Efficient enantioselective hydrolysis of d,l-phenylglycine methyl ester catalyzed by immobilized Candida antarctica lipase B in ionic liquid containing systems

Immobilized Candida antarctica lipase B (Novozym 435)-catalyzed enantioselective hydrolysis of d,l-phenylglycine methyl ester to enatiopure d-phenylglycine was successfully conducted in the systems with ionic liquids (ILs). Novozym 435 exhibited excellent activity and enantioselectivity in the system containing the IL BMIM·BF4 compared to several typical organic solvents tested. It has been found that the cations and, particularly, the anions of ILs have a significant effect on the reaction, and the IL BMIM·BF4, which shows to be the most suitable for the reaction, gave the highest initial rate and enantioselectivity among various ILs examined. The reaction became much less active and enantioselective in the systems with BMIM·HSO4. Also, it was noticed that the enzymatic hydrolysis was strongly dependent on BMIM·BF4 content in the co-solvent systems and the favorable content of the IL was 20% (v/v). Of the assayed four co-solvents and phosphate buffer, the lowest apparent Km and activation energy, and the highest Vmax of the reaction were achieved using 20% (v/v) BMIM·BF4 co-solvent with phosphate buffer. Additionally, various influential variables were investigated. The optimum pH, substrate concentration, reaction temperature and shaking rate were 8.0, 80 mM, 25–30 °C and 150 rpm, respectively, under which the initial rate, the residual substrate e.e. and the enantioselectivity were 2.46 mM/min, 93.8% (at substrate conversion of 53.0%) and 38, respectively. When the hydrolysis was performed under reduced pressure, the initial rate (2.64 mM/min) and the enantioselectivity (E = 43) were boosted.