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Microcystin found in commercially produced cyanobacteria

The study of cyanobacteria has long been linked with that of plants, in part because of the original classification of cyanobacteria as an alga, and in part because of the many shared genes and processes that arose from the endosymbiotic event that led to plastids. There is an agricultural side to cyanobacteria, however, long seen with the cultivation of Spirulina and more recently with the harvesting of Aphanizomenon flos-aquae on a large scale. Both commercial ventures are aimed at the health food market.

In 1999, Health Canada issued a report on cyanobacterial products on the market warning against their possible contamination with the hepatotoxin microcystin. Although neither Spirulina nor Aphanizomenon is known to produce any microcystin, there was concern that toxic Microcystis aeruginosa may grow alongside the edible cyanobacteria, leading to contamination. A later report cleared Spirulina.

Researchers in the Health Division of the State of Oregon (U.S.A.) also weighed in, since much of the Aphanizomenon that is on the market is harvested from Klamath Lake in the southern part of the state.Their report, published in Environmental Health Perspectives (2000) 108:435-439, supported the concerns voiced in the Canadian study. Of 87 samples from cyanobacterial products, 63 contained microcystin higher than the 1 µg/g regulatory limit. The predominant compound was the most toxic form, microcystin-LR.