脂肪酶催化合成异维生素C棕榈酸酯及其动力学

Kinetics of formation of isoascorbyl palmitate by lipase-catalyzed esterification

对来自于Candidasp.99-125的脂肪酶在有机溶剂中催化合成异维生素C棕榈酸酯反应进行了研究。结果表明,初始反应速率v0与棕榈酸和异维生素C摩尔浓度的比值有关。v0随着cpal/ciso的增大先是增大,至cpal/ciso值接近15时v0基本不变。另外,考察了溶剂、温度、转速、酶量、初始水含量对酶促反应的影响。研究表明该反应的反应机理很好的符合乒乓反应模型,确定了最大反应速率vm和米氏常数k′m,由双倒数曲线可以得到,vm=5.86μmol/(min.g),k′m=0.092 mmol/L。

The kinetics of the esterification reaction of isoascorbic acid with palmitic acid catalyzed by lipase from Candida sp.99-125 have been studied in different organic solvents.The results showed that the initial rate v0 is related to the ratio of molar concentrations,cpal/ciso.The value of v0 initially increases with cpal/ciso and then reaches a maximum and remains constant at that value as cpal/ciso is increased further.The highest initial rate was obtained in acetone as solvent.The effects of varying temperature,shaking speed,initial water content and lipase concentration on the initial rate were investigated.On the basis of the kinetic model obtained,the reaction mechanism can be described by a Ping-Pong model with vm=5.686 μmol/(min·g),and k′m=0.092 mmol/L.