Whole-Cell Biocatalysis in Deep-Eutectic-Solvents/Aqueous Mixtures

Whole-cell biocatalysis with the use of baker's yeast is demonstrated in different mixtures of water with deep eutectic solvents (DESs; choline chloride/glycerol, 1:2 mol/mol). Enantioselective ketone reduction is observed for long reaction times (>200 h), which suggests that the whole cells remain stable in these neoteric solvents. By changing the proportion of the DES added, a complete inversion of enantioselectivity is observed, from approximately 95% enantiomeric excess (ee) (S) in pure water to approximately 95% ee (R) in the pure DES. Presumably, some (S)-oxidoreductases present in baker's yeast are inhibited by DESs.