Arthrospira is a genus of free-floating filamentous cyanobacteria characterized by cylindrical, multicellular trichomes in an open left-hand helix.

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.

[2] The common name, spirulina, refers to the dried biomass of Arthrospira platensis,[3] a type of Cyanobacteria, which are oxygenic photosynthetic bacteria.

[5] At present, taxonomy states that the name spirulina for strains which are used as food supplements is inappropriate, and agreement exists that Arthrospira is a distinct genus, consisting of over 30 different species, including A. platensis and A.

As a result, researchers proposed a new genus closer to Limnoraphis and Neolyngbya called Limnospira comprising L. fusiformis, L. maxima and L.

[8] The genus Arthrospira comprises helical trichomes of varying size and with various degrees of coiling, including tightly-coiled morphology to a straight form.

[12] Species of the genus Arthrospira have been isolated from alkaline brackish and saline waters in tropical and subtropical regions.

[6] A. platensis and A. maxima occur naturally in tropical and subtropical lakes with alkaline pH and high concentrations of carbonate and bicarbonate.

[12] The largest commercial producers of spirulina are located in the United States, Thailand, India, Taiwan, China, Pakistan, Myanmar, Greece and Chile.

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.

[16] Further, promising results in the treatment of certain cancers, allergies and anemia, as well as hepatotoxicity and vascular diseases were found.

To achieve maximum output, factors such as the temperature, light and photoinhibition, nutrients and carbon dioxide level, need to be adjusted.

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.

Typically, channels are built in form of a raceway from concrete or PVC coated earth walls, and water is moved by paddle wheels.

Typical forms such as tubes or polyethylene bags, also offer a larger surface-to-volume ratios than open pond systems,[28] thus increasing the amount of sunlight available for photosynthesis.

[29] Cultivation of Arthrospira has occurred for a long period of time,[vague] especially in Mexico and around Lake Chad on the African continent.