Robust Hierarchical Nanostructure Biocatalyst for Cascade Reaction

Enzymes are smart and native biocatalyst that significantly accelerate and speed up the rate of chemical processes that take place within living cells. These transformations in living cells, happened when a number of enzymes work together in multi-step reactions for formation of the stable products, which the whole process would be called a biocatalytic cascade or domino reactions [1-5].In order to improve the reusability and stability of the biocatalysts, different enzymes can be linked to the same support by coimmobilization to mimic multi-enzyme complexes present in cellular systems.Multi-enzymes can be covalently bound to an insoluble carrier. By choosing appropriate support material and immobilization method, enzyme immobilization provides unique advantages such as easy separation from the reaction medium, elimination of enzyme contamination in the product and prevention of microbial impurities in the industrial applications. Inspired by the metabolic channeling of live cells, herein, we constructed an artificial biomimetic microsystem by coimmobilizing GOD and GA onto nanocarrier to accomplish the direct one-pot conversion of starch to gluconic acid. This approach may provide a novel strategy to construct in vitro multi-enzymatic assemblies [6-8].In this work, we explored an excellent double enzymatic microsystem prepared from co-immobilization of glucose oxidase (GOD) and glucoamylase (GA) on silver dendritic hierarchical nanostructure (Ag-DHN) through Ugi four-component reaction. Glucose oxidase (GOD) (E.C. 1.1.3.4) is an oxidoreductase and catalyzes the oxidation of β-Dglucose to gluconic acid.A variety of analytical tools were used to study the morphological, structural, and chemical properties of the biocatalysts. The success preparation of the exclusive biocatalyst system was confirmed by FT-IR, UV-Vis, XRD and scanning electron microscopy (SEM).The obtained biocatalyst was employed for transformation of starch to gluconic acid as a special cascade reaction under mild conditions.The results of biocatalyst systems exhibited the substantial improvement of reactivity, reusability, and stability of GOD because of this immobilization strategy.

Keywords:

Nanobiocatalyst , Cascade Reaction , enzyme immobilization , Hierarchical nanostructure