Effect of CO₂ supply conditions on lipid production of Chlorella vulgaris from enzymatic hydrolysates of lipid-extracted microalgal biomass residues

The hydrolysates from lipid-extracted microalgal biomass residues (LMBRs) were used as a source of nutrients for the cultivation of Chlorella vulgaris for lipid production under various CO₂ supply conditions, including different CO₂ concentrations and aeration rates. Both parameters had a significant effect on lipid production. A CO₂ concentration of 5% was found to be most suitable for microalgal growth. Microalga grew best at a CO₂ aeration rate of 0.5 vvm. At this rate, biomass concentration and lipid productivity were at a maximum of 3.83 g L^-1 and 157 mg L^-1 d^-1, respectively, but decreased at lower or higher aeration rates. The present results showed that LMBRs utilization was effective in microalgal lipid production under suitable CO₂ supply conditions.