微波辐射对酶促合成甘油酯位置选择性的影响

Effect of Microwave Irradiation on 1,3-Specificity of Novozyme 435 in Glyceride Synthesis

研究了微波辐射和常规加热下脂肪酶Novozyme 435催化甘油与n-辛酸的反应。在2种加热模式下,n-辛酸与甘油反应的初速度随着反应温度（50-75℃）的升高而加快;同样条件下,微波辐射下的反应初速度略高于常规加热条件下的。微波辐射的产物中的2-单甘酯和1,2-二甘酯的含量增加,但仍明显低于1-单甘酯和1,3-二甘酯的含量,即微波辐射并未根本改变脂肪酶的1,3-专一性;但实验条件下微波辐射均削弱了Novozyme 435的1,3-专一性：微波辐射反应产物中1-单甘酯与2-单甘酯的量比由常规加热下的26.9-43.4下降为16.2-40.4,其中1,3-二甘酯与1,2-二甘酯的量比亦由10.5-19.6降为7.6-15.3。

Enzymatic esterification of glycerol and n-caprylic acid was studied under the catalysis of Novozyme 435 by means of microwave irradiation and conventional heating. Microwave irradiation increased initial reaction rate more than conventional heating did, and the initial reaction rate increased with increasing reaction temperature for both heating modes at 50 - 75 ℃. The contents of 2-monoglyceride and 1,2-diglyceride in the microwaved reaction mixture were higher than those in thermo heated reaction mixture, but the irradiation didn＇t change the lipase＇s 1, 3-specificity. In general the microwave irradiation weakens the 1,3-specificity of enzymatic glycerol esterification of Novozyme 435 and the weakening effect is related to the reaction conditions. By conventional heating, the molar ratios of 1-monoglyceride to 2-monoglyceride（1-MG/2-MG） in the product were 26. 9-43.4, and the ratio of 1,3-diglyceride to 1,2-diglyceride （1,3-DG/1,2-DG） were 10. 5 - 19.6; whereas by microwave irradiation, the 1-MG/2-MG were decreased to16. 2 -40.4 and the 1,3- DG/1,2-DG became 7.6 - 15.3.