Effect of medium treatment on microbial degradation of sterols by Nocardia.

The rate of transformation of cholesterol by Nocardia sp. is affected by the culture medium composition as well as by the way it has been treated before inoculation. When 1% of peptone was sterilized separately and afterwards added to the basic medium, the transformation of cholesterol to bisnorchola-1,4-dienic acid, as well as further aerobic degradation, was accelerated by a factor of 2. If this enriched medium was kept at rest overnight, the rate of transformation was lowered to half. Heating of additional peptone together with a basic medium resulted only in a slight diminution of the transformation of the preceding 4-ene metabolite to the final 1,4-diene when compared with a normal basic medium without any additive.