초록
<P>Hydrophilic ionic liquids (ILs) were employed as green solvents to construct an IL-containing co-solvent system for improving the asymmetric reduction of 4-(trimethylsilyl)-3-butyn-2-one by immobilized <I>Candida parapsilosis</I> cells. Among 14 hydrophilic ILs examined, 1-(2′-hydroxyl)ethyl-3-methylimidazolium nitrate (C<SUB>2</SUB>OHMIM·NO<SUB>3</SUB>) was considered as the most suitable IL for the bioreduction with the fastest initial reaction rate, the highest yield and the highest product <I>e.e.</I>, which may be due to the good biocompatibility with the cells. For a better understanding of the bioreduction performed in the C<SUB>2</SUB>OHMIM·NO<SUB>3</SUB>-containing co-solvent system, the effects of several crucial variables were systematically investigated. The optimal C<SUB>2</SUB>OHMIM·NO<SUB>3</SUB> content, substrate concentration, buffer pH, co-substrate concentration and temperature were 10% (v/v), 3.0 mmol/L, 5.0, 98.1 mmol/L and 30°C, respectively. Under the optimal conditions, the initial reaction rate, the maximum yield and the product <I>e.e.</I> were 17.3 µmol/h g<SUB>cell</SUB>, 95.2% and >99.9%, respectively, which are much better than the corresponding results previously reported. Moreover, the immobilized cells remained more than 83% of their initial activity even after being used repeatedly for 10 batches in the C<SUB>2</SUB>OHMIM·NO<SUB>3</SUB>-containing system, exhibiting excellent operational stability.</P>