基于树枝状聚合物复合磁性纳米材料的制备表征及其固定化纤维素酶的应用研究

发布时间：2017-12-28 22:22

本文关键词：基于树枝状聚合物复合磁性纳米材料的制备表征及其固定化纤维素酶的应用研究　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：纤维素是最丰富的可再生和可生物降解的聚合物。自然界里的纤维素年产量预计为1011 1012吨,虽然有如此多的纤维素来源,但是人们对于这种生物质资源的利用不是很高。纤维素酶是生物来源的催化剂,在温和条件下具有较高的选择性、特异性。但是由于纤维素酶的工作条件比较苛刻,在催化水解的过程中容易失去活性。因此纤维素酶的催化水解效率不高。由于固定化酶在较温和的pH值、温度、压力条件下进行催化,有着高活性和无与伦比的选择性,酶的固定化变的越来越重要。本文讨论了两种复合材料固定化纤维素酶,一种是四臂型聚乙二醇树枝状聚合物修饰在四氧化三铁磁性纳米粒子的上面。第二种是接枝两种不同臂长的四臂型聚乙二醇树枝状聚合物修饰在磁性氧化石墨烯表面。本文选定了以蛋白载量,固定化酶的活力,比活力为衡量标准,讨论了加酶量、时间、温度三个条件对固定化纤维素酶的影响。又比较了游离酶与固定化纤维素酶的酶学性质,另外还比较两种不同臂长的四臂型聚乙二醇树枝状聚合物修饰在磁性氧化石墨烯表面固定化纤维素酶的酶学性质。主要是从最适最适pH、温度、米氏常数、热稳定性、重复使用稳定性以及贮藏稳定性这几个方面研究其酶学性质。研究结果表明:游离酶的催化反应最适温度为45℃,而固定化酶的为50℃,游离酶的pH为5,固定化酶催化最适pH为4。四臂型聚乙二醇树枝状聚合物修饰在四氧化三铁磁性纳米粒子固定化纤维素酶、接枝分子接枝分子量5 K的四臂型聚乙二醇树枝状聚合物修饰在磁性氧化石墨烯表面固定化纤维素酶、接枝分子量10 K的四臂型聚乙二醇树枝状聚合物修饰在磁性氧化石墨烯表面固定化纤维素酶的米氏常数分别是11.9471 g/L,3.0411 g/L,1.6220 g/L。固定化酶在热稳定性、重复使用稳定性、其贮藏稳定性都比游离纤维素酶的好。最后做了三种酶的催化水解应用实验,发现接枝分子量10 K的四臂型聚乙二醇树枝状聚合物修饰在磁性氧化石墨烯表面固定化纤维素酶的催化效果比接枝分子接枝分子量5 K的四臂型聚乙二醇树枝状聚合物修饰在磁性氧化石墨烯表面固定化纤维素酶好,接枝分子接枝分子量5 K的四臂型聚乙二醇树枝状聚合物修饰在磁性氧化石墨烯表面固定化纤维素酶的催化效果比四臂型聚乙二醇树枝状聚合物修饰在四氧化三铁磁性纳米粒子固定化纤维素酶效果好。
[Abstract]:Cellulose is the most abundant renewable and biodegradable polymer. The annual yield of cellulose in nature is estimated to be 10111012 tons. Although there are so many cellulose sources, the utilization of this biomass resource is not very high. Cellulase is a catalyst for biological origin, which has high selectivity and specificity under mild conditions. However, because of the harsh working conditions of cellulase, it is easy to lose its activity during the process of catalytic hydrolysis. Therefore, the efficiency of the catalytic hydrolysis of cellulase is not high. Immobilized enzyme is highly active and unequalled under mild pH value, temperature and pressure. Immobilization of enzyme is becoming more and more important. In this paper, two kinds of composite immobilized cellulase are discussed, one is the four arm polyethylene glycol dendrimer modified on magnetic iron oxide nanoparticles. The second is the grafting of two different arm length four arm polyethylene glycol dendrimers on the surface of magnetic graphene oxide. In this paper, protein loading, immobilized enzyme activity and specific activity were selected as criteria. The effects of three conditions, enzyme dosage, time and temperature on immobilized cellulase were discussed. The enzymatic properties of free enzyme and immobilized cellulase were compared. In addition, two different arm length four arm polyglycol dendrimers modified on the surface of magnetic graphene oxide were applied to immobilize cellulase. The properties of the enzyme are studied mainly from the most suitable and optimum pH, temperature, Michaelis constant, thermal stability, reuse stability and storage stability. The results show that the optimum temperature for the catalytic reaction of the free enzyme is 45, while the immobilized enzyme is 50, the pH of the free enzyme is 5, and the optimum pH of the immobilized enzyme is 4. Four arm type peg dendrimers modified Fe3O4 magnetic nanoparticles in immobilization of cellulase, the grafted molecular weight polyethylene glycol graft four arm type dendrimers 5 K modified in four arm type polyethylene glycol dendrimer magnetic graphene oxide surface immobilized cellulase, grafted with a molecular weight of 10 K in the modified Michaelis constant magnetic graphene oxide surface immobilized cellulase were 11.9471 g/L, 3.0411 g/L, 1.6220 g/L. The immobilized enzyme is better in thermal stability, reuse stability and storage stability than that of free cellulase. Finally the application experiment of three kinds of enzyme catalyzed hydrolysis, found four arm type polyethylene glycol dendrimer four arm type dendrimer grafted polyethylene glycol 10 K molecular weight modified on the surface of graphene oxide catalytic effect of magnetic immobilized cellulase than grafted graft molecular weight of 5 K on the surface of graphene oxide modified magnetic immobilized cellulase, four arm type dendrimer grafted polyethylene glycol grafted a molecular weight of 5 K modified on the surface of graphene oxide catalytic effect of magnetic immobilized cellulase than polyethylene glycol four arm type dendritic polymer modified Fe3O4 magnetic nanoparticles in immobilized cellulase effect.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：Q814.2;TB383.1

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