Process for preparing 9.alpha.-hydroxyandrostenedione

A process for preparing 9.alpha.-hydroxyandrostenedione which comprises cultivating Mycobacterium fortuitum NRRL B-8119 in an aqueous nutrient medium under aerobic conditions in the presence of a mixture of two or more steroids wherein each steroid contains from 2 to 10 carbon atoms, inclusive, in the 17-alkyl side chain.

A process for preparing 9.alpha.-hydroxyandrostenedione which comprises cultivating a mutant microorganism selected from the group consisting of Arthrobacter, Bacillus, Brevibacterium, Corynebacterium, Microbacterium, Protaminobacter, Serratia, and Streptomyces, said mutant being characterized by its ability to selectively degrade steroids having 17-alkyl side chains of from 2 to 10 carbon atoms, inclusive, and accumulate 9.alpha.-hydroxyandrostenedione in the fermentation beer, in an aqueous nutrient medium under aerobic conditions in the presence of a steroid containing from 2 to 10 carbon atoms, inclusive, in the 17-alkyl side chain.