N-alkane Solvent-enhanced Biotransformation of Steroid DHEA by Beauveria bassiana as Biocatalyst

Aims: The hydroxylation capacity of Beauveria bassiana was enhanced with n-alkane solvents, resulting in a selective and eco-friendly scheme for the synthesis of steroids. A biocatalytic system was engineered to augment the 11α-hydroxylation of dehydroepiandrosterone (DHEA) to valuable intermediates. Exposing and inducing cells into n-alkanes improved the synthesis of 11α-hydroxy derivatives.

Methodology and Results: Reactions were carried out with cells grown with n-dodecane (n-C12) and n-hexadecane (n-C16), resulting in 65%±6.3 conversion of DHEA to androstenediol (40.3%mM) and 3β,11α,17β-trihydroxyandrost-5-ene (22.8%mM), as determined by HPLC and NMR analyses. Experiments without the presence of n-alkanes resulted in 17% conversion of DHEA. Isolated products in this case included: Androstenediol (11.8%mM) and 3β,11α,17β-trihydroxyandrost-5-ene (4.78%mM). Results indicate that only the 3,17-hydroxy derivatives of DHEA undergo the 11α-hydroxylation pathway.

Conclusions: The appearance of the products suggests that the reduction of the C-17 ketone of DHEA is preceded by the 11α-hydroxylation reaction when n-alkanes are present. This differs from reports in the literature, which proposed the activation of an unfunctionalized carbon to 11α-hydroxy-17-oxo derivatives before obtaining a 3β,11α,17β-triol product.