甘蓝黑腐病黄单胞菌细胞膜离子通道透性对黄原胶生物合成的影响

本文研究了K^ ,Na^ 离子浓度改变对甘蓝黑腐病黄单胞菌（Xanthomonas campestris)胞膜离子通道透性的影响。通过发酵过程采样点电子显微镜照片的软件分析和后期数据的统计处理分析，结合电镜照片，源用胞膜基本理论阐述了甘蓝黑腐病黄单胞菌（Xanthomonas campestris)胞膜离子通透的透性对黄原胶生物合成的影响，结果表明，胞膜通道的透性对黄原胶合成前体物质的运输有极其重要的影响。     

《食品科学》2003年总目录

基础研究农药生物传感器所用酶的比较研究…………………………王仲海等(1-21)紫胶可食性内包装膜成膜特性及应用研究……………………………唐莉英等(1-23)酒类酒球菌分离培养基研究…………张春晖等(1-28)枳椇子浸提液影响乙醇吸收的研究………………………………任发政等(1-31)小红栲淀粉颗粒特性研究……………谢 涛等(1-33)壳聚糖-Ca(II)配位聚合物的合成及其性能表征………………………周元臻等(1-36)番茄红素在油脂氧化时的稳定性初探………………………邱伟芬等(1-39)甘蓝黑腐病黄单胞菌胞膜离子通道透性对黄原胶生物合成的影…     

黄原胶及其在食品工业上的应用

<正> 黄原胶亦称黄单胞细菌多糖。美国称Xanthan gum(简称Xc)。 一、历史 已证明自然界中存在有许多种黄单胞细菌属细菌。伯爵氏手册第八版记载有已命名的158个种和尚待命名的44个种黄单胞菌。然而,其中仅有少数的几个种是黄原胶生产菌株,如野油菜黄单胞菌(亦名甘兰黑腐病黄单胞菌,Xanthomonas campestris)。菜豆黄单胞菌(X.phaseoli)、锦葵黄单胞菌(X.malvacearum)和胡萝卜黄单胞菌(X.carotae)可有效地产生黄原胶。     

携氧剂(正十二烷)对黄原胶发酵的影响

黄原胶(XanthanGum)是由野油菜黄单胞菌(Xanthomonascampestris)以碳水化合物为主要底物,经发酵产生的一种酸性胞外杂多糖。其发酵中后期黏度增大,氧的溶解能力下降,从而影响了黄原胶的产量。研究黄原胶生物合成过程中,烷烃对提高供氧、提高产胶率的影响,同时电镜观察不同发酵时期野油菜黄单胞菌的产胶情况。试验结果表明:8%为最适正十二烷添加量,产胶率达4.16%而对照样仅为2.15%。     

黄原胶的结构性能及其在食品中的应用

黄原胶(Xanthan gum)是新发展起来的一种微生物多糖,由于它有许多优良而独特的理论性能,且经毒理学安全试验达到了食品卫生标准,所以1983年在罗马召开的国际食品添加剂会议上被世界卫生组织批准为一种新的食品添加剂。黄原胶在食品中有着极其广泛的应用。一、黄原胶的微生物来源黄原胶是由甘兰黑腐病黄单胞菌(Xanthomonas campestris)发酵产生的一     

黄原胶简介

<正> Xanthan gum译名黄原胶,是一种高分子天然碳水化合物,是由甘兰黑腐病黄单胞菌(Xanthomonas campestris)发酵产生的一种酸性胞外杂多糖。 近年来,微生物胞外多糖的研究发展甚快。多种有应用价值的微生物胞外多糖正迅速发展成一门新型的发酵工业。黄原胶优良的性能,广泛的应用以及高效的社会化生产被世界誉为微生物胞外多糖生产和应用的“杰出模式”。 一、黄原胶的发展历史 五十年代初,为了寻找有应用价值的生物聚合物,美国农业部北方地区研究室的Jeanes等人从微生物中筛选发现,甘兰黑腐病黄单胞菌NRRL B-1459(Xanthomonas campestris NRRL B-1459)发酵产生一种有巨大应用潜力的微生物胞外多糖,定名为Xanthan gum。     

食品添加剂——黄原胶

<正> 在自然界中有许多细菌都能产生粘多糖类大分子化合物,黄原胶是其中的一种。它是由一种植物病害——甘兰黑腐病产生的,其菌种为野油菜黄单胞菌。黄原胶就是用此菌种以淀粉的原料发酵生产的。黄原胶理化性状独特,耐酸,碱、热,抗生物酶的降解。耐高盐环境,抗污染力强,增稠性、流变性、乳化稳定性和悬浮能力良好。它     

优质食品级黄原胶制备工艺技术研究

采用甘兰黑腐黄单胞菌对以蔗糖为碳源,谷氨酸钠、新鲜玉米为复合氮源的培养基进行发酵,发酵液经微滤、超滤及喷雾干燥,制得优质的食品级黄原胶。     

黄原胶的表面施胶工艺

高分子量的天然碳水化合物-黄原胶，是以玉米淀粉为主要原料，由甘蓝黑腐病黄单胞杆菌（Xanthomonas Capestris）经微生物多级发酵和一系列生化处理而得到的一种高分子量的多糖物质，具有良好的增稠、乳化、悬浮和稳定作用。我们对黄原胶的施胶工艺进行了试验和分析。     

我国食品级黄原胶生产现状与发展前景

<正> 一,黄原胶国内外开发与生产概况 黄原胶(Xanthan gum)是国际上70年代发展起来的新型发酵产品,它是由甘兰黑腐病黄单胞菌以碳水化合物为主要原料,经生物工程的手段发酵得到的一种高聚物。由于它具有独特的流变性,良好的水溶性,对热及酸碱的稳定性,与各种盐类很好的相容性,其应用覆盖面达20多个行业,30～40种产品。它在石油钻井中可用作泥浆处理剂;食品工业中用作增稠剂或成型剂;     

Expression of TASK and TREK, two-pore domain K+ channels, in human myometrium

Two-pore domain K+ channels are an emerging family of K+ channels that may contribute to setting membrane potential in both electrically excitable and non-excitable cells and, as such, influence cellular function. The human uteroplacental unit contains both excitable (e.g. myometrial) and non-excitable cells, whose function depends upon the activity of K+ channels. We have therefore investigated the expression of two members of this family, TWIK (two-pore domain weak inward rectifying K+ channel)-related acid-sensitive K+ channel (TASK) and TWIK-related K+ channel (TREK) in human myometrium. Using RT-PCR the mRNA expression of TASK and TREK isoforms was examined in myometrial tissue from pregnant women. mRNAs encoding TASK1, 4 and 5 and TREK1 were detected whereas weak or no signals were observed for TASK2, TASK3 and TREK2. Western blotting for TASK1 gave two bands of approximately 44 and 65 kDa, whereas TREK1 gave bands of approximately 59 and 90 kDa in myometrium from pregnant women. TASK1 and TREK1 immunofluorescence was prominent in intracellular and plasmalemmal locations within myometrial cells. Therefore, we conclude that the human myometrium is a site of expression for the two-pore domain K+ channel proteins TASK1 and TREK1.     

Acetone-h6 or -d6 + OH reaction products: evidence for heterogeneous formation of acetic acid in a simulation chamber

Simulation chamber experiments have been carried out at room temperature to investigate the products of the acetone + OH and acetone-d6 + OH reactions using two photoreactors made of Teflon or Pyrex and coupled to GC-FTIR-FID analytical techniques. In the Pyrex chamber, the results demonstrated that the channel forming acetic acid is a minor oxidation route in the atmospheric acetone-h6 + OH reaction (yield <5%), whereas a higher yield of about 20% was obtained in the case of the acetone-d6 + OH reaction, in good agreement with previous studies. Existence of a heterogeneous way of formation of acetic acid has also been identified in the Teflon photoreactor.     

A Modified Methodology to Evaluate Viscosity of Non-Newtonian Liquid Foods with a Flow Channel Instrument

Through experimental analysis of the liquid flows in a flow channel instrument, prompt evaluation of the physically defined viscosity of non-Newtonian liquid foods was investigated for development into a structurally simple and easy-to-use viscometer. For Newtonian and non-Newtonian test liquids, a relation between the friction coefficient and Reynolds number, which was dimensionless as derived from an expression of analysis as a gravity current, indicated a condition under which the flow in the instrument was laminar and under which an average shear rate was on the order of less than 1 s~. Prediction organized based on this empirical relation reproduced practically the flow curve determined for the liquid foods using a rotor type viscometer. Utilization of the channel instrument as a viscometer was formulated in terms of physical meanings of measurements such as the flow length and elapsed time.     

斑点叉尾鮰鱼头水解物的风味成分分析

对斑点叉尾鮰鱼头和鱼头酶解物干燥粉的风味成分进行了分析和比较,研究结果表明,斑点叉尾鮰鱼头和鱼头酶解物中都含有丰富的氨基酸和核苷酸。相对于新鲜的斑点叉尾鮰鱼头,鱼头酶解物中的风味氨基酸、游离氨基酸和核苷酸的含量都更高。斑点叉尾鮰鱼头酶解物中含有对风味贡献比较大的钾、钙、钠、镁等无机元素,而有害的铅、汞等重金属元素的含量均低于国家标准规定。对新鲜的斑点叉尾鮰鱼头、鱼头酶解物的挥发性风味成分分析结果表明,鱼头在酶解时产生了大量风味物质。在斑点叉尾鮰鱼头酶解物检测发现34种挥发性成分,其中呈现风味的主要成分之一杂环类化合物含量达到85.09%,使得鱼头酶解物干燥粉具有远高于新鲜鱼头的浓郁鱼香味。此实验结论可为斑点叉尾鮰鱼头的利用提供一定理论依据。     

New phenotypes of functional expression of the mKir2.1 channel in potassium efflux-deficient Saccharomyces cerevisiae strains

The functional expression of the mouse Kir2.1 potassium channel in yeast cells lacking transport systems for potassium and sodium efflux (ena1-4delta nha1delta) resulted in increased cell sensitivity to high external concentrations of potassium. The phenotype depended on the level of Kir2.1 expression and on the external pH. The activity of Kir2.1p in the yeast cells was almost negligible at pH 3.0 and the highest at pH 7.0. Kir2.1p was permeable for both potassium and rubidium cations, but neither sodium nor lithium were transported via the channel. Measurements of the cation contents in cells confirmed the higher concentration of potassium in cells with Kir2.1p. Specific inhibition of the mKir2.1 channel activity by Ba2+ cations was observed. The use of a mutant strain lacking both potassium efflux and uptake transporters (ena1-4delta nha1delta trk1delta trk2delta) enabled the monitoring of channel activity on two levels--the provision of the necessary amount of intracellular K+ in media with low potassium concentrations, and simultaneously, the channel's contribution to cell potassium sensitivity in the presence of high external K+. This combination of mutations proved to be a new, sensitive and practical tool for characterizing the properties of heterologously expressed transporters mediating both the efflux and influx of alkali-metal-cations.     

Acute enhancement of synaptic transmission and chronic inhibition of synaptogenesis induced by perfluorooctane sulfonate through mediation of voltage-dependent calcium channel

Perfluorooctane sulfonate (PFOS) is a persistent and bioaccumulative pollutant ubiquitous in wildlife and humans. Although the distribution and fate of PFOS have been widely studied, its potential neurotoxicity remains largely unknown. In the present study, the acute and chronic effects of PFOS on the development and synaptic transmission of hippocampal neurons was examined. Perfusion with PFOS markedly increased the frequency of miniature postsynaptic currents (mPSCs) and slightly elevated the amplitude of mPSCs in cultured hippocampal neurons. Perfusion with PFOS also increased the amplitude of field excitatory postsynaptic potentials (fEPSPs) recorded in the CA1 region of hippocampal slices. Both of these effects were largely blocked by the L-type Ca2+ channel antagonist nifedipine. Further studies showed that PFOS enhanced inward Ca2+ currents and increased intracellular Ca2+ in cultured neurons; these effects were also substantially inhibited by nifedipine. Moreover, prolonged treatment with PFOS moderately inhibited neurite growth and dramatically suppressed synaptogenesis in cultured neurons in a nifedipine-sensitive manner. Thus, through enhancement of Ca2+ channels, PFOS may exhibit both acute excitotoxic effects on synaptic function and chronically inhibit synaptogenesis in the brain.     

品牌童装渠道协同对渠道绩效的影响

为解决品牌童装企业销售渠道冲突带来的问题,提高渠道绩效,在研究线上线下营销渠道冲突、渠道协同能力和渠道绩效的基础上,进行渠道协同维度、渠道绩效维度和渠道协同能力等级划分。在理论分析的基础上,提出研究假设并构建逻辑模型。基于问卷调研数据,以渠道协同能力为中介变量,运用多元回归法实证分析了品牌童装企业渠道协同对渠道绩效的影响。研究结果表明:渠道协同的5个维度对渠道绩效有显著的正向影响;渠道协同能力与渠道绩效有显著的正相关关系;渠道协同能力在渠道协同与渠道绩效中具有部分中介效应;品牌童装企业应通过渠道协同解决渠道冲突及提高渠道协同能力和渠道绩效。     

应用STAR-CCM+的旋流喷嘴内部三维流场数值模拟与分析

在环锭细纱机上安装旋流喷嘴,能较好地减少细纱毛羽。应用软件STAR-CCM+对旋流喷嘴内部流场进行数值模拟,表征了喷嘴纱道流场的分布情况,解析喷嘴纱道中径向、切向、轴向三向速度分布规律。当喷嘴气道与纱道相交方向和相切点不同时,结合气流对纤维的作用,分析旋流喷嘴纱道中的气流分布规律。从模拟结果得出：旋流喷嘴纱道与气道相切点沿X轴负方向长度为14mm,且喷嘴气道与纱道相交方向向上时,所形成的气流可以减少占大多数的顺向毛羽。     

钾离子通道在黄曲霉菌孢子萌发中的作用

黄曲霉毒素严重污染农产品,威胁人畜生命健康,而孢子萌发是黄曲霉菌生存及侵染过程中的决定性事件,从最上游阻断孢子萌发可能是有效控制黄曲霉污染、开发新型抗菌药物的突破口之一。研究发现一定浓度的胞外KCl能够影响黄曲霉孢子的萌发。通过使用K+特异性荧光探针PBFI-AM,发现适合孢子萌发的特定浓度K+能够激发黄曲霉孢子瞬间产生较高的钾离子流,说明K+响应可能是黄曲霉孢子萌发的早期信号。4-AP作为特异性电压门控钾离子通道阻滞剂,能够明显抑制并延迟孢子的萌发。通过生物信息学预测,发现黄曲霉菌KCNA具有钾离子通道选择器序列,具备电压门控钾离子通道的α亚基属性。进一步构建KCNA非洲爪蟾卵母细胞表达体系,用双电极电压钳系统测得KCNA外向型电流,一定程度上证明了KCNA电压门控钾离子通道蛋白质属性,也说明电压门控钾离子通道参与了黄曲霉孢子萌发。     

Zn2+对球等鞭金藻3011细胞膜电位和膜通透性的影响

目的:用亲脂性阴离子荧光染料双(1,3-二巴比妥酸)-三次甲基氧烯洛尔和碘化丙啶标记球等鞭金藻3011(Isochrysis galbana 3011),研究Isochrysis galbana 3011受Zn2+作用时膜电位和膜通透性的变化。方法:对处理藻液进行流式细胞技术检测和荧光显微镜镜检,通过对比实验设计,实验数据使用SPSS17.0统计软件进行方差分析。结果:5μg/L Zn2+作用4min可使Isochrysis galbana 3011细胞内荧光强度明显增强,并促使膜的通透性发生剧烈变化,与对照组比较具有统计学意义。结论:找到一种快速动态测定Isochrysis galbana 3011细胞膜状态的方法,发现5μg/L的Zn2+能引起Isochrysis galbana 3011细胞膜的部分去极化,并改变膜的通透性,Zn2+的吸收有可能与钠通道联动有关。