The Preparation Of Metal Organic Framworks And Its Application In The Immobilization Of Microcystins Degrading Enzyme

With the continuous development of human society,the environmental problems have become increasingly prominent.The shortage of water resources has become a se-rious factor that restricts the economic and social development in our country.In recent years,the frequent outbreak of cyanobacteria bloom has seriously affected the safety of drinking water.On the one hand,the large population of cyanobacteria multiply,resulting in the decrease of dissolved oxygen in the water,the deterioration of water quality and the massive death of aquatic organisms.On the other hand,after the growth or death of cyanobacteria Will release a large number of algae toxins,these toxins will seriously af-fect the safety of human and animal life,long-term consumption of drinking water con-taining algae toxin will make the heart,kidney,liver,reproductive disease,eventually contributing to the occurrence of cancer.Algae toxin degrading enzyme is an enzyme that degrades algal toxins efficiently.However,enzymes are very sensitive to the external en-vironment and must be operated under mild conditions.In strong acid,alkali,high tem-perature and other conditions will make the enzyme denaturation,thereby reducing the enzyme activity.Application of immobilized enzyme technology to improve the enzyme stability and reusability,making the enzyme in large-scale industrial use.In the immobi-lized enzyme process,the immobilization of the carrier,the method is particularly im-portant.In this paper,a new nanomaterial metal-organic framework for the immobiliza-tion of the carrier,introduces the status of the different methods of immobilization and its application,provide a reference for further research and rational use of immobilized en-zymes.This article mainly from the enzyme immobilization has done the following re-search:First,Preparation and characterization of immobilized enzyme(MIL-101-NH2@MCDE)Nanometer multi-functional material MIL-101-NH2 was prepared by solvothermal method.The materials were characterized by SEM,FTIR and TGA.Algae toxin degrad-ing enzyme(MCDE)was immobilized on the surface of metal organic framework(MOF)by electrostatic attraction.The material exhibits high immobilization efficiency(98.6%)and the entire fixation process will be completed in just 2 minutes.The new nanocatalyst immobilized enzyme(MIL-101-NH2@MCDE)greatly exceeds free MCDE in terms of thermal stability and pH stability,and has reusability and storage stability.Second,Preparation and characterization of immobilized enzyme(UiO-66-NH2@MCDE)UiO-66-NH2 was prepared by solvothermal method.The successful synthesis of UiO-66-NH2 was confirmed by SEM,XRD,FTIR and TGA.The results showed that the amino group on the surface of the material can be covalently bound to the carboxyl group of the enzyme so that the algal toxin degrading enzyme(MCDE)can be effectively im-mobilized on the MOF.The material has a high immobilization efficiency(95.5%)and can be immobilized in less than 5 minutes.Immobilized enzyme(UiO-66-NH2@MCDE)has better thermal stability and pH stability than free enzyme.UiO-66-NH2@MCDE re-tained 97.5%activity after 1 hour incubation at 45? while free MCDE retained about 88.7%activity under the same conditions.After 4 times of repeated use,the relative en-zyme activity of immobilized enzyme UiO-66-NH2@MCDE reached over 80%.Third,Preparation and characterization of immobilized enzyme(ZIF-8@MCDE)The immobilized enzyme(ZIF-8@MCDE)was prepared by one-pot method in aqueous system.The immobilized enzyme(ZIF-8@MCDE)In nanopore channels,mild conditions provide the prerequisite for the maintenance of enzyme activity during the preparation of immobilized enzymes.The structural and functional characterization indi-cates that the introduction of enzyme molecules does not change the pore structure of the ZIF-8 material.Compared with the former two methods,the introduction of enzyme molecules into the whole framework material not only increases the immobilization of enzyme,but also mainly increases the catalytic efficiency of the immobilized enzyme by utilizing the high specific surface area of the ZIF-8 material,The rigid shielding provided by the three-dimensional pores effectively improves the stability of the enzyme under extreme reaction conditions.