Aureobasidium subglaciale F134 is a bifunctional whole-cell biocatalyst for Baeyer–Villiger oxidation or selective carbonyl reduction controllable by temperature

Abstract

The microbial production of either ester/lactones or enantio-enriched alcohols through Baeyer–Villiger oxidation or stereoselective reduction of ketones, respectively, is possible by using whole cells of A. subglaciale F134 as a bifunctional biocatalyst. The chemoselective pattern of acetophenone biotransformation catalyzed by these cells can be regulated through reaction temperature, directing the reaction either towards oxidation or reduction products. The Baeyer–Villiger oxidation activity of A. subglaciale F134 whole cells is particularly dependent on reaction temperature. Acetophenone was transformed efficiently to phenol via the primary Baeyer–Villiger product phenyl acetate at 20 °C after 48 h with 100% conversion. In contrast, at 35 °C, enantio-enriched ( S )-1-phenylethanol was obtained as the sole product with 64% conversion and 89% ee . In addition, A. subglaciale F134 cells also catalyze the selective reduction of various structurally different aldehydes and ketones to alcohols with 40% to 100% yield, indicating broad substrate spectrum and good enantioselectivity in relevant cases. Our study provides a bifunctional biocatalyst system that can be used in Baeyer–Villiger oxidation as well as in asymmetric carbonyl reduction, setting the stage for future work concerning the identification and isolation of the respective enzymes.