Directionally Modulated β-Carotene of the Green Alga under Red Light Stress.

Carotenoids, which are natural pigments found abundantly in wide-ranging species, have diverse functions and high industrial potential. The carotenoid biosynthesis pathway is very complex and has multiple branches, while the accumulation of certain metabolites often affects other metabolites in this pathway. The gene that encodes lycopene cyclase was selected in this study to evaluate β-carotene production and the accumulation of β-carotene in the alga . Compared with the wild type, the transgenic algal species overexpressed the gene, resulting in a significant enhancement of the total carotenoid content, with the total amount reaching 8.46 mg/g for an increase of up to 1.26-fold. Interestingly, the production of α-carotene in the transformant was not significantly reduced. This result indicated that the regulation of on the metabolic flux distribution of carotenoid biosynthesis is directional. Moreover, the effects of different light-quality conditions on β-carotene production in strains were investigated. The results showed that the carotenoid components of β-carotene and β-cryptoxanthin were 1.8-fold and 1.23-fold higher than that in the wild type under red light stress, respectively. This suggests that the accumulation of β-carotene under red light conditions is potentially more profitable.