Preparation Of Bacterial Cellulose And Its Application On Enzyme Immobilization

Bacterial cellulose(BC) is pure cellulose that obtained by the fermentation of theAcetobacter xylinum.Compared with other natural plant cellulose,BC displays manyunique properties including nanofiber-network structure, higher purity, higher crystallinity, high tensile strength and elastic modulus, stronger biological adaptabilityand so on. Due to its unusual material properties,BC has recently become a kind ofattractive biomedical material in the international research that is extensively applied to food, biomedical materials, paper, textile, acoustic diaphragms and so on, in the international researches. This paper covers the research work in the following aspects: the methods of immobilization of laccase and glucose oxidase on the bacterial cellulose membrane carriers and the characterization of the immobilized enzymes, the application of bacterial cellulose pellets as carriers for laccase immobilization, the preliminary on cellulose physical and chemical properties and its production by using coconut milk as carbon source.Laccase. or glucose oxidase was immobilized on the bacterial cellulose membrane by adsorption. The experiment evaluated the effects of different membrane size, surface area, adsorption time and the amount of enzyme on immobilized enzymes with five targets:enzyme activity, protein binding capacity, specific activity, percent of adsorption, and activity recovery. Some characters of immobilized enzymes by adsorption and adsorption-crosslink, such as optimum temperature, optimum pH value, the thermal stability, the pH stability and the operation stabilities have been studied through the comparison with free enzyme. The result of the experiment on the property of immobilized enzymes prove that the optimum temperature of immobilized laccase was 60℃, the optimum pH of immobilized laccase by adsorption and adsorption-crosslink was 3.5 and 4.0, respectively. The optimum temperature of immobilized glucose oxidase was 35℃, the optimum pH of immobilized glucose oxidase by adsorption and adsorption-crosslink was 5.0 and 6.0, respectively. The thermal stability, pH stability and operation stability of immobilized laccse and glucose oxidase were improved considerably.Laccase was immobilized on bacterial cellulose pellets by adsorption too. After immobilization, the optimum reaction temperature was 60℃and the optimum pH was 3.5.The better operation pH range for immobilized enzyme is wider than free enzyme obviously, and it has a preferable pH stability in the range of 2.5-4.0.In the research, the coconut milk was used as carbon source for BC production. The result in the preliminary study showed that the optimal concentration of total sugar was 25 g/L and the optimum initial pH was 4.5. The pull-strength of BC increased with its improved production, but the initial pH of culture medium had significant effect on the fiber's strength. The best pre-treated mode was sterilization at 110℃at pH5.0 and the best shape of culture flasks for BC production was conical flask.The the physical and chemical properties of BC such as shape, fiber network structure, diameter distribution, thermo-gravimetric analysis (TGA) and different scanning calorimetry (DSC) were analyzed by using the scanning electron microscope (SEM), thermo-gravimetric analyzer and so on.The research work that has been done in this paper widens the application fields of BC and provides necessary experimental and theoretical base for the further development of the immobilized enzymes, whicn are in good quality and suitable for industrial production.