Preparation Of Magnetic Nanocomposite Materials For Immobilization Of Celluase

In recent years, the cellulosic ethanol prepared by the fermentation of lignocellulosic biomass has attracted more and more attention and becomes a focus for its advantages, such as easily available materials and low combustion pollution. As we all known, cellulase can effectively hydrolyze cellulose to glucose through a series of synergistic effects, which is one of the most promising hydrolyzed methods to produce cellulosic ethanol. In addition, immobilization of cellulase could make cellulose obtain higher activity even in the harsh conditions, increase the number of recovery and repeated use, and reduce the cost of hydrolysis. And the design and preparation of immobilized enzyme carrier that can be recovered by magnetic separation has been a simple and effective approach to improve the efficiency of the enzyme. Thus, in this thesis we selected magnetic Fe3O4 nanoparticles as main materials, and chitosan, graphene oxide and dopamine were as supporting materials, to prepare a series of novel magnetic nanocomposites for immobilized cellulose were. And their characteristics were studied by FTIR, TEM, and XRD. The properties of the relative activity of cellulase and repeated use were also studied in the different pH and temperature conditions. The main work of this thesis was described as below:1. Magnetic Fe3O4 nanoparticles were prepared by co-precipitation method. Compared with conventional methods, this co-precipitation method was simpler, and obtained particles were smaller. The properties of magnetic separation could be effectively achieved. The magnetic nanoparticles based on chitosan (Fe3O4@CS) were prepared by reversed-phrase cross linked method, and glutaraldehyde was used as a crosslinker. The resulted Fe3O4@CSparticles had good property of magnetic separation. Loading efficiency and properties of immobilized enzyme were determined by coomassie brilliant blue and DNS method. The results showed that the thermal and pH stability of the immobilized enzyme were higher than that of the free enzyme.2. Magnetic nanocomposites based on graphene oxide modified dendrimers (Fe3O4/GO/PAMAM) were prepared. PAMAM dendrimers with ethylenediamine as inner core were prepared by the ultrasonic method, which were further grafted onto the surface of grapheme oxide. And magnetic Fe3O4 nanoparticles were prepared by in site reaction between graphene oxide modified dendrimers. The results showed that the immobilized cellulose showed good dispersity and magnetic separation. In addition, immobilized cellulase also exhibited better pH and thermal stability compared with free enzyme, and had good stability of repeated use and recovery.3. Magnetic Fe3O4 nanoparticles coated by dopamine were prepared, and cellulase was spontaneously immobilized on magnetic nanoparticles through the adhesive attraction of dopamine. This method was simple, and could reduce cost and improve the functional efficiency of the magnetic nanoparticles, which was an efficient method for immobilization. In this work, we selected biomimetic method to obtain immobilized cellulase, which could effectively avoid the inactivation of cellulase in the immobilized process.