一种适合于糖酯合成的微乳液体系的建立

糖酯是一种重要的非离子型表面活性剂,它具有良好的乳化性能,在食品、化妆品及医药工业中应用非常广泛,在洗涤剂、染料和油漆工业中也有重要应用.过去糖酯的合成主要采用化学法;近年来,国外许多研究者开始采用酶法合成.酯交换反应合成糖酯的原料为糖和油脂,无论是化学法或酶法,考虑到糖与油脂的溶解度问题,均采用吡啶、二甲基甲酰胺等有机     

一种适合于糖酯合成的微乳液体系的建立

糖酯是一种重要的非离子型表面活性剂,它具有良好的乳化性能,在食品、化妆品及医药工业中应用非常广泛,在洗涤剂、染料和油漆工业中也有重要应用。过去糖酯的合成主要采用化学法;近年来,国外许多研究者开始采用酶法合成。酯交换反应合成糖酯的原料为糖和油脂,无     

脂肪酶催化糖酯合成的研究进展

糖酯是应用广泛的无毒非离子表面活性剂。相比于传统化学合成方法,酶催化合成糖酯具有众多优点,非常适合于食品添加剂的生产。酶催化合成糖酯的研究主要集中在酶的筛选,反应介质,反应底物,反应条件等方面。本文主要对近年来酶催化合成糖酯研究进展进行论述,并讨论了其中的问题和发展方向。     

离子液体在酶促合成糖酯中的应用

糖酯是一类非离子型生物表面活性剂,广泛应用于食品、医药、化妆品行业,部分糖酯及其衍生物还具有抗肿瘤和抗菌活性。在糖酯传统合成方法中,存在着糖类易焦化、区域选择性差、有机溶剂残留、酶易失活等问题。离子液体作为环境友好溶剂和催化剂,具有结构可设计等优势,成为糖酯合成研究中热点领域,本文总结其优缺点,指出今后的研究重点。     

多糖的酶法合成及其过程强化

多糖的酶法合成与过程调控是生物工程及药物开发领域的研究热点。以同多糖、杂多糖和多糖复合物等为代表的多糖类物质的酶法合成技术开发受到广泛关注,多糖的酶法合成以其高度区域选择性和立体选择性、酶可重复利用且环境友好无污染等优点,开始从实验室进入产业领域。酶法合成过程的强化是其产业化应用的关键,通过合成酶固定化、酶的定向变异、化学法与酶法结合等途径可以有效解决酶法合成目前存在的合成酶制备困难、合成反应复杂且产物相对分子质量分布难以控制等不足。酶法合成将成为功能性多糖及糖类聚合物研发与制备的有效途径。     

无溶剂体系中固定化脂肪酶催化合成香茅醇酯

在无溶剂体系中以大孔树脂NKA吸附固定的褶皱假丝酵母脂肪酶(Candida rugosalipase)为催化剂,以脂肪酸为酰基供体,酶法合成香茅醇脂肪酸酯。考察了褶皱假丝酵母脂肪酶对酰基供体的选择性,以及反应温度、摇床转速、酶用量、底物比例及微量水添加等对酯化反应的影响,建立了无溶剂中香茅醇酯的酶法合成工艺。研究表明,在酸醇物质的量比为1,摇床转速为200 r/min,固定化酶用量为1250 U/L,反应温度为50℃,微量水添加量为4μL的条件下,反应10h,月桂酸香茅酯及油酸香茅酯的转化率分别可达95.6%和87.6%,明显高于在有机溶剂体系中的酯化率。     

新型环保增塑剂研究进展

综述了国内外新型环保增塑剂的种类,重点介绍了国内外主要的环保增塑剂的合成方法、性能、应用领域及研究现状,包括环己烷二羧酸酯系列、柠檬酸酯系列、偏苯三酸三酯系列、对苯二甲酸二辛酯系列、聚己二酸酯系列、环氧化环己烷邻二甲酸酯系列、山梨醇二正己酸酯等系列产品。     

酵母脂肪酶酶促合成虾青素琥珀酸酯及优化

研究了酵母脂肪酶在有机溶剂中以琥珀酸酐为酰化试剂酯化合成虾青素琥珀酸酯。液相色谱质谱联用检测表明,酯化产物中既有虾青素单酯也有虾青素二酯。对酶促反应脂肪酶、反应介质、反应底物摩尔比、反应温度等酯化影响因素进行了详细探讨和优化。在所选的几种脂肪酶中,假丝酵母脂肪酶(Candida sp.)的催化活性最好,二甲基亚砜为适宜的反应溶剂,最佳反应温度为45℃。底物摩尔比是决定反应能否进行的关键因素,底物摩尔比为40以上,反应才能进行,摩尔比达到800时,虾青素转化率达到90%以上。底物摩尔比还显著影响产物中单酯和二酯分布,高摩尔比下二酯才能产生。对体系初始含水量和酶量的影响进行了优化。实验结果表明酶法合成虾青素琥珀酸酯具有很好的可行性。     

碳酸甲乙酯酯交换法生产工艺的研究

介绍了碳酸甲乙酯的用途及合成方法,重点阐述了以乙醇钠为催化剂,碳酸二甲酯和乙醇在一定的温度和压力条件下合成碳酸甲乙酯的反应原理和工艺流程。从反应温度、反应压力、精馏方式、催化剂回收等方面对生产工艺过程控制进行了探讨。     

绿色增塑剂柠檬酸三辛酯合成催化剂研究进展

针对柠檬酸三辛酯合成催化剂进行了综述,重点介绍了无机盐、杂多酸、固体超强酸、钛酸酯、离子液体、功能树脂等在制备柠檬酸三辛酯工艺研究中的进展,为开发环保、高效、经济的柠檬酸三辛酯合成催化剂提供借鉴。     

Research progress of lipase-catalyzed synthesis of L-ascorbyl organic acid ester

为了拓宽L-抗坏血酸酯在维护人体健康中的应用,将L-抗坏血酸转化成L-抗坏血酸酯是经济可行的手段。综述了近年来酶催化L-抗坏血酸有机酸酯的研究进展,重点介绍了有机相中L-抗坏血酸饱和脂肪酸酯、不饱和脂肪酸酯、脂肪酸混合酯的酶促合成,对于酶的种类、有机溶剂的选择及分离纯化方法进行了探讨,并对酶催化L-抗坏血酸有机酸酯合成前景进行了展望。     

酶催化区域选择性合成蔗糖酯的研究进展

详细综述了非水相酶催化合成蔗糖酯的研究进展。主要介绍了酶的种类、反应介质、底物性质、外加辅助手段等因素对蔗糖酯产率以及对酶区域选择性的影响。酶催化区域选择性合成蔗糖酯的难点在于蔗糖具有多个可酰化羟基及其与酰基供体的不相溶性,提出通过介质工程、底物修饰改性、外加物理场如微波和超声波辅助等改善底物相溶性,通过筛选酶、蔗糖修饰等可以得到高区域选择性的蔗糖酯。最后指出酶催化合成蔗糖酯存在的问题、发展前景等。     

Enzyme‐catalyzed regioselective synthesis of sugar esters and related compounds

In this review, a comprehensive and illustrative survey is made of the regioselective synthesis of esters of sugars and related compounds using lipases. The main emphasis has been given to the screening and use of commercially available lipases for the enzymatic esterification of neutral monosaccharides, disaccharides, sugar alcohols and their selected ether and ester derivatives. The effect of solvents and solubilizing agents in improving the yields of the resultant sugar fatty acid esters has been incorporated. Further, solvent‐free esterification with molten fatty acids, use of ionic liquids and microwave radiations for improvement in the methodology have also been discussed. Copyright © 2006 Society of Chemical Industry     

Enzymatic Synthesis of Glucose- and Xylose Laurate Esters Using Different Acyl Donors,Higher Substrate Concentrations,and Membrane Assisted Solvent Recovery

Glucose- and xylose laurate esters are enzymatically synthesized using equimolar substrate concentrations in 2-methyl-2-butanol, comparing free lauric acid with methyl- and vinyl-laurate as acyl donors. All reactions result in ≥70% acyl donor conversions after 72 h but the activated donors are also partially hydrolyzed to lauric acid, highlighting the difficulty in controlling water presence in this particular reaction system. The esterification of xylose generates a complex product profile, with several regioisomers of monoesters and diesters. The esterification of glucose is quite selective, forming mainly the 6-O monoester (≥96%) with a small presence of two diester isomers (4%). Increasing substrate concentration up to 800 millimoles kg⁻¹ results in lower conversion values (down to 58%) but shows that the reaction proceeds successfully even in the presence of high amounts of insoluble glucose. However, the reaction is less selective and the proportion of diester increases, becoming up to 46% (molar fraction) of the final product. Solvent recovery after esterification can be achieved by organic solvent nanofiltration through a polymeric membrane able to retain ≥80% of all reaction substrates and products. Practical Applications: The use of high substrate concentrations during the enzymatic synthesis of sugar ester biosurfactants leads to product titers that are more industrially appealing, without the need to find a solvent that can solubilize all initial substrate. The sustainability of the enzymatic conversion at mild temperatures can be enhanced by recycling of the reaction solvent through organic solvent nanofiltration, an energy efficient alternative to other traditional methods like distillation.     

Poly(ester amide)s derived from 1,4-butanediol, adipic acid and 6-aminohexanoic acid. Part II: composition changes and fillers

BAK poly(ester amide)s differing in the amide/ester ratio have been synthesized and characterized, considering spectroscopic data and both thermal and mechanical properties. Degradability under different media (water at 70 °C, acid or enzymatic catalysis at 37 °C) has also been studied by evaluating the changes in intrinsic viscosity, in the NMR spectra and in the surface texture of samples. The use of chain extenders, such as hexamethylene diisocyanate and 1,3-butadiene diepoxide, has been investigated and the optimal reaction conditions are reported here. Changes on mechanical properties due to the incorporation of biodegradable reinforces have also been evaluated. Finally, the synthesis and determination of thermal properties of related poly(ester amide)s constituted by glutaric or succinic acid instead of adipic acid have been investigated.     

Papain-specific activating esters in aqueous dipeptide synthesis

Enzymatic peptide synthesis has the potential to be a viable alternative for chemical peptide synthesis. Because of the increasing commercial interest in peptides, new and improved enzymatic synthesis methods are desirable. In recently developed enzymatic strategies such as substrate mimetic approaches and enzyme-specific activation, use of the guanidinophenyl ester (OGp) group has been shown to suffer from some drawbacks. OGp esters are sensitive to spontaneous chemical hydrolysis and the group is expensive to synthesize and therefore not suitable for large-scale applications. On the basis of earlier computational studies, we hypothesized that OGp might be replaceable by simpler ester groups to make the enzyme-specific activation approach to peptide bond formation more accessible. To this end, a set of potential activating esters (Z-Gly-Act) was designed, synthesized, and evaluated. Both the benzyl (OBn) and the dimethylaminophenyl (ODmap) esters gave promising results. For these esters, the scope of a model dipeptide synthesis reaction under aqueous conditions was investigated by varying the amino acid donor. The results were compared with those obtained from a previous study of Z-X(AA) -OGp esters. Computational docking analysis of the set of esters was performed in order to provide insight into the differences in the reactivities of all the potential activating esters. Finally, selected ODmap- and OBn-activated amino acids were applied in the synthesis of two biologically active dipeptides on preparative scales.     

Fully Enzymatic N→C‐Directed Peptide Synthesis Using C‐Terminal Peptide α‐Carboxamide to Ester Interconversion

Chemoenzymatic peptide synthesis is potentially the most cost‐efficient technology for the synthesis of short and medium‐sized peptides with some important advantages. For instance, stoichiometric amounts of expensive coupling reagents are not required and racemisation does not occur rendering purification easier compared to chemical peptide synthesis. In this paper, a novel interconversion reaction of peptide C‐terminal α‐carboxamides into primary alkyl esters with alcalase was used to develop a fully enzymatic peptide synthesis strategy. For each elongation step a cost‐efficient amino acid carboxamide building block was used followed by the interconversion of the elongated peptide carboxamide to the corresponding primary alkyl ester. These peptide esters are the starting materials for the next enzymatic peptide elongation step.     

Membranes in the enzymatic synthesis of biotensides from renewable sources

A novel integrated process of enzymatic synthesis of sugar fatty acid esters from renewable sources was proposed for the system oleic acid/-methylglucoside focussing on the application of different membrane techniques. The operational parameters were studied and optimised carrying out the reaction in an enzymatic membrane reactor (EMR) where the catalyst remained retained by means of ultrafiltration. A pervaporation unit coupled to the EMR was applied for by-product removal (water). A proper product separation and isolation was achieved applying combined techniques including filtration, evaporation, extraction and alternatively stepwise elution chromatography or dialysis.     

Synthesis of fatty hydroxamic acids catalyzed by the lipase ofMucor miehei

Biotechnological synthesis of a new class of amphiphilic molecules—fatty hydroxamic acids—was carried out using the lipase ofMucor miehei by reacting hydroxyl amine with the fatty acids in their free or methyl ester form. Concurrently with enzymatic synthesis, chemical synthesis of hydroxamic fatty acids has also been developed by adapting methods that already existed for water-soluble acids. Different parameters were studied to determine the optimum operating conditions: temperature, molar ratio of reagents, quantity of biocatalyst and length of reaction. A general method, whatever the type of fatty acids used, is described.     

Performance of Perstractive Enzyme Reactor for Synthesis of Aspartame Precursor

A perstractive enzyme reactor was used for the synthesis of N-(benzyloxycarbonyl)-L -aspartyl-L -phenylalanine methyl ester (ZAPM), the precursor of the artificial sweetener, aspartame. The synthesis of ZAPM in the reactor proceeded by an enzymatic reaction between N-(benzyloxycarbonyl)-L -aspartic acid (ZA) and L -phenylalanine methyl ester (PM) in the aqueous phase. The synthesized ZAPM in the aqueous phase was mainly extracted into the organic phase, therefore, the concentration of ZAPM in the aqueous phase could be kept low. As a result, high conversion of ZAPM was obtained with this system. The partition coefficients of substances in the aqueous/butyl acetate biphasic system, the mass transfer coefficients of substances through the membrane and the enzymatic kinetics of ZAPM synthesis were determined experimentally. The reaction model which was based on the material mass balance equations was discussed to estimate the performance of the perstractive enzyme reactor system. The calculation values using the model and the experimental data showed good agreement with the concentration changes of the substances in the system. © 1997 SCI