Baker’s yeast-mediated asymmetric reduction of ethyl 3-oxobutanoate in deep eutectic solvents

[Display omitted] •The DES were evaluated for yeast-mediated reduction of ethyl 3-oxobutanoate.•Among tested DES the sugar containing ones possess the best biocompatibility.•Enantioselectivity is influenced by the water content in DES and/or DES itself.•The DES are promising candidates for green whole-cell biocatalysis. Cholinium-based deep eutectic solvents (DES) were evaluated as solvents for yeast-mediated reduction of ethyl 3-oxobutanoate to ethyl 3-hydroxybutanoate. The type of hydrogen bond donor and the amount of water present in DES considerably influenced the reaction yield. At water content of 50% (w/w), sugar and alcohol containing DES were the most appropriate solvents for the given reduction, with yields similar to those obtained in phosphate buffer (