Enhancing lipid production of dunaliella tertiolecta by manipulating the interactive effect of salinity and nitrogen

Abstract

Low lipid yield is a major bottleneck towards the scale-up application of microalgae for biodiesel production. The focus of this study was to improve the lipid production of Dunaliella tertiolecta (a marine microalga) by altering the concentration of salinity and nitrogen (as nutrients). The unique aspect of this study was to investigate the interactive effect of nitrogen and salinity on lipid production and their correlation with biomass yield and nitrogen uptake. In this experiment, microalgae were grown under various combinations of salinity and nitrogen. At first, lipid production was observed under varied nitrogen concentration (0-75 mg L-1 as NaNO3) and fixed salinity, 37.7 Practical Salinity Unit (PSU). The maximum cell growth rate of 288.4 mg L-1 d-1 and lipid production of 29.3 % were achieved at 75 mg L-1 of NaNO3. Now, this concentration of nitrogen was fixed and the effects of salinity concentrations were observed. The lipid production increased to 34 %, and cell growth rate decreased to 201.3 mg L-1 d-1 at 3.77 PSU of salinity. However, further reduction of the nitrogen concentration down to 18.75 mg L-1 of NaNO3 increased the lipid production to 42 % and decreased biomass to 0.64 g L-1. It was also found that lipid production was linearly correlated with nitrogen uptake. Microalgae cells consumed all of the nitrogen in the first 24 hours of acclimation; however, lipid yield did not change much over time.