Covalently immobilized laccase onto graphene oxide nanosheets: Preparation, characterization, and biodegradation of azo dyes in colored wastewater

In this study, graphene oxide (GO) was synthesized via modified Hummer's method and exploited as an ideal enzyme immobilization support due to its exclusive chemical and structural features. Then, laccase from genetically modified Aspergillus was covalently immobilized onto GO (nanobiocatalyst). Enzymatic characterization of the nanobiocatalyst exhibited promising results: laccase loading of 156.5 mg g−1 and immobilization yield of 64.6% at laccase concentration of 0.9 mg/ mL. Further employment of various structural characterization techniques including Fourier Transform Infrared Spectroscopy (FTIR), X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermo-Gravimetric Analysis (TGA), and Transmission Electron Microscopy (TEM) comprehensively confirmed the morphological properties of the prepared nanomaterials. Furthermore, bioconversion of two anionic dyes (i.e. Direct Red 23 (DR23) and Acid Blue 92 (AB92)) using nanobiocatalyst, was investigated and optimized. Also, the average decolorization effectiveness of the nanobiocatalyst was more than 75% for both of dyes after six cycles, implies its excellent operational stability and good reusability.