Preparation, Degradation and Antibacterial Properties of Nanocellulose
|Keywords||Bacterial cellulose bio-degradtion cellulase activity Nanometer ZnO Nanocomposite material anti-bacterial properties|
Synthesized by some microbes, bacterial cellulose(BC) is a kind of ultra-fine and highly pure nano-scale fibrils. In comparison with plant cellulose in nature, BC is characterized as higher crystallinity, higher degree of polymerization, higher water absorption capacity, better tensile strength, stronger bio-adaptability and easier degardation in nature. BC has been regarded as the best cellulose in the world and has extensive commercial applications. At present, research on bacterial cellulose has become a heated topic in the biomaterial field.The thesis contains five chapters.Chapter one introduces the current BC research areas and the objective of this thesis.Chapter two describes the production process of BC using Acetobacter xylinum, and also studies the effects on the productivity of BC of some main factors, such as inoculum concentration, content in flask,cultivation temperature and time, initial pH. In addition, residual sugar content、residual nitrogen content,pH and the changing trend of BC output have been measured in the course of cultivation. The characterization, physical and chemical structure and morphology of BC have been analyzed by using Fourier transform infrared(FTIR)spectroscopy,x-ray diffraction(XRD),Scanning electron microscope(SEM) and Thermogravimetric Analysis (TGA). The water-holding ratio of the wet membrane of BC is calculated as 98.17 % by weight method, and the Re- hydration ratio of the drying membrance of BC 66.37 %.The vital mechanical properties index of BC have been obtained through mechanical test.Chapter three addresses the deriving method of mutant strains from Acetobacter xylinum. The cellulose -producing strain was mutagenized by ultraviolet rays(UV),Diethyl sulfate(DES)and sodium nitrite(NaNO2). Three mutagens on the death dosage of Acetobacter xylinum have been studied, and thus three death rate curves have been obtained. The 5 strains have been selected from 150 strains to screen further with suitable mutagen dosage.Chapter four focuses on the study of the bio-degradability of BC. Through the experiments, wave for determining cellulase activity was set as 530 nm, and the blank solution should be reactant of substrate, citrate buffer and DNS. I studied various factors that affect cellulase activity including temperature, pH and concentration of enzyme. The cellulase activity and the cellulase activity in different temperature and in different pH have also been calculated. The kinetics curve of degradation of BC has been drawn. Initial velocity of enzyme-catalyzed reaction has been obtained from the slope of the curve.Chapter five studies the characteristics of BC as a new kind of nanocomposite material. The ZnO/BC and modified ZnO/BC nanocomposites have been synthesized, and some research about its anti-bacterial has been done as well.