Lipid production in Dunaliella salina under autotrophic, heterotrophic, and mixotrophic conditions

The effects of autotrophic, heterotrophic, and mixotrophic conditions were examined on micro green alga Dunaliella salina (UTEX 200) in terms of cell growth, total chlorophyll concentration, and lipid production. Results revealed a minimum growth rate of microalgae in the heterotrophic condition which is not recommended for D. salina. When the cells were cultured in mixotrophic conditions containing different concentrations of acetate or glucose, in 100 mM acetate or 60 mM glucose, the highest levels of growth rate and lipid production were obtained compared with autotrophic culture; however, the chlorophyll concentration decreased. Moreover, a significant correlation between ROS production and lipid synthesis was observed. When the combined acetate and glucose was added to the culture, no increase in growth rate and lipid synthesis was observed. This might be due to substrate inhibition. In the presence of glucose, the acidification of culture and bleaching occurred. Results indicated that lipid production is not affected by acidified conditions. In general, our results confirmed that mixotrophic culture with 100 mM acetate or 60 mM glucose is the most appropriate culture for D. salina concerning high lipid production as well as high growth rate in the shortest period of time.