酶法合成sn-2位富含DHA的中长链结构脂Enzymatic synthesis of medium and long-chain structured lipids rich in docosahexaenoic acid at sn-2 position

采用两步酶法制备sn-2位富含DHA的中长链结构脂。首先，利用固定化脂肪酶Lipozyme 435催化DHA藻油发生醇解反应，溶剂萃取以获得富含DHA的单甘酯，再利用脂肪酶催化单甘酯和癸酸的酯化反应合成sn-2位富含DHA的中长链结构脂，并对中长链结构脂的组成进行分析。结果表明，最优酶法酯化反应条件为真空度0.05 MPa，单甘酯与癸酸摩尔比1∶ 3，固定化脂肪酶Lipozyme TL IM添加量为底物质量的8%，反应温度25 ℃，反应时间9 h。在最优条件下，酯化产物中甘油三酯（TAG）含量为96.55%，TAG脂肪酸组成中，DHA占总脂肪酸的40.04%，占sn-2位脂肪酸的72.15%。纯化的产品TAG中中长链结构脂占99.14%，含DHA的中长链结构脂占67.69%。 Medium and long-chain structured lipids (MLSL) rich in docosahexaenoic acid (DHA) at sn-2 position were prepared by a two-step enzymatic method. In the first step, Lipozyme 435 was used to catalyze the alcoholysis of DHA oil, and monoglyceride (MAG) rich in DHA was obtained by solvent extraction. Then the lipase-catalyzed esterification of MAG and capric acid (CA) was employed to obtain MLSL rich in DHA at sn-2 position. The results showed that the optimal enzymatic esterification conditions were obtained as follows: vacuum 0.05 MPa, Lipozyme TL IM dosage 8%(based on the mass of substrates), ratio of MAG to CA 1∶ 3, reaction time 9 h, and reaction temperature 25 ℃. Under the optimal conditions, the triglycerides (TAG)content in the product was 96.55%, among which the DHA accounted for 40.04% of the total fatty acids and 72.15% of the sn-2 fatty acids. In the purfied product of TAG, the content of total MLSL was 99.14% and the MLSL with DHA accounted for 67.69%