Preparation Of Metal-Coordinated Nano-Materials For Enzyme Immobilization And Cascade Reaction System Construction

Adsorption is deemed as a facile yet efficient method for enzyme immobilization with well-preserved biocatalytic activity.An“ideal”adsorbent for enzyme immobilization is expected to possess the following features:i)high structural stability against acidic/alkaline conditions,ii)high surface area and porous structure for high-capacity with fast loading of enzymes,and also fast mass transfer,iii)appropriate interactions between enzyme and adsorbents for non-leaching of enzymes and better stabilization of enzymes.Two types of metal-cooardinated nano-materials(Cu-based and Zr-based)were prepared and applied in enzyme immobilization.The influence of enzyme-carrier interaction on enzyme loading,catalytic activity and stability were investigated.Fast and efficient enzyme loading as well as high initial reaction rate were achieved.An enzyme immobilization was then selected and applied in pyruvic acid production through cascade reaction system,where an efficient synthesis of indole-3-pyruvic acid was achieved.The details of the study were summarized as follows:The copper phyllosilicate assemblies were prepared via metal-cooardination and ion exchange strategy.A high specific suaface area could be achieved through varying the Cu wt%in the assemblies,leading to a high loading capacity of 140.0 mg g^-1 and a leaching rate less than 10%.Due to the inter-coordination between Cu(II)and enzyme,and the well-developed pore structure in the assemblies,the L-Cu Si O₃exhibited higher laoding capacity and catalytic activity compared with that of mesoporous silica and microporous silica.Hierarchical Zr-based metal oaganic frameworks(H-Ui O)were prepared via metal-cooardination and monocarboxylic acid assisted template etching process.H-Ui O with different particle size,specific surface area,pore structure were synthesized and applied for enzyme immobilization.H-Ui O with 10-20 nm mesopores was obtained by regulating the amount of template and monocarboxylic acid during the synthesis of H-Ui O.The H-Ui O demonstrated superior performance than micro Ui O in enzyme immobilization,with a loading capacity as high as 192.0 mg g^-1 and an initial reaction rate reaching 33.70%of the free enzyme.Due to the coordination between Zr and enzyme,the high specific area and well-developed pore structure of H-Ui O,efficient and stable enzyme immobilization was achieved.Metal catalyst doped composite carriers were prepared via metal-coordination,where an enzyme-metal cascade reaction system was constructed by integrating Pt nanoparticles and amino acid oxidase.By removing the biotoxic H₂O₂ through metal-catalysis,the biocatalytic activity of enzyme was well preserved.The reaction was positively promoted by inhibiting the side reaction,thus leading to a higher product yield of the cascade reaction system(99.70%)compared with that of the free enzyme system.Meanwhile,the impacts of H₂O₂ transport behavior on reaction rate and product yield were revealed by regulating the capacity of Pt nanoparticles in the composite carriers.