【作者】 吴红平；

【导师】 夏咏梅；

【作者基本信息】 江南大学 ， 应用化学， 2008， 硕士

【摘要】 非水相酶催化酸和醇合成酯已被广泛用于食品、化妆品及医药等行业,其中溶剂工程的调控是一个重要的手段。离子液体具有良好的热稳定性、溶解范围广、可以忽略的蒸汽压和物性可调控等优良的性质,特别是其较强的极性,可溶解高极性底物,使其更有望成为酶催化反应溶剂工程的调控工具。本文以辛酸和戊醇的酯化反应为研究对象,选择脂肪酶RM IM和Novozym 435为催化剂,研究了离子液体及微波辐射下离子液体对该反应的影响,具体研究内容和结果如下:1.用脂肪酶RM IM在不同溶剂系统中催化合成辛酸戊酯,考察了[BMIM][PF6]对该反应初速度及反应进程的影响。在含1%(占辛酸质量)[BMIM][PF6]的有机溶剂体系中,反应初速度随溶剂log P(2.0~5.1)的变化趋势与有机溶剂中的变化趋势一致。[BMIM][PF6](占辛酸质量1%)的加入即可改变该酯化反应溶剂体系的溶剂行为,但其对该反应的影响与反应溶剂无关,只与离子液体的加入有关。荧光光谱分析表明,酶活性的表现与酶分子的构象变化有一定的相关性。当[BMIM][PF6]加入量为辛酸质量1%～3%时,以壬烷为溶剂的反应初速度随[BMIM][PF6]加入量的增加而降低。进一步研究表明在[BMIM][PF6]加入量为辛酸质量1%～5%范围内,[BMIM][PF6]对脂肪酶RM IM的抑制作用是不可逆抑制。2.考察了[BMIM][PF6]对脂肪酶RM IM最适反应温度和操作稳定性的影响。结果显示,在40 oC~70 oC范围内,当[BMIM][PF6]加入量为辛酸质量2%时,以壬烷为溶剂酶催化反应的最适温度为60 oC,此温度高于不加离子液体的最适反应温度(50 oC)。同时,离子液体(占辛酸质量1%)的存在可以提高固定化脂肪酶RM IM的操作稳定性。3.考察了离子液体加入量为辛酸质量1%时离子液体的结构对酶RM IM催化合成辛酸戊酯的影响。当阳离子均为[BMIM]+时,酶促酯化反应在阴离子为PF6–的离子液体-壬烷中辛酸转化率明显高于其阴离子为BF4–、Cl–中的;而阴离子均为PF6–时,辛酸转化率随离子液体咪唑环上烷基链的增长而降低。在含不同结构离子液体的壬烷中,微波辐射都表现出提高酶催化反应初速度的特点,且这种效应随着离子液体阴、阳离子的不同而有所变化。4.研究了微波辐射下[BMIM][PF6]对脂肪酶Novozym 435催化合成辛酸戊酯的影响,考察了具有不同log P的有机溶剂以及[BMIM][PF6]的加入对该反应的影响。结果表明,微波辐射下反应初速度随溶剂log P(2.0~5.1)的变化趋势与常规加热下的变化趋势基本一致;在极性大的芳烃溶剂中微波能更明显地提高酶的活性。[BMIM][PF6] (占辛酸质量1%)的加入不会改变该反应的最适加水量(占辛酸质量2%)。微波辐射下,以壬烷为溶剂,当[BMIM][PF6]为辛酸质量1%～3%时,反应初速度与其加入量负相关,而当其加入量为辛酸质量3%～8%(占辛酸质量)时,反应初速度与其加入量正相关。采用ChemPower微波合成仪进行在壬烷或含[BMIM][PF6](占辛酸质量1%)壬烷中的酯化反应,微波辐射均提高了辛酸转化率。更多还原

【Abstract】 Enzymatic esterification in nonaqueous media has been widely used in foods, medicine and cosmetic industry. Regulation of solvent engineering is one of important tools in nonaqueous enzymatic catalysis. Ionic liquids, as one of new solvents for their unique properties, such as good thermal stability, special solubility, negligible vapor pressure and variable physical properties, especially its strong polarity hold the promise of regulating instrument in solvent engineering. In this paper, the role of ionic liquids in the synthesis of amyl caprylate catalyzed by lipase from R. miehi (RM IM) or from Candida Antarctica (Novozym 435) was investigated, assisted by microwave irradiation and conventional heating respectively. The main contents and results are as follows:1. The effect of [BMIM][PF6] on the initial reaction rate and reaction profile in the synthesis of amyl caprylate catalyzed by lipase RM IM in different organic solvents were studied. The trend of initial reaction rate with log P (2.0-5.1) in organic solvent in the presence of 1% [BMIM][PF6] was similar as that in organic solvent. The effect of [BMIM][PF6] on the reaction was only related to its addition rather than the solvent mixed with it.The fluorescence spectral analysis indicated that the conformational change coordinated to the change of enzyme activity. The initial reaction rate was decreased with the increase of the dosage of [BMIM][PF6] (1%-3% of caprylic acid, w/w) employed in the reaction in nonane. Further more, inhibition of different amount of [BMIM][PF6] on lipase RM IM was irreversible.2. The effects of [BMIM][PF6] on the optimum reaction temperature and operation stability of immobilized lipase RM IM were investigated. It was found that the optimum reaction temperature in nonane in the presence of 2% [BMIM][PF6] (60 oC ) was higher than that in nonane (50 oC ). Further more, the amount of 1% ionic liquid could improve operation stability of lipase RM IM.3. For ionic liquids with same cationic motie, the conversion of caprylic acid in nonane with 1% ionic liquid of PF6–was obviously higher than that in nonane with 1% ionic liquids of BF4–、Cl–. While for ionic liquids with same anionic motie, PF6–, the conversion of caprylic acid was decreased with the increasing of alkyl chain of imidazole ring. Microwave irradiation also improved the initial reaction rate in the presence of different ionic liquids.4. The effect of [BMIM][PF6] on the synthesis of amyl caprylate catalyzed by lipase Novozym 435 under microwave irradiation was studied. The effects of organic solvents with different log P and the addition of small amount of [BMIM][PF6] on reaction were investigated. The trend of initial reaction rate with log P (2.0-5.1) under microwave irradiation was similar as that under conventional heating in organic solvent. Microwave improved the lipase activity more obviously in polarer solvent. Addition of 2% [BMIM][PF6] didn’t change the optimum water dosage (2% of caprylic acid, w/w). The initial reaction rate decreased first and then increased with the increase of the dosage of [BMIM][PF6](1%-8% of caprylic acid, w/w) in nonane under microwave irradiation. Applying the esterification in a ChemPower microwave reactor, microwave irradiation enhanced the reaction either in nonane or in nonane with [BMIM][PF6] (1% of caprylic acid, w/w).更多还原