Steroid 9α‐Hydroxylation during Testosterone Degradation by Resting Rhodococcus equi Cells

The conversion pathway of testosterone to androst‐4‐ene‐3,17‐dione and 9α‐hydroxy androstane metabolites, 9α‐hydroxyandrost‐4‐ene‐3,17‐dione and 9α,17β‐dihydroxyandrost‐4‐en‐3‐one was proposed for the ring degradation in steroids by a minimal liquid medium (NMMP)‐dispersed Rhodococcus equi ATCC 14887. The microorganism produced 9α‐hydroxy androstane metabolites from testosterone at high conversion ratio without the addition of ring degradation inhibitory agents. Several NMMP‐based media showed the similar effect on the microbial transformation, in which the respective molar yields of 9α‐hydroxyandrost‐4‐ene‐3,17‐dione and 9α,17β‐dihydroxyandrost‐4‐en‐3‐one were approx. 3 to 47% and approx. 3 to 11%, respectively, whereas nutrient broth, a rich medium, basically showed no accumulation. On the basis of this evidence, magnesium sulfate and casamino acids among the components of NMMP were found to compromise the determinant for the production of the 9α‐hydroxy androstane metabolites without appreciable decomposition of the steroid ring system.