Model development and process evaluation for algal growth and lipid production

Microalgae grabbed the attention worldwide because of their application in renewable energy with a number of environmental benefits such as carbon dioxide assimilation to produce biofuel. In this study, a kinetic model aiming to analyze algae growth and lipid production was developed. Biomass was divided into two parts, algae residual cell and lipid, to analyze their kinetics distinctively and to find out the inside process mechanism. The model was calibrated and validated with different experimental datasets, varying carbon sources, and phosphate concentrations. The capability of the model to predict the dynamics of algal culture over a broad range of growth conditions was investigated. The presence of acetate reduced the bicarbonate uptake for algal growth and growth on organic carbon was higher compared to that of carbon dioxide. The presence of ammonium showed a very strong inhibition effect on algae and lipid production rate but enhanced lipid content. Phosphate caused both limitation and inhibition effects on algae growth and lipid production rate. The maximum growth was found at 12 mg/L PO₄^3- concentration and 3.10 mg/L NO₃^--N concentration. Lipid content was enhanced by limiting phosphate. Overall, the developed model allows optimizing of nutrient concentrations and operating conditions specifically to enhance lipid productivity.