Factors limiting the microbial conversion of sterols to 17-ketosteroids in the presence of metal chelate inhibitors.

Bioconversion of sterols to 17-ketosteroids by an Arthrobacter species occurred in the presence of hydrophobic metal-chelating agents but the production of 17-ketosteroids (17-KS) was seriously limited by the rapid loss of the viability of cells in the presence of these inhibitors. Besides, the conversion was inhibited by 17-KS at concentrations of 500 ppm or more. The 17-KS formed consisted exclusively of 1,4-androstadiene-3,17-dione (ADD) and 4-androstene-3,17-dione (AD) and these were found in the extracellular medium predominantly in bound form or as molecular aggregates which may limit their accumulation. It was concluded that enhanced production of 17-KS could be achieved by protecting the viability of cells and by removing the steroid metabolites from the site of inhibition.