Microbial Transformation of Sterols

Abstract

Cholesterol decomposing ability of 1589 microbial strains was examined. Two hundreds and thirty six strains from actinomycetes, bacteria, molds, and yeasts were found capable of oxidizing cholesterol into cholestenone. Cholesta-1,4-dien-3-one was produced by 5 strains of Streptomyces. The complete decomposition of cholesterol molecule was observed in the genera: Arthrobacter, Bacillus, Brevibacterium, Corynebacterium, Microbacterium, Mycobacterium, Nocardia, Protaminobacter, Serratia, and Streptomyces. α,α′-Dipyridyl and arsenite inhibited decomposing enzymes giving rise to cholestenone, cholesta-1,4-dien-3-one, and an intermediate probably devoid of the sterol side chain. Selective cleavage of the side chains of various sterols at C-17, giving rise to androsta-1,4-diene-3,17-dione (ADD), occurred in the presence of α,α′-dipyridyl by microorganisms of the following genera: Arthrobacter, Bacillus, Brevibacterium, Corynebacterium, Microbacterium, Mycobacterium, Nocardia, Protaminobacter, Serratia, and Streptomyces. The degradation pathway of cholesterol, for example, was shown as follows: Other sterols such as campesterol, β-sitosterol, stigmasterol and 7-dehydrocholesterol were degraded by the same sequence. The pathway exemplified in cholesterol is considered to be the general degradation pathway of sterols by their decomposing microorganisms. It was further demonstrated that ADD thus formed from sterols was converted into 3-hydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione.