Caffeic acid phenethyl ester(CAPE) is a natural and rare ingredient with several biological activities, but its industrial production using lipase-catalyzed esterification of caffeic acid(CA) and 2-phenylethanol(PE) in ionic liquids(ILs) is hindered by low substrate concentrations and long reaction time. To set up a high-efficiency bioprocess for production of CAPE, a novel dimethyl sulfoxide(DMSO)–IL co-solvent system was established in this study.The 2%(by volume) DMSO–[Bmim][Tf2N] system was found to be the best medium with higher substrate solubility and conversion of CA. Under the optimum conditions, the substrate concentration of CA was raised 8-fold,the reaction time was reduced by half, and the conversion reached 96.23%. The kinetics follows a ping-pong bi-bi mechanism with inhibition by PE, with kinetic parameters as follows: Vmax= 0.89 mmol · min-1· g-1, Km,CA=42.9 mmol · L-1, Km,PE= 165.7 mmol · L-1, and Ki,PE= 146.2 mmol · L-1. The results suggest that the DMSO cosolvent effect has great potential to enhance the enzymatic synthesis efficiency of CAPE in ILs.
Caffeic acid phenethyl ester(CAPE)is a rare,naturally occurring phenolic food additive.This work systematically reported fundamental data on conversion of caffeic acid(CA),yield of CAPE,and reactive selectivity during the lipase-catalyzed esterification process of CA and phenylethanol(PE)in ionic liquids(ILs).Sixteen ILs were selected as the reaction media,and the relative lipase-catalyzed synthesis properties of CAPE were measured in an effort to enhance the yield of CAPE with high selectivity.The results indicated that ILs containing weakly coordinating anions and cations with adequate alkyl chain length improved the synthesis of CAPE.[Emim][Tf2N]was selected as the optimal reaction media.The optimal parameters were as follows by response surface methodology(RSM):reaction temperature,84.0°C;mass ratio of Novozym 435 to CA,14︰1;and molar ratio of PE to CA,16︰1.The highest reactive selectivity of CAPE catalyzed by Novozym 435 in[Emim][Tf2N]reached 64.55%(CA conversion 98.76%and CAPE yield 63.75%,respectively).Thus,lipase-catalyzed esterification in ILs is a promising method suitable for CAPE production.
