Effect of graphene oxide with different morphological characteristics on properties of immobilized enzyme in the covalen
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RESEARCH PAPER
Effect of graphene oxide with different morphological characteristics on properties of immobilized enzyme in the covalent method Han Zhang1 · Shao‑Feng Hua1 · Cong‑qiang Li1 · Lei Zhang1 · Yun‑Chang Fan1 · Peigao Duan1 Received: 14 March 2020 / Accepted: 8 May 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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 crosslinking 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. Keywords Graphene oxide · Oxidation degree · Enzyme immobilization · Enzyme activity
Introduction Enzyme technology caters for the development trend of “green development” and has the advantages of high conversion efficiency, less by-product, milder reaction conditions and lower environmental toxicity, when it was compared with artificial catalysts. That is why, considerable attention has been attracted by enzyme catalysis in the fields of pharmaceutical, bioenergy, industrial food and environmental applications [1–4]. Nonetheless, the direct use of such biocatalyst in industrial production shows lots of significant problems, including short lifetime, highly sensitive to the environment conditions, unsatisfactory operational stability, and difficulties in recovery. Immobilized enzyme is superior to the free one owing to its repetitive use. Furthermore, the reaction product can avoid being contaminated by the enzyme molecule, which is particularly useful in the industries of food and pharmacy [5, 6].
* Shao‑Feng Hua [email protected] 1
School of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo 454000, Henan, China
Plenty of carriers from various origin have been previously used to immobilized enzyme, including polymers— poly (methyl methacrylate) [7], biopolymers—polydopamine [8], composite materials—magnetic silica and alumina [9], and inorganic materials—nano-TiO2 [10]. Graphene oxide (GO), a kind of two-dimensional carbon nanomaterial, is an ideal enzyme carrier with advantages of one-atom thickness, high mechanical streng
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