Simultaneous enhancement of CO2 fixation and lutein production with thermo-tolerant Desmodesmus sp. F51 using a repeated fed-batch cultivation strategy

• Lutein production of Desmodesmus sp. F51 was enhanced with fed-batch cultivation.
• Fed-batch culture controlling both medium feeding and illumination gave best results.
• Lutein accounted for 50–66% of the total carotenoids in the microalgal biomass.
• Repeated fed-batch operations improved both CO2 fixation and lutein production.

This study aimed to improve lutein production using a thermo-tolerant lutein-rich microalga Desmodesmus sp. F51. To achieve this goal, four fed-batch cultivation strategies were investigated for CO2 fixation and lutein production of Desmodesmus sp. F51. Among them, Fed-batch IV showed the best performance, giving the highest CO2 fixation rate and lutein productivity of 1582.4 mg/L/d and 3.91 mg/L/d, respectively. Both increasing the light intensity and limiting the nutrients led to a lower carotenoids content in the microalga, with a higher proportion of lutein and lower proportion of β-carotene being obtained in the carotenoids. The carotenoid present in the biomass was mainly lutein, accounting for 50–66% of total carotenoids. Repeated operations of the Fed-batch IV strategy could effectively improve CO2 fixation and lutein production of Desmodesmus sp. F51, giving the best results of 1826.0 mg/L/d, and 4.61 mg/L/d, respectively. This performance is better than most of the previously reported values.