Impact of the nitrate concentration on the biomass growth and the fatty acid profiles of microalgae Chlorella sorokiniana

Abstract

Chlorella sorokiniana microalga is one of the species of interest that could be used for the production of valuable compounds such as lipids. Nitrogen stress is a common strategy used to enhance the lipid content in microalgae biomass. The present study compares the effects of several nitrate concentrations in the cultivation medium on the growth and fatty acid composition of the biomass of Chlorella sorokiniana. Results show that nitrogen starvation negatively impacts the growth of the biomass while nitrate repletion increased the biomass growth rates. The effect of initial concentrations of KNO3 from 0.1 g/l to 0.3 g/l did not show significant differences on the biomass productivity. Higher concentrations of KNO3 (0.4 g/l) are shown to decrease the yields of biomass. The highest yield of total lipids (25%) was obtained from the biomass grown under nitrogen deficiency, followed by the biomass grown in the medium containing 0.3 g/l of nitrates (23%). The study of the fatty acid profiles showed that nitrogen starvation decreased the accumulation of polyunsaturated fatty acids (PUFA), especially omega-3 (linolenic acid), and increased the concentration of trans and saturated fatty acids. This cultivation strategy could be more suitable for the production of biodiesel. For the food and feed industry, the presence of nitrogen in the cultivation medium could be preferable as; in this case, the biomass cumulates higher concentrations of linolenic acid.