Selenite as a Lipid Inductor in Marine Microalga Dunaliella tertiolecta: Comparison of One-Stage and Two-Stage Cultivation Strategies.

Microalgae have emerged as one of the most promising alternative sources of biofuels due to their high lipid accumulation ability. High lipid content is of pivotal importance for biodiesel production. In order to obtain high lipid content, modifications of culture conditions and development of an efficient lipid induction method are called for. In the present study, the possibility of using selenium in a form of sodium selenite as a lipid inductor in marine microalga Dunaliella tertiolecta was investigated during one- and two-stage cultivation modes. The effects of selenite on algal growth, pigment content, oxidative stress, and neutral lipid content were determined during both cultivation modes. The results revealed that the two-stage cultivation on 10.00-40.00 mg L-1 of selenite resulted in up to twofold higher algal cell density compared to the one-stage cultivation. Selenite concentrations from 2.50 to 20.00 mg L-1 increased lipid peroxidation during both cultivation modes, emphasizing the selenite-induced oxidative stress accompanied by the increased lipid accumulation in microalgae cells. During one- and two-stage cultivation on 20.00 mg L-1 of selenite, lipid content increased 2.39- and 5.73-fold at days 9 and 14 of cultivation, respectively. Moreover, the highest obtained neutral lipid content during the two-stage cultivation was 5.40-fold higher than lipid content obtained during the one-stage cultivation. Collectively, these results suggest that the two-stage cultivation strategy, initiated with optimal culture conditions for biomass production and followed by the addition of selenite as a stress inductor, can be successfully deployed to enhance the lipid content in D. tertiolecta.