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| image_caption = A single ''Arthrospira platensis'' colony
| taxon = Arthrospira
| authority = Sitzenberger ex Gomont, 1892
| subdivision_ranks = Species
| subdivision = About 35.
*''[[Arthrospira ardissonei]]''
*''[[Arthrospira erdosensis]]''
*''[[Arthrospira fusiformis]]''
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==Taxonomy==
The common name, [[Spirulina (dietary supplement)|spirulina]], refers to the dried biomass of ''[[Arthrospira
At present, taxonomy states that the name spirulina for strains which are used as [[food supplement]]s is inappropriate, and agreement exists that ''Arthrospira'' is a distinct genus, consisting of over 30 different species, including ''A. platensis'' and ''A. maxima''.<ref> {{cite journal
| title = Genomic Structure of an Economically Important Cyanobacterium, ''Arthrospira'' (''Spirulina'') platensis NIES-39
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| volume=17
| issue = 2
| journal=DNA
| pages=85–103
}} In its turn, it references:
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| year = 2007
| pages = 542–3
}}</ref> A 2019 analysis of ''Arthrospira'' species using [[16S ribosomal RNA|16S rRNA gene sequence]] suggests that certain species of this genus (''A.'' ''jenneri'') is much closer to ''[[Planktothrix]]'' [[Cladistics|clade]] than previously thought. It also lacks characteristics of mass produced species (such as preference of alkaline habitats). As a result, researchers proposed a new genus closer to ''Limnoraphis and Neolyngbya'' called '''''Limnospira''' comprising [[L. fusiformis]], [[Arthrospira maxima|L. maxima]]'' and ''[[Arthrospira indica|L. indica]]''.<ref>{{Cite journal |last=Nowicka-Krawczyk |first=Paulina |last2=Mühlsteinová |first2=Radka |last3=Hauer |first3=Tomáš |date=2019-01-24 |title=Detailed characterization of the Arthrospira type species separating commercially grown taxa into the new genus Limnospira (Cyanobacteria) |url=https://www.nature.com/articles/s41598-018-36831-0 |journal=Scientific Reports |language=en |volume=9 |issue=1 |pages=694 |doi=10.1038/s41598-018-36831-0 |issn=2045-2322 |pmc=6345927 |pmid=30679537}}</ref>
==Morphology==
The genus ''Arthrospira'' comprises helical [[Trichome|trichomes]] of varying size and with various degrees of coiling, including tightly-coiled morphology to a straight form.<ref name="ciferri"/>
The helical parameters of the shape of ''Arthrospira'' is used to differentiate between and even within the same species.<ref>{{cite journal |last1=Rich |first1=F |title=Notes on ''Arthrospira platensis'' |journal=
▲journal|last1=Rich|first1=F|title=Notes on Arthrospira platensis|journal=Rev. Algol.|date=1931|volume=6|pages=75–79}}</ref><ref>{{cite journal|last1=Marty|first1=F|last2=Busson|first2=F|title=Données cytologiques sur deux Cyanophycées:Spirulina platensis (Gom.) Geitler et Spirulina geitleri J. de Toni|journal=Schweizerische Zeitschritf für Hydrologie|date=1970|volume=32|issue=2|pages=559–565|doi=10.1007/bf02502570|s2cid=44855904}}</ref> These differences may be induced by changing environmental conditions, such as temperature.<ref>{{cite journal|last1=Van Eykelenburg|first1=C|title=On the morphology and ultrastructure of the cell wall of Spirulina platensis|journal=Antonie van Leeuwenhoek|date=1977|volume=43|issue=2|pages=89–99|doi=10.1007/bf00395664|pmid=413479|s2cid=22249310}}</ref> The helical shape of the trichomes is only maintained in a liquid environment.<ref name="ReferenceB">{{cite book|author=FAO Report|title=A review on culture, production and use of spirulina as food for humans and feeds for domestic animals and fish|date=2008|publisher=Food and agriculture organization of the united nations|location=Rome}}</ref> The filaments are solitary and reproduce by [[binary fission]], and the cells of the trichomes vary in length from 2 to 12 μm and can sometimes reach 16 μm.
==Biochemical composition==
{{Further|Spirulina (dietary supplement)}}
''Arthrospira'' is very rich in [[protein]]s,<ref name="ciferri" /><ref name="
Its protein harbours all [[Essential amino acid|essential amino acids]].<ref name="
==Occurrence==
Species of the genus ''Arthrospira'' have been isolated from alkaline [[Brackish water|brackish]] and [[Saline water|saline waters]] in tropical and subtropical regions. Among the various species included in the genus,'' A. platensis'' is the most widely distributed and is mainly found in Africa, but also in Asia. ''A. maxima'' is believed to be found in California and Mexico.<ref name=":0"/> ''A. platensis'' and ''A. maxima'' occur naturally in tropical and subtropical lakes with alkaline [[pH]] and high concentrations of [[carbonate]] and [[bicarbonate]].<ref name="FAO Spirulina Review">{{cite web|title=A Review on Culture, Production and Use of Spirulina as Food dor Humans and Feeds for Domestic Animals and Fish|url=ftp://ftp.fao.org/docrep/fao/011/i0424e/i0424e00.pdf|publisher=Food and Agriculture Organization of The United Nations|access-date=November 20, 2011|author=Habib, M. Ahsan B.|author2=Parvin, Mashuda|author3= Huntington, Tim C.|author4= Hasan, Mohammad R.|year=2008}}</ref> ''A. platensis'' occurs in Africa, Asia and South America, whereas ''A. maxima'' is confined to Central America. ''A. pacifica'' is endemic to the Hawaiian islands.<ref name="vonshak">{{cite book|last1=Vonshak
==Present and future uses==
Spirulina is widely known as a [[food supplement]], but there are other possible uses for this cyanobacterium. As an example, it is suggested to be used medically for patients for whom it is difficult to chew or swallow food, or as a natural and cheap drug delivery system.<ref>{{cite journal|last1=Adiba|first1=B. D.|display-authors=etal|title=Preliminary characterization of food tablets from date (
In the creation of textiles it harbors some advantages, since it can be used for the production of antimicrobial textiles<ref name="ReferenceC">{{cite journal|last1=Mahltig|first1=B|display-authors=etal|title=Modification of algae with zinc, copper and silver ions for usage as natural composite for antibacterial applications|journal=Materials Science and Engineering|date=2013|volume=33|issue=2|pages=979–983|doi=10.1016/j.msec.2012.11.033|pmid=25427514|doi-access=}}</ref> and paper or polymer materials.<ref name="ReferenceC"/> They also may have an antioxidant effect<ref>{{cite journal |last1=Kumaresan
==Cropping systems==
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When growing in water depths of 12–15 cm, self-shading governs the growth of the individual cell.
However, research has shown, that growth is also photoinhibited, and can be increased through shading.<ref>{{cite book|last1=Vonshak|first1=A|last2=Guy|first2=R|title=Photoinhibition as a limiting factor in outdoor cultivation of Spirulina platensis. In Stadler et al. eds. Algal Biotechnology|date=1988|publisher=Elsevier Applied Sci. Publishers|location=London}}</ref> The level of photoinhibition versus the lack of light is always a question of cell concentration in the medium.
The optimal growth temperature for ''A. platensis'' is 35–38 °C. This poses a major limiting factor outside the tropics, confining growth to the summer months.<ref>{{cite book|last1=Vonshak|first1=A|title=Spirulina platensis (Arthrospira). In Physiology, Cell Biology and Biotechnology|date=1997|publisher=Taylor and Francis|location=Basingstoke, Hants, London}}</ref> ''A. platensis'' has been grown in fresh water, as well as in brackish water and sea water.<ref>{{cite journal|last1=Materassi|first1=R|display-authors=etal|title=''Spirulina'' culture in sea-water|journal=
Waste effluents are more readily available in rural locations, allowing small scale production.<ref>{{cite book|last1=Laliberte|first1=G|display-authors=etal|title=Mass cultivation and wastewater treatment using Spirulina. In A. Vonshak, ed. Spirulina platensis (Arthrospira platensis) Physiology, Cell Biology and Biotechnology|date=1997|publisher=Taylor and Francis|location=Basingstoke, Hants, London|pages=159–174}}</ref>
One of the major hurdles for large scale production is the complicated harvesting process which accounts for 20–30% of the total production costs. Due to their small cell size, and diluted cultures (mass concentration less than 1 g/L) with densities close to that of water microalgae, they are difficult to separate from their growing medium.<ref>{{cite journal|last1=Barros|first1=Ana I.|display-authors=etal|title=Harvesting techniques applied to microalgae: A review|journal=Renewable and Sustainable Energy Reviews|date=2015|volume=41|pages=1489–1500|doi=10.1016/j.rser.2014.09.037|url=https://repositorio-aberto.up.pt/handle/10216/103426|hdl=10216/103426|hdl-access=free}}</ref>
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Open pond systems are the most common way to grow ''A. platensis'' due to their comparatively low cost. Typically, channels are built in form of a raceway from concrete or PVC coated earth walls, and water is moved by paddle wheels. The open design, however allows contamination by foreign algae and/or microorganisms.<ref name="vonshak"/>
Another problem includes water loss due to evaporation. Both of these problems can be addressed by covering the channels with transparent [[polyethylene]] film.<ref
===Closed system===
Closed systems have the advantage of being able to control the physical, chemical and biological environment. This allows for increased yield, and more control of the nutrient level. Typical forms such as tubes or polyethylene bags, also offer a larger surface-to-volume ratios than open pond systems,<ref>{{cite journal|last1=Tredici|first1=M|last2=Materassi|first2=R|title=From open ponds to vertical alveolar panels: the Italian experience in the development of reactors for the mass cultivation of phototrophic microorganisms|journal=Journal of Applied Phycology|date=1992|volume=4|issue=3|pages=221–231|doi=10.1007/bf02161208|s2cid=20554506}}</ref> thus increasing the amount of sunlight available for photosynthesis. These closed systems help expanding the growing period into the winter months, but often lead to overheating in summer.<ref>{{cite journal|last1=Tomaselli|first1=L|display-authors=etal|title=Recent research on ''Spirulina'' in Italy|journal=Hydrobiology|date=1987|volume=151/152|pages=79–82|doi=10.1007/bf00046110|s2cid=9903582}}</ref>
==Market potentials and feasibility==
Cultivation of ''Arthrospira'' has occurred for a long period of time,{{Vague|reason=date?|date=December 2020}} especially in Mexico and around Lake Chad on the African continent. During the
Especially as a small-scale crop, ''Arthrospira'' still has considerable potential for development, for example for nutritional improvement.<ref name="smart fish">{{cite journal|date=2011|title=Spirulina – a livelihood and a business venture|journal=Report: SF/2011|author=Smart Fish}}</ref> New countries where this could happen, should dispose of alkaline-rich ponds on high altitudes or saline-alkaline-rich groundwater or coastal areas with high temperature.<ref name="FAO Spirulina Review" /> Otherwise, technical inputs needed for new spirulina farms are quite basic.<ref name="smart fish" />
The international market of spirulina is divided into two target groups: the one includes NGO’s and institutions focusing on malnutrition and the other includes health conscious people. There are still some countries, especially in Africa, that produce at a local level. Those could respond to the international demand by increasing production and [[economies of scale]]. Growing the product in Africa could offer an advantage in price, due to low costs of labour. On the other hand, African countries would have to surpass quality standards from importing countries, which could again result in higher costs.<ref name="smart fish" />
== References ==
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== External links ==
* {{AlgaeBase genus|name=Arthrospira|id=
{{Taxonbar|from=Q987596}}
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