Covalent Immobilization of Glucose Oxidase onto New Modified Acrylonitrile Copolymer/Silica Gel Hybrid Supports

Vitreoscilla hemoglobin enhances the catalytic performance of industrial oxidases in vitro

Oxidases are a group of oxidoreductases and need molecular oxygen in the catalytic process. Vitreoscilla hemoglobin (VHb) can improve the growth and productivity of host cells under hypoxic conditions, rendering it attractive for industrial application. In this work, we demonstrated the addition of immobilized VHb increased the catalytic activity of immobilized D-amino acid oxidase of Trigonopsis variabilis by two-fold when catalyzing cephalosporin C under oxygen-limited conditions. A similar increase of activities was observed in glucose oxidase, alcohol oxidase, and p-hydroxymandelate synthase by adding free VHb or immobilized VHb under hypoxic conditions. When L-glutamate oxidase was used to catalyze L-glutamate to produce α-ketoglutarate, the yield increased from 80.6 to 96.9% by fusing VHb with L-glutamate oxidase. Results demonstrated that the addition of free VHb, immobilized VHb, or fused VHb could increase the catalytic efficiency of oxidases, which was considered by increasing the concentration of the microenvironmental oxygen. Thus, VHb may become a potential additive agent to promote the efficiency of oxidases on industrial scale . KEY POINTS: • First time confirmation of facilitation of VHb on several industrial oxidases in vitro • VHb functions under hypoxic conditions rather than oxygen-enriched conditions • VHb functions in vitro in the form of free, immobilized protein and fusion enzyme.

Covalent anchoring of chloroperoxidase and glucose oxidase on the mesoporous molecular sieve SBA-15

Functionalization of porous solids plays an important role in many areas, including heterogeneous catalysis and enzyme immobilization. In this study, large-pore ordered mesoporous SBA-15 molecular sieves were synthesized with tetraethyl orthosilicate (TEOS) in the presence of the non-ionic triblock co-polymer Pluronic P123 under acidic conditions. These materials were grafted with 3-aminopropyltrimethoxysilane (ATS), 3-glycidoxypropyltrimethoxysilane (GTS) and with 3-aminopropyltrimethoxysilane and glutaraldehyde (GA-ATS) in order to provide covalent anchoring points for enzymes. The samples were characterized by nitrogen adsorption, powder X-ray diffraction, solid-state NMR spectroscopy, elemental analysis, diffuse reflectance fourier transform infrared spectroscopy and diffuse reflectance UV/Vis spectroscopy. The obtained grafted materials were then used for the immobilization of chloroperoxidase (CPO) and glucose oxidase (GOx) and the resulting biocatalysts were tested in the oxidation of indole. It is found that enzymes anchored to the mesoporous host by the organic moieties can be stored for weeks without losing their activity. Furthermore, the covalently linked enzymes are shown to be less prone to leaching than the physically adsorbed enzymes, as tested in a fixed-bed reactor under continuous operation conditions.

Co-immobilization of glucose oxidase and hexokinase on silicate hybrid sol-gel membrane for glucose and ATP detections

The co-immobilization of glucose oxidase (GOD) and hexokinase/glucose-6-phosphate dehydrogenase (HEX) in the silica hybrid sol-gel film for development of amperometric biosensors was investigated. The silica hybrid film fabricated by hydrolysis of the mixture of tetraethyl orthosilicate and 3-(trimethoxysiyl)propyl methacrylate possessed a three-dimension vesicle structure and good uniformity and conformability, and was ready for enzyme immobilization. The electrochemical and spectroscopic measurements showed that the silica hybrid sol-gel provided excellent matrice for the enzyme immobilization and that the immobilized enzyme retained its bioactivity effectively. The immobilized GOD could catalyze the oxidation of glucose, which could be used to determine glucose at +1.0 V without help of any mediator. The competition between GOD and HEX for the substrate glucose involving ATP as a co-substrate led to a decrease of the glucose response, which allowed us to develop an ATP sensor with a good stability. The fabricated silica hybrid sol-gel matrice offered a stage for further study of immobilization and electrochemistry of proteins.