Unlabelled: Recombinant Saccharomyces cerevisiae expressing exogenous carotenogenic genes can synthesize carotenoids. NADPH is a key cofactor for carotenoid biosynthesis, while glucose-6-phosphate dehydrogenase (Zwf1) and an NADH kinase (Pos5) are the two main NADPH-supplying sources in S. cerevisiae. Here, the effect of ZWF1 and POS5 overexpression on carotenoid yield in recombinant S. cerevisiae was explored. The initial carotenogenic strain Sc-EYBIH+I which expressed crtE, crtYB, crtI, cHMG1 and another copy of crtI could synthesize 1·35 ± 0·13 mg l(-1) of lycopene and 0·32 ± 0·02 mg l(-1) of β-carotene. When ZWF1 was overexpressed (Sc-EYBIZH+I), glucose-6-phosphate dehydrogenase activity increased by 103-fold, the transcription level of crtE and crtI increased significantly, the lycopene and β-carotene yield increased to 2·29 ± 0·06 and 0·38 ± 0·02 mg l(-1) respectively. When POS5 was overexpressed (Sc-EYBIPH+I), NAD kinase activity increased by 5·5-fold, the transcription level of crtE, crtYB and crtI increased obviously, the lycopene and β-carotene yield increased to 2·50 ± 0·11 and 0·53 ± 0·03 mg l(-1) respectively. Therefore, improvement of NADPH supply contributed to carotenoids biosynthesis in S. cerevisiae and overexpression of POS5 was more effective than overexpression of ZWF1. This study provides a new strategy for enhancing carotenoid biosynthesis.

Significance and impact of the study: NADPH is a key cofactor for carotenoid biosynthesis. Glucose-6-phosphate dehydrogenase (Zwf1) and an NADH kinase (Pos5) are effective NADPH-supplying sources in Saccharomyces cerevisiae. When ZWF1 and POS5 were overexpressed in a carotenoid-producing S. cerevisiae strain individually, the total yield of lycopene and β-carotene increased by 59·9% and 81·4%, respectively, and the final product β-carotene yield increased by 18·8% and 65·6% respectively. This suggests the improvement of NADPH supply as a useful strategy for carotenoids biosynthesis.

• PMID: 26179622
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Journal Article

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Zhao X, Shi F, Zhan W

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