EFFECT OF NITROGEN AND PHOSPHORUS LEVELS ON THE LIPID PRODUCTION OF CHLORELLA VULGARIS AND EVALUATION OF ULTRASOUND-ASSISTED LIPID EXTRACTION

The effect of nitrogen and phosphorus levels on the lipid production and fatty acid composition of Chlorella vulgaris was investigated. In addition, ultrasound-assisted lipid extraction was evaluated based on its efficiency. Results showed that nitrogen concentration in the culture medium affected the lipid yield, biomass production and lipid composition significantly. The highest lipid yield of 34.4 g (lipid)/100g (biomass) was obtained under the initial NaNO3 concentration of 35 mg L-1. The highest lipid production occurred when the initial NaNO3 concentration was 150 mg L-1. The major fatty acids detected include C16:0, C18:0, C18:1, C18:2 and C18:3. Nitrogen limitation led to an increase of C18:1 and a decrease of C18:3. The phosphorus level did not influence the lipid production and composition obviously, while insufficient phosphorus caused poor biomass production. Ultrasound-assisted lipid extraction was effective for C. vulgaris, of which the ultrasonic treatment time was the most important parameter to affect the lipid yield.