无溶剂及微乳液体系中脂肪酶催化红花油水解的动力学

 在无溶剂及二(2-乙基己基)丁二酸酯磺酸钠(AOT)/异辛烷/磷酸盐缓冲液微乳液体系中,研究了黑曲霉脂肪酶催化红花油水解反应的动力学. 结果表明,无溶剂及微乳液体系中反应的活化能分别为32.205和7.391 kJ/mol. 酶在无溶剂体系中的热稳定性高于微乳液中. 无溶剂及微乳液体系中的表观米氏常数分别为0.135和0.101 mol/L. 在两种体系中,乙醇对水解反应的抑制作用均为竞争性可逆抑制,且均在底物浓度大于0.819 mol/L时出现底物抑制现象. 结合胶团催化理论和酯键水解机理对两种体系中酶水解性能的差异进行了解释.

Kinetics of Lipase-Catalyzed Safflower Oil Hydrolysis in Solvent-Free and Microemulsion Media

The kinetics of safflower oil hydrolysis catalyzed by a lipase from Aspergillus niger was investigated in a solvent-free medium and an AOT/isooctane/phosphate buffer microemulsion medium.The activation energy of the reaction was calculated from the Arrhenius plot to be 32.205 and 7.391 kJ/mol in the solvent-free medium and the microemulsion medium,respectively.The denaturation of the lipase in microemulsion was faster than that in the solvent-free medium.The apparent Michaelis constant K_m was 0.135 mol/L in the solvent-free medium and 0.101 mol/L in the microemulsion medium.The experiment indicated that the inhibition of alcohol towards the lipase was reversible and competitive in both the solvent-free medium and the microemulsion medium.In addition,the inhibition by substrate appeared in these two systems when the substrate concentration exceeded 0.819 mol/L.The micelle catalysis theory and ester bond hydrolysis mechanism were used to explain the difference of lipase-catalyzed oil hydrolysis in the solvent-free medium and the microemulsion medium.