Lipase-catalyzed enantioselective esterification of racemic ibuprofen coupled with pervaporation

Enantioselective esterification of racemic ibuprofen catalyzed by Candida rugosa lipase in isooctane was coupled with pervaporation of water by-produced by the reaction. A cross-linked poly(vinyl alcohol) (PVA) membrane and commercially available perfluorinated membranes (Nafion® 117 and Nafion® NE 450) were tested for selective removal of water from the reaction mixture. Effects of the reaction temperature, the concentration and nature of alcohol on the reaction rate and enantioselectivity were investigated systematically with and without pervaporation. The PVA pervaporation membrane appeared to be more suitable for the enantioselective esterification of ibuprofen than the Nafion® membranes. The highest initial rate and enantiomeric ratio were obtained at an equimolar ratio of 1-octanol/1-decanol to racemic ibuprofen regardless of the application of pervaporation. Raising the reaction temperature from 30 to 60 °C increased the reaction rate, but decreased the enantiomeric ratio. However, in most cases, the concomitant pervaporation operation brought about the enhancement of the reaction rate and the enantiomeric ratio. This was thought to be due to the selective removal of excess water by pervaporation, leading to the reduction of undesirable effects on the enzymatic reaction by the excess water.