Two-stage trophic strategy coupled with fed-batch operation for simultaneous enhancement of cell growth and lutein synthesis in Chlorella sorokiniana

Abstract

The versatile trophic adaptability of Chlorella sorokiniana has garnered significant attention, establishing it as a promising alga for efficient lutein production. In this study, the lutein production characteristics of C. sorokiniana FZU60 were compared under autotrophic, mixotrophic, and heterotrophic conditions. The results demonstrated that glucose supplementation promoted algal cell growth but concurrently reduced lutein content. In contrast, light induction was essential for enhancing lutein synthesis. Consequently, two-stage trophic strategies were developed to simultaneously facilitate cell growth and lutein synthesis. It was determined that optimal lutein production could be achieved by employing the heterotrophy-mixotrophy strategy in conjunction with white light at 500 μmol/m²/s during the second stage (mixotrophic stage). Furthermore, combining the heterotrophy-mixotrophy strategy with fed-batch operation further enhanced the efficacy of lutein production in FZU60. The resulting lutein productivity demonstrated a remarkable 365.1 % improvement over the heterotrophy strategy (Strategy I) and an 80.8 % increase over the mixotrophy strategy (Strategy III), when both were coupled with fed-batch operation. These findings were subsequently validated in a 5 L fermenter where FZU60 exhibited exceptional lutein content, yield, and productivity reaching 6.14 mg/g, 285.02 mg/L, and 44.95 mg/L/d, respectively. Overall, this study successfully develops an effective cultivation strategy to address the inherent conflict between cell growth and lutein synthesis in algal cells, thereby demonstrating considerable potential as an industrial pathway for efficient lutein production.