Synthesis of fatty acid ethyl esters with conventional and microwave heating systems using the free lipase B from Candida antarctica

Abstract

Free Candida antarctica lipase B (Lipozyme, CALB L®) was used to produce fatty acid ethyl esters (FAEE) from refined soybean oil in solvent-free media using the conventional (CHS) and microwave (MHS) heating systems. Statistical analyses (95% confidence level) for both reaction products, FAEE and free fatty acids (FFA), were performed. An increase in ethanol:oil molar ratio decreased the catalytic performance of CALB L (p < .05). The best conditions using the microwave radiation were a molar ratio of ethanol:oil of 3:1, a water content of 20.3 wt.% and an enzyme loading of 3 wt.% and this resulted in a total ester content of 64.7% in 15 min, while the same condition using the conventional heating gave only 21.4%. Moreover, the reaction equilibrium was reached 16 times faster with microwave than with conventional heating. High ethanol:oil molar ratios had a negative effect on FAEE synthesis with both CHS and MHS, probably due to the partial inactivation of the enzymes. MHS improved the reaction performance of CALB L, but other process parameters will have to be optimized to enhance the resulting FAEE yields. The recovery and reuse of CALB L using a MHS was demonstrated. Hence, the use of microwave radiation under the conditions applied in this study was not detrimental to the catalytic performance of CALB L for at least one reuse.