聚羟基烷酸酯酶降解动力学研究

研究了羟基丁酸 羟基戊酸共聚物 (PHBV)在脂肪酶中的降解行为 ,用滴定法测定降解速度并进行酶促反应动力学研究 .探讨了降解速度与酶浓度和底物浓度的数学关系和Michaelis Menten常数 ,从实验上和理论上证实了PHBV的物理形态和几何尺寸对酶降解过程的影响 ,以及实验数据与非均相动力学模型的拟合

KINETIC STUDY FOR ENZYMATIC DEGRADATION OF POLYHYDROXYALKANOATES

The microbial polyesters have attracted attention as an biodegradable materials for a wide range of agricultural,marine and medical applications.It is important to investigate the biodegradation behavior and kinetics of the biodegradable reaction.Traditional Michaelis-Menten kinetics was originally derived for homogeneous reactions in which both the enzyme and the substrate are soluble.The enzymatic degradation of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) is a heterogeneous reaction,because PHBV is an insoluble substrate,and the kinetic relation needs to be altered to fit it.In this paper,the kinetics of the enzymatic degradation behavior of PHBV was studied.It is well known that the enzymatic hydrolysis of water-insoluble film of PHB by depolymerases produces water-soluble products composed of monomers and dimers of R-3-hydroxybutyric acid.The rates of degradation were determined by the titrimetric methods,which are quantitative by directly measuring the acid groups formed as a result of ester bond hydrolysis.The degradation of PHA samples with different shapes and morphology was studied.The kinetic analysis revealed that the degradation reaction exponentials of PHBV powder,solution-casting film and solution-casting-leaching porous film were different,which were inconsistent with classical enzymatic kinetics.The variations of kinetics curves depended on the concentration of enzyme and PHA.A heterogeneous kinetics treatment was derived to describe the relationship of degradation rates with enzyme concentrations and substrates.The influence of PHBV physical morphology on their degradation was also investigated.The results show that the specific surface area and the shape of PHA samples effect the adsorption and combination of enzyme to substrates and finally conduce to the changes of enzymatic degradation process and the rate of degradation of PHBV.