Production of 11-Oxo-β-Amyrin in Saccharomyces cerevisiae at High Efficiency by Fine-Tuning the Expression Ratio of CYP450:CPR

The production of glycyrrhetinic acid (GA) and 11-oxo-β-amyrin, the major bioactive components in liquorice, was typically inhibited by P450 oxidation in Saccharomyces cerevisiae. This study focused on optimizing CYP88D6 oxidation by balancing its expression with cytochrome P450 oxidoreductase (CPR) for the efficient production of 11-oxo-β-amyrin in yeast. Results indicated that a high CPR:CYP88D6 expression ratio could decrease both 11-oxo-β-amyrin concentration and turnover ratio of β-amyrin to 11-oxo-β-amyrin, whereas a high CYP88D6:CPR expression ratio is beneficial for improving the catalytic activity of CYP88D6 and 11-oxo-β-amyrin production. Under such a scenario, 91.2% of β-amyrin was converted into 11-oxo-β-amyrin in the resulting S. cerevisiae Y321, and 11-oxo-β-amyrin production was further improved to 810.6 mg/L in fed-batch fermentation. Our study provides new insights into the expression of cytochrome P450 and CPR in maximizing the catalytic activity of P450s, which could guide the construction of cell factories in producing natural products.