Bioconversion of sterol esters to steroid intermediates through Mycobacterium sp. fermentation

Sterol esters are naturally present in the by-product of edible oil processing, which is generally converted to sterols through saponification. Steroid intermediates play a crucial role in the production of pharmaceuticals, and these intermediates are predominantly synthesized via fermentation of sterol. This research explored the direct conversion of sterol esters into steroid intermediates using Mycobacterium sp. as a fermentation agent. The results demonstrated the successful identification of four steroid intermediates: androstenedione, 1,4-androstadienedione, 22-hydroxy-23,24-bisnorchol-4-ene-3-one, and 22-hydroxy-23,24-bisnorchol-1,4-dien-3-one, their individual intermediate concentrations were as follows: 144.2, 176.2, 30.8, 53.6 mg/L, with a total yield of 404.8 mg/L and a conversion rate of 29.5%. The optimized fermentation conditions included soybean oil at 3%, an initial pH of 7.0, a nitrogen source of 4.5 g/L, and hydroxypropyl-β-cyclodextrin of 15.0 g/L. Proteomic analysis revealed that sterol esters conversion pathway mirrors that of sterol, with an additional hydrolysis process. This work significantly expands our understanding of steroid intermediates production and offers valuable insights for the bioproduction industry.