Production of malodorous steroids from androsta-5,16-dienes and androsta-4,16-dienes by Corynebacteria and other human axillary bacteria.

The biotransformations of a number of steroids, chiefly 5,6,16,17-tetradehydro-androstanes, are reported. The strains investigated were Corynebacteria sp. G38, G40, G41, B, Brevis sp. CW5 and Micrococcus sp. M-DH2. Corynebacterium sp. G41 proved remarkably efficient in effecting oxidative isomerisation of 5-ene-3-sterols into the corresponding 4-en-3-ones. The main biochemical reactions involved were oxidation at C-3; no reduction processes were observed. Conversions of 3beta-sterols into the C-3 oxo-steroids were high, but were correspondingly low for the 3alpha-sterol epimers. Androsta-4,16-dien-3-one and 5beta-androsta-16-en-3-one are crucial to the formation of malodour. The rate of formation of these compounds was measured over 72 h incubation periods using three substrates: androsta-5,16-dien-3beta-ol, androsta-4,16-dien-3beta-ol and androsta-5,16-dien-3-one. Induction studies of the transformation of the androsta-5,16-dien-3beta-ol into the very odorous compound androsta-4,16-dien-3-one showed that cells incubated with a mixture of antibiotics displayed the same extent of biotransformation as normal cells if the concentration of antibiotic was low (1, 3, 5 and 7 microg/ml), although at concentrations higher than 10 microg/ml, biotransformation yields were reduced. Pre-incubation with a 3beta-fluoro-steroid inhibited the formation of the odorous androsta-4,16-dien-3-one.