固定化脂肪酶在非水相合成中的应用

脂肪酶是分解脂肪的酶,非水体系可促使反应平衡逆向进行,因而脂肪酶又具有合成功能。目前非水相脂肪酶催化合成技术在食品、医药、化妆品等多个领域中都有广泛的应用。本文对非水相中脂肪酶的反应体系、影响非水相酶促反应的因素以及其应用领域进行了综述,对于深入研究非水体系中脂肪酶催化的合成反应具有较强的参考价值。     

脂肪酶催化拆分1-(4-甲氧基苯基)乙醇的研究

研究筛选了多种脂肪酶对1-(4-甲氧基苯基)乙醇对映体进行酶法催化拆分,表明来自洋葱假单胞茵脂肪酶(PS IM)在催化拆分中表现出了最高的活力和立体选择性,一种来自小麦胚芽的脂肪酶(WGL)在催化的过程中表现出了与其它脂肪酶相反的选择性.研究了有机溶剂体系中温度和水活度对PS IM催化拆分效果的影响,表明35C是最佳温度,水活度0.69为最佳水活度,在此条件下,转化率和对映体选择性分别达到很好的效果(C 50%,eep99%,ees99%).     

非水相介质杂醇油酶法转化天然酯类香料的研究

为提高杂醇油的利用率和附加值,研究非水相条件下杂醇油的脂肪酶催化酯化反应,优化其转化为天然酯类香料的工艺条件.结果表明,酶用量、分子筛用量、乙酸加入次数及间隔时间、摇床转速、反应温度、反应时间等因素条件对产物酯的生成有重要影响,采用间歇式加酸、加入适量分子筛吸水剂可明显提高混合酯得率.在正已烷10mL、杂醇油3ml、乙酸1.5mL的反应体系中,正交试验设计优化后的工艺条件(乙酸异戊酯产率最高时):脂肪酶Novozym435FG用量70mg、乙酸分6次加入、加入乙酸间隔时间3h、分子筛用量2g、摇床转速140r/min、反应温度45℃、反应时间36h.该条件下,乙酸异戊酯、乙酸异丁酯和乙酸丙酯的产率分别为90.1％,91.3％,78.1％.     

微生物脂肪酶的研究与应用

脂肪酶是一类能够催化酯的水解反应以及在非水相体系中催化脂肪酸和醇类发生酯化反应的酶类。随着酶学技术的快速发展,微生物脂肪酶也受到了越来越多的关注。作为生物催化剂,脂肪酶一直以来都是生物技术领域中最重要的一类酶。本文探讨了脂肪酶的来源、理化性质、脂肪酶活力测定,同时对脂肪酶的非水相催化特性以及脂肪酶在食品工业,医药、洗涤剂、皮革、造纸和生物柴油工业领域中的应用进行了讨论。     

非水相脂肪酶催化合成维生素酯的研究进展

综述了近年来非水相脂肪酶催化合成几种维生素酯的研究进展,主要介绍了维生素A酯、维生素C酯和维生素E酯的酶催化合成过程中,脂肪酶、有机溶剂、体系水活度以及其它反应条件的影响,分析了目前还存在的问题,并对酶法合成维生素酯的发展前景进行了展望。     

L-抗坏血酸棕榈酸酯的酶法合成

详细研究了脂肪酶在有机溶剂中催化合成L-抗坏血酸棕榈酸酯的反应,并且对影响产物浓度的几种主要因素进行讨论（如脂肪酶、溶剂、温度、底物比、添加剂）,首次通过加入相转移剂提高反应产物浓度,确定了合成L-抗坏血酸棕榈酸酯的最适反应条件：3mL叔戊醇为溶剂,催化剂为Novozyme435,其最佳用量为0.05g,底物棕榈酸与抗坏血酸摩尔比3：1,0.3g4A分子筛作为吸水剂,0.3g四丁基溴化铵作为相转移剂,反应温度50℃,反应时间72h,得到产物浓度为16.6mg/mL。     

L-抗坏血酸不饱和脂肪酸酯的酶法合成工艺

以不饱和脂肪酸含量高的食用油为酰基供体,研究了脂肪酶在有机溶剂中通过酯交换反应催化合成L-抗坏血酸不饱和脂肪酸酯的工艺条件。结果表明,在20 m L用分子筛充分除水的叔丁醇中,0.35 g抗坏血酸与3.72 g油茶籽油(L-抗坏血酸和脂肪酸的底物摩尔比为1∶6)在150 mg脂肪酶Novozym 435的催化下,反应初始加入1.0 g分子筛4?,温度55℃,转速200 r/min,反应36 h后底物转化率可达65%。     

正己烷反应体系中酶法转化乙酸3-甲硫基丙醇酯的工艺条件

研究了脂肪酶催化合成天然香料乙酸3-甲硫基丙醇酯（EMTP）的关键因素及条件。以发酵3-甲硫基丙醇、己酸为主要原料酶法合成EMTP的反应中,固定化Novozym435脂肪酶为最佳催化剂,正己烷作为溶剂有利于提高酶活力;在正己烷反应体系中,Novozym435用量、分子筛吸水剂用量、乙酸加入次数、反应温度、反应时间等因素对EMTP合成有重要的影响,添加Novozyme435 50mg、分子筛2g、反应温度40℃、乙酸分3次加入、摇瓶速率100～150r／min,反30h为较佳的反应条件,其EMTP产量为6．5mg／mL.     

水/有机溶剂双相体系中色氨酸合成酶酶法合成2-甲基-L-色氨酸

本文作者研究了水/有机溶剂双相体系中利用色氨酸合成酶催化L-丝氨酸和2-甲基吲哚合成2-甲基-L-色氨酸,考察了有机溶剂、有机溶剂体积分数、p H、反应温度、表面活性剂、金属离子和底物浓度对色氨酸合成酶催化合成2-甲基-L-色氨酸的影响。有机溶剂包括二甲苯、甲苯、乙酸乙酯、乙酸丁酯和辛醇,表面活性剂包括吐温80、聚乙二醇辛基苯基醚(OP)、CTAB和Trion X-100,金属离子包括Mg2+、Ca2+、Cu2+、Co2+和Zn2+。结果表明,酶法最佳转化条件为:有机相溶剂为甲苯,甲苯体积分数为2%,反应温度为40℃,水相p H为8,底物L-丝氨酸浓度为150mmol/L,表面活性剂Trion X-100质量分数为2%,金属离子Ca2+浓度为0.1 mmol/L,色氨酸合成酶酶促反应5 h,2-甲基-L-色氨酸的质量浓度为21.17 g/L。重组大肠杆菌DM206可作为2-甲基-L-色氨酸生产菌,具有较好的2-甲基-L-色氨酸生产潜力。     

重组脂肪酶全细胞催化单糖酯的合成

利用毕赤酵母表面展示南极假丝酵母脂肪酶B(Candida antarctica lipaseB,CALB)为全细胞催化剂,以不同单糖(葡萄糖、果糖和甘露糖)为酰基受体,不同脂肪酸(月桂酸、油酸和棕榈酸)为酰基供体,在以不同有机溶剂为介质的非水相体系中催化合成糖酯.探讨全细胞脂肪酶CALB合成糖酯的反应条件,结果表明:毕赤酵母表面展示CALB全细胞催化剂在叔戊醇/二甲基亚砜(4:1,v/v)介质中可以有效的合成糖酯,研究中各种酰基受体和酰基供体在全细胞脂肪酶催化下均能合成糖酯,其中果糖作为酰基受体产物浓度最高.     

Comparison of extraction solvents and techniques used for the assay of isoflavones from soybean

The impact of extraction solvents and techniques on the assay of isoflavones from soybean was investigated. This systematic study was undertaken to address substantial variations in the solvents and procedures used for the extraction of isoflavones from soybeans by different research groups as described in the recent peer-reviewed published literature. Comparison of four previously optimized and commonly deployed solvent mixtures (acetonitrile:water 58:42 (v/v); ethanol:water 70:30 (v/v); methanol:water 90:10 (v/v); superheated pressurized water) was carried out for the extraction of isoflavones. In addition, we also examined the extraction efficiencies of three additional new solvent mixtures (dimethyl sulphoxide:acetonitrile:water, 5:58:37 (v/v/v); dimethyl sulphoxide:ethanol:water, 5:70:25 (v/v/v); Genapol:water 5:95 (v/v)) for the extraction of isoflavones from soybeans. Assessments of six commonly used extraction techniques (shaking, vortexing, sonication, stirring, Soxhlet, and pressurized liquid extraction (PLE)) with an optimized extraction solvent mixture was also performed. Both, the total isoflavones content and the isoflavones HPLC profile varied significantly with different extraction solvents and techniques. Optimum total isoflavones recoveries from soybean samples were obtained with dimethyl sulphoxide:ethanol:water (5:75:25, v/v/v) solvent mixture using a PLE. Intermediate extraction recoveries of total isoflavones from soybean samples were obtained with the other extraction solvent mixtures and techniques tested. The extraction efficiencies of isoflavones with shaker, vortex, stirring, and Soxhlet were between 65% and 70% as compared to PLE. Total isoflavones extracted by the sonication procedure was 93.3% as compared to PLE.     

Stability of immobilized thermolysin in organic solvents

Various factors affecting the stability of thermolysin immobilized by cross-linking with glutaraldehyde were elucidated, particularly in the water-immiscible organic solvents such as ethyl acetate and tert-amyl alcohol. The main reason for enzyme inactivation in water-immiscible organic solvents was found to be autolysis in the water phase, which may surround the enzyme immobilized inside the support. By contrast, in water-miscible organic solvents thermal denaturation was the predominant cause of enzyme inactivation. Courses of inactivation were expressed by second-order kinetics in the initial stage, after which inactivation proceeded at a slower rate. The extent of autolysis was found to strongly depend on the kind of organic solvent, the water content, and type of support and these dependencies were explained by the difference in the amount and state of water inside the support. Thermolysin was immobilized onto Amberlite XAD-7 as a compact aggregate inside the support which may increase the stability of the enzyme. Finally, it was shown that the stability of the immobilized enzyme could be correlated with the logP value for water-miscible organic solvents and with the solubility of water for water-immiscible organic solvents.     

Effects of Reaction Medium on Grafting of Acrylonitrile Onto Sodium Salt of Partially Carboxymethylated Amylose

The grafting of acrylonitrile (AN) onto sodium salt of partially carboxymethylated amylose (Na-PCMA) using ceric ammonium nitrate (CAN) as an initiator has been studied in water/solvent mixtures. The solvents used include methanol, ethanol, propanol, butanol, acetone and carbon tetrachloride. The results have been discussed. The effect of reaction medium on the molecular weight of grafted PAN has also been studied. The chain transfer constants (C_s) for solvents like methanol, ethanol, propanol, butanol, acetone and carbon tetrachloride have been evaluated at 30°C by the help of Mayo's equation.     

非水介质中脂肪酶催化合成正戊酸异戊酯的研究

德氏根霉菌(Rhizopusdelemar) 经固态发酵生产脂肪酶,以此酶为催化剂,在非水介质中合成了正戊酸异戊酯。研究了反应温度、溶剂、底物浓度、底物摩尔比、吸水剂用量等因素对酯化反应的影响,确定了正戊酸异戊酯的最佳合成条件为:反应温度为5 0℃,异辛烷为反应介质,底物浓度为0 15mol/L ,酸醇摩尔比为1∶1 4。在反应体系中需加入0 2 5 g/mL的5 分子筛,以吸收酯化反应生成的水。在优化的条件下,反应6h后,酯合成转化率达98%。     

顶空气相色谱法测定奥贝胆酸原料药中有机溶剂的残留量

目的建立同时测定奥贝胆酸原料药中甲醇、乙醇、异丙醇、乙腈、二氯甲烷、正己烷、乙酸乙酯、四氢呋喃、三乙胺、甲苯10种有机溶剂残留量的方法。方法采用顶空气相色谱法。以Agilent DB-624毛细管柱为色谱柱,经程序升温,采用氢火焰离子化检测器,外标法计算溶剂残留量。结果在此色谱条件下,甲醇、乙醇、异丙醇、乙腈、二氯甲烷、正己烷、乙酸乙酯、四氢呋喃、三乙胺、甲苯10种待测有机残留溶剂的分离度均大于2.0,线性、准确度、精密度良好,9批样品中10种有机溶剂残留均符合要求。结论经方法学验证,该方法操作简单,重复性好,准确度高,适用于奥贝胆酸原料药中10中有机溶剂残留的同时测定。     

Changes in interfacial tension of chlorinated solvents following flow through U.K. soils and shallow aquifer material

The interfacial tension (IFT) that arises at the interface between water and an immiscible organic liquid is a key parameter affecting the transport and subsequent fate of the organic liquid in water-saturated porous media. In this paper, data are presented that show how contact between a range of soil types and chlorinated hydrocarbon solvent (CHS) dense nonaqueous phase liquids (DNAPLs) can affect DNAPL/water IFT values. The soils examined are indicative of U.K. soil types and shallow aquifer materials. The solvents investigated were tetrachloroethylene (PCE) and trichloroethylene (TCE). Lab grade, recovered field DNAPL and industrial waste chlorinated solvent mixtures were used. The data from batch and column experiments invariably revealed that water/DNAPL IFT values change following contact with unsaturated soils. In the majority of cases, the IFT values increase following soil exposure. However, after contact with an organic-rich soil, the IFT of the lab grade solvents decreased. The experimental evidence suggests that these reductions are linked to the removal of organic material from the soil and its subsequent incorporation into the solvent IFT increases in the case of lab solvents are shown to be linked to the removal of stabilizers (added by the manufacturers to obviate degradation) that are removed by adsorption to soil mineral surfaces. Similarly, it is conjectured that adsorption of surface-active compounds from the industrial waste samples to soil surfaces is responsible for increases in the IFT in these samples. Finally, it was observed that invading CHSs are capable of dissolving and subsequently mobilizing in-situ soil contaminants. GC/MS analysis revealed these mobilized soil contaminants to be polyaromatic hydrocarbons and phthalate esters.     

Lipase-catalyzed synthesis of fatty acid fructose esters

Fatty acid sugar esters are non-ionic surfactants which are widely used in food, cosmetic and pharmaceutical industry. Lipase-catalyzed synthesis of fructose with fatty acid in organic medium was performed in a batch reactor at atmospheric pressure. Influence of different reaction parameters, such as different kinds of lipase preparations and organic solvents, biocatalyst concentration, molecular sieve concentration, temperature, stirring rate and the use of different fatty acids as acyl donors was studied. Optimum conditions were found using 10% (w/w of substrates) lipase from Candida antarctica B (Novozym 435) and 12.1% (w/w) of molecular sieves at 60 °C and stirring rate of 600 rpm. The highest conversion was obtained in ethyl methylketon (82%), which is permitted for general use in the manufacture of food additives.     

硝酸银吸附柱分离亚麻酸乙酯过程中影响因素的研究

研究了负载型硝酸银吸附柱分离亚麻酸乙酯过程中的影响因素,考察了载体类型(硅胶、氧化铝)、溶剂种类(石油醚、正己烷、超临界CO2)等对亚麻酸乙酯分离效果的影响.研究结果表明,超临界流体分离效果优于石油醚和正己烷等有机溶剂,氧化铝载体分离效果优于硅胶,超临界流体结合硝酸银吸附柱分离亚麻酸乙酯具有较好的效果,可得到纯度约95%的亚麻酸乙酯,其工业应用前景诱人.     

LIPASE-CATALYZED ACYLATION OF MENTHOL WITH VINYL ACETATE IN ORGANIC MEDIA

Menthyl acetate was prepared using vinyl acetate with lipase PS-30 from Pseudomonas sp . as biocatalyst in organic media. Immobilization of the lipase by adsorption onto 0.5 mm diameter glass beads and the presence of molecular sieves improved the yield of menthyl acetate from 24 to 50%. Approximately 40% yield of menthyl acetate was achieved after 48 h incubation with the immobilized lipase. Equimolar ratio of substrates gave higher yields of product compared to higher mole ratios. Synthesis of menthyl acetate increased as the reaction temperature increased from 20 to 60C. An acceptable yield of menthyl acetate was achieved with 400 units of immobilized lipase PS. Less polar solvents appeared to be better than polar solvents for the enzymatic synthesis of menthyl acetate by transesterification.     

The Dehydration of Fructose Towards 5-Hydroxymethylfurfural Using Activated Carbon as Adsorbent

5-Hydroxymethylfurfural (HMF) can be selectively adsorbed onto activated carbon with loadings up to 30% (w/w), depending on the type of carbon used. Adsorption isotherms of HMF on several types of carbon and in different solvents are presented. Activated carbon is used in in the dehydration of fructose towards HMF in order to suppress the formation of side-products (e. g. levulinic acid). A dehydration set-up in which the formation and adsorption of HMF take place at different temperatures is presented. The HMF is recovered by extraction of the loaded activated carbon with organic solvent.