Biocatalytic Conversion of Coconut Oil to Natural Flavor Esters Optimized with Response Surface Methodology

Lipase (Lipozyme TL IM)-mediated biocatalysis in a solvent-free system was effectively employed to convert coconut oil and fusel oil to flavor-active octanoic acid esters (mainly ethyl-, butyl-, isobutyl- and (iso)amyl octanoate). Response surface methodology based on five-level-three-factor central composite design was applied to investigate the effects of single and multiple interactive factors on the conversion. Results indicated that the studied independent parameters including reactant molar ratio, enzyme loading and shaking speed were all significant factors that affected the formation of octanoic acid esters during transesterification reaction. According to the developed polynomial model (R (2) = 0.947), the optimum transesterification conditions were determined as follows: molar ratio of 3.25:1 (alcohol/oil), enzyme loading of 16.7 % (wt%) and shaking speed of 160 rpm. Under the optimized reaction conditions an average conversion of 62.0 % was achieved which was in reasonable agreement with the predicted value of 64.1 % and about 9.4 mg of ethyl octanoate, 14.4 mg of isobutyl octanoate, 0.3 mg of butyl octanoate and 49.2 mg of (iso)amyl octanoate were produced per gram of coconut oil.