酶催化酸性油连续法制备脂肪酸乙酯

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

采用从嗜热真菌(Thermomyces lanuginosus)中提取的Lipozyme TL IM(Novozymes,Seoul, Korea)作为固定化脂肪酶,考察了其催化酸性油与乙醇反应制备脂肪酸乙酯的合成工艺。其中原料酸性油主要是由米糠油精制过程中产生的副产物(皂脚)的酸化获得。研究了水含量、反应温度和物料比对该工艺的影响,并对固定化脂肪酶重复利用过程中Lipozyme TL IM的相对活性进行了评价。研究结果表明:反应物中水含量对酯的收率影响很大,最佳含水量为4%;最佳反应温度是20℃,酸性油/乙醇的最佳物料比为1:4。在最佳工艺条件下,最大收率为92%,产物组成为92%脂肪酸乙酯、3%脂肪酸和5%酰基甘油。通过间歇性的乙醇洗涤工艺可将反应生成的甘油去除,并且脂肪酶在循环使用了27次后依然可以保持82%以上的相对活性。以平均4 h滞留时间计算,Lipozyme TL IM在不进行乙醇洗涤和进行乙醇洗涤两种工艺中的半衰期分别为39和45次循环。

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 Iipase derived from Thermomyces lanuginosus was purchased from Novozymes （Seoul, Korea）. The acid oil was prepared by the acidification of s0apstock formed as a byproduct 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 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.