Enzymatic phenethyl octanoate synthesis: lipase selection and reaction optimization by response surface methodology

Abstract

Phenethyl octanoate (PEO) is a natural flavour compound found in rum, spirits and wine. Six commercial and non-commercial lipase preparations were screened for 2-phenethyl octanoate synthesis activity, the most active enzymes were Lipozyme® RM IM and Pala­tase® 20000 L (immobilized and soluble Rhizomucor miehei lipases). Three substrates acyl-donors (octanoic acid, glyceryl trioctanoate and coconut oil) and two solvents (hexane and tert-butanol) were compared in the synthesis reactions. Higher conversions and reaction rates were observed in hexane using immobilized enzyme. The optimal reaction conditions determined by means of Response Surface Methodology (RSM) were as follows: reaction time 120 minutes, temperature of 30 °C, 0.8 M and 0.267 M concentrations of 2-phenyl­ethanol and glyceryl trioctanoate, respectively, 7% concentration of enzyme Lipozyme® RM IM, resulting in 80% reaction conversion. The phenylethyl ester synthesis reaction was transferred to a solvent-free system using a natural substrate coconut oil.