Chlorophyll-deficient triggers heterotrophic lutein-directed biosynthesis in a novel mutant strain of Chlorella sorokiniana (Chlorophyta): Process characterization and underlying mechanism

Chlorella sorokiniana is a promising candidate for lutein production. However, the diversified pigment composition results in a complex and costly extraction process. In this study, a chlorophyll-deficient mutant (MT03) of C. sorokiniana FZU60 was generated by chemical mutagenesis, exhibiting lutein as the primary pigment under heterotrophic conditions with higher content and production than the wild type (WT). Transcriptomic and biochemical composition analyses showed the decreased contents of carbohydrates, lipids, and chlorophylls in MT03, which might lead to the increased biosynthesis of lutein and protein. The inhibition of chlorophyll biosynthesis also triggered the enhanced heme biosynthesis, potentially promoting the functions of cytochrome P450 carotenoid hydroxylases and subsequently facilitating lutein biosynthesis in MT03. Sequencing analysis indicated that the mutation of G1106 to D1106 in MT03 CHLH might hinder the magnesium chelating reaction, leading to the deficiency in chlorophyll biosynthesis. These findings highlight the potential of MT03 as a promising strain for lutein-directed biosynthesis and provide a straightforward and cost-effective approach for enhancing microalgae-based lutein production. [Display omitted] •Chlorophyll-deficient mutant MT03 of C. sorokiniana was obtained by EMS.•Mutant strain appeared golden yellow due to lutein being the main pigment.•Chlorophyll-deficient led to the reallocation of intracellular carbon.•Comparative transcriptome revealed the underlying molecular mechanisms.•The chlorophyll deficiency of MT03 might be due to the mutation of CHLH.