Optimization of mixotrophic cultivation of microalgae Chlorella sp. for biofuel production using response surface methodology

•Cost effective production of microalgae biomass was proposed.•We applied the surface response methodology for optimization of algae cultivation.•Optimal conditions of Chlorella sp. cultivation for biofuel production were selected.•Microalgae growth is strongly dependent on the nitrogen concentration.•Addition of technical glycerol increased the biomass formation.

Microalgae invite the attention of scientists due to their unique properties, including their ability to grow quickly, accumulate lipids and other valuable materials, fix carbon dioxide and treat wastewater. Several studies have aimed to identify cost-effective production methods for microalgae biomass. In this paper, several potential inexpensive waste materials for microalgae Chlorella sp. biomass production rate were investigated, including technical glycerol and liquid waste (i.e., the liquid fraction of the digestate after biogas production). In addition, the cultivation of microalgae biomass was optimized using these materials. The optimization procedure was performed using response surface methodology. Biomass cultivation process was optimized depending on the amount of technical glycerol and the nitrogen concentrations in the growth medium, which was prepared using liquid waste. The highest Chlorella sp. biomass concentration of 2.41 g L− 1 was achieved in the growth medium that contained 0.114 g L− 1 nitrogen and 2.70 g L− 1 technical glycerol.