Cascade biotransformation of dehydroepiandrosterone (DHEA) by Beauveria species

Beauveria bassiana is an entomopathogenic fungus used as a biological control agent. It is a well-known biocatalyst for the transformation of steroid compounds. Hydroxylations at the 7 alpha or 11 alpha position and oxidation to D-homo lactones are described in the literature. In our study, we examined the diversity of metabolism of five different B. bassiana strains and compared them to already known pathways. According to the literature, 7 alpha and 11 alpha-hydroxy derivatives as well as 3 beta,11 alpha-dihydroxy-17a-oxa-D-homo-androst-5-en-17-one have been observed. Here we describe new DHEA metabolic pathways and two products not described before: 3 beta-hydroxy-17a-oxa-D-homo-androst-5-en-7,17-dione and 3 beta,11 alpha-dihydroxyandrost-5-en-7,17-dione. We also used for the first time another species from this genus, Beauveria caledonica, for steroid transformation. DHEA was hydroxylated at the 7 alpha, 7 beta and 11 alpha positions and then reactions of oxidation and reduction leading to 3 beta,11 alpha-dihydroxyandrost-5-en-7,17-dione were observed. All tested strains from the Beauveria genus effectively transformed the steroid substrate using several different enzymes, resulting in cascade transformation.