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离子液体中脂肪酶催化拆分外消旋烯丙酮醇反应 总被引:2,自引:0,他引:2
以离子液体为溶剂,考察了溶剂类型、水活度、温度、 pH值和共溶剂等因素对脂肪酶催化拆分外消旋烯丙酮醇(R,S)-4-羟基-3-甲基-2-(2-丙烯基)-2-环戊烯-1-酮反应的影响,并与常用于外消旋烯丙酮醇拆分的有机溶剂乙酸乙烯酯进行了比较. 结果表明,在离子液体[bmim]PF6中脂肪酶的催化性能较好,酶初始反应速率为18.48 μmol/(g·min), 半衰期为74.53 h, 高于在乙酸乙烯酯中的相应值(9.18 μmol/(g·min)和64.29 h). 但离子液体中拆分反应的转化率低于在乙酸乙烯酯中的转化率,可以通过向离子液体中补加酰基供体来提高外消旋烯丙酮醇的转化率. 两种反应介质中最佳酶反应条件均为水活度0.17, 温度40 ℃和pH=7, 但加入共溶剂后,离子液体中脂肪酶催化拆分外消旋烯丙酮醇的效率降低,而在乙酸乙烯酯中则有所提高. 相似文献
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水对脂肪酶非水相催化拆分2-辛醇的影响 总被引:1,自引:0,他引:1
利用假单胞菌脂肪酶在有机溶剂中催化的对映选择性酯化反应,对外消旋(R,S)-2-辛醇进行了动力学拆分,考察了水对脂肪酶非水相催化性能的影响.结果表明,酶在有机溶剂中的活力显著依赖于系统的加水量,二者呈钟罩形曲线,但最佳加水量范围以及酶的活力大小因溶剂不同而异;在最佳加水量范围内,系统含水量的变化对酶的对映选择性影响不大,但加水量增大(>1%,V/V)会导致逆反应(酯的水解)加剧而降低醇的光学纯度;在反应进行一定时间后,添加分子筛移走酯化反应生成的水,可显著提高反应的转化率,并增大醇的对映体过量,但当超过快反应(R-醇的酯化)的平衡转化率时,反而会造成残留醇的光学纯度下降.用二甲基甲酰胺和乙二醇取代部分或全部的水添加于非水相酶反应系统,也能起到与水类似的甚至更强的激活酶的作用. 相似文献
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以N-保护消旋氨基酸为羧基组分的酶促合成肽的研究 总被引:1,自引:0,他引:1
用不同的氨基保护的消旋氨基酸或酯作为羧基组分,在α-胰凝乳蛋白酶或木瓜蛋白酶的催化下与另一氨基酸的酰胺或酯缩合形成预期的光活性肽产物。以L-构型底物计算肽的产率为55%~83%,化合物的物理学常数与用相应的N-保护-L-氨基酸或酯为羧基组分,分别用化学法或酶促法测定所得结果一致。研究结果表明:利用酶的立体专一性,在形成肽键的过程中进行立体选择可得到光学活性的产物而不需预先拆分;只要溶剂体系中含有酶所需要的微量必需水,酶促反应在有机溶剂中可以顺利地进行。 相似文献
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用悬浮聚合法合成了一系列聚甲基丙烯酸羟乙酯载体,考察了它们固定化酵母脂肪酶活力与载体的交联度和致孔剂用量之间的关系。研究了这些固定化酵母脂肪酶在有机溶剂中催化酯合成反应的活性,脂肪酶的固定化使之活力表达更为充分,对亲水性较强的有机溶剂有更强的耐受性,并能为其在有机溶剂中催化酯合成反应提供必需水。考察了PH值,底物种类对固定化酵母脂肪酶催化酯合成反应的影响。 相似文献
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以4-肼基-7-硝基-2,1,3-苯并氧杂二唑肼为荧光底物,乙烯基羧酸酯、伯醇为转酯化反应底物通过荧光分光光度法比较了几种能以固体聚合物为底物的商品化酶制剂在有机溶剂中催化转酯化反应的性质.该方法使用微量溶剂和底物进行反应,测定快捷,具有很高的直观性.实验所用4种酶制剂均可在异辛烷、甲苯和乙腈中催化转酯化反应,催化能力是脂肪酶LPL-3>蛋白酶Alcalase 3.0 T>蛋白酶subtilisin Carhberg>蛋白酶bacillolysin,但有机溶剂的疏水性对转酯化反应影响较大,疏水性高的有机溶剂比较适合做酶催化转酯化反应的溶剂.和月桂酸乙烯酯相比,小分子的丙酸乙烯酯更有利于酶催化转酯化反应的进行. 相似文献
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Salleh AB Basri M Taib M Jasmani H Rahman RN Rahman MB Razak CN 《Applied biochemistry and biotechnology》2002,102(1-6):349-357
Recent studies on biocatalysis in water—organic solvent biphasic systems have shown that many enzymes retain their catalytic
activities in the presence of high concentrations of organic solvents. However, not all enzymes are organic solvent tolerant,
and most have limited and selective tolerance to particular organic solvents. Protein modification or protein tailoring is
an approach to alter the characteristics of enzymes, including solubility in organic solvents. Particular amino acids may
play pivotal roles in the catalytic ability of the protein. Attaching soluble modifiers to the protein molecule may alter
its conformation and the overall polarity of the molecule. Enzymes, in particular lipases, have been chemically modified by
attachment of aldehydes, polyethylene glycols, and imidoesters. These modifications alter the hydrophobicity and conformation
of the enzymes, resulting in changes in the microenvironment of the enzymes. By these modifications, newly acquired properties
such as enhancement of activity and stability and changes in specificity and solubility in organic solvents are obtained.
Modified lipases were found to be more active and stable in organic solvents. The optimum water activity (a
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) for reaction was also shifted by using modified enzymes. Changes in enantioselective behavior were also observed. 相似文献
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对筛选的假丝酵母菌株Candida.sp.GXU08所产脂肪酶催化15-羟基十五烷酸甲酯合成环十五内酯进行了研究,使用超声震荡将脂肪酶酶液分散到环己烷中,以此形成水/有机溶剂乳化体系,考察了不同因素对环十五内酯产量的影响。实验结果表明,在水/环己烷乳化体系中,脂肪酶催化15-羟基十五烷酸甲酯合成环十五内酯的最适条件为:在40℃、180r/min的条件下,1g脂肪酶(pH=7.0)催化8mmol/L的15-羟基十五烷酸甲酯反应72h,单位酶活生成环十五内酯的最大质量为47.77×10-3mg,是在纯有机溶剂环己烷中单位酶活生成环十五内酯最大质量14.54×10-3mg的3.285倍。反应后的脂肪酶重复使用1次能大大提高环十五内酯的生成量。直接使用一定浓度的酶液代替酶粉催化合成环十五内酯具有转化率高、省时、节能等优点。 相似文献
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有机相中蚕丝固定化脂肪酶催化酯化反应性能研究 总被引:2,自引:0,他引:2
研究了有机相中蚕丝固定化脂肪酶催化酶化反应的催化活性。考究了有机溶剂,底物、反应温度,PH值和体系含水量等因素对固定化脂肪酶催化活性的影响。结果表明,以异辛烷为有机溶剂,在反应温度为50℃PH值为7.4时,酶催化活性最好。 相似文献
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脂肪酶的固定化及其在有机酶促反应中稳定性研究 总被引:15,自引:3,他引:12
利用吸附法,将圆柱状假丝酵母脂肪酶固定于4种疏水性不同的载体上,固定化酶的活性及稳定性随载休疏水性的增大而增大。用YGW-C6H5作为载体,在有机溶剂-水双液相体系中催化萘普生甲酯的不对称水解,反应120h转化率为24.72%,产品的对映体过量值为94.82%。 相似文献
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A screening of commercially available lipases for the synthesis of vitamin E succinate showed that lipase from Candida rugosa presented the highest yield. The synthesis of vitamin E succinate in organic solvents with different lgP values ranging from -1.3 to 3.5 was investigated. Of particular interest was that dimethyl sulfoxide (DMSO) with the lowest lgP exhibited the highest yield among all the organic solvents used. It suggests that lgP is incapable of satisfactorily predicting the biocompatibility of organic solvents due to the complexity of enzymatic reaction with hydrophilic and hydrophobic substrates in organic solvent. Effects of different operating conditions, such as molar ratio of substrate, enzyme concentration, reaction temperature, mass transfer, and reaction time were also studied. Under the optimum conditions of 10 g/L enzyme, a stirring rate of 100 r/min, a substrate molar ratio of 5:1 at 55℃ for 18 h, a satisfactory yield(46.95%) was obtained. The developed method has a potential to be used for efficient enzymatic production of vitamin E succinate. 相似文献
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研究了疏水性离子液体[BMIM][PF6]对脂肪酶R. miehei有机相催化合成辛酸戊酯反应的影响,并结合荧光发射光谱分析R. miehei构象变化与酶活性表达的关联。结果表明,该酯化反应在饱和烷烃中的初速度比在芳烃中的大,且当溶剂logP为1.5~3.5时,反应初速度随logP的增加而降低。在不同有机溶剂中,加入占辛酸质量1%的[BMIM][PF6]均导致反应初速度降低15%左右,降低幅度几乎不与溶剂种类有关。表明[BMIM][PF6]对该反应的影响与所在溶剂系统无关,而只与离子液体的加入有关。[BMIM][PF6]加入量为辛酸质量1%~3%时,以壬烷为溶剂时的反应初速度随[BMIM][PF6]加入量的增加而降低,进一步表明离子液体的加入量是影响反应初速度的重要因素。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。 相似文献
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Convenient enzymatic methods have been developed for the preparation of chiral 1- and 2-hydroxyalkanephosphonates bearing a trifluoromethyl moiety with high enantiomeric excess via Candida antarctica lipase B-, Mucor miehei lipase-catalyzed alcoholysis and C. rugosa lipase-catalyzed hydrolysis in organic media. The enantiomeric excess of such trifluoromethylated carbinols was determined using quinine as a chiral solvating agent. The catalytic preference was assigned according to the Kusumi-Ohtani method. 相似文献
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Ping Xue Xiang Hui Yan Zheng Wang 《中国化学快报》2007,18(8):929-932
Pseudomonas cepacia lipase (PSL) immobilized on the carboxyl-functionalized meso-cellular foams (HOOC-MCF) was used for the transesterification resolution of (R,S)-1-phenylethanol in organic solvent.The results showed that the ee value of (S)-1- phenylethanol and (R)-1-phenylethyl acetate reached 99% with 50% conversion of 1-phenylethanol using toluene as solvent. Furthermore,it was found that PSL/HOOC-MCF exhibited high enantioselectivity in organic solvent with log P≤2 such as toluene and hexane. 相似文献