Computer control of carbon-nitrogen ratio in Spirulina platensis.

An on-line computer was used to control the ratio of carbon to nitrogen in algal biomass. An indirect method of growth and biomass estimation was utilized. This was based on balancing the amount of CO(2) carbon in and out of the algal bioreactor. It was shown that growth conditions govern the morphology and composition of Spirulina platensis. Cells grown under light limitation were narrower, had high levels of phycocyanin pigments, and were packed full of small lipid granules. Whereas cells grown under nitrogen limitation lost their characteristic blue-green color, had reduced levels of phycocyanin, were fatter, and were packed full of larger lipid granules.