Abstract:This study systematically compared the effects of different glucose concentrations, nitrogen sources, and C/N ratios on the biomass and astaxanthin accumulation in Chromochloris zofingiensis under mixotrophic conditions. The aims were to obtain the highest biomass along with a relatively high content of astaxanthin in a short period of time, and provide a scientific basis for high-density seed-train expansion of Chromochloris zofingiensis and astaxanthin induction applied technologies. The results revealed that under mixotrophic conditions with a constant glucose concentration, NaNO3 was the most favorable nitrogen source for C. zofingiensis cell growth. The highest biomass concentration of 9.23 g/L was achieved on the sixth day of cultivation, with the average growth rate as 0.24/d, corresponding astaxanthin yield as 12.38 mg/L, and astaxanthin accounting for about 46.94% of total carotenoids in algal cells. As for the effects of different glucose concentrations and C/N ratios on cell growth and astaxanthin accumulation of C. zofingiensis, glucose concentration at 30 g/L and C/N ratio at 34 were found to be the optimal conditions for cell growth, resulting in the highest biomass of 11.28 g/L and average growth rate as 0.32/d, with significantly higher astaxanthin yield (21.77 mg/L, p < 0.05) and percentage of astaxanthin in total carotenoids (increased to 52.71%). The results obtained in this study will provide the guidance for rapid seed culture expansion and large-scale astaxanthin production by Chromochloris zofingiensis.
