microalgae

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The chemical composition of microalgae is not an intrinsic constant factor but varies over a wide range of factors, both depending on species and on cultivation conditions. Some microalgae have the capacity to acclimate to changes in environmental conditions by altering their chemical composition in response to environmental variability. A particularly dramatic example is their ability to replace phospholipids with non-phosphorus membrane lipids in phosphorus-depleted environments.{{cite journal|last1=Bonachela|first1=Juan|last2=Raghib|first2=Michael|last3=Levin|first3=Simon|title=Dynamic model of flexible phytoplankton nutrient uptake|journal=PNAS|date=Feb 21, 2012|volume=108|issue=51|pages=20633–20638|doi=10.1073/pnas.1118012108|pmid=22143781|pmc=3251133|doi-access=free}} It is possible to accumulate the desired products in microalgae to a large extent by changing environmental factors, like temperature, illumination, pH, CO₂ supply, salt and nutrients.

Microphytes also produce chemical signals which contribute to prey selection, defense, and avoidance. These chemical signals affect large scale tropic structures such as algal blooms but propagate by simple diffusion and laminar advective flow.{{cite journal |last1=Wolfe |first1=Gordon |date=2000 |title=The chemical Defense Ecology o Marine Unicelular Plankton: Constraints, Mechanisms, and Impacts |journal=The Biological Bulletin |volume=198 |issue=2 |pages=225–244 |citeseerx=10.1.1.317.7878 |doi=10.2307/1542526 |jstor=1542526 |pmid=10786943}} Microalgae such as microphytes constitute the basic foodstuff for numerous aquaculture species, especially filtering bivalves.

The majority of microalgae is not edible, so most of its uses are not connected to food or energy. Instead, they are used in various biofertilizers, cosmetics, and pharmaceuticals. {{Cite web |title=Microalgae: what are they and how to grow and use them |url=https://www.eufic.org/en/food-production/article/microalgae-what-are-they-and-how-to-grow-and-use-them#:~:text=And%20since%20the%20vast%20majority,in%20cosmetics,%20pharmaceuticals,%20biofertilizers. |access-date=2025-04-20 |website=www.eufic.org |language=en}} Microalgae are seen as valuable biofertilizers because they help to improve both plant growth and soil fertilization. They are known to be a more sustainable option compared to agrochemicals due to their ability to decrease the usage of synthetic fertilizers, improve soil fertility, and optimize nutrients. {{Cite journal |last1=Braun |first1=Julia C. A. |last2=Colla |first2=Luciane M. |date=2023-03-01 |title=Use of Microalgae for the Development of Biofertilizers and Biostimulants |url=https://link.springer.com/article/10.1007/s12155-022-10456-8 |journal=BioEnergy Research |language=en |volume=16 |issue=1 |pages=289–310 |doi=10.1007/s12155-022-10456-8 |bibcode=2023BioER..16..289B |issn=1939-1242|url-access=subscription }} The use of microalgae in cosmetic products is also becoming more prevalent. This is due to some of the benefits that arise from microalgae's compounds, including anti-aging, skin brightening, and UV protection. Algal can be found in many cosmetic products that people use on a daily basis. The compounds are used in antioxidants, moisturizing agents, skin sensitizers, sunscreens, thickening agents, etc. {{Cite journal |last1=Martínez-Ruiz |first1=Manuel |last2=Martínez-González |first2=Carlos Alberto |last3=Kim |first3=Dong-Hyun |last4=Santiesteban-Romero |first4=Berenice |last5=Reyes-Pardo |first5=Humberto |last6=Villaseñor-Zepeda |first6=Karen Rocio |last7=Meléndez-Sánchez |first7=Edgar Ricardo |last8=Ramírez-Gamboa |first8=Diana |last9=Díaz-Zamorano |first9=Ana Laura |last10=Sosa-Hernández |first10=Juan Eduardo |last11=Coronado-Apodaca |first11=Karina G. |last12=Gámez-Méndez |first12=Ana María |last13=Iqbal |first13=Hafiz M. N. |last14=Parra-Saldivar |first14=Roberto |date=2022-05-30 |title=Microalgae Bioactive Compounds to Topical Applications Products-A Review |journal=Molecules (Basel, Switzerland) |volume=27 |issue=11 |pages=3512 |doi=10.3390/molecules27113512 |doi-access=free |issn=1420-3049 |pmc=9182589 |pmid=35684447}} There are many different uses for microalgae in the pharmaceutical world. They produce bioactive compounds which possess therapeutic properties and serve as a drug delivery system. The extracellular-vesicles, which are derived from the microalgae, can be used for drug delivery. They are capable of crossing biological barriers, encapsulating proteins, nucleic acids, and small molecules. {{Cite journal |last1=Kaur |first1=Manpreet |last2=Bhatia |first2=Surekha |last3=Gupta |first3=Urmila |last4=Decker |first4=Eric |last5=Tak |first5=Yamini |last6=Bali |first6=Manoj |last7=Gupta |first7=Vijai Kumar |last8=Dar |first8=Rouf Ahmad |last9=Bala |first9=Saroj |date=2023-08-01 |title=Microalgal bioactive metabolites as promising implements in nutraceuticals and pharmaceuticals: inspiring therapy for health benefits |url=https://link.springer.com/article/10.1007/s11101-022-09848-7 |journal=Phytochemistry Reviews |language=en |volume=22 |issue=4 |pages=903–933 |doi=10.1007/s11101-022-09848-7 |pmid=36686403 |bibcode=2023PChRv..22..903K |issn=1572-980X|pmc=9840174 }}

Photosynthetic and chemosynthetic microbes can also form symbiotic relationships with host organisms. They provide them with vitamins and polyunsaturated fatty acids, necessary for the growth of the bivalves which are unable to synthesize it themselves. Microalgae also is a rich source of bioactive compounds and nutrients. They are considered to be valuable in environmental applications, food, and pharmaceuticals due to the presence of lipids, proteins, and vitamins found within. {{Cite journal |last1=Dolganyuk |first1=Vyacheslav |last2=Belova |first2=Daria |last3=Babich |first3=Olga |last4=Prosekov |first4=Alexander |last5=Ivanova |first5=Svetlana |last6=Katserov |first6=Dmitry |last7=Patyukov |first7=Nikolai |last8=Sukhikh |first8=Stanislav |date=2020-08-06 |title=Microalgae: A Promising Source of Valuable Bioproducts |journal=Biomolecules |volume=10 |issue=8 |pages=1153 |doi=10.3390/biom10081153 |doi-access=free |issn=2218-273X |pmc=7465300 |pmid=32781745}} In addition, because the cells grow in aqueous suspension, they have more efficient access to water, CO₂, and other nutrients.

Microalgae play a major role in nutrient cycling and fixing inorganic carbon into organic molecules and expressing oxygen in marine biosphere.

While fish oil has become famous for its omega-3 fatty acid content, fish do not actually produce omega-3s, instead accumulating their omega-3 reserves by consuming microalgae. These omega-3 fatty acids can be obtained in the human diet directly from the microalgae that produce them.

Microalgae can accumulate considerable amounts of proteins depending on species and cultivation conditions. Due to their ability to grow on non-arable land microalgae may provide an alternative protein source for human consumption or animal feed.{{cite journal |last1=Becker |first1=E. W. |title=Micro-algae as a source of protein |journal=Biotechnology Advances |date=1 March 2007 |volume=25 |issue=2 |pages=207–210 |doi=10.1016/j.biotechadv.2006.11.002 |pmid=17196357 |url=https://www.sciencedirect.com/science/article/pii/S073497500600139X|url-access=subscription }} Microalgae proteins are also investigated as thickening agents{{cite journal |last1=Grossmann |first1=Lutz |last2=Hinrichs |first2=Jörg |last3=Weiss |first3=Jochen |title=Cultivation and downstream processing of microalgae and cyanobacteria to generate protein-based technofunctional food ingredients |journal=Critical Reviews in Food Science and Nutrition |date=24 September 2020 |volume=60 |issue=17 |pages=2961–2989 |doi=10.1080/10408398.2019.1672137 |pmid=31595777 |s2cid=203985553 |url=https://www.tandfonline.com/doi/abs/10.1080/10408398.2019.1672137?journalCode=bfsn20|url-access=subscription }} or emulsion and foam stabilizers{{cite journal |last1=Bertsch |first1=Pascal |last2=Böcker |first2=Lukas |last3=Mathys |first3=Alexander |last4=Fischer |first4=Peter |title=Proteins from microalgae for the stabilization of fluid interfaces, emulsions, and foams |journal=Trends in Food Science & Technology |date=February 2021 |volume=108 |pages=326–342 |doi=10.1016/j.tifs.2020.12.014 |doi-access=free |hdl=20.500.11850/458592 |hdl-access=free }} in the food industry to replace animal based proteins.

Some microalgae accumulate chromophores like chlorophyll, carotenoids, phycobiliproteins or polyphenols that may be extracted and used as coloring agents.{{Cite journal |last1=Aizpuru |first1=Aitor |last2=González-Sánchez |first2=Armando |date=2024-07-20 |title=Traditional and new trend strategies to enhance pigment contents in microalgae |journal=World Journal of Microbiology and Biotechnology |language=en |volume=40 |issue=9 |pages=272 |doi=10.1007/s11274-024-04070-3 |issn=1573-0972 |pmc=11271434 |pmid=39030303}}{{cite journal |last1=Hu |first1=Jianjun |last2=Nagarajan |first2=Dillirani |last3=Zhang |first3=Quanguo |last4=Chang |first4=Jo-Shu |last5=Lee |first5=Duu-Jong |title=Heterotrophic cultivation of microalgae for pigment production: A review |journal=Biotechnology Advances |date=January 2018 |volume=36 |issue=1 |pages=54–67 |doi=10.1016/j.biotechadv.2017.09.009 |pmid=28947090 |url=https://www.sciencedirect.com/science/article/pii/S0734975017301209|url-access=subscription }}

{{Main article|Culture of microalgae in hatcheries}}

Microalgae cultivation can take place in closed systems and open ponds. Open ponds are often seen as a more economically sound choice for production in a commerical setting. {{Cite journal |last1=Bora |first1=Abhispa |last2=Thondi Rajan |first2=Angelin Swetha |last3=Ponnuchamy |first3=Kumar |last4=Muthusamy |first4=Govarthanan |last5=Alagarsamy |first5=Arun |date=2024-10-10 |title=Microalgae to bioenergy production: Recent advances, influencing parameters, utilization of wastewater – A critical review |url=https://www.sciencedirect.com/science/article/abs/pii/S004896972404378X |journal=Science of the Total Environment |volume=946 |pages=174230 |doi=10.1016/j.scitotenv.2024.174230 |bibcode=2024ScTEn.94674230B |issn=0048-9697|url-access=subscription }}A range of microalgae species are produced in hatcheries and are used in a variety of ways for commercial purposes, including for human nutrition,{{cite web | last=Leckie | first=Evelyn | title=Adelaide scientists turn marine microalgae into 'superfoods' to substitute animal proteins | website=ABC News |publisher=Australian Broadcasting Corporation | date=14 Jan 2021 | url=https://www.abc.net.au/news/2021-01-14/marine-microalgae-could-be-the-solution-to-protein-shortage/13054084 | access-date=17 Jan 2021}} as biofuel,{{cite journal |first=Yusuf |last=Chisti |year=2008 |title=Biodiesel from microalgae beats bioethanol |journal=Trends in Biotechnology |volume=26 |issue=3 |pages=126–131 |pmid=18221809 |doi=10.1016/j.tibtech.2007.12.002 |url=http://www.massey.ac.nz/~ychisti/Trends08.pdf }} in the aquaculture of other organisms,{{cite journal |author=Arnaud Muller-Feuga |year=2000 |title=The role of microalgae in aquaculture: situation and trends |journal=Journal of Applied Phycology |volume=12 |issue=3 |pages=527–534 |doi=10.1023/A:1008106304417 |bibcode=2000JAPco..12..527M |s2cid=8495961 |url=http://archimer.ifremer.fr/doc/2000/publication-497.pdf }} in the manufacture of pharmaceuticals and cosmetics,{{cite journal |author1=Isuru Wijesekara |author2=Ratih Pangestuti |author3=Se-Kwon Kim |year=2010 |title=Biological activities and potential health benefits of sulfated polysaccharides derived from marine algae |journal=Carbohydrate Polymers |volume=84 |issue=1 |pages=14–21 |doi=10.1016/j.carbpol.2010.10.062}} and as biofertiliser.{{cite journal |author1=Upasana Mishra |author2=Sunil Pabbi |year=2004 |title=Cyanobacteria: a potential biofertilizer for rice |journal=Resonance |volume=9 |issue=6 |pages=6–10 |doi=10.1007/BF02839213 |s2cid=121561783 |url=http://www.ias.ac.in/resonance/June2004/pdf/June2004p6-10.pdf }} However, the low cell density is a major bottleneck in commercial viability of many microalgae derived products, especially low cost commodities.{{cite journal |author1=Yuvraj |author2=Ambarish Sharan Vidyarthi |author3=Jeeoot Singh |year=2016 |title=Enhancement of Chlorella vulgaris cell density: Shake flask and bench-top photobioreactor studies to identify and control limiting factors |journal=Korean Journal of Chemical Engineering |volume=33 |issue=8 |pages=2396–2405 |doi=10.1007/s11814-016-0087-5 |s2cid=99110136 |url=https://doi.org/10.1007/s11814-016-0087-5 |url-access=subscription }}

Studies have investigated the main factors in the success of a microalgae hatchery system to be:{{cite journal |author1=Yuvraj |author2=Padmini Padmanabhan |year=2017 |title=Technical insight on the requirements for {{CO2}}-saturated growth of microalgae in photobioreactors |journal=3 Biotech |volume=07 |issue=2 |page=119 |doi=10.1007/s13205-017-0778-6 |pmid=28567633 |pmc=5451369 |url=https://doi.org/10.1007/s13205-017-0778-6 }}{{cite journal |author1=Yuvraj |author2=Ambarish Sharan Vidyarthi |author3=Jeeoot Singh |year=2016 |title=Enhancement of Chlorella vulgaris cell density: Shake flask and bench-top photobioreactor studies to identify and control limiting factors |journal=Korean Journal of Chemical Engineering |volume=33 |issue=8 |pages=2396–2405 |doi=10.1007/s11814-016-0087-5 |s2cid=99110136 |url=https://doi.org/10.1007/s11814-016-0087-5 |url-access=subscription }}

• Geometry and scale of cultivation systems (referred as photobioreactors);
• Light intensity;
• Concentration of carbon dioxide ({{CO2}}) in the gas phase
• Nutrient levels (mainly N, P, K)
• Mixing of culture

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• AlgaeBase
• Raceway pond

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{{reflist|refs=

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{{cite web

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[https://phys.org/tags/microalgae/ phys.org: News on microalgae], [https://web.archive.org/web/20250130211017/https://phys.org/tags/microalgae/ backup] Citat: "...Depending on the species, their sizes can range from a few micrometers (μm) to a few hundreds of micrometers..."

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