Immobilization of Enzyme on Hydrophobic Room Temperature Solid-Phase Ionic Liquids and Its Use for Biocatalytic Transesterification in Organic Solvent: Remarkably Enhanced Activity of Lipase

Abstract

secondary alcohol in an organic solvent, resulting in an about 2–11-fold increase in enantioselectivity compared to that of a nonimmobilized enzyme. 14 Recently, we found that an enzyme in buffer solution can be immobilized on bulk aggregates of hydrophobic RTSPILs based on alkyl imidazolium (or pyridinum) cation and PF6 anion, which have not functional moieties such as methacryloyl group, via ionic attraction with surface of enzyme. Herein, we further report the activity of an enzyme immobilized on various RTSPILs for the transesterification of sec-phenethyl alcohol with vinyl acetate in an organic solvent (Scheme 1). Interestingly, we found that the RTSPILimmobilized enzyme exhibited an around two-orders-ofmagnitude increase in catalytic activity and could be reused in an organic solvent. The ten RTSPILs with PF6 anion (1-10) used in this study were prepared according to the procedure reported previously: 1-ethyl-3-methylimidazolium ([EMIM], 1, mp 60 o C), 1-(3-phenylpropyl)-3-methyl-imidazolium ([PPMIM], 2, mp 52 o C), 1-(3-phenylpropyl)-2,3-dimethylimidazolium ([PPDMIM], 3, mp 116 o C), 1-dodecyl-3-methylimidazolium ([C12MIM], 4, mp 50 o C), 1-dodecyl-2,3-dimethylimidazolium ([C12DMIM], 5, mp 69 o C), 1-ethyl-4-methylpyridinum ([E4MPy], 6, mp 78 o C), 1-butyl-4-methylpyridinum ([B4MPy], 7, mp 43 o C), 1-(3-phenylpropyl)-4methylpyridinum ([PP4MPy], 8, mp 80 o C), and 1-(3-phenylpropyl)-3-methylpyridinum ([PP4MPy], 9, mp 74 o C).