Effect of two-steps substrate addition on steroids 11β-hydroxylation by Curvularia lunata CL-114

In this paper, the effect of substrate 17α-hydroxypregn-4-ene-3,20-dione-21-acetate (RSA, Cortexolone-21-acetate) on the expression of cytochrome P450 and the production of hydrocortisone by Curvularia lunata CL-114 was studied. Meanwhile the effect of pH on the production of hydrocortisone was observed. Based on the effect of substrate RSA two-steps addition on cytochrome P450 expression and hydrocortisone production, a novel fermentation process was established as follows: 0.3 g/L RSA was added for the first time after 16 h of inoculation, followed by the second addition of 0.7 g/L RSA after 8 h later, then pH was regulated to constant 6.5 after another 8 h till the end of fermentation. The results showed that the novel process was much better than the original one on improving the induction of cytochrome P450 and production of hydrocortisone, and the hydrocortisone yield had achieved an improvement of 17.6% higher than that of the original process correspondingly.