酶法生产L-高苯丙氨酸的研究进展

L-高苯丙氨酸(L-homophenylalanine,L-HPA)作为一种重要的非天然氨基酸,是合成治疗高血压的普利类药物等的关键中间体,具有广阔的市场前景。目前L-高苯丙氨酸的合成主要依赖于化学法,但化学合成L-高苯丙氨酸具有原料昂贵、步骤繁琐和污染严重等缺点,限制了广泛应用。因此,国内外研究者对L-高苯丙氨酸的酶法生产进行了深入的研究。本文就目前酶法合成L-高苯丙氨酸的工艺,包括脱氢酶法、转氨酶法、海因酶法和脱羧酶法的研究进展进行了综述,为酶法合成L-高苯丙氨酸提供一定的借鉴,为最终实现L-高苯丙氨酸的酶法工业化生产奠定基础。     

酶法生产稀少糖的研究进展

稀少糖是指自然界中存在稀少的单糖及其衍生物,可应用于食品、制药和营养等许多领域,同时也可以作为各种天然产品和候选药物的原料。目前大多数稀少糖因其在自然界中含量稀少而非常昂贵,而且这些稀少糖的化学合成原料价格高昂,不利于其大量生产。由于酶催化反应具有反应条件温和、特异性强、效率高、可持续性强等优点,稀少糖酶法生物合成已成为这一领域的有力工具。文中就稀少糖,包括D-阿洛酮糖、D-塔格糖、D-山梨糖、L-果糖、D-阿洛糖等其他稀少糖的生物学功能及应用,以及稀少糖相关酶的研究和酶法生产进行综述。     

生物酶法制备D-对羟基苯甘氨酸的研究

生物酶法生产D-对羟基苯甘氨酸具有良好的应用前景。通过介绍生物酶法生产D-对羟基苯甘氨酸的研究现状,从酶的分离纯化、酶和细胞的固定化、反应介质研究和反应动力学研究以及基因工程进展几个方面作了总结。     

微生物酶法制备D-对羟基苯甘氨酸的研究进展

D-对羟基苯甘氨酸(D-p-HPG)是半合成青霉素和头孢霉素的重要前体。综述了微生物酶法生产D-对羟基苯甘氨酸的方法种类及其优缺点并对酶的来源即菌种的选育方法做了总结。此外,还简介了基因工程领域内的研究状况。     

Advances in ethanol production

Barriers to the commercialization of lignocellulosic ethanol include the development of more robust biocatalysts, reduction of cellulase costs, and high capital cost associated with a complex process. Improvements have been made in all areas during the past two years. Oxidoreductases, transporters, and regulators have been identified that can increase the tolerance of biocatalysts to inhibitors formed during pretreatment. Biocatalysts are being developed that grow under conditions that are optimal for cellulase activity and others have been engineered to produce glycoside hydrolases. Ethanol yields resulting from most current process configurations are similar, approximately 0.21 g ethanol/g dry cellulosic feedstock. Potentially, this can be increased to at least 0.27 g ethanol/g biomass (83 gal/ton) using simpler processes.     

Perspectives for the industrial enzymatic production of glycosides

Glycosides are of commercial interest for industry in general and specifically for the pharmaceutical and food industry. Currently chemical preparation of glycosides will not meet EC food regulations, and therefore chemical preparation of glycosides is not applicable in the food industry. Thus, enzyme-catalyzed reactions are a good alternative. However, until now the low yields obtained by enzymatic methods prevent the production of glycosides on a commercial scale. Therefore, high yields should be established by a combination of optimum reaction conditions and continuous removal of the product. Unfortunately, a bioreactor for the commercial scale production of glycosides is not available. The aim of this article is to discuss the literature with respect to enzymatic production of glycosides and the design of an industrially viable bioreactor system.     

Biodiesel production via enzymatic catalysis

A review of current work in biodiesel production via enzymatic catalysis has been done. The parameters of the process as determined by laboratories are represented and analyzed. The main factors affecting interesterification are considered. The major types of oils and alcohols used in biodiesel synthesis are listed. The means of lipase enzyme immobilization, including exposure on the cell surface, are discussed.     

Microbial and enzymatic production of l-carnitine

l-Carnitine (vitamin B_T) plays a vital role in the transportation of long-chain fatty acids into mitochondrial matrix in mammals. l-Carnitine has a wide range of applications in pharmaceuticals, food products, and feed additives. Due to the increasing demand for l-carnitine in food and pharmaceutical applications, production of this compound has become prominent. However, very little has been reported on the production of l-carnitine. This review discusses the microbial and the enzymatic production of l-carnitine from different starting materials (substrates).     

酶法转化生产α-酮酸的研究进展

α-酮酸是一种同时含有羧基和酮基的双官能团有机化合物,广泛应用于食品、药品和化妆品等行业。为了满足环境友好、安全高效和可持续发展的社会要求,利用酶转化法生产α-酮酸受到人们的广泛关注。文中从酶的筛选、酶的改造以及酶的转化条件优化3个方面介绍丙酮酸、α-酮戊二酸、酮亮氨酸、酮缬氨酸、苯丙酮酸和酮蛋氨酸酶法合成的研究状况,并展望了α-酮酸进一步高效生产的发展方向。     

Advances in transgenic rat production

Predictable and reproducible production of transgenic rats from a standardized input of egg donors and egg recipients is essential for routine rat model production. In the course of establishing a transgenic rat service, transgenic founders were produced from three transgenes in outbred Sprague-Dawley (SD) rats and four transgenes in inbred Fischer 344 (F344) rats. Key parameters that affect transgenesis efficiency were assessed, including superovulation treatments, methods to prepare pseudopregnant recipients, and microinjection technique. Five superovulation regimens were compared and treatment with 20 IU PMSG and 30 IU HCG was selected for routine use. Four methods to prepare pseudopregnant egg recipients were compared and estrus synchronization with LHRHa and mating to vasectomized males was selected as most effective. More than 80% of eggs survived microinjection when modified pronuclear microinjection needles and DNA buffers were used. The efficiencies of transgenic production in rats and C57BL/6J (B6J) mice were compared to provide a context for assessing the difficulty of transgenic rat production. Compared to B6J mice, SD rat transgenesis required fewer egg donors per founder, fewer pseudopregnant egg recipients per founder, and produced more founders per eggs microinjected. Similar numbers of injection days were required to produce founders. These results suggest that SD rat transgenesis can be more efficient than B6J mouse transgenesis with the appropriate technical refinements. Advances in transgenic rat production have the potential to increase access to rat models.     

An overview of enzymatic production of biodiesel

Biodiesel production has received considerable attention in the recent past as a biodegradable and nonpolluting fuel. The production of biodiesel by transesterification process employing alkali catalyst has been industrially accepted for its high conversion and reaction rates. Recently, enzymatic transesterification has attracted much attention for biodiesel production as it produces high purity product and enables easy separation from the byproduct, glycerol. But the cost of enzyme remains a barrier for its industrial implementation. In order to increase the cost effectiveness of the process, the enzyme (both intracellular and extracellular) is reused by immobilizing in a suitable biomass support particle and that has resulted in considerable increase in efficiency. But the activity of immobilized enzyme is inhibited by methanol and glycerol which are present in the reacting mixture. The use of tert-butanol as solvent, continuous removal of glycerol, stepwise addition of methanol are found to reduce the inhibitory effects thereby increasing the cost effectiveness of the process. The present review analyzes these methods reported in literature and also suggests a suitable method for commercialization of the enzymatic process.     

Chitooligosaccharides enzymatic production by Metarhizium anisopliae

The products of chitosan hydrolysis are chitooligosaccharides and are used mainly for medical applications due to their specific biological activities. The objective of this study was to detect and identify the products of enzymatic hydrolysis of chitosan (dimers to hexamers) using a crude extract of chitosanolytic enzymes produced by the fungus Metarhizium anisopliae. These fungus was able to produce, during 48 h cultivation in a medium containing chitosan, chitooligosaccharides ranging from dimers, trimers, tetramers and pentamers at concentrations 0.2, 0.19, 0.06, 0.04 mg/mL, respectively, and the enzymatic activity was 2.5 U/L. Using the crude enzyme extract for chitosan hydrolysis, we detected the presence of dimers to hexamers at hydrolysis times of 10, 20, 30, 40, 50 and 60 min of enzymatic reaction, but the yields were higher at 10 min (54%). The hexamers was obtained only with 30 min of reaction with concentration of 0.004 mg/mL.     

Quantitative enzymatic production of 6-O-acylglucose esters

Selective production of emulsifiers from glucose and fatty acids has been achieved using an immobilized Candida antarctica lipase. Optimization of process selectivity considers the solubilities of the sugar and its monoesters in acetone at different temperatures, the percentage of this organic solvent in the reaction mixture, and the reaction temperature. The solvent (acetone) is both easily eliminated and accepted by the European Community for use in the manufacture of foods and/or food additives. Different fatty acids with a longer length chain than that of caprylic acid may be employed. For saturated fatty acids longer than lauric acid, continuous precipitation of the monoester as it is formed at 40 degrees C permits nearly complete conversion (98%) of glucose to the monoester within 2-3 days. The procedure does not require total dissolution of the sugar, and precipitation of the monoester permits selective conversion of charges of glucose higher than 100 mg/mL solvent. A scaleup of the process under the optimum conditions gives high yields of 6-O-lauroyl glucose, which may be readily prepared on a gram scale. Copyright 1998 John Wiley & Sons, Inc.     

Advances in electrochemical cofactor regeneration: enzymatic and non-enzymatic approaches

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Advances in the production and downstream processing of antibodies

Sales of monoclonal antibody (mAbs) therapies exceeded $ 40 billion in 2010 and are expected to reach $ 70 billion by 2015. The majority of the approved antibodies are targeting cancer and autoimmune diseases with the top 5 grossing antibodies populating these two areas. In addition over 100 monoclonal antibodies are in Phase II and III of clinical development and numerous others are in various pre-clinical and safety studies. Commercial production of monoclonal antibodies is one of the few biotechnology manufacturing areas that has undergone significant improvements and standardization over the last ten years. Platform technologies have been established based on the structural similarities of these molecules and the regulatory requirements. These improvements include better cell lines, advent of high-performing media free of animal-derived components, and advances in bioreactor and purification processes. In this chapter we will examine the progress made in antibody production as well as discuss the future of manufacturing for these molecules, including the emergence of single use technologies.     

微生物酶法消除黄酒中氨基甲酸乙酯研究进展

氨基甲酸乙酯(Ethyl carbamate,EC)具有致癌性,广泛存在于酒精饮料中。我国的黄酒因EC含量高而带来的食品安全问题越来越受到人们的关注。微生物酶法消除黄酒中的EC具有直接、高效的特性而被深入研究。文中从黄酒中EC的形成机制、酸性脲酶研究现状、氨基甲酸乙酯水解酶研究现状等方面概述了微生物酶法消除黄酒中EC的研究进展及存在的问题。并针对这些问题,提出了寻找新型氨基甲酸乙酯水解酶、Fe~(3+)依赖型双功能酸性脲酶食品级表达与定向进化及双酶并用将尿素和EC一起消除的策略。     

Advances in the production of membrane proteins in Pichia pastoris

Membrane proteins play key roles in diverse cellular functions and have become the target for a large number of pharmacological drugs. Despite representing about 20-30% of cellular proteins, their characterization is long overdue since they are difficult to handle, to purify from their natural source or to obtain as recombinant proteins. Pichia pastoris is a methylotrophic yeast species increasingly used as a host for heterologous protein expression for both research and industrial purposes. Over the past few years many efforts have allowed important advances in the development of this expression system for the expression and production of membrane proteins. The most recent achievements in improving yield and proper folding of integral membrane proteins are summarized in this review.