of studies indicate that the content of vitamin E in microalgae can be much higher than in plants. In this regard, microalgae are a valuable source for vitamin E production [ 84 ].

Smerilli et al. [ 85 ] studied the dependence of the vitamin C content in the microalga Skeletonema marinoi on the spectral composition and light intensity. It has been found that with an increase in the intensity of ultraviolet light, the content of vitamin C in microalgae increases.

Papadaki et al. [ 86 ] extracted various biologically active substances from microalgae Haematococcus pluvialis and Phaeodactylum tricornutum using ultrasound (to restore β-carotene, astaxanthin, fucoxanthin, eicosapentaenoic and arachidonic acid from selected microalgae, coconut oil was used as solvent). The yield of the targeted biologically active substances (vitamins E, B, C and pigments) reached about 80%.

Grudzinski et al. [ 87 ] studied the mechanism of the adaptive response of microalgae ( Chlorella protothecoides and Chlorella vulgaris ) to the effect of intense illumination (400 μmol photons m −2 s −1 ). It has been established that the color change of microalgae from green to yellow under the influence of intense illumination is associated with the accumulation of xanthophilic pigments, mainly zeaxanthin. The results obtained indicate that the carotenoids synthesized in response to intense illumination are not energetically associated with chlorophylls and are not photosynthetically active. These pigments can potentially be used as antioxidants, they stabilize the membrane and protect cells from intense light.

Soares et al. [ 88 ] investigated various methods for the extraction of lutein and β-carotene from the microalga Desmodesmus sp. When choosing the best extraction method, various types of solvents were analyzed and also their proportional ratio under ultrasonic extraction conditions, extraction efficiency, the effect of pretreatment on the yield of the target product, the stability of the extracts and the assessment of the qualitative and quantitative profile of pigments.

Pataro et al. [ 89 ] evaluated the effect of pretreatment by pulsed electric fields on the efficiency of the release of carotenes and chlorophyll a from the microalgae Nannochloropsis oceanica using supercritical CO 2 extraction. The joint use of these processes contributed to a significant increase in the yield of the studied pigments.

Singh et al. [ 90 ] studied the effect of stressful conditions on the carotene yield of Dunaliella salina microalgae and evaluated the antioxidant and cytotoxic activity of the obtained carotene-enriched extracts. Stress conditions were created by varying the concentrations of salt, nitrogen and the temperature of cultivation. It was shown that D. salina grown under various stress conditions (varying NaCl concentration and temperature) increases carotene production. An increase in antioxidant and cytotoxic activities is caused by the accumulation of carotenes.

Sathasivam et al. [ 91 ] selected the optimal concentrations of NaCl and KNO 3 to intensify the synthesis of β-carotene in the microalga Dunaliella salina KU11. The highest yields of β-carotene (115.5 ± 0.4 μg/mL) were obtained by creating stress conditions for the concentration of salts with a concentration of 2.5 M NaCl and 0.5 g/L KNO 3 .

The pigment complex of microcultures includes carotenoids and chlorophylls a and b [ 88 ]. Depending on the type of microculture and the composition of the nutrient medium, the quantitative content of the pigment complex may vary. The main part of the pigments of the studied microalgae samples ( Chlorella vulgaris , Chlamydomonas reinhardtii , Botryococcus braunii , Scenedesmus obliquus , Neochloris cohaerens , Haematococcus pluvialis and Nannochloropsis gaditana ) are chlorophylls. Analysis of the data ( Table 9 ) allows conclusion that the content of chlorophyll a is predominant in the pigment complexes of microalgae; however, for the microalga Scenedesmus obliquus , the content of chlorophyll b is 1.85-times higher than that of chlorophyll a.

Chlorophyll a and b content in microalgae (table built using combined data from previous studies [ 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 ]).

It was found [ 79 , 80 , 81 ] that in the microalgae Botryococcus braunii , Neochloris cohaerens , Chlamydomonas reinhardtii , Nannochloropsis gaditana and Chlorella vulgaris , the content of chlorophyll a exceeds the quantitative content of chlorophyll b. Therefore the microalgae Botryococcus braunii contains 6.58 ± 0.19 mg/g and 2.17 ± 0.07 mg/g of chlorophyll a and b, respectively. Microalgae cells of Neochloris cohaerens contain 3.9-times less chlorophyll b (6.13 ± 0.18 mg/g and 1.57 ± 0.05 mg/g). Cultures of the genus Chlamydomonas reinhardtii are characterized by a content of 2.53 ± 0.07 mg/g and 1.72 ± 0.04 mg/g of chlorophyll a and b, respectively. The microculture of Nannochloropsis gaditana is slightly inferior to the microculture of the microalga Chlorella vulgaris in the content of chlorophyll a, but not inferior in the content of chlorophyll b.

8. The Biological Activity of Various Substances from Microalgae

This section provides a brief analysis of the works aimed at assessing the biological effects of various substances from microalgae.

8.1. Antitumor Activity

Oncological diseases are one of the main causes of death in the modern world [ 92 , 93 ]. In recent years, studies on the search for new substances with antitumor properties have become increasingly relevant. Alginates, fucoidans, zosterol, unique sulfated polysaccharides, enzymes and peptides of microalgae possess antitumor activity [ 94 ].

Lauritano et al. [ 95 ] analyzed the antitumor properties of extracts from 32 species of microalgae against human melanoma cells A2058. Different types of algae were grown under three different cultivation conditions, the studied extracts were tested for possible antioxidant, anti-inflammatory, antitumor, antidiabetic, antibacterial and antibiofilm activities. One clone of the S. marinoi species (FE60) exhibited antitumor activity on human melanoma cells A2058, but only when cultured under nitrogen starvation. Another clone, FE6, was not active against cancer cells. Both clones (FE60 and FE6) exhibited antibacterial properties, inhibiting the survival of S. aureus . However, FE60 had antibacterial properties only when cultured under nitrogen starvation conditions, and FE6 only under phosphate starvation conditions.

Somasekharan et al. [ 96 ] evaluated the antitumor activity of an aqueous extract of microalgae from Canadian waters against various human cancer cell lines, including lung, prostate, stomach, breast, pancreas cancer and osteosarcoma. The authors analyzed the ability of microalgae extract to inhibit the formation of colonies in cancer cells. In vitro microalgae extract showed pronounced anticolony-forming activity.

Chen et al. [ 97 ] extracted sulfated polysaccharides from filamentous microalgae Tribonema sp. and tested their activity on liver cancer cells, HepG2. The MTT test showed that the sulfated polysaccharide from Tribonema sp. possessed antitumor activity, causing induced cell apoptosis.

Samarakoon et al. [ 98 ] studied the antitumor activity of the alcoholic fatty acid ester synthesized by the microalgae Phaeodactylum tricornutum Bohlin. Antitumor activity was evaluated for three different cancer cell lines (human leukemia (HL-60), human lung cancer (A549) and mouse melanoma (B16F10)). The strongest suppression of cancer cell growth was observed in HL-60 (IC 50 = 65.15 μM) compared with other cancer cells in vitro.

Jabeen et al. [ 99 ] estimated the effect of enzymatic treatment on the antitumor activity of microalgae extracts. Before extraction, the microalgae cells were treated with cellulase and lysozyme. The antitumor activity of the extracts was evaluated against four cancer cell lines (A549, MCF-7, MDA MB-435, LNCap).

8.2. Antimicrobial Activity

Recently, more and more research has been aimed at finding alternative antimicrobial agents, in connection with the progressive problem of microbial resistance, arising from the widespread use of antibiotics in the modern world. Microalgae are able to synthesize a number of metabolites with antimicrobial, antiviral and antifungal properties. In addition, some microalgae can grow under quite extreme conditions, which leads to the synthesis of unique substances for adaptation to changing environmental conditions. Thus, the content of biologically active substances directly depends on the environmental conditions of cultivation. It is known that many algae can synthesize a chemical defense system in order to survive in a competitive environment. Lutein and ferulic acid, polyunsaturated fatty and organic acids, active metabolites and other unique biologically active substances isolated from microalgae exhibit antimicrobial activity [ 100 ].

Krishnakumar et al. [ 101 ] estimated the antimicrobial activity of biologically active metabolites produced by the microalgae Dunaliella salina . It was found that the highest antimicrobial activity was shown by biologically active substances extracted with a mixture of chloroform and methanol.

Kilic et al. [ 102 ] studied the influence of environmental components and cultivation conditions on the synthesis of antimicrobial substances by microalgae of the genus Dunaliella . The most productive Dunaliella species ( Dunaliella sp. 1–4) with high biomass yield and the most resistant to various pollutants were selected. It was established that the highest antimicrobial activity was exerted by biologically active substances produced by microalgae Dunaliella sp. 2. The optimal conditions for the cultivation of biomass for the synthesis of biologically active substances with the highest antimicrobial activity (1.0 g/L nitrogen, 20% (weight/volume) NaCl, light intensity 4800 lux, cultivation time 14 days) were selected. Various types of solvents were analyzed (ethanol, methanol, hexane, chloroform, Tris-HCl and water) for the extraction of biologically active substances. The highest antimicrobial activity among the studied solvents was exerted by biologically active substances extracted with chloroform. When analyzing the obtained biologically active substances, it was suggested that lutein and ferulic acid were the main compounds responsible for higher antimicrobial activity under stressful conditions. The authors view Dunaliella sp. 2 as a safe biomaterial and recommend its use in the field of pharmacology in accordance with its biologically active properties.

8.3. Antioxidant Activity

The antioxidant is a biological molecule that protects the body or vital compounds from oxidative processes under the influence of radicals [ 103 ]. Many natural antioxidants are often included in various cosmetics as an active ingredient and to protect their components from oxidative processes. Antioxidants are also actively used in the production of functional foods [ 104 , 105 ]. Microalgae, as photosynthetic organisms, are often exposed to reactive oxygen species, as a result of which they can accumulate various antioxidant complexes and have developed a mechanism for protecting cells from the action of free radicals. The wide variety of species, the possibility of modulation of growth and simplicity of cultivating microalgae mean they can be considered one of the promising natural resources for the production of antioxidant compounds. Caratinoids, dimethyl sulfoxide, unique phenolic and nitrogen compounds isolated from microalgae possess antioxidant activity of microalgae [ 106 ].

Widowati et al. [ 107 ] investigated the antioxidant activity of methanol extracts from three different microalgae: Dunaliella salina, Tetraselmis chuii and Isochrysis galbana clone Tahiti. All three microalgae showed high antioxidant activity. Dunaliella salina and Tetraselmis chuii showed the best result. The inhibition rate in D. salina was 62.19% at a concentration of 500 ppm, and T. chuii showed the best result (71.36%) at a concentration of 1000 ppm.

Phenolic compounds play an important role in the classification of antioxidants in plants. However, the role of phenolic compounds as antioxidants in microalgae remains unknown. Gürlek et al. evaluated the antioxidant activity of a number of phenolic compounds obtained from Galderia sulphuraria, Neochloris texensis, Stichococcus bacillaris, Ettlia carotinosa, Chlorella minutissima, Schizochytrium limacinum, Crypthecodinium cohnii and Chlorella vulgaris microalgae extracts [ 3 ]. The maximum antioxidant activity and the content of phenolic compounds were detected in the Galderia sulphuraria extract. A high correlation coefficient between antioxidant activity and the content of phenolic compounds was established—in this regard, we can assume that the antioxidant activity of microalgae can be due to the presence of phenolic compounds in their composition.

Blagojevic et al. [ 108 ] studied the effect of nitrogen content on the antioxidant activity and profile of phenolic compounds in ethanol extracts of ten strains of cyanobacteria. As promising producers of antioxidants and phenolic compounds, the authors recommended cyanobacteria: Nostoc, Anabaena and Arthrospira .

Agregán et al. [ 109 ] evaluated the antioxidant potential of extracts obtained using ultrasound from microorganisms Chlorella and Spirulina . It was found that extracts of the studied microalgae as sources of phenolic antioxidants are more suitable for use as a component of human food. The relatively low antioxidant potential (in terms of polyphenols) makes microalgae extracts unsuitable for industrial use, unlike macroalgae.

Dantas et al. [ 110 ] evaluated the antioxidant and antibacterial activity of various extracts from the microalgae Scenedesmus subspicatus . The studied extracts were able to inhibit the growth of Bacillus subtilis . However, only dimethyl sulfoxide (as an extractant) inhibited the growth of Klebsiella pneumoniae and Escherichia coli . Obtaining an aqueous extract (the presence of antioxidant effectiveness has been proven) is an economical method and avoids the use of toxic substances.

Sansone et al. [ 111 ] analyzed the biological activity of the aqueous-alcoholic extract of the microalgae Tetraselmis suecica containing high concentrations of carotenoids. The studied extract had a high antioxidant and reparative activity.

Bioactive peptides obtained after protein hydrolysis can have various beneficial effects. Hu et al. [ 112 ] found that enzymatic hydrolysates of microalgae exhibit antioxidant properties. Chen et al. [ 113 ] evaluated the hepatoprotective effect of the antioxidant peptide obtained by enzymatic hydrolysis from the microalgae Isochrysis Zhanjiangensis on alcohol damage to HepG2 cells.

8.4. Anti-Inflammatory Activity

An inflammatory reaction is a pathological process that occurs in response to damage, irritation or injury. Regardless of what was the first stimulus, the classic inflammatory response includes pain, fever, redness and swelling. Microalgae substances with a unique structure and properties, such as phycocyanin, polysaccharides, monosaccharides, enzymes, polyunsaturated fatty acids, peptides, and polyphenols have anti-inflammatory properties [ 114 ].

Spirulina (Arthrospira platensis) is a highly nutritious blue-green microalgae widely used worldwide as a nutraceutical food supplement. In addition to its nutritional value, it also exhibits therapeutic properties, including anti-inflammatory activity. Spirulina contains a unique component, phycocyanin, which inhibits the formation of pro-inflammatory cytokines such as TNFα, reduces the production of prostaglandin E(2) and inhibits the expression of cyclooxygeanase-2 (COX-2) [ 115 ]. β-carotene, another compound present in Spirulina , the accumulation of which suppresses the transcription of IL-1β, IL-6 and IL-12, inflammatory cytokines, in the macrophage cell line stimulated by lipopolysaccharide or IFNγ [ 116 ].

Spirulina biomass also promotes the growth of probiotic bacteria such as Lactobacillus casei, Streptococcus thermophilus, Bifidobacteria and Lactobacillus acidophilus . Such prebiotic properties of microalgae are caused not only by the presence of polysaccharides in their structure, but also by monosaccharides, enzymes, PUFAs, peptides and polyphenols [ 117 ].

Extracts of Phaeodactylum tricornutum and Chlorella stigmatophora also exhibit anti-inflammatory properties along with some analgesics and antioxidants [ 118 ].

8.5. Antiplatelet Activity

Cardiovascular diseases remain the main global cause of death, which indicates the need to identify all possible factors that reduce primary and secondary risk.

Villar et al. [ 119 ] found that the crude aqueous extract of the microalga Dunaliella tertiolecta has a strong inhibitory effect on human platelet aggregation caused by thrombin, arachidonic acid and ionomycin isolated from microalgae. Extraction of the crude microalgae aqueous extract and subsequent fractionation with solvents with increasing polarity concentrated the activity in more polar fractions.

Ischemic disorders involving platelet aggregation and blood coagulation are the leading cause of disability and death worldwide. Antithrombotic therapy is unsatisfactory and may cause side effects. Thus, there is a need to search for molecules with antithrombotic properties. Marine organisms produce substances with various well-defined environmental functions. In addition, some of these molecules also exhibit pharmacological properties, such as antiviral, anticancer, antiphoid and anticoagulant properties. The study aimed to evaluate, using in vitro tests, the effect of two brown algae extracts and ten marine sponges from Brazil on platelet aggregation and blood coagulation. The results showed that most extracts were able to inhibit platelet aggregation and clotting, as measured by plasma recalcification tests, prothrombin time, activated partial thromboplastin time and fibrinogenolytic activity. On the other hand, five out of ten species of sponges caused platelet aggregation. Marine organisms studied in this paper may have molecules with antithrombotic properties that represent the biotechnological potential for antithrombotic therapy. Further chemical studies should be conducted on active species in order to discover useful molecules for the development of new drugs for the treatment of coagulation disorders [ 120 ].

9. Conclusions

Microalgae are considered a valuable biological resource, and in recent years they have received great attention. Their economic importance worldwide is associated with a wide range of applications of microalgae, from the food industry to medicine, from immunostimulants to biofuels, from cosmetology to agriculture. They are able to synthesize proteins, polysaccharides, lipids, polyunsaturated fatty acids, vitamins, pigments, enzymes, phycobiliproteins, etc. Biologically active substances from microalgae exhibit antioxidant, antibacterial, antiviral, antitumor, regenerative, antihypertensive, neuroprotective and immunostimulating effects. Microalgae biomass is a promising source of both nutritional and functional additives.

Only a few species of microalgae ( Arthrospira (Spirulina) platensis, Chlorella or Chlorella vulgaris, Dunaliella, Aphanizomenon and Nostoc ) are allowed for human consumption. These microalgae are a promising object for large-scale cultivation due to the high content of biologically active substances and the relatively cheap manufacturing process. Other microalgae species such as Chlamydomonas sp., Chlorococcum sp., Scenedescmus sp., Tetraselmis chuii and Nanochloropsis sp. have established themselves as a source of useful components in aquaculture, feed, fertilizers and cosmetics, but they do not have GRAS (Generally recognized as safe) status yet [ 93 ].

Due to the wide variety of microalgae, high metabolic flexibility and various cultivation conditions, their real potential has not yet been fully evaluated. Researchers working with microalgae are facing the following tasks:

• – improvement of photobioreactors;
• – improvement of strain productivity (selection and genetic engineering methods);
• – search for strains with new properties;
• – study of the influence of cultivation conditions on the content of biologically active substances in cells;
• – optimization of cultivation processes (lower costs and increased product yield);
• – greening of production (introduction of closed production cycles, reducing waste, the most comprehensive use of useful components);
• – assessment of environmental, economic and medical risks of scaling up production.

The multifaceted and joint work on these tasks will make it possible to replace the currently unstable production processes with alternative, less destructive ones. Innovative developments for the microalgae production optimization will make their use economically feasible and sought-after in the future.

Author Contributions

Conceptualization, V.D. and S.S.; methodology, O.B. and A.P.; formal analysis, N.P. and S.S.; analysis and interpretation of the data, V.D., D.B., D.K. and N.P.; writing—review and editing, O.B., A.P. and S.I.; All authors have read and agreed to the published version of the manuscript.

This research was funded by the Russian Foundation for basic research, grant number 19-316-60001.

Conflicts of Interest

The authors declare no conflict of interest.

Title: Challenges and opportunities in a lean automation model implementation: characterising micro, small and medium-sized enterprises of developing countries

Authors : Daniel Alexandre Morelli; Pedro Henrique Ribeiro Botene; Gabriella Carlucci Tavares Colombo; Giovana Catussi Paschoalotto; Paulo Sergio de Arruda Ignacio; Anibal Tavares de Azevedo; Antônio Carlos Pacagnella Júnior; Alessandro Lucas da Silva

Addresses : Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil

Abstract : The approach that associates innovative Industry 4.0 technologies with lean production principles is called lean automation (LA). This paper aims to explore LA models, investigating challenges and opportunities to their practical application in micro, small and medium-sized enterprises (MSMEs) in Brazil, contributing to technological development in emerging countries. As such, this article mapped the main combinations of Industry 4.0 and Lean principles, structured a conceptual just-in-time (JIT) delivery model, and characterised the conditions of MSMEs of emerging countries in relation to LA standards. The data collection was generated through a survey, and its analysis was performed using the Promethee-Gaia method. The results allowed us to compare different sectors, revealing their strengths and weaknesses. This study verified that business segments with the worst LA adherences presented low rates in concepts such as: 'planning and scheduling', 'pull-system', 'lot size reductions' and 'cyber security'. We organised a feasible three-steps roadmap for the LA implementation.

Keywords : lean automation; Industry 4.0; I4.0; lean production systems; LPS; just-in-time; JIT; delivery; micro small and medium-sized enterprises; MSMEs; developing countries; survey; Promethee.

DOI : 10.1504/IJSOM.2024.140421

International Journal of Services and Operations Management, 2024 Vol.48 No.4, pp.481 - 510

Received: 21 Jun 2022 Accepted: 24 Jun 2022 Published online: 08 Aug 2024 *

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Study on micro-vibration mechanism and flow characteristics of aerostatic bearings based on proper orthogonal decomposition

• Cheng, Cheng
• Zhao, Zhihui
• Liu, Zhengxian
• Hou, Weijie
• Li, Zhanxin
• Chen, Sheng
• Xu, Lianchao

The unsteady flow field in the aerostatic bearing always induces micro-vibrations, which are severely detrimental to the stability and precision of the bearing. Extensive research has been conducted on the mechanism of micro-vibration, but a consensus has not yet been reached. To this end, the large eddy simulation (LES) and proper orthogonal decomposition methods were employed to analyze the flow field of an annular aerostatic bearing in this paper. A mechanism for inducing micro-vibration and the identification of a novel flow behavior were ultimately revealed. First, the accuracy of our LES method has been validated through quantitative comparison with experimental data. Then, the mode decomposition has been conducted to analyze the flow field under various gas supply pressures. The results demonstrate that when the supply pressure P s = 0.4 MPa, the micro-vibration is dominated by a pair of adjacent large-scale vortices with low frequencies in the recess. However, when P s = 0.5 and 0.6 MPa, the convection and shearing processes near the orifice outlet and the rectangular recess inlet become intense, resulting in the displacement of large-scale vortices. Eventually, the small-scale high-frequency pressure fluctuation structures have been also observed, which are closely related to the convection process within recess. With the increase in gas supply pressure, the high-frequency pressure fluctuations at the circular recess outlet gradually diminish, while those at the orifice outlet emerge and gradually enlarge. Meanwhile, the mode dominant frequency is transferred from around 200 kHz to around 1000 kHz. The energy fraction of the high-frequency pressure fluctuations is also greatly increased.

Lab on a Chip

Micro blood analysis technology (μbat): multiplexed analysis of neutrophil phenotype and function from microliter whole blood samples †.

* Corresponding authors

a Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA E-mail: [email protected]

b Morgridge Institute for Research, Madison, WI, USA E-mail: [email protected]

c Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, WI, USA

d Department of Pediatrics, School of Medicine and Public Health, University of Wisconsin-Madison, WI, USA

e University of Wisconsin Carbone Cancer Center, University of Wisconsin, Madison, WI, USA

There is an ongoing need to do more with less and provide highly multiplexed analysis from limited sample volumes. Improved “sample sparing” assays would have a broad impact across pediatric and other rare sample type studies in addition to enabling sequential sampling. This capability would advance both clinical and basic research applications. Here we report the micro blood analysis technology (μBAT), a microfluidic platform that supports multiplexed analysis of neutrophils from a single drop of blood. We demonstrate the multiplexed orthogonal capabilities of μBAT including functional assays (phagocytosis, neutrophil extracellular traps, optical metabolic imaging) and molecular assays (gene expression, cytokine secretion). Importantly we validate our microscale platform using a macroscale benchmark assay. μBAT is compatible with lancet puncture or microdraw devices, and its design facilitates rapid operations without the need for specialized equipment. μBAT offers a new method for investigating neutrophil function in populations with restricted sample amounts.

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Micro blood analysis technology (μBAT): multiplexed analysis of neutrophil phenotype and function from microliter whole blood samples

T. D. Juang, J. Riendeau, P. G. Geiger, R. Datta, M. Lares, R. C. Yada, A. M. Singh, C. M. Seroogy, J. E. Gern, M. C. Skala, D. J. Beebe and S. C. Kerr, Lab Chip , 2024, Advance Article , DOI: 10.1039/D4LC00333K

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