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.

Conversion of liposomal 4-androsten-3,17-dione by A. simplex immobilized cells in calcium pectate

Arthrobacter simplex ATCC 6946 free and immobilized cells were assayed for their ability to convert 4-androsten-3,17-dione (AD) to 1,4-androstadien-3,17-dione (ADD) in aqueous and liposomal media. Bioconversions were carried out in a 100 ml flask containing 25 ml of AD liposomal or aqueous medium for 3h, and AD concentrations ranging from 0.3 to 1.0 mM were tested. AD/ADD ratios in samples were determined by HPLC. Biotransformation of substrate entrapped in multilamellar vesicles (MLV) was demonstrated to be better than the corresponding free form. In the former case, 2h were necessary to completely bioconvert 1 mM AD. By contrast, 3h were needed to reach 50% bioconversion in (4%) ethanol medium containing 0.63 mM AD. The liposomal medium allows us to perform steroid conversions at high concentrations of AD, reusing immobilized cells in suitable conditions which are non-toxic for microorganisms.