Study On The Preparation And Characterization Of Dendrimer Based Composite Magnetic Nanomaterials And The Application Of Immobilized Cellulase

Cellulose is the most abundant renewable and biodegradable polymers.The nature of cellulose in annual production is estimated at 1011-1012 tons,although there are so many sources of cellulose,but the use of this biomass resources is not high.Cellulase is catalyst of biological origin with advantages of high selectivity,specificity under mild conditions,but due to the working conditions of cellulase are harsh,and cellulase is easy to lose activity in the process of catalytic hydrolysis.Therefore the catalytic hydrolysis efficiency of cellulase is not high.Because of the high catalytic activity of the immobilized enzyme under mild pH,temperature and pressure conditions,immobilization of enzymes becomes more and more importantIn this paper,we selected two kinds of synthetic materials to immobilize cellulase.The first is Fe₃O₄-NH₂@10K-4-arm-PEG-NH₂ and the second are GO@Fe₃O₄@5K-4-arm-PEG-NH₂ and GO@Fe₃O₄@10K-4-arm-PEG-NH₂,which are as a comparision with different molecular weight.We chose protein loading,immobilized enzyme and specific activity as a measure standard,and discussed the influence of immobilized cellulase with the three conditions of the amount of enzyme,time and temperature.We compared these properties of free enzyme and immobilized enzyme,the properties of GO@Fe₃O₄@5K-4-arm-PEG-NH₂-cellulase and GO@Fe₃O₄@10K-4-arm-PEG-NH₂-cellulase were also compared.The research of the property of the immobilized enzyme was mainly from the optimum temperature,optimum pH,Michaelis constant,thermal stability,characterization of reused stability and storage stability.The results show that the optimum catalytic temperature of free enzyme is 45 ?,while the immobilized enzyme is 45⁵0 ?,the optimum pH of the three kinds of immobilized enzyme are 4.The Km of the three kinds of immobilized enzyme are 11.9471 g/L,3.0411 g/L,1.6220 g/L respectively.The immobilized enzymes are more stable compared with the free cellulase at the aspects of the thermal stability,the reused stability and the storage stability.The GO@Fe₃O₄@10K-4-arm-PEG-NH₂-cellulase has better performance than the GO@Fe₃O₄@5K-4-arm-PEG-NH₂-cellulase.Finally,the catalytic hydrolysis effect ofthree kinds of immobilized enzyme were developed,and the results showed that the catalytic effect of the GO@Fe₃O₄@10K-4-arm-PEG-NH₂-cellulase was better than the GO@Fe₃O₄@5K-4-arm-PEG-NH₂-cellulase,and the catalytic effect of the GO@Fe₃O₄@5K-4-arm-PEG-NH₂-cellulase was better than that of the Fe₃O₄-NH₂@10K-4-arm-PEG-NH₂.