Enhanced Biosynthesis of Dihydromyricetin in Saccharomyces cerevisiae by Coexpression of Multiple Hydroxylases

Dihydromyricetin (DHM) is a traditional plant-extracted flavonoid with some health benefits. This study aimed to metabolically engineer the strains for DHM bioproduction. Two strains of BK-11 and BQ-21 were integrated with flavonoid 3-hydroxylase (F3H) or both F3H and flavonoid 3'-hydroxylase (F3'H). The resulting strains have expressed the enzymes of GmCPR and SlF3'5'H, and then, the promoters of INO1p and TDH1p were used to enhance further the DHM production from naringenin in Saccharomyces cerevisiae. Through multiple-copy integration, 709.6 mg/L DHM was obtained by adding 2.5 g/L naringenin in a 5 L bioreactor, implying that the synergistic effect between F3'H and flavonoid 3'5'-hydroxylase is likely to promote the DHM production. An yield of 246.4 mg/L DHM was obtained from glucose by deleting genes for branch pathways and integrating PhCHS, MsCHI, Pc4CL, and FjTAL. To our knowledge, this is the highest production reported for the de novo biosynthesis of DHM.