磁性离子液体复合材料及其在酶催化中的应用
文献类型：学位论文
| 作者 | 江洋洋 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-06-04 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 过程工程研究所 |
| 导师 | 刘会洲 |
| 关键词 | 离子液体 磁性离子液体 复合材料 固定化 磁性纳米颗粒 酶催化 界面调控 酯化 酯交换 水解 气体吸收 |
| 其他题名 | Magnetic Ionic Liquids Composite Materials and Application in Enzyme Catalysis |
| 学位专业 | 化学工艺 |
| 中文摘要 | 生物酶催化是催化学科的前沿之一，具有反应条件温和、低污染、选择性高等优点。但是仍存在酶易失活、分散性差、难以回收等问题；酶的活性和选择性还有待进一步提高。离子液体作为酶催化环境可以提高酶的稳定性、选择性。但是离子液体黏度大、易流失、酶在其中的分散性差，酶和离子液体难以回收等问题严重限制了离子液体在酶催化中的应用。 本论文设计合成了磁性离子液体复合材料并用于脂肪酶的固定化，负载离子液体为酶提供了离子液体催化微环境，提高了酶的分散性及稳定性；而磁性载体的引入解决了离子液体与酶的回收再生问题；此外，离子液体结构可调的特性可为酶的固定化提供结构可设计的磁性载体。主要创新性工作及成果如下： (1) 合成了[C4mim]FeCl4、[C4mim]Br/FeCl3等多种磁性离子液体并研究了其性质。磁性离子液体具有顺磁性，阴离子具有正四面体结构。磁性离子液体在水中的溶解度随温度升高而降低，其在水中形成胶团。水分子在磁性离子液体中以自由态通过氢键与阴离子作用。磁性离子液体对常见有机溶剂的溶解性大于普通离子液体，根据这一现象，以磁性离子液体作为苯挥发气的吸收剂，强化了吸收过程。设计了磁旋转反应器，反应器中心采用永磁铁旋转搅拌方式来加快吸收，结果表明吸收速率随磁铁转速增加而增大。 (2) 合成了咪唑阳离子具有双长链烷基取代的离子液体，通过物理吸附将离子液体负载于磁性Fe3O4纳米颗粒表面，得到了磁性离子液体复合材料。采用这一磁性离子液体复合材料体系作为载体吸附脂肪酶，固定化酶的热稳定性显著提高。 (3) 设计合成了具有双官能团的离子液体，通过其中的硅烷基团与超顺磁性SiO2表面的羟基共价连接实现磁性SiO2负载离子液体，平均粒径为55 nm，具有较好的分散性和稳定性。利用磁性纳米颗粒负载离子液体在中性条件下带正电的特性，通过静电作用吸附脂肪酶。采用FTIR研究脂肪酶酰胺I带的二级结构定量信息，发现磁性颗粒负载离子液体吸附脂肪酶后蛋白分子间氢键作用增强，结构更加有序化。 (4) 将磁性纳米颗粒负载离子液体吸附脂肪酶体系用于催化无溶剂酯化反应，发现其活性为游离酶的1.1~1.2倍。提高离子液体疏水性能够增大固定化酶对疏水性底物的催化活性。在有机相及离子液体溶剂相的酯交换反应中，固定化酶的活性均高于游离酶，且具有较高的热稳定性及操作稳定性。磁性纳米颗粒负载离子液体固定化酶在离子液体溶剂相中具有良好的分散性，催化活性远高于有机溶剂相。固定化酶对具有共轭结构的底物催化活性更高。 (5) 设计了磁性纳米颗粒负载离子液体共价连接脂肪酶体系。采用具有双官能团的离子液体作为脂肪酶与磁性纳米颗粒的连接剂，其中的羧基与Fe3O4表面羟基偶联得到磁性颗粒负载的离子液体，醛基官能团与脂肪酶的氨基通过共价键连接脂肪酶。Fe3O4纳米颗粒负载离子液体的平均粒径为15 nm。在油/水两相催化中，离子液体连接的脂肪酶在界面富集，通过调节离子液体结构调控界面层的性质从而优化脂肪酶的界面活性。离子液体连接的脂肪酶催化速率高于游离酶。提高离子液体亲水性，催化活性提高。磁性纳米颗粒负载离子液体共价连接脂肪酶与底物的亲和力是游离酶体系的2-7倍。固定化后脂肪酶的稳定性提高，疏水离子液体连接脂肪酶的稳定性更好。 |
| 英文摘要 | Biocatalysis is an important part of catalysis. It can be conducted at mild experimental conditions with higher selectivity and lower pollutions. However, the stability and dispersity of enzyme are poor, and the catalyst is difficult to be recovered. Besides, the enzyme activity and stability still need to be improved. Enzymes in ionic liquids exhibit high selectivity and stability. However, the viscosity of ionic liquids is too high. Enzymes aggregate in ionic liquids and the recycle of ionic liquids and enzyme is difficult. These disadvantages greatly restrict the application of ionic liquids in enzyme catalysis. This thesis aims at designing magnetic ionic liquids composite materials for lipase catalysis. Using magnetic nanoparticles supported ionic liquids to immobilize lipase can provide micro environment for lipase catalysis and efficiently solve the problem of the recycle of ionic liquids and enzyme. The enzymatic stability can be improved. The tunable structure of ionic liquids makes magnetic ionic liquids composite materials designable supports for enzyme catalysis and separation. (1) Magnetic ionic liquids such as [C4mim]FeCl4、[C4mim]Br/FeCl3 are synthesized and their properties are studied. Magnetic ionic liquids are paramagnetic. The anions have tetrahedron structure. Magnetic ionic liquids aggregate into micelles in water. The solubility of magnetic ionic liquids in water decreases with increasing temperature. Water molecules in magnetic ionic liquids interact with the anions through hydrogen bonding. The solubility of organic solvents is higher in magnetic ionic liquids than in common ionic liquids. The adsorption and desorption of the vapor of benzene, toluene and ethylbenzene are studied. Magnetic ionic liquids have higher adsorption ability over other ionic liquids. Magnetically rotational reactor is developed using a central permanent magnet core as impetus for the agitation of magnetic ionic liquids, enhancing mass transfer and making benzene better dispersed in the absorbent. (2) Ionic liquid with two long chain alkyl-substitutions in the imidazolium cation is synthesized. The ionic liquid is adsorbed on superparamagnetic Fe3O4 nanoparticles. The Fe3O4 nanoparticles supported ionic liquid is used to adsorb lipase. The thermal stability of immobilized lipase is improved. (3) Functional ionic liquids with two substitutions are synthesized. The silane group is used to covalently bind ionic liquids on magnetic SiO2 nanoparticles. The magnetic nanoparticles supported ionic liquids have good dispersity and stability with a diameter of 55 nm. Magnetic nanoparticles supported ionic liquids are positively charged at neutral condition, and lipase is loaded on the support through ionic adsorption. FTIR is used to study the secondary structure of the immobilized lipase. The intermolecular hydrogen bonding of immobilized protein is strengthened. (4) Magnetic nanoparticles supported ionic liquids immobilized lipase is used to catalyze the solvent free esterification, and the activity is 1.1~1.2 times of that of the native lipase. Increasing the hydrophobicity of ionic liquids can increase the activity of hydrophobic substrates. In organic solvents and ionic liquids bulk phase, the activity of the immobilized lipase in catalyzing transesterification is much higher than the native enzyme. Ionic liquids immobilized lipase disperses well in the ionic liquids bulk phase, so the catalytic activity is higher than that in organic solvents. The immobilized lipase shows higher activity when catalyzing substrates with conjugate structure. Magnetic nanoparticles supported ionic liquids protect the enzyme from thermal and operational destruction. (5) Ionic liquids controlled ester hydrolysis at oil/water interface by immobilized lipase is developed. Functional ionic liquids are synthesized and employed as linker to immobilize lipase on magnetic nanoparticles with a diameter of 15 nm. Ionic liquids interlayer creates a new pseudo-three-phase different from the conventional oil/water biphase system, and ionic liquids grafted lipase preferentially resides at the interface. The interface hydrolysis by immobilized lipase can be controlled by ionic liquids. The enzymatic activity increased with increasing the hydrophilicity of ionic liquids. 2-7 fold enrichment of the substrates is obtained in ionic liquids grafted lipase system than that of native enzyme. The ionic liquids environment favores the affinity of polar esters and improves the substrate specificity. The thermal and operational stability of immobilized lipase are greatly improved. |
| 语种 | 中文 |
| 公开日期 | 2013-09-16 |
| 页码 | 147 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1310]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 江洋洋. 磁性离子液体复合材料及其在酶催化中的应用[D]. 过程工程研究所. 中国科学院过程工程研究所. 2009. |
入库方式： OAI收割
来源：过程工程研究所
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