Biocatalytic anti-Prelog stereoselective reduction of 4′-methoxyacetophenone to (R)-1-(4-methoxyphenyl)ethanol with immobilized Trigonopsis variabilis AS2.1611 cells using an ionic liquid-containing medium

The biocatalytic anti-Prelog enantioselective reduction of 4-methoxyacetophenone (MOAP) to (R)-1-(4-methoxyphenyl)ethanol {(R)-MOPE} using immobilized Trigonopsis variabilis AS2.1611 cells was, for the first time, successfully conducted in an ionic liquid (IL)-containing system. Of all the tested ILs, the best results were observed in the co-solvent system containing 1-(2-hydroxyl)ethyl-3-methylimidazolium nitrate (C2OHMIM·NO3), which showed the good biocompatibility with the cells and only a moderate increase in the cell membrane permeability. It was found that the optimal content of C2OHMIM·NO3, buffer pH, reaction temperature, substrate concentration and shaking rate were 2.5% (v/v), 8.5, 30 °C, 15 mM and 200 r min-1, respectively. Under these optimized conditions, the initial reaction rate, the maximum yield and the product e.e. were 7.1 mol h-1, 97.2% and >99%, respectively, which are much higher than the corresponding values previously reported. The presence of C2OHMIM·NO3 in aqueous buffer allowed the cells to tolerate relatively high temperatures and substrate concentrations compared with those in aqueous buffer without IL. Additionally, the immobilized cells manifested excellent operational and storage stability. Hence, the whole-cell biocatalytic anti-Prelog reduction of MOAP to (R)-MOPE on a preparative scale in the presence of C2OHMIM·NO3 appears to be a promising and competitive reaction