Microalgae

Source: Wikipedia, the free encyclopedia.
Nannochloropsis microalgae
Collection of microalgae cultures in CSIRO's lab

Microalgae or microphytes are

freshwater and marine systems, living in both the water column and sediment.[1] They are unicellular
species which exist individually, or in chains or groups. Depending on the species, their sizes can range from a few micrometers (μm) to a few hundred micrometers. Unlike higher plants, microalgae do not have roots, stems, or leaves. They are specially adapted to an environment dominated by viscous forces.

Microalgae, capable of performing photosynthesis, are important for life on earth; they produce approximately half of the atmospheric oxygen[2] and use the greenhouse gas carbon dioxide to grow photoautotrophically. "Marine photosynthesis is dominated by microalgae, which together with cyanobacteria, are collectively called phytoplankton."[3] Microalgae, together with bacteria, form the base of the food web and provide energy for all the trophic levels above them. Microalgae biomass is often measured with chlorophyll a concentrations and can provide a useful index of potential production.[4][5]

The

biofuels and has also emerged as a promising microorganism in bioremediation.[9]

An exception to the microalgae family is the colorless Prototheca which are devoid of any chlorophyll. These achlorophic algae switch to parasitism and thus cause the disease protothecosis in human and animals.

Characteristics and uses

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A variety of unicellular and colonial freshwater microalgae

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.[10] 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.[11][12] Microalgae such as microphytes constitute the basic foodstuff for numerous aquaculture species, especially filtering bivalves
.

Photo- and chemosynthetic algae

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.[13] 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.

thickening agents[15] or emulsion and foam stabilizers[16]
in the food industry to replace animal based proteins.

Some microalgae accumulate

carotenoids, or phycobiliproteins that may be extracted and used as coloring agents.[17]

Cultivation of microalgae

Main article: Culture of microalgae in hatcheries

A range of microalgae species are produced in hatcheries and are used in a variety of ways for commercial purposes, including for

biofertiliser.[22] However, the low cell density is a major bottleneck in commercial viability of many microalgae derived products, especially low cost commodities.[23]

Studies have investigated the main factors in the success of a microalgae hatchery system to be:[24][25]

  • 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

See also

References

  1. ^ Thurman, H. V. (1997). Introductory Oceanography. New Jersey, USA: Prentice Hall College.
    ISBN 978-0-13-262072-7
    .
  2. ^ Williams, Robyn (25 October 2013). "Microscopic algae produce half the oxygen we breathe". The Science Show. ABC. Retrieved 11 November 2020.
  3. PMID 18983264
    .
  4. S2CID 23502276
    .
  5. S2CID 219431866
    .
  6. Flanders Today
    , Retrieved 8 December 2012
  7. ^ Cardozo, Karina H.-M.; Thais, Guaratini; Marcelo P., Barros; Vanessa R., Falcão; Angela P., Tonon; Norberto P., Lopes; Sara, Campos; Moacir A., Torres; Anderson O., Souza; Pio, Colepicolo; Ernani, Pinto (2006-06-29). "Metabolites from algae with economical impact". Comparative Biochemistry and Physiology C. 146 (1–2): 60–78.
    PMID 16901759
    .
  8. S2CID 18430041
    .
  9. ISBN 978-981-16-4445-0
    .
  10. PMID 22143781
    .
  11. PMID 10786943
    .
  12. ^ "growing algae". WUR. Retrieved 2009-05-19.
  13. ^ "ENERGY FROM ALGAE (includes scientific names)". ifremer. Archived from the original on 2006-11-28. Retrieved 2006-09-13.
  14. PMID 17196357
    .
  15. S2CID 203985553
    .
  16. hdl:20.500.11850/458592
    .
  17. PMID 28947090
    .
  18. ^ Leckie, Evelyn (14 Jan 2021). "Adelaide scientists turn marine microalgae into 'superfoods' to substitute animal proteins". ABC News. Australian Broadcasting Corporation. Retrieved 17 Jan 2021.
  19. PMID 18221809
    .
  20. S2CID 8495961
    .
  21. doi:10.1016/j.carbpol.2010.10.062
    .
  22. S2CID 121561783
    .
  23. S2CID 99110136
    .
  24. PMID 28567633
    .
  25. S2CID 99110136
    .
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