Improved production of astaxanthin in heterotrophic Chromochloris zofingiensis through optimized culture conditions incorporating an efficient fed-batch strategy

Abstract

Chromochloris zofingiensis, capable of high-cell-density heterotrophic cultivation, is deemed a highly promising contender for producing astaxanthin. However, the relatively low astaxanthin content impedes the improvement of its production. Herein, the cultivation conditions for heterotrophic astaxanthin production were optimized in this study. An optimized medium was proposed with a culture temperature of 30 °C and an initial biomass concentration of 0.6 g/L. Additionally, a two-stage cultivation strategy, supplying glucose upon carbon depletion, was explored to enhance both biomass concentration and astaxanthin content. Furthermore, a continuous fed-batch cultivation strategy, maintaining the glucose concentration at around 5 g/L under nitrogen deficiency, was established in a 5 L fermenter. This approach resulted in an impressive astaxanthin content of 1.92 mg/g and an outstanding astaxanthin production of 238.83 mg/L, surpassing most reported results obtained solely through fed-batch operation under heterotrophic cultivation. The findings highlight the immense potential of the proposed cultivation strategy for commercial astaxanthin production using C. zofingiensis.