Bioconversion of 4-androstene-3,17-dione to androst-1,4-diene-3,17-dione by recombinant Bacillus subtilis expressing ksdd gene encoding 3-ketosteroid-Δ1-dehydrogenase from Mycobacterium neoaurum JC-12

The enzyme 3-ketosteroid-Δ1-dehydrogenase (KSDD), involved in steroid metabolism, catalyzes the transformation of 4-androstene-3,17-dione (AD) to androst-1,4-diene-3,17-dione (ADD) specifically. Its coding gene was obtained from Mycobacterium neoaurum JC-12 and expressed on the plasmid pMA5 in Bacillus subtilis 168. The successfully expressed KSDD was analyzed by native-PAGE. The activities of the recombinant enzyme in B. subtilis were 1.75 U/mg, which was about 5-fold that of the wild type in M. neoaurum. When using the whole-cells as catalysts, the products were analyzed by tin-layer chromatography and high-performance liquid chromatography. The recombinant B. subtilis catalyzed the biotransformation of AD to ADD in a percent conversion of 65.7% and showed about 18 folds higher than M. neoaurum JC-12. The time required for transformation of AD to ADD was about 10 h by the recombinant B. subtilis, much shorter than that of the wild-type strain and other reported strains. Thus, the efficiency of ADD production could be improved immensely. For industrial applications, the recombinant B. subtilis containing KSDD provides a new pathway of producing steroid medicines.

► The gene ksdd from Mycobacterium neoaurum JC-12 was successfully expressed in Bacillus subtilis 168.
► The enzyme activities in recombinant were about 1.75 ± 0.09 U/mg, about 5 folds higher than that of M. neoaurum JC-12.
► The recombinant can catalyze AD to ADD by the whole-cell transformation.
► The maximum transformation rate of AD reached 65.7% in 10 h by the recombinant while 25% in 132 h by M. neoaurum JC-12.