维生素E琥珀酸酯的酶促合成及优化

在有机溶剂中以维生素E和琥珀酸酐为底物在脂肪酶的催化下合成了维生素E琥珀酸酯。首先对酶促反应的脂肪酶、反应介质和反应温度进行了考察,在所选的几种脂肪酶中,假丝酵母脂肪酶(Candidasp.)的催化活性最好;叔丁醇和DMSO组成的混合溶剂(体积比为2∶3)为最合适的反应介质;30℃为适宜的反应温度。并采用Box-Behnken实验设计和响应面因子分析法对底物摩尔比等其他反应条件进行了优化。维生素E琥珀酸酯最优反应条件为:维生素E浓度0.26mmol.ml-1,维生素E和琥珀酸酐摩尔比1∶5,在5ml叔丁醇和DMSO混合溶剂(体积比为2∶3)中,30℃下在0.02gCandidasp.脂肪酶的催化下反应71h,维生素E琥珀酸酯产率达到98.71%。     

癸醇琥珀酸单酯磺酸钠的合成条件优化及性能测定

本文用正交试验法对癸醇琥珀酸酯磺酸钠的合成条件进行了优化研究，对其表面化学性能进行了分析测定，并探讨了其应用前景。     

脂肪酶促糖酯合成研究进展

对脂肪酶采取一定的预处理可以改善其催化活性、稳定性和选择性,主要方法有固定化、分子印迹、表面活性剂或葡聚糖修饰等.同种脂肪酶对糖环上不同羟基的选择性由糖或糖苷的结构以及溶剂的极性来决定.反应的副产物水、甲醇等对反应转化率和酶活都有影响,针对不同体系有分子筛吸附、减压低共沸蒸馏、饱和盐溶液控制水活度等解决方案.溶剂的选择是脂肪酶促糖酯合成反应的关键,既要对2种底物都有可观的溶解度又不能对酶活有很大的负面影响,当前的策略有复合溶剂、离子液体、无溶剂体系、对糖进行修饰、拟固态法和过饱和溶液等.     

十四醇琥珀酸单酯磺酸钠的合成条件优化及性能研究

用正交试验法对十四醇琥珀酸单酯磺酸钠的合成条件进行了优化研究,对其表面活性进行了分析测定,并探讨了应用前景。     

琥珀酸酯磺酸盐的合成与性能

本文论述了珀琥酸酯磺酸盐类阴离子表面活性剂的类型、合成原理、合成方法以及产品的性能和应用，列举了部分合成实例。对此类表面活性剂的研究、开发、生产和应用有一定的参考价值。     

均匀设计法优化安息香单琥珀酸酯合成工艺研究

用均匀设计法优化了安息香单琥珀酸酯的最佳工艺条件，得到第一步反应安香的收率为８１．８５％，第二步反应安息单下琥珀酸酯的收率为９４．３５％。     

蓖麻油磺基琥珀酸酯盐的合成及性能

本文介绍了蓖麻油磺基琥珀酸酯盐合成的较佳工艺条件,并对产品的性能进行了初步的测试。     

有机相酶法合成己二酸单乙烯蔗糖酯的研究

以蔗糖和己二酸二乙烯酯(DVA)为原料,采用单因素法和均匀设计法对脂肪酶Novozym-435在有机溶剂中选择性地催化合成己二酸单乙烯蔗糖酯进行了研究。考察了有机溶剂种类及含水量、反应温度、酶质量浓度、底物摩尔比对产物产率的影响,得到蔗糖单(己二酸单乙烯酯)酯(SMVA)、蔗糖双(己二酸单乙烯酯)酯(SDVA)的适宜合成条件及相应的产率分别为:在叔丁醇介质中,不含水,反应温度49℃,酶质量浓度30 mg/mL,糖酯摩尔比1∶3.2的条件下,反应4 d,SMVA的产率为13.69%;在丙酮介质中,不含水,反应温度47.5℃,酶质量浓度30 mg/mL,糖酯摩尔比1∶3.3的条件下,反应3 d SDVA的产率为28.82%。用FTIR、HPLC、HPLC-MS和TLC等对产物SMVA、SDVA等进行了表征。     

Optimisation of the enzymatic synthesis of n‐octyl oleate with immobilised lipase in the absence of solvents

The enzymatic synthesis of n‐octyl oleate by direct esterification of the oleic acid and the octanol in a solvent‐free medium was previously shown to be efficiently catalysed by a lipase from Rhizomucor miehei covalently linked to a graft copolymer, the partially hydrolysed poly(ethylene)‐g co‐hydroxyethyl methacrylate (PE‐g co‐HEMA). In this work we went further towards an optimisation of the production of n‐octyl oleate taking into account several parameters that affect the catalytic activity of the preparation. The physical characteristics of the support, such as the particle size and the degree of hydrolysis of the copolymer, the amount of lipase used in the method of immobilisation, the water content of the reaction mixture and the operational conditions of reaction, in particular the temperature, were evaluated in order to achieve not only high activities but also a good stability of the preparation. © 1999 Society of Chemical Industry     

Enhanced activities of lipase pretreated with organic solvents

The catalytic activities of lipases derived from Pseudomonas sp and pretreated with various organic solvents were investigated. The activity of the solvent‐pretreated lipase was greater than that of native lipase in both the esterification reaction in an organic medium and the hydrolysis reaction in an aqueous medium. With esterification calalysed by pretreated lipase, the product, benzyl octanoate, was detected without time‐lag. Conversions at equilibrium state were correlated with the hydrophobicities of the solvents used. In the hydrolysis reaction, most pretreated lipases yielded increased acid production compared with native lipase. A linear correlation was observed between the solvent hydrophobicity and the relative initial reaction rate of the hydrolysis reaction when using pretreated lipases. © 2001 Society of Chemical Industry     

Lipase-catalyzed synthesis of kojic acid esters in organic solvents

Kojic acid is an inhibitor of bacteria, viruses, and fungi. It is used for inhibiting the browning effect of tyrosinase in the food and cosmetic industries. To improve its lipophilic properties, Pseudomonas cepacia lipase and Penicillium camembertii lipase were used for catalyzing the esterification of kojic acid to synthesize kojic acid monolaurate and kojic acid monooleate. These products showed a 69.5% inhibitory effect on tyrosinase in hydrophobic organic solvent. The yields of kojic acid esters were affected by enzymes, substrates, organic solvent, and temperature. Lauric and oleic acids were the best substrates for esterification among various fatty acids tested. CaCl₂ and MnCl₂ stimulate Pseudomonas cepacia lipasecatalyzed esterification by 7.0%. On the contrary, MgCl₂, SrCl₂, and ZnCl₂ inhibited the reaction. The best pH of buffer for lipase pretreatment was pH 6.0. Pseudomonas and Penicillium lipases can be reused for the synthesis of kojic acid esters. After reaction at 40°C for 10 d, the Penicillium and Pseudomonas lipases still retained 57.0% and 92.0% of their initial activities, respectively.     

脂肪酶N435在低沸点溶剂中催化合成聚丁二酸丁二醇酯

脂肪酶N435在温和条件下可以有效地催化合成聚丁二酸丁二醇酯.采用溶剂蒸出的多级酶催化法成功在低沸点溶剂正己烷、四氢呋喃、甲苯和乙腈中合成出聚丁二酸丁二醇酯,得到聚丁二酸丁二醇酯的重均分子量分别为1460、1636、3066和4231,多分散系数分别为1.69、1.48、1.78和1.67.低沸点溶剂甲苯和乙腈是N43...     

固定化脂肪酶合成肉豆蔻酸异丙酯的研究

采用固定化脂肪酶(Novozym 435)在有机溶剂体系中催化肉豆蔻酸和异丙醇酯化合成了肉豆蔻酸异丙酯.研究了各种因素如有机溶剂种类、反应物摩尔比、反应温度及酶用量等因素对酯化率的影响.结果表明,肉豆蔻酸异丙酯合成的较佳条件为:1.14 g肉豆蔻酸,0.45 g异丙醇,0.02 g Novozym 435,10 mL石油醚(其中加入0.5 g 3A分子筛吸水),在55℃下振荡反应4 h,酯化率为99.2%(肉豆蔻酸可基本完全转化为肉豆蔻酸异丙酯).实验过程中固定化酶稳定性较好,可连续使用7批左右.     

雨生红球藻合成虾青素过程中分泌铵离子的研究

雨生红球藻在在缺氮(NF)的条件下,随着虾青素的合成,肽链内切酶(EP)的活性上升而蛋白质含量下降,天冬酰氨酸含量在前4天增加然后又减少,铵离子浓度则持续上升。相比之下,在氮充足(NR)的培养液中,藻细胞不合成虾青素,蛋白质和天冬酰氨酸的含量以及EP的活性基本稳定,培养液中也没有检测到铵离子。上述结果表明:①降解的蛋白质为虾青素的合成提供了碳源,②EP参与了蛋白质的降解反应,③为避免铵离子的毒害作用,蛋白质降解所产生的部分氨临时贮存在天冬酰氨酸中,而其余的则分泌到细胞外。     

盐胁迫诱导雨生红球藻合成虾青素的机理

为研究盐胁迫诱导雨生红球藻合成虾青素的机理,分析了在添加氯化钠(HS)和未添加氯化钠(CK)的培养液中,细胞内氮和碳代谢的变化。结果表明:HS中硝酸还原酶(NR)和1,5-二磷酸核酮糖羧化酶(Rub isco)活性迅速下降。虾青素在第4天开始合成时,二者分别降至初始值或最高值的46.5%和25.7%。相比之下,在对照(CK)中,NR和Rub isco活性仍然很高,仅下降了26.1%和25.6%,细胞内没有虾青素积累。上述数据表明盐胁迫条件下NR活性被抑制,细胞内氮源供应不足(氮饥饿)并进一步抑制了Rub isco的合成,导致CO2固定量减少(碳饥饿)。为了生存,藻细胞开始合成虾青素。