Carboxypeptidase A Immobilization With Zeolite Imidazolate Framework For Enhancement Of Ochratoxin A Degradation Ability

Based on the wide application of metal organic frameworks in enzyme immobilization and catalysis,it has been applied to the field of enzymatic degradation of mycotoxins.ZIF-8,one of the Zeolitic Imidazolate Frameworks,was selected as immobilized material for loading and protecting of carboxypeptidase A(CPA),which could efficiently degrade ochratoxin A(OTA).The degradation activity of CPA before and after loading was compared under different conditions.The results showed that ZIF-8 material could effectively enhance the ability of CPA to degrade OTA and adapt to complex system conditions through loading.It was also proved that the compound could be applied to the degradation of OTA in fruit juice.In this paper,the loading of CPA by Zeolitic Imidazolate Frameworks-8 was studied and applied to the degradation of OTA.The TEM,FTIR,XRD and BET were characterized in the research process.Main research of this paper was as follows:(1)The CPA/ZIF-8 complex was prepared by coprecipitation method with zinc acetate and 2-methylimidazole.The product of CPA/PVP was prepared by modifying and protecting CPA with polyvinyl pyrrolidone(PVP).Furthermore,CPA/PVP complex was encapsulated in ZIF-8 by coprecipitation method after optimizing the synthesis conditions.The product was characterized and its biological activity was verified.Meanwhile,the optimum loading and loading rate of ZIF-8 on carboxypeptidase A(CPA)were investigated.The results showed that the mass ratio of ZIF-8 to CPA and CPA / PVP was 5.5: 1(mg / mg)and 1:46.6(mg / mg)under optimum loading conditions,respectively.(2)The enzyme activity and degradation rate of free CPA,CPA/ZIF-8 complex and CPA/PVP/ZIF-8 complex were studied from the aspects of temperature,pH,concentration of organic reagent,times of recycling and preservation time,so as to evaluate the degradation efficiency and stability of the complex.The results showed that the activity of the immobilized enzymes was higher than that of the free enzyme.Although the enzyme activity of CPA/PVP/ZIF-8 complex was lower than that of CPA/ZIF-8 complex under the optimal conditions,the comprehensive properties of CPA/PVP/ZIF-8 complex synthesized by adding PVP was better.Its tolerance to pH and temperature was wider than that of CPA/ZIF-8 complex,and its tolerance to organic reagents was higher.The activity of CPA/ZIF-8 complex was always higher than that of CPA/PVP/ZIF-8 complex in ten times of recycling.The longer the storage time was,the better the superiority of CPA/PVP/ZIF-8complex would be.(3)The standard of OTA was added to the fruit juice of actual sample juice,and the degradation experiments of OTA were carried out with free CPA and complex respectively to evaluate the degradation effect of complex on OTA.The degradation rate of OTA in watermelon juice by CPA/ZIF-8 complex was 94.49% at 45 min,while that by CPA/PVP/ZIF-8 complex was 76.75% at 24 h.