Statistical optimization of parameters affecting lipid productivity of microalga Chlorella protothecoides cultivated in photobioreactor under nitrogen starvation

In the present work, a lab scale photobioreactor was used to evaluate lipid productivity and carbon dioxide fixation rate of microalgae Chlorella protothecoides under nitrogen deplete conditions. Effect of environmental conditions such as pH, temperature, light intensity, photoperiod (light to dark cycle ratio), CO2 concentration in air and aeration rate on lipid productivity and carbon fixation rate of microalga was studied. Response surface methodology was adopted to optimize these conditions. All the parameters were found to be statistically significant. Best operating conditions were evaluated to be: pH-6.51, Temperature-28.63 °C, light intensity-5.31 klux, Photoperiod-15.36 h:8.64 h, CO2 concentration in air-6.26% (v/v), Aeration rate −2.92 lpm. Lipid productivity under these conditions was found to be 274.15 mg/(L day) which was 3.94 times higher than the value obtained in N+ experiment (69.46 mg/(L day)). Carbon fixation rates under N+ and N− conditions were 286.12 and 273.66 mg/(L day) respectively.