Effects of calcium, magnesium and sodium chloride in enhancing lipid accumulation in two green microalgae

Biodiesel from microalgae has the potential as a sustainable fuel, since some species show exceptionally high lipid accumulation potential under various stresses. Effects of different concentrations of Ca, Mg and NaCl in the growth medium on biomass yield and lipid accumulation of Chlorella vulgaris and Scenedesmus obliquus grown under batch culture mode were investigated. Starvation of Mg showed a marginal rise in lipid content for a short period of time. Ca-starved cultures, however, demonstrated a profound rise in lipid content, i.e. 40% of dry cell wt. (dcw) was recorded against 11.9% control for C. vulgaris and 37% (dcw) against 11.3% for S. obliquus. Under increased concentration of Mg, significant rise in biomass and lipid yield was recorded. Effect of NaCl-induced osmotic stress showed lipid accumulation of approximate to 40% (dcw) in both the test algae, whereas the biomass yield was severely affected. The fatty acid profiles under the above stresses were analysed and discussed.