基于硅胶吸附甘油的酶法甘油解制备甘油二酯油工艺Preparation of diacylglycerol oil by enzymatic glycerolysis based on glycerol absorption onto silica gel

为高效制备甘油二酯（DAG）油，以山茶油为原料，采用酶法甘油解制备DAG油，探究添加硅胶对甘油进行吸附处理和脂肪酶种类对粗产物中DAG含量的影响，在此基础上通过单因素实验优化基于硅胶吸附甘油的酶法甘油解制备DAG油工艺条件，并采用分子蒸馏对产物进行纯化，测定纯化前后产物脂质组成。结果表明：甘油经硅胶吸附后，Lipozyme RM IM和Lipozyme TL IM在甘油解反应中的催化合成DAG性能显著提升，而Novozym 435的催化合成DAG性能降低，在硅胶吸附后的甘油解体系中，Lipozyme RM IM是制备DAG油的最佳脂肪酶；酶法甘油解制备DAG的最优工艺条件为硅胶与甘油质量比1∶ 1、山茶油与甘油物质的量比1∶ 1、Lipozyme RM IM添加量8%（基于山茶油质量）、反应温度60 ℃、反应时间6 h，在此条件下甘油解粗产物中DAG含量为53.6%，游离脂肪酸含量为3.5%；经分子蒸馏纯化后，纯化产物中DAG含量达到60.0%，游离脂肪酸含量降至1%以下。综上，甘油经硅胶吸附后可显著提升某些脂肪酶在甘油解反应中的催化性能，降低产物中游离脂肪酸含量。 To effectively prepare diacylglycerol (DAG) oil, enzymatic glycerolysis was employed to prepare DAG oil with camellia seed oil as material. The effect of silica gel addition to adsorb glycerol and lipase type on the DAG content in the crude product was investigated. On this basis, the process conditions for preparing DAG oil by enzymatic glycerolysis based on silica gel adsorption of glycerol were optimized through single-factor experiments. Molecular distillation was used to purify the crude product, and the lipid composition of the product before and after purification was determined. The results showed that the catalytic performances of Lipozyme RM IM and Lipozyme TL IM in the glycerolysis were significantly enhanced after the glycerol adsorbed onto silica gel. However, the catalytic performance of Novozym 435 for DAG synthesis was reduced. In the glycerolysis system after silica gel adsorption, Lipozyme RM IM was the best lipase for preparing DAG oil. The optimum enzymatic glycerolysis conditions were obtained as follows: mass ratio of glycerol to silica gel 1∶ 1, molar ratio of camellia seed oil to glycerol 1∶ 1, Lipozyme RM IM dosage 8%(based on the mass of camellia seed oil),reaction temperature 60 ℃ and reaction time 6 h. Under these conditions, DAG content in the crude product reached 53.6% and the content of free fatty acid was 3.5%. The DAG content increased to 60.0%, and the content of free fatty acid decreased to lower than 1% after purification of crude product by molecular distillation. In conclusion, glycerol adsorbed by silica gel can significantly enhance the catalytic performance of certain lipases in glycerolysis and reduce the contents of free fatty acids in the products.