N-alkane Solvent-enhanced Biotransformation of Steroid DHEA by Beauveria bassiana as Biocatalyst
Richard Gonzalez
Department of Chemical and Biochemical Engineering, the University of Iowa 4133 Seamans Center, the University of Iowa, Iowa City, IA. 52242-1527, USA.
Felipe Nicolau
Department of Chemical and Biochemical Engineering, the University of Iowa 4133 Seamans Center, the University of Iowa, Iowa City, IA. 52242-1527, USA.
Tonya L. Peeples *
Department of Chemical and Biochemical Engineering, the University of Iowa 4133 Seamans Center, the University of Iowa, Iowa City, IA. 52242-1527, USA.
*Author to whom correspondence should be addressed.
Abstract
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.
Keywords: Beauveria bassiana, DHEA, steroid biotransformation, bio hydroxylations, biocatalytic reactions, microbial transformation