Statistical optimization using Central Composite Design for biomass and lipid productivity of microalga: A step towards enhanced biodiesel production

• Sewage wastewater born microalga, Oocystis sp. IM-04 was characterized as potential biodiesel feedstock.
• Response Surface Methodology is an effective approach for optimization of nitrate, phosphate and temperature levels.
• 750 mg/l of sodium nitrate, 0 mg/l of di potassium hydrogen phosphate at 30 °C temperature were found as optimal conditions for high lipid and biomass productivity of Oocystis sp.

Central Composite Design (CCD) was utilized to optimize the levels of nutrients (nitrate and phosphate) and temperature for high biomass and lipid productivity in Oocystis sp. IM-04 isolated from domestic wastewater. Effect of varying temperature, nitrate and phosphate levels and their interactions was studied for different response variables i.e. lipid productivity (R1), biomass productivity (R2) and lipid concentration (R3). The predicted second-order quadratic model for response variables was significant (p < 0.01). Further R2 values i.e. 0.8878 (R1), 0.9944 (R2), indicated satisfactory fit of the model. On the basis of statistical analysis of results, sodium nitrate (750 mg/l), Di potassium hydrogen phosphate (0 mg/l) at 30 °C temperature i.e. N750P0T30, was found to be the best combination for highest lipid productivity (7.0 mg/l/d), biomass productivity (47.8 mg/l/d) and lipid concentration (109.5 mg/l).

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