CCD-RSM optimization of CO2, nitrate, and nanoparticle levels for enhanced biomass, lipid, and carbohydrate yields in Chlorella pyrenoidosa

The study employed a central composite design (CCD) response surface method (RSM) to optimize initial CO2 levels, nitrate concentrations, and ZnO nanoparticle concentration in the culture media for enhancing biomass, lipid, and carbohydrate yield in Chlorella pyrenoidosa. The predicted second-order quadratic model for response variables was found to be significant (p < 0.01), and the analysis of variance (ANOVA) showed a high coefficient of determination with R-2 being 0.99 for biomass, 0.98 for lipid, and 0.99 for carbohydrate. The maximum biomass, lipid, and carbohydrate yield of 1.5 +/- 0.06 g L-1, 43.6 +/- 1.9%, and 22.8 +/- 3.1%, respectively, were obtained by RSM optimized culture medium containing an initial CO2 concentration of 1.31 g L-1, a nanoparticle dose of 50 mg L-1, and a nutrient concentration of 150 mg L-1. The lipid and carbohydrate yield in the optimized conditions are 60% and 85% higher than in microalgae grown in commercially available BG11 media. This research demonstrates that the targeted optimization of CO2, nitrate, and ZnO nanoparticle concentrations can significantly enhance the biomass, lipid, and carbohydrate yield in C. pyrenoidosa. These findings underscore the viability of using C. pyrenoidosa as a feedstock for biofuel production, particularly in biodiesel and bioethanol applications.