Efficient synthesis of 15α-hydroxysteroid derivatives by Fusarium redolens

Microbial hydroxylation of steroids at specific positions offers a sustainable and selective strategy for the synthesis of pharmacologically valuable derivatives. Through microorganism screening, the strain Fusarium redolens exhibited the highest catalytic efficiency toward androst-4-en-3,17-dione (AD) and enabled the selective synthesis of 15α-hydroxylated derivatives. Under optimized transformation conditions, 10 g/L of AD was efficiently converted into 15α-hydroxy-AD or 11α,15α-dihydroxy-AD with high titers of 7.3 g/L and 7.1 g/L, respectively. The space-time yield (STY) for 15α-hydroxy-AD was 4.9 g/L/d, while the STY for 11α,15α-dihydroxy-AD was 1.1 g/L/d. By controlling the transformation time, 15α-hydroxy-AD and 11α,15α-dihydroxy-AD were obtained with isolated yields of 61.5% and 57.6%, respectively. The dihydroxylation proceeded via a sequential pathway, with initial C15 hydroxylation followed by subsequent C11 hydroxylation. Transcriptomic analysis suggested that both hydroxylation steps might be catalyzed by a cytochrome P450 CYP-1. Moreover, F. redolens displayed broad substrate tolerance toward various steroidal compounds, and several previously unreported 15α-hydroxysteroid derivatives were obtained, highlighting its potential as a versatile biocatalyst for expanding the diversity of hydroxylated steroids. These results demonstrate the promising application of F. redolens as an efficient biocatalytic platform for the selective functionalization of steroid molecules.