Mycobacterium phlei mutants convert sterols to androsta-1,4-diene-3,17-dione and androsta-4-ene-3,17-dione

A process for preparing a mixture of androsta-1,4-diene-3,17-dione and androst-4-ene-3,17-dione which comprises cultivating Mycobacterium phlei NRRL B-8154 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 chain and recovering androsta-1,4-diene-3,17-dione and androst-4-ene-3,17-dione.

A process for preparing a mixture of androsta-1,4-diene-3,17-dione and androst-4-ene-3,17-dione which consists of cultivating a mutant microorganism of Mycobacterium phlei, 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 androsta-1,4-diene-3,17-dione and androst-4-ene-3,17-dione 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 and recovering androsta-1,4-diene-3,17-dione and androst-4-ene-3,17-dione.