Media optimization design towards maximizing biomass production of Tetradesmus obliquus under mixotrophic conditions

Maximizing biomass production is a key factor in developing large-scale microalgae cultivation. One major aspect to address is the cultivation medium composition in regards to the process objective. In this study, the effect of eight important nutrients/factors (glucose, nitrate, phosphate, sulfate, magnesium, iron, manganese, and calcium) and their interactions were investigated on the biomass production of the microalgae Tetradesmus obliquus under mixotrophic conditions. The Taguchi method, a robust tool for experimental design optimization, was used to find the optimum media composition for biomass production, with only a few well-defined experimental sets. Using Taguchi's L18 orthogonal array resulted to a 4-fold enhancement in biomass yields, with a maximum of about 7.98 g/L. Nitrate exhibited the most significant effect. Iron and phosphate showed a strong influence on short-term cultivations (6 to 9 days), while glucose and calcium had more impact on long-term cultivations (15 days). The overall optimum experimental conditions were provided.