Synthesis of Fatty Acid Ethyl Ester from Acid Oil in a Continuous Reactor via an Enzymatic Transesterification

Synthesis of a fatty acid ethyl ester via the lipase-catalyzed transesterification of acid oil and ethanol was investigated in a continuous reactor. Lipozyme TL IM was employed as the immobilized lipase. This immobilized lipase derived from Thermomyces lanuginosus was purchased from Novozymes (Seoul, Korea). The acid oil was prepared by the acidification of soapstock formed as a by-product during the refining of rice bran oil. The parameters investigated were water content, temperature, and molar ratio of substrates. The relative activity of Lipozyme TL IM was assessed during the repeated use of the immobilized lipase. The water content of the substrate had a considerable effect on the yield and the optimum water content was 4 %. The optimum temperature and molar ratio of acid oil to ethanol were 20 °C and 1:4, respectively. The maximum yield of approximately 92 % was achieved under the optimum conditions. The corresponding compositions were 92 % fatty acid ethyl esters, 3 % fatty acids, and 5 % acylglycerols. When glycerol formed during the reaction was removed by intermittent washing with ethanol, the relative activity of lipase was maintained over 82 % for a total usage of 27 cycles. For a mean residence time of 4 h, the half-life times of Lipozyme TL IM on the control (unwashed) and treatment (washed) were 39 and 45 cycles, respectively.