Preparation of Functionalized Graphene Oxide Nanocomposites for Covalent Immobilization of NADH Oxidase

A novel functional graphene oxide nanocomposites was synthesized, activated and used as the carrier for immobilization of NADH oxidase (NOX) from Streptococcus mutans. After the optimization, a high immobilization yield of 92% and an efficiency of 91% were achieved at pH 5.0 and 35 °C. The immobilized NOX showed better pH stability and thermostability, reusability and storage stability than that of the free one. The optimal pH of free NOX was 7.0, while it was shifted to 5.6 after immobilization. The immobilized NOX retained 82% activity after incubation while the free NOX only remaining 51% activity at 45 °C about 2 h. Immobilized NOX preserved about 60% of its initial activity after 500 h storage at 4 °C, while free NOX was totally denatured after 200 h at the same conditions. The results indicate that prepared graphene oxide composites in the present work has a good potential as carrier for immobilization of enzymes.