反应萃取法在氨基酸分离中的应用

反应萃取法是分离提取氨基酸的一种重要方法,具有分离效率高,萃取剂可重复利用,分离过程中产生的废水废液少,具有广泛的应用前景。本文综述了常见的反应萃取剂及在氨基酸分离中的应用,分析了反应萃取法分离氨基酸的影响因素,介绍了几种与反应萃取法结合分离氨基酸的技术。     

提高氨基酸分析仪分离度方法的研究

日立L8800氨基酸全自动分析仪应用广泛,因氨基酸的种类较多,性质相似,常出现分离度达不到要求的现象,本文研究改进缓冲液的配方和各种缓冲液的切换时间,提高了氨基酸分析仪的分离度,17种氨基酸的分离度全部大于1.2,符合该种仪器使用说明书对新出厂仪器的"性能保证指标"中"分离度大于1.2及以上"的要求,提高了该项目分析结果的准确性。     

萃取分离氨基酸研究进展

综述了萃取分离氨基酸的各种方法的研究进展。在此基础上，提出了氨基酸核电中性分子的萃取分离途径，并实验证明通过质子转移反应分离氨基酸荷电中性分子的可能性。     

混合氨基酸的分离技

本文介绍了特殊沉淀法、离子交换法、溶剂萃取法分离混合氨基酸的技术并指出了它们的缺点,详细地介绍了反胶团萃取法分离氨基酸的最新研究成果,对反胶团萃取分离混合氨基酸提出了发展设想。     

乳状液膜法分离二元氨基酸的研究

定义了乳状液膜法分离氨基酸的分离系数，并以苯丙氨酸(Phe)／天冬氧酸(Asp)作为研究对象，探讨了影响分离系数的主要因素。研究结果表明：用稳态条件下液膜体系中两种氨基酸的传质通量之比定义两种氨基酸的分离系数，能够较全面反映两种氨基酸及液膜体系所具有的特性以及影响分离系数的复杂因素，为改善分离效果提供理论指导。对于采用酸性萃取剂为载体的液膜体系来说，pH值是影响两种氨基酸分离系数的主要因素，而载体浓度对分离系数的影响程度相对较小。     

多级连续电渗析分离丝氨酸和脯氨酸

为解决等电点相近的氨基酸的分离问题,采用多级连续电渗析,以丝氨酸（Ser）和脯氨酸（Pro）为例,探讨了级数、电流和NaOH浓度对分离性能的影响。实验结果表明,用多级连续电渗析分离近等电点氨基酸是可行的。增加级数,可提高脯氨酸产品纯度,但丝氨酸产品纯度变化不大。增大电流,脯氨酸产品纯度有所提高,而丝氨酸产品纯度略有下降。在原料中加入适量的NaOH有利于提高分离性能。     

壳聚糖改性纸层析分离氨基酸

用壳聚糖及经戊二醛交联的壳聚糖涂覆层析滤纸分离氨基酸,可以快速简便地将混合氨基酸加以分离,其分离效果较一般滤纸要好。     

电驱动膜过程在氨基酸发酵液处理中的研究进展

在发酵法生产氨基酸的过程中,需要后续工艺对发酵液进行分离纯化以提取目标产物.电驱动膜过程正逐渐成为该领域研究与应用的热点.本文介绍了近年来国内外普通电渗析(ED)、双极膜电渗析(BMED)、离子取代电渗析(ISED)、电复分解反应器(BMT)等常见的电驱动膜过程在氨基酸发酵液处理中的研究进展,简述了常见的膜堆构型及其工作原理、特点与应用实例.分析表明电驱动膜过程可以实现混合氨基酸分离、无机盐脱除以及氨基酸的制备,膜堆结构、操作参数的优化以及新型分离膜的研究与应用可以提高过程性能.同时也指出目前该领域的研究尚处于实验室研究阶段,研究对象以模拟发酵液为主,规模化应用的报道还不多见.但是可以预见高效、环保的电驱动膜过程将会在氨基酸发酵液处理中发挥重要作用.     

国内外氨基酸技术指标对比及分析方法研究进展

氨基酸是一切生命的物质基础,氨基酸的制备、分离纯化及分析检测等技术对生命科学和医药等的研究发展具有重要意义。随着上述研究及产业领域的快速发展,对高纯度氨基酸的需求也日益增加。发展高效的氨基酸分离纯化方法,建立不同纯度氨基酸的技术指标及标准分析方法,是规范行业发展、提升产品质量的关键。以L-谷氨酸为例,对比了国内外类似纯度产品的技术指标和分析方法。进一步综述了现阶段氨基酸的分离纯化及分析方法的发展概况。     

卡那霉素修饰醋酸纤维素膜的制备及应用

应用卡那霉素对醋酸纤维素膜进行手性修饰,由于修饰后的纤维素膜对D型和L型的氨基酸结合能力不同,所以可以根据氨基酸的渗透速率不同来实现手性分离。实验对色氨酸、酪氨酸以及苯丙氨酸三种氨基酸对映体进行研究。实验结果表明,与色氨酸和苯丙氨酸对映体相比,酪氨酸对映体的分离度最高,即手性分离效果最好。实验过程中,还对实验条件进行了探索,发现不同条件下,手性拆分效果也是不同的。     

用电渗析法从谷氨酰胺模拟发酵液中脱除谷氨酸

为改进微生物发酵法生产谷氨酰胺的流程,提出用电渗析方法来分离谷氨酰胺和谷氨酸。在对混合氨基酸溶液中离子成分进行分析的基础上,预测了此方法的可行性,并通过电渗析方法对模拟发酵液进行实验来验证此预测结果。还考察了在混合物中含有硫酸铵时的情况。通过理论预测和实验验证,可以用电渗析法直接分离谷氨酰胺和谷氨酸,且原料中少量的硫酸铵有利于分离过程的进行。     

Separation and identification of amino acids from lignite humic acids by thin layer chromatography

Thin layer chromatography with and without temperature gradient was used to identify ten amino acids in the humic acid hydrolysate of Rovinari lignite, using cellulose and volcanic tuff as stationary phases. The acids found were L-leucine, isoleucine, phenylalanine, L-valine, tyrosine, proline, L-alanine, glutamic acid, threonine and L-lysine.     

Biochemical Studies on Pepper Seeds at Different Maturity Stages and Stored for Various Periods

Fatty acid, unsaponifiable matter and amino acid compositions of pepper seeds extracted from green, green with red streaks and red-ripe fruits and stored for various periods were studied. Linoleic and palmitic acids were increased and decreased during seed ripening, respectively. A reverse observation was found during storage. The concentration of individual unsaponifiable matter varied according to the different maturity stages. The ratio between sterols might govern the germination rate of pepper seeds. A progressive increase in the concentration of all amino acids and in particular arginine and glutamic acids during seed ripening was found. The amino acid pattern of pepper seeds was not affected by the different maturity stages and storage periods.     

Surface treatment with amino acids of porous collagen based scaffolds to improve cell adhesion and proliferation

The purpose of this study was to improve the biocompatibility of glutaraldehyde (GA) cross‐linked chitosan coated collagen scaffold for cartilage tissue regeneration. In order to prevent the potential toxicity of GA, we treated the designed scaffold with either glutamic acid or glycine. Amino acid treated scaffolds were characterized by scanning electron microscopy (SEM) techniques. Afterward, chondrocyte interaction with the composite scaffold was investigated assessing cell adhesion and proliferation using Hoechst staining and MTT cell proliferation assay, respectively. The SEM analyses of the scaffolds’ surface and cross‐section confirmed the adhesion of amino acids on the surface of the scaffolds. We also observed that scaffolds’ porosity was reduced due to the coverage of the pores by chitosan and amino acids, leading to low porosity. The use of amino acid improved the chondrocyte adhesion and proliferation inside the scaffolds’ pores when cells were cultured onto the chitosan‐coated collagen scaffolds. Overall, our in vitro results suggest the use of amino acid to improve the biocompatibility of natural polymer composite scaffold being crosslinked with glutaraldehyde. Such scaffold has improved mechanical properties; biocompatibility thus may be useful for tissue regeneration such as cartilage.

     

Mechanistic understanding of the fermentative L‐glutamic acid overproduction by Corynebacterium glutamicum through combined metabolic flux profiling and transmembrane transport characteristics

Since the 1950s when Micrococcus glutamicus later renamed Corynebacterium glutamicum was discovered, the production of amino acids by fermentative methods has become an important aspect of industrial microbiology. Numerous studies to understand and improve the metabolic conditions leading to amino acid overproduction have been carried out. Most amino acids are currently produced by use of mutants that contain combinations of auxotrophic and regulatory mutations. L ‐Glutamic acid is the amino acid produced in the greatest quantities (10⁶ tonnes per year) and Corynebacteria are central to its industrial production. However, further improvements to strain performance are difficult to obtain by empirical optimization and a more rational approach is required. The use of metabolic flux analysis provides valuable information regarding bottlenecks in the formation of desired metabolites. Such techniques have found application in elucidating flux control, provided insight into metabolic network function and developed methods to amplify or redirect fluxes in engineered bioprocesses. Hence, branch points in biosynthesis, precursor supply in fuelling reactions and export of metabolites can be manipulated, resulting in high glutamic acid overproduction by Corynebacterium glutamicum fermentations. In this review, in addition to reviewing the state of play in metabolic flux analysis for glutamate overproduction, the metabolic pathways involved in the production of L ‐glutamic acid, the mechanisms mediating its efflux and secretion as well as their manipulation to achieve higher glutamate production, are discussed. The link between metabolic flux and transmembrane transport of glutamic acid are also considered. Copyright © 2004 Society of Chemical Industry     

Preparation and cell compatibility evaluation of chitosan/collagen composite scaffolds using amino acids as crosslinking bridges

In this study, a novel freeze‐gelation method instead of the conventional freeze‐drying method was used to fabricate porous chitosan/collagen‐based composite scaffolds for skin‐related tissue engineering applications. To improve the performance of chitosan/collagen composite scaffolds, we added 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide (EDC) and amino acids (including alanine, glycine, and glutamic acid) in the fabrication procedure of the composite scaffolds, in which amino acid molecules act as crosslinking bridges to enhance the EDC‐mediated crosslinking. This novel combination enhanced the tensile strength of the scaffolds from 0.70 N/g for uncrosslinked scaffolds to 2.2 N/g for crosslinked ones; the crosslinked scaffolds also exhibited slower degradation rates. The hydrophilicity of the scaffolds was also significantly enhanced by the addition of amino acids to the scaffolds. Cell compatibility was demonstrated by the in vitro culture of human skin fibroblasts on the scaffolds. The fibroblasts attached and proliferated well on the chitosan/collagen composite scaffolds, especially the one with glutamic acid molecules as crosslinking bridges, whereas cells did not grow on the chitosan scaffolds. Our results suggest that the collagen‐modified chitosan scaffolds with glutamic acid molecules as crosslinking bridges are very promising biomaterials for skin‐related tissue engineering applications because of their enhanced tensile strength and improved cell compatibility with skin fibroblasts. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

野生植物白酒草的营养成分

对野生植物白酒草的营养成分进行了分析,结果表明,白酒草中含有多种营养成分,丰富的矿质元素和维生素及其β-胡萝卜素,至少含有17种氨基酸。其中总糖、谷氨酸、VB2、钙含量较高。     

Ligand-Exchange Chromatography of Amino Acids on Copper-Loaded Chitosan

Abstract

Amino acids are retained on the copper form and on the amino copper form of chitosan, especially aspartic acid, glutamic acid, tryptophan, and cysteine. The best conditions for collection and for elution are in phosphate buffers at pH 7 and 12, respectively. No leakage of copper occurs; the amino acids are recovered as copper complexes with a ratio of 1:2 copper: amino acid. Several advantages of chitosan over the resin Chelex are pointed out; namely, absence of swelling, great copper capacity. hydrophilicity, and porous structure.     

加盐方式对鸡汤中呈味物质的影响分析

为了考察加盐方式对鸡汤呈味物质的影响,采用高效液相色谱法对煮制前加盐、煮制后加盐和不加盐3种煮制鸡汤中的核苷酸、有机酸、游离氨基酸含量进行了检测与分析,以鸡汤中呈味物质的滋味活性值(TAV)和味精当量(EUC)为评价指标,结果发现,煮制前加盐鸡汤中5?-胞苷酸、5?-鸟苷酸、乳酸、琥珀酸、组氨酸、谷氨酸含量和游离氨基酸总量均大于其他两种加盐方式煮制的鸡汤。3种煮制样品中乳酸和琥珀酸的TAV均大于1,对鸡汤的滋味有直接贡献,而天冬氨酸在3种煮制方式中的含量没有显著变化。感官评价结果显示,煮制前加盐鸡汤的整体风味最好。     

Production and purification of glutamic acid: A critical review towards process intensification

Amidst growing environmental awareness and stringent discharge regulations, chemical and allied process industries are now desperately seeking replacement of the conventional, polluting processes by clean and green processes. In this context, production and purification of amino acids like l-glutamic acid assumes significance. Concerned conventional process involves several steps like fermentation, centrifugation, carbon adsorption, evaporation, crystallization, ion-exchange and so on to get glutamic acid in desired concentration and purification. Despite its tremendous potential for large scale use in a wide variety of applications, cost-effective production of high purity glutamic acid has remained a challenge for decades, mainly due to several downstream processing steps and the associated cost factors. With emergence of tailor-made membranes and modules, possibility of using membranes in downstream purification of glutamic acid appears imminent with expectation of a turnaround in amino acid manufacturing industry. The present study through a brief yet comprehensive review of the very critical aspects of glutamic acid production and purification, attempts to direct research efforts towards process intensification encompassing the concepts of green processing, compact and flexible design with promise of more economically attractive production with better quality.