Effects of nitrogen depletion on lipid and biomass production of three microalgae

It is still necessary to select the correct species, reduce production costs and determine the optimal growth conditions, in order to make large-scale production of fuels derived from microalgae feasible. The species Chlorella vulgaris Beijerinck, Desmodesmus spinosus (Chodat) E. Hegewald and Ankistrodesmus fusiformis Corda were isolated and cultured in laboratory under controlled conditions under two stressful concentrations of sodium nitrate (10 g/L and 5 g/L). Growth was monitored by OD570 and the lipid content extracted through Bligh & Dyer (1959) method. Stressing D. spinosus increased lipid accumulation, but also a dramatic decrease in growth. C. vulgaris did not show any significant change in total lipid content or growth. Both C. vulgaris and A. fusiformis showed no signifi cant variation in total lipid content or growth, with only subtle changes. With different responses to the treatments for each species, it becomes clear the need for knowledge on the physiology and autoecology of the strain for commercial scale production.