The MLM -type structured lipids (SLs)were synthesized by lipozyme RM IM catalyzed transes-terification of soybean oil, caprylic acid (C8:0) and capric acid (Cl0:0) in solvent -free system. Capric acid content in the product was higher than caprylic acid with fast reaction rate when they reacted with soybean oil separately. There was no significant difference in the esterification between two reaction systems (system I: soybean oil with caprylic acid or capric acid, system II: soybean oil with the mixture of caprylic acid and capric acid) , and system II was selected for SLs synthesis. On the basis of the target product (27% caprylic acid and 10% capric acid) , the influences of molar ratio of caprylic acid to capric acid, molar ratio of substrates (molar ratio of fatty acid to soybean oil) , reaction temperature and Lipozyme RM IM dosage (based on the total mass of substrates) on the content of caprylic acid and capric acid in the finished product were discussed. In addition, the recycling times of the enzyme was studied. The optimal conditions were determined as follows: molar ratio of caprylic acid to capric acid 4:1, molar ratio of substrates 6:1, reaction temperature 55℃, Lipozyme RM IM dosage 7% and reaction time 4 h. Under the optimal conditions, the requirement of the target product could be reached after 12 batches (24 h of one batch).%采用Lipozyme RM IM脂肪酶为催化剂,在无溶剂体系中,催化大豆油和辛酸(C8∶0)、癸酸(C10∶0)进行酯交换反应制备MLM型结构脂.辛酸、癸酸单独与大豆油反应时,癸酸在产品中的含量比辛酸高并且反应速率快；辛酸、癸酸混合与大豆油反应同其分别单独与大豆油反应没有区别,因此选择辛酸、癸酸混合与大豆油进行酯交换反应.在目标产品(27％ C8∶0和10％ C10∶0)的基础上,探讨了辛酸与癸酸摩尔比、底物摩尔比(酸与大豆油摩尔比)、反应温度及Lipozyme RM IM添加量(基于底物总质量)对酯交换产品中辛酸、癸酸含量的影响,同时对脂肪酶可重复利用次数进行了考察.得到的最佳反应条件为:辛酸与癸酸摩尔比4∶1,底物摩尔比6∶1,反应温度55℃,Lipozyme RM IM添加量7％；在此条件下达到目标产品要求的反应时间仅需4h.在最佳反应条件下,利用该酶反应了12批次(每批次为24 h)后,结果仍可达到目标产品的要求.
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