Ionic liquids improve the selective synthesis of hydrophilic glyceryl ferulates by the enzymatic transesterification of ethyl ferulate with monostearin: Comparison with organic solvents

Abstract

Glyceryl ferulates (GMF + GDF, combination of glyceryl monoferulate and glyceryl diferulate), and feruloylated acylglycerols (FMAG + FDAG, combination of feruloylated monoacylglycerols, and feruloylated diacylglycerols) are hydrophilic and lipophilic derivatives of ferulic acid (FA), which can be used as antioxidants and UV absorbers in food and other fields. In this study, the effect of ionic liquids (ILs) and organic solvents on the enzymatic transesterification of ethyl ferulate (EF) with monostearin was investigated. The effects of reaction time, temperature, and enzyme load on EF conversion and reaction selectivity were also evaluated and optimized using response surface methodology. Among ILs tested, high EF conversion (98.4 ± 0.5%), and reaction selectivity for GMF + GDF (0.81) were obtained in [Emim]TF2N; and for organic solvents tested, EF conversion (72.7 ± 1.5%) and reaction selectivity (0.75) were achieved in n‐hexane. Results also showed that, compared with n‐hexane, [Emim]TF2N can improve the selective synthesis of GMF + GDF, and [Emim]TF2N also shows significant protection on the enzyme inactivation at high temperature (90°C). The activation energies (Ea) of hydrolysis to form GMF + GDF and transesterification to form FMAG + FDAG were 51.98 and 43.49 kJ/mol in [Emim]TF2N, 72.35, and 53.11 kJ/mol in n‐hexane, respectively. , , and in [Emim]TF2N were 0.01, 0.19 mol/L, and 4.13 × 10−4mol/(L · min), respectively.Practical applications: In this work, FMAG + FDAG and GMF + GDF were prepared by enzymatic transesterification of EF with monostearin. During the reaction, the competitive reaction of the hydrolysis of monostearin to form hydrophilic GMF + GDF and the transesterification of monostearin and EF to form lipophilic FMAG + FDAG take place in parallel. The effect of ionic liquids (ILs) and organic solvents on the competitive reaction was investigated. Compared with organic solvent (n‐hexane), IL ([Emim]TF2N) is apt to the formation of hydrophilic GMF + GDF; and [Emim]TF2N shows remarkably protective effect on the inactivation of enzyme at high temperature up to 90°C than that (65°C) of n‐hexane. This study can give information about the influence of different reaction media on the enzymatic transesterification and reaction selectivity.Enzymatic transesterification of ethyl ferulate (EF) with monostearin to produce hydrophilic glyceryl monoferulate (GMF)+glyceryl diferulate (GDF) and lipophilic feruloylated monoacylglycerols (FMAG)+feruloylated diacylglycerols (FDAG) in ionic liquids or organic solvents.