Resistance to androstanes as an approach for androstandienedione yield enhancement in industrial mycobacteria.

The resistance to androstandienedione (ADD) of industrial mycobacteria was demonstrated as a valuable approach to increasing ADD yield in sterol fermentations. Colonies growing at 1 mg/ml ADD in culture medium after nitrosoguanidine mutagenesis showed a differential behavior in respect to parentals in cholesterol biotransformation. In the presence of exogenous ADD, a substantial depletion of ADD production was observed in parental strains B3683 and Ex4, whereas it was unaffected, and even increased, in resistant colonies. An apparent reduction from ADD to androstandione and testosterone was also noticed. Furthermore, the ADD resistance phenotype may be related to the increase in steroid 1,2 dehydrogenase activity.