Biosynthesis of Dihydroquercetin in .

Dihydroquercetin is a vital flavonoid compound with a wide range of physiological activities. However, factors, such as metabolic regulation, limit the heterologous synthesis of dihydroquercetin in microorganisms. In this study, flavanone 3-hydroxylase (F3H) and flavanone 3'-hydroxylase (F3'H) were screened from different plants, and their co-expression in was optimized. Promoter engineering and redox partner engineering were used to optimize the corresponding expression of genes involved in the dihydroquercetin synthesis pathway. Dihydroquercetin production was further improved through multicopy integration pathway genes and systems metabolic engineering. By increasing NADPH and α-ketoglutarate supply, the catalytic efficiency of F3'H and F3H was improved, thereby effectively increasing dihydroquercetin production (235.1 mg/L). Finally, 873.1 mg/L dihydroquercetin titer was obtained by fed-batch fermentation in a 5-L bioreactor, which is the highest dihydroquercetin production achieved through microbial synthesis. These results established a pivotal groundwork for flavonoids synthesis.