Effect of graphene oxide with different morphological characteristics on properties of immobilized enzyme in the covalent method

Although graphene oxide (GO) has great potential in the field of immobilized enzyme catalysts, the detailed effects of GO with different morphological structures on immobilized enzyme are not well understood. GOs were prepared from 8000 mesh and nanoscale graphite at different reaction temperatures, and used as carriers to immobilize alpha-amylase by cross-linking method. The properties of GOs were characterized through Atomic force microscope, Fourier-transformed infrared, X-ray photoelectron spectroscopy, Raman and UV–Vis. Furthermore, the dosage of cross-linking agent, cross-linking time, optimum temperature/pH, thermal/pH/storage stability, reusability and kinetic parameters of immobilized enzymes were investigated. The results showed that the loading of alpha-amylase on GOs was 162.3–274.2 mg g −1 . The reusability experiments revealed high activity maintenance of immobilized alpha-amylase even after seven reaction cycles. Moreover, the storage stability of immobilized enzyme improved via immobilization in comparison with free one and it maintained over 70% of their initial activity after 20 days storage at 4 °C.