Solvent-free enzymatic transesterification of ethyl ferulate and monostearin: Optimized by response surface methodology

Abstract

In this study, enzymatic transesterification of ethyl ferulate (EF) and monostearin for feruloylated lipids production was investigated. Enzyme screening and the effect of feruloyl acceptors on the transesterification were also studied. Effects of reaction variables (reaction temperatures, enzyme load, and reaction time) on the transesterification were optimized using response surface methodology (RSM). The optimum conditions were as follows: reaction temperature 74°C, reaction time 23h, and enzyme load 20% (w/w, relative to the weight of substrates). Under these conditions, EF conversion was 98.3±1.1%, and the transesterification product was consisted of 19.2±2.1% glyceryl ferulate (FG), 32.9±1.9% diferuloylated glycerols (DFG), 36.6±2.2% feruloylated monoacylglycerols (FMAG), 9.1±2.0% feruloylated diacylglycerols (FDAG), and 0.5% ferulic acid (FA). Analysis of variance (ANOVA) showed that the regression equation was adequate for predicting EF conversion. The activation energies for hydrolysis to form FG+DFG and transesterification to form FMAG+FDAG were calculated as 22.45 and 51.05kJ/mol, respectively, based on Arrhenius law.