Batch Growth of Chlorella Vulgaris CCALA 896 versus Semi-Continuous Regimen for Enhancing Oil-Rich Biomass Productivity

The aim of this study was to induce lipid accumulation in Chlorella cells by creating stressful growth conditions. Chlorella vulgaris CCALA 896 was grown under various batch growth modes in basal and modified BG-11 and Kolkwitz culture broths, using a continuous light regimen of 150 mu E/m(2)/s, at 30 degrees C. In order to perform the experiments, two indoor photobioreactor shapes were used: a cylindrical glass photobioreactor (CGPBR) with a working volume of 350 mL, and a flat glass photobioreactor (FGPBR) with a working volume of 550 mL. Stress-eliciting conditions, such as nitrogen and phosphorous starvation, were imposed in order to induce lipid accumulation. The results demonstrated that more than 56% of the lipids can be accumulated in Chlorella biomass grown under two-phase batch growth conditions. The highest biomass productivity of 0.30 g/L/d was obtained at the highest nominal dilution rate (0.167 day(-1)) during a semi-continuous regimen, using a modified Kolkwitz medium. During the pH-stress cycles, the amount of lipids did not increase significantly and a flocculation of Chlorella cells was noted.