[Breeding of high 3beta,7alpha,15alpha-trihydroxy-5-androsten-17-one transforming strains and their conversion process optimization].

In order to improve transformation efficiency of dehydroepiandrosterone (DHEA) into 3beta,7alpha,15alpha-trihydroxy-5-androsten-17-one (7alpha,15alpha-diOH-DHEA) by Gibberella intermedia CA3-1, we investigated the strains breeding and their conversion process optimization. G. intermedia CA3-1 strains were treated with 0.12 mg/mL 1-methyl-3-nitro-1-nitroso-guanidin (NTG) for 30 min and chosen by 350 micromol/L minimum inhibitory concentration ketoconazole resistance marker. The high production strain named M-10 with a good genetic stability was selected and the product molar yield achieved to 70.2%, which was 20% higher than that of original strain. Under the improved conversion process with the DHEA concentration of 5 g/L, the product molar yield of the mutant M-10 reached 75.6%, which was improved by 31.3% than that of original strain.