Microalgae

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Nannochloropsis microalgae CSIRO ScienceImage 10697 Microalgae.jpg
Nannochloropsis microalgae
Collection of microalgae cultures in CSIRO's lab CSIRO ScienceImage 2970 Collection of microalgae cultures.jpg
Collection of microalgae cultures in CSIRO's lab

Microalgae or microphytes are microscopic algae invisible to the naked eye. They are phytoplankton typically found in 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.

Contents

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 biodiversity of microalgae is enormous and they represent an almost untapped resource. It has been estimated that about 200,000-800,000 species in many different genera exist of which about 50,000 species are described. [6] Over 15,000 novel compounds originating from algal biomass have been chemically determined. [7] Examples include carotenoids, fatty acids, enzymes, polymers, peptides, toxins and sterols. [8] Besides providing these valuable metabolites, microalgae are regarded as a potential feedstock for 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

A variety of unicellular and colonial freshwater microalgae Vodorosli presnovodnogo vodoema.jpg
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. [14] Microalgae proteins are also investigated as thickening agents [15] or emulsion and foam stabilizers [16] 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. [17] [18]

Cultivation of microalgae

A range of microalgae species are produced in hatcheries and are used in a variety of ways for commercial purposes, including for human nutrition, [19] as biofuel, [20] in the aquaculture of other organisms, [21] in the manufacture of pharmaceuticals and cosmetics, [22] and as biofertiliser. [23] However, the low cell density is a major bottleneck in commercial viability of many microalgae derived products, especially low cost commodities. [24]

Studies have investigated the main factors in the success of a microalgae hatchery system to be: [25] [26]

See also

Related Research Articles

<span class="mw-page-title-main">Algae</span> Diverse group of photosynthetic eukaryotic organisms

Algae are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular microalgae, such as Chlorella, Prototheca and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 metres (160 ft) in length. Most are aquatic and lack many of the distinct cell and tissue types, such as stomata, xylem and phloem that are found in land plants. The largest and most complex marine algae are called seaweeds. In contrast, the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra and stoneworts. Algae that are carried by water are plankton, specifically phytoplankton.

<span class="mw-page-title-main">Algal bloom</span> Spread of planktonic algae in water

An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term algae encompasses many types of aquatic photosynthetic organisms, both macroscopic multicellular organisms like seaweed and microscopic unicellular organisms like cyanobacteria. Algal bloom commonly refers to the rapid growth of microscopic unicellular algae, not macroscopic algae. An example of a macroscopic algal bloom is a kelp forest.

<span class="mw-page-title-main">Phytoplankton</span> Autotrophic members of the plankton ecosystem

Phytoplankton are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words φυτόν, meaning 'plant', and πλαγκτός, meaning 'wanderer' or 'drifter'.

<span class="mw-page-title-main">Algaculture</span> Aquaculture involving the farming of algae

Algaculture is a form of aquaculture involving the farming of species of algae.

<span class="mw-page-title-main">Photobioreactor</span> Bioreactor with a light source to grow photosynthetic microorganisms

A photobioreactor (PBR) refers to any cultivation system designed for growing photoautotrophic organisms using artificial light sources or solar light to facilitate photosynthesis. Photobioreactors are typically used to cultivate microalgae, cyanobacteria, and some mosses. Photobioreactors can be open systems, such as raceway ponds, which rely upon natural sources of light and carbon dioxide. Closed photobioreactors are flexible systems that can be controlled to the physiological requirements of the cultured organism, resulting in optimal growth rates and purity levels. Photobioreactors are typically used for the cultivation of bioactive compounds for biofuels, pharmaceuticals, and other industrial uses.

<span class="mw-page-title-main">Algal nutrient solution</span>

Algal nutrient solutions are made up of a mixture of chemical salts and seawater. Sometimes referred to as "Growth Media", nutrient solutions, provide the materials needed for algae to grow. Nutrient solutions, as opposed to fertilizers, are designed specifically for use in aquatic environments and their composition is much more precise. In a unified system, algal biomass can be collected by utilizing carbon dioxide emanating from power plants and wastewater discharged by both industrial and domestic sources. This approach allows for the concurrent exploitation of the microalgae's capabilities in both carbon dioxide fixation and wastewater treatment. Algae, macroalgae, and microalgae hold promise in addressing critical global challenges. Sustainable development goals can be advanced through algae-based solutions, to promote a healthy global ecosystem.

<i>Scenedesmus</i> Genus of green algae

Scenedesmus is a genus of green algae, in the class Chlorophyceae. They are colonial and non-motile. They are one of the most common components of phytoplankton in freshwater habitats worldwide.

<i>Choricystis</i> Genus of algae

Choricystis is a genus of green algae in the class Trebouxiophyceae, considered a characteristic picophytoplankton in freshwater ecosystems. Choricystis, especially the type species Choricystis minor, has been proposed as an effective source of fatty acids for biofuels. Choricystis algacultures have been shown to survive on wastewater. In particular, Choricystis has been proposed as a biological water treatment system for industrial waste produced by the processing of dairy goods.

<span class="mw-page-title-main">Extracellular polymeric substance</span> Gluey polymers secreted by microorganisms to form biofilms

Extracellular polymeric substances (EPSs) are natural polymers of high molecular weight secreted by microorganisms into their environment. EPSs establish the functional and structural integrity of biofilms, and are considered the fundamental component that determines the physicochemical properties of a biofilm. EPS in the matrix of biofilms provides compositional support and protection of microbial communities from the harsh environments. Components of EPS can be of different classes of polysaccharides, lipids, nucleic acids, proteins, lipopolysaccharides, and minerals.

<span class="mw-page-title-main">Algae fuel</span> Use of algae as a source of energy-rich oils

Algae fuel, algal biofuel, or algal oil is an alternative to liquid fossil fuels that uses algae as its source of energy-rich oils. Also, algae fuels are an alternative to commonly known biofuel sources, such as corn and sugarcane. When made from seaweed (macroalgae) it can be known as seaweed fuel or seaweed oil.

<i>Nannochloropsis</i> Genus of algae

Nannochloropsis is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh and brackish water. All of the species are small, nonmotile spheres which do not express any distinct morphological features that can be distinguished by either light or electron microscopy. The characterisation is mostly done by rbcL gene and 18S rRNA sequence analysis.

<span class="mw-page-title-main">Algae bioreactor</span> Device used for cultivating micro or macro algae

An algae bioreactor is used for cultivating micro or macroalgae. Algae may be cultivated for the purposes of biomass production (as in a seaweed cultivator), wastewater treatment, CO2 fixation, or aquarium/pond filtration in the form of an algae scrubber. Algae bioreactors vary widely in design, falling broadly into two categories: open reactors and enclosed reactors. Open reactors are exposed to the atmosphere while enclosed reactors, also commonly called photobioreactors, are isolated to varying extents from the atmosphere. Specifically, algae bioreactors can be used to produce fuels such as biodiesel and bioethanol, to generate animal feed, or to reduce pollutants such as NOx and CO2 in flue gases of power plants. Fundamentally, this kind of bioreactor is based on the photosynthetic reaction, which is performed by the chlorophyll-containing algae itself using dissolved carbon dioxide and sunlight. The carbon dioxide is dispersed into the reactor fluid to make it accessible to the algae. The bioreactor has to be made out of transparent material.

<i>Arthrospira</i> Genus of Cyanobacteria

Arthrospira is a genus of free-floating filamentous cyanobacteria characterized by cylindrical, multicellular trichomes in an open left-hand helix. A dietary supplement is made from A. platensis and A. maxima, known as spirulina. The A. maxima and A. platensis species were once classified in the genus Spirulina. Although the introduction of the two separate genera Arthrospira and Spirulina is now generally accepted, there has been much dispute in the past and the resulting taxonomical confusion is tremendous.

<i>Nannochloropsis</i> and biofuels

Nannochloropsis is a genus of alga within the heterokont line of eukaryotes, that is being investigated for biofuel production. One marine Nannochloropsis species has been shown to be suitable for algal biofuel production due to its ease of growth and high oil content, mainly unsaturated fatty acids and a significant percentage of palmitic acid. It also contains enough unsaturated fatty acid linolenic acid and polyunsaturated acid for a quality biodiesel.

<span class="mw-page-title-main">Culture of microalgae in hatcheries</span>

Microalgae or microscopic algae grow in either marine or freshwater systems. They are primary producers in the oceans that convert water and carbon dioxide to biomass and oxygen in the presence of sunlight.

<span class="mw-page-title-main">Phycosphere</span> Microscale mucus region that is rich in organic matter surrounding a phytoplankton cel

The phycosphere is a microscale mucus region that is rich in organic matter surrounding a phytoplankton cell. This area is high in nutrients due to extracellular waste from the phytoplankton cell and it has been suggested that bacteria inhabit this area to feed on these nutrients. This high nutrient environment creates a microbiome and a diverse food web for microbes such as bacteria and protists. It has also been suggested that the bacterial assemblages within the phycosphere are species-specific and can vary depending on different environmental factors.

Sammy Boussiba is a professor emeritus at the French Associates Institute for Agriculture and Biotechnology of Drylands at the Jacob Blaustein Institutes for Desert Research at Ben-Gurion University of the Negev, Israel.

<i>Chlorella vulgaris</i> Species of green alga

Chlorella vulgaris is a species of green microalga in the division Chlorophyta. It is mainly used as a dietary supplement or protein-rich food additive in Japan.

Freshwater phytoplankton is the phytoplankton occurring in freshwater ecosystems. It can be distinguished between limnoplankton, heleoplankton, and potamoplankton. They differ in size as the environment around them changes. They are affected negatively by the change in salinity in the water.

<span class="mw-page-title-main">Marine primary production</span> Marine synthesis of organic compounds

Marine primary production is the chemical synthesis in the ocean of organic compounds from atmospheric or dissolved carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are called primary producers or autotrophs.

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. ↑ Parker, Micaela S.; Mock, Thomas; Armbrust, E. Virginia (2008). "Genomic Insights into Marine Microalgae". Annual Review of Genetics . 42: 619–645. doi:10.1146/annurev.genet.42.110807.091417. PMID   18983264.
  4. ↑ Thrush, Simon; Hewitt, Judi; Gibbs, Max; Lundquist, Caralyn; Norkko, Alf (2006). "Functional Role of Large Organisms in Intertidal Communities: Community Effects and Ecosystem Function". Ecosystems. 9 (6): 1029–1040. doi:10.1007/s10021-005-0068-8. S2CID   23502276.
  5. ↑ Sun, Ning; Skaggs, Richard L.; Wigmosta, Mark S.; Coleman, André M.; Huesemann, Michael H.; Edmundson, Scott J. (July 2020). "Growth modeling to evaluate alternative cultivation strategies to enhance national microalgal biomass production". Algal Research. 49: 101939. doi: 10.1016/j.algal.2020.101939 . ISSN   2211-9264. S2CID   219431866.
  6. ↑ Starckx, Senne (31 October 2012) A place in the sun - Algae is the crop of the future, according to researchers in Geel 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. doi:10.1016/j.cbpc.2006.05.007. PMID   16901759.
  8. ↑ Ratha SK, Prasanna R (February 2012). "Bioprospecting microalgae as potential sources of "Green Energy"—challenges and perspectives". Applied Biochemistry and Microbiology. 48 (2): 109–125. doi:10.1134/S000368381202010X. PMID   22586907. S2CID   18430041.
  9. ↑ Yuvraj (2022). "Microalgal Bioremediation: A Clean and Sustainable Approach for Controlling Environmental Pollution". Innovations in Environmental Biotechnology. Vol. 1. Singapore: Springer Singapore. pp. 305–318. doi:10.1007/978-981-16-4445-0_13. ISBN   978-981-16-4445-0.
  10. ↑ Bonachela, Juan; Raghib, Michael; Levin, Simon (Feb 21, 2012). "Dynamic model of flexible phytoplankton nutrient uptake". PNAS. 108 (51): 20633–20638. doi: 10.1073/pnas.1118012108 . PMC   3251133 . PMID   22143781.
  11. ↑ Wolfe, Gordon (2000). "The chemical Defense Ecology o Marine Unicelular Plankton: Constraints, Mechanisms, and Impacts". The Biological Bulletin . 198 (2): 225–244. CiteSeerX   10.1.1.317.7878 . doi:10.2307/1542526. JSTOR   1542526. PMID   10786943.
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  13. ↑ "ENERGY FROM ALGAE (includes scientific names)". ifremer. Archived from the original on 2006-11-28. Retrieved 2006-09-13.
  14. ↑ Becker, E. W. (1 March 2007). "Micro-algae as a source of protein". Biotechnology Advances. 25 (2): 207–210. doi:10.1016/j.biotechadv.2006.11.002. PMID   17196357.
  15. ↑ Grossmann, Lutz; Hinrichs, Jörg; Weiss, Jochen (24 September 2020). "Cultivation and downstream processing of microalgae and cyanobacteria to generate protein-based technofunctional food ingredients". Critical Reviews in Food Science and Nutrition. 60 (17): 2961–2989. doi:10.1080/10408398.2019.1672137. PMID   31595777. S2CID   203985553.
  16. ↑ Bertsch, Pascal; Böcker, Lukas; Mathys, Alexander; Fischer, Peter (February 2021). "Proteins from microalgae for the stabilization of fluid interfaces, emulsions, and foams". Trends in Food Science & Technology. 108: 326–342. doi: 10.1016/j.tifs.2020.12.014 . hdl: 20.500.11850/458592 .
  17. ↑ Aizpuru, Aitor; González-Sánchez, Armando (2024-07-20). "Traditional and new trend strategies to enhance pigment contents in microalgae". World Journal of Microbiology and Biotechnology. 40 (9): 272. doi:10.1007/s11274-024-04070-3. ISSN   1573-0972. PMC   11271434 . PMID   39030303.
  18. ↑ Hu, Jianjun; Nagarajan, Dillirani; Zhang, Quanguo; Chang, Jo-Shu; Lee, Duu-Jong (January 2018). "Heterotrophic cultivation of microalgae for pigment production: A review". Biotechnology Advances. 36 (1): 54–67. doi:10.1016/j.biotechadv.2017.09.009. PMID   28947090.
  19. ↑ 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.
  20. ↑ Chisti, Yusuf (2008). "Biodiesel from microalgae beats bioethanol" (PDF). Trends in Biotechnology . 26 (3): 126–131. doi:10.1016/j.tibtech.2007.12.002. PMID   18221809.
  21. ↑ Arnaud Muller-Feuga (2000). "The role of microalgae in aquaculture: situation and trends" (PDF). Journal of Applied Phycology. 12 (3): 527–534. doi:10.1023/A:1008106304417. S2CID   8495961.
  22. ↑ Isuru Wijesekara; Ratih Pangestuti; Se-Kwon Kim (2010). "Biological activities and potential health benefits of sulfated polysaccharides derived from marine algae". Carbohydrate Polymers. 84 (1): 14–21. doi:10.1016/j.carbpol.2010.10.062.
  23. ↑ Upasana Mishra; Sunil Pabbi (2004). "Cyanobacteria: a potential biofertilizer for rice" (PDF). Resonance. 9 (6): 6–10. doi:10.1007/BF02839213. S2CID   121561783.
  24. ↑ Yuvraj; Ambarish Sharan Vidyarthi; Jeeoot Singh (2016). "Enhancement of Chlorella vulgaris cell density: Shake flask and bench-top photobioreactor studies to identify and control limiting factors" . Korean Journal of Chemical Engineering. 33 (8): 2396–2405. doi:10.1007/s11814-016-0087-5. S2CID   99110136.
  25. ↑ Yuvraj; Padmini Padmanabhan (2017). "Technical insight on the requirements for CO2-saturated growth of microalgae in photobioreactors". 3 Biotech. 07 (2): 119. doi:10.1007/s13205-017-0778-6. PMC   5451369 . PMID   28567633.
  26. ↑ Yuvraj; Ambarish Sharan Vidyarthi; Jeeoot Singh (2016). "Enhancement of Chlorella vulgaris cell density: Shake flask and bench-top photobioreactor studies to identify and control limiting factors" . Korean Journal of Chemical Engineering. 33 (8): 2396–2405. doi:10.1007/s11814-016-0087-5. S2CID   99110136.
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