Optimization of the Phytosterol Bioconversion into the 17β-Reduced C19-Steroids by a Transgenic Mycolicibacterium neoaurum VKM Ac-1816D Strain

A one-step biotechnological method based on the microbial conversion of plant sterols using a transgenic strain originated from the Mycolicibacterium neoaurum strain, co-expressing genes encoding 17β-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus and glucose-6-phosphate dehydrogenase from the bacterium Mycobacterium tuberculosis under the control of the acetamide-regulated promoter [Pami], allows for the phytosterols conversion with accumulation of the valuable 17β-reduced C19-steroids: testosterone and its ∆1-analogue. Optimization of bioconversion conditions for phytosterols at a high concentration (20 g/L) using a transgenic M. neoaurum-based strain, including the selection of solubilizing agents and optimization of inducer and glucose supplementation regimes, led to an increase in testosterone yield from 5.3 to 6.9 g/L.