Development of a Chlorella vulgaris mutant by chemical mutagenesis as a producer for natural violaxanthin

Abstract

Carotenoid pigments have been reported the bioactive substances having an antioxidant effect and anti-cancer effect. Recently, the industrial application of natural violaxanthin with anticancer properties has been expanding. Accordingly, in this study, lutein-deficient Chlorella vulgaris, a high producer of violaxanthin, was generated by chemical random mutagenesis. The lutein-deficient mutant was containing only 15.2% lutein compared to wild type. As a cause of this phenomenon, a single point mutation (A336V) on lycopene epsilon cyclase was identified. Consequently, the competitive metabolic pathway of alpha-branch of xanthophyll synthesis was elevated, causing a 3.18-fold increase in violaxanthin production, compared to that of the wild type. Additionally, the improvement of the growth rate of the mutant (1.3 fold higher than wild type) was observed that caused by enhancement of photosynthesis. As a result of optimization of violaxanthin production, the highest amount of violaxanthin production was achieved under 100 mu mol photons m(-2) s(-1) with acetic acid as the carbon source. Consequently, 3.70 +/- 0.45 mg/g violaxanthin, along with 0.45 +/- 0.03 mg/g and 0.44 +/- 0.02 mg/g of antheraxanthin and zeaxanthin were accumulated in the mutant respectively. These results demonstrate that lutein-deficient Chlorella vulgaris can produce violaxanthin at a concentration equivalent to the highest levels previously reported in marine microalgae and suggesting its potential as a new violaxanthin-producing natural host.