Co-production of lutein, zeaxanthin, and β-carotene by utilization of a mutant of the green alga Chromochloris zofingiensis

The unicellular green alga Chromochloris zofingiensis is a promising species for producing natural carotenoids. In this study, the mutant CZ-LZM3 was successfully obtained by screening the chemical mutagenesis pool of a C. zofingiensis strain. This mutant could achieve ultrahigh cell density and simultaneously accumulate lutein, zeaxanthin, and β-carotene under heterotrophic conditions. The insertional mutation was identified in the beta-carotene ketolase encoding gene, which may cause the block of astaxanthin biosynthesis in CZ-LZM3. Ultrahigh-cell-density of 185 g·L−1 was achieved under the optimum heterotrophic cultivation conditions in 7.5 L fermenters on Day 10, while the lutein, zeaxanthin, and β-carotene were 0.122, 0.22, 0.097 % of DW, respectively. By the combined utilization of gibberellin acid-3 (GA3) with the high C/N ratio and NaCl concentration under heterotrophic cultivation, the mutant could accumulate lutein, zeaxanthin, and β-carotene up to 0.726 % of DW. These findings demonstrated that the two-stage heterotrophic cultivation strategy is technically feasible for co-production of lutein, zeaxanthin, and β-carotene by utilizing the mutant of C. zofingiensis.