食品中展青霉素的产生机制及污染防控策略

展青霉素是由真菌产生的一种聚酮类次级代谢产物,是污染水果及其加工制品的最重要的真菌毒素之一。食品中污染的展青霉素主要由扩展青霉(Penicillium expansum)产生。P.expansum是常见大宗和特色果品的主要采后病原菌,其在引起果实腐烂的同时产生大量的展青霉素,伴随鲜食流通和加工过程进入食物链,危害消费者的健康。展青霉素可侵害人和动物的多个器官,引起急性和慢性症状。由展青霉素污染引起的食品安全问题越来越得到重视,展青霉素的相关研究逐渐成为热点。对展青霉素的产生和调控机制研究进行了系统的总结,介绍了展青霉素生物合成基因簇的组成,生物合成途径中不同步骤的催化酶,展青霉素生物合成和中间产物转运的分子路径;从合成途径特异性调控因子,光、pH值、碳源、硫源等环境信号-全局性调控因子,以及参与组蛋白甲基化和乙酰化修饰的表观遗传因子等不同层次归纳了展青霉素生物合成的复杂调控网络。从源头防控和直接脱除2个方面阐述了食品中展青霉素污染的防控策略,分别概述了基于物理、化学和生物原理的主要防控技术,并讨论了不同防控策略的优缺点。最后,讨论了展青霉素产生机制研究与污染防控技术研发的关系,并指出绿...     

Long‐Aliphatic‐Segment Polyamides: Salt Preparation and Subsequent Anhydrous Polymerization

Long‐aliphatic‐segment polyamides were prepared based on hexamethylenediamine and α,ω‐(CH₂)_x biosynthetic diacids (x = 10, 11, 12). The pertinent monomers (salts) were isolated as solids, thoroughly characterized for the first time, and then submitted to an anhydrous melt prepolymerization technique. The obtained prepolymers exhibited in the range of 5 100–11 800 g · mol^?1, and the molecular weight was further increased by up to 55% through solid‐state finishing. The suggested overall polyamidation cycle was conducted at short melt‐reaction times, so as to avoid any thermal degradation, and was proved efficient, indicating similar reactants polymerizability independently of the methylene content.

     

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     

食品中赭曲霉毒素A的产生机制及污染防控策略

赭曲霉毒素A(ochratoxin A,OTA)主要是由曲霉属(Aspergillus)和青霉属(Penicillium)真菌产生的有毒次级代谢产物,具有肾毒性、肝毒性、致畸性、神经毒性以及潜在致癌性,是世界范围内重点关注的真菌毒素之一。当前关于OTA产毒菌的分类、OTA合成途径及调控机制仍存在争议,制约了食品中OTA污染的高效精准控制。对曲霉属和青霉属中主要OTA产毒菌进行了系统梳理,特别是基于基因组比较数据将一度被认为是主要产毒菌的A. ochraceus中的部分菌株重新鉴定为A. westerdijkiae,介绍了主要产毒菌的产毒能力;系统介绍了OTA生物合成基因簇及关键合成与调控基因,特别是近年发现的新基因——环化酶otaY基因,其可能参与催化OTA生物合成途径初始步骤中的聚酮环化反应,基于最新研究结果进一步完善了OTA生物合成途径;针对食品生产不同环节,介绍了生物、物理和化学防控脱毒策略,重点介绍了针对产毒菌的生物防治方法,针对OTA毒素的生物降解菌及脱毒酶,并比较了不同方法的优缺点。最后,提出了食品OTA污染控制应基于“全链条控制”和“源头防控”的思路,保障食品安全、粮食安全和人民生命健康;分析了生物防治和生物脱毒技术的优缺点,指出绿色、安全的生物防控策略具有广阔的应用前景,是未来研究的重点方向。     

Bioactivities,biosynthesis and biotechnological production of phenolic acids in Salvia miltiorrhiza

ABSTRACT

Salvia miltiorrhiza (Danshen in Chinese), is a well-known traditional Chinese medicinal plant, which is used as not only human medicine but also health-promotion food. Danshen has been extensively used for the treatment of various cardiovascular and cerebrovascular diseases. As a major group of bioactive constituents from S. miltiorrhiza, water-soluble phenolic acids such as salvianolic acid B possessed good bioactivities including antioxidant, anti-inflammatory, anti-cancer and other health-promoting activities. It is of significance to improve the production of phenolic acids by modern biotechnology approaches to meet the increasing market demand. Significant progresses have been made in understanding the biosynthetic pathway and regulation mechanism of phenolic acids in S.miltiorrhiza, which will facilitate the process of targeted metabolic engineering or synthetic biology. Furthermore, multiple biotechnology methods such as in vitro culture, elicitation, hairy roots, endophytic fungi and bioreactors have been also used to obtain pharmaceutically active phenolic acids from S. miltiorrhiza. In this review, recent advances in bioactivities, biosynthetic pathway and biotechnological production of phenolic acid ingredients were summarized and future prospective was also discussed.     

环脂肽的研究进展

脂肽主要通过微生物的非核糖体合成酶途径合成。由于其具有广谱抗菌活性、生物表面活性剂活性、低毒、可生物降解等多种生物学功能而引起人们广泛的关注。环脂肽是由非极性的脂肪酸链结合极性的氨基酸肽链部分构成,其中,氨基酸肽链自身成环或与部分脂肪酸链结合成环。从环脂肽的结构、生物合成机制、合成调控、发酵方式、产量优化策略及利用废弃物生产脂肽等方面综述其研究进展。     

食品中主要真菌毒素生物合成途径研究进展

真菌毒素是真菌重要的次生代谢产物。食品和饲料等农产品在收获、储藏、加工过程中广泛受其污染,造成品质下降、经济损失巨大,并严重威胁人身健康。本文对食品中5种常见真菌毒素(黄曲霉毒素、赭曲霉毒素、伏马菌素、玉米赤霉烯酮和脱氧雪腐镰刀菌烯醇)的生物合成途径分别进行阐释。采用克隆基因的传统分子生物学方法和基因组测序的现代测序技术研究发现,真菌毒素的生物合成基因大多成簇存在,该簇中包含控制合成基因表达的调控基因,并受多种应对外部环境的调控基因所控制。因此本文还结合5种真菌毒素的生物合成基因簇及其基因功能进行综合解析。真菌毒素生物合成的研究将为食品和饲料等农产品的防控、预警以及脱毒提供理论基础和指导方向。     

微生物法合成生物高分子——聚羟基脂肪酸(酯)进展

生物高分子不但具有重要的生理作用,而且以其卓越的结构特性广泛应用于工业领域。微生物法合成生物高分子具有原料来源丰富、反应条件温和、易规模化生产等优点,正在逐渐成为生产天然高分子聚合物的重要方法。文中系统阐述了聚羟基脂肪酸(酯)天然高分子聚合物的微生物法合成途径、高产菌株筛选、发酵过程优化策略、产物提取及工业化生产前景和应用领域,以期为天然生物高分子聚合物的深入研究和广泛应用提供借鉴。     

灵菌红素的研究进展

灵菌红素最初由于其多功能生物活性而在医药领域备受关注。除在医药领域应用外,灵菌红素作为微生物代谢产生的色素在食品领域也有很大的应用潜力。灵菌红素还可以作为除藻剂和抗紫外物质应用在环境和化妆品领域,作为太阳能电池中的光敏剂代替化学敏化剂来开发染料敏化太阳能电池。该文就灵菌红素的应用、发酵工艺、生物合成途径以及生产菌株的改造进行综述,以期为灵菌红素的发展及应用提供参考。