葡萄酒生境对乳酸菌代谢的影响

在葡萄酒酿造中,为了提高其稳定性及质量,经常利用乳酸菌进行苹果酸.乳酸发酵.苹果酸一乳酸发酵一般自发进行,也可以接种乳酸菌.本文从酿酒酵母与乳酸菌的交互作用及酚类物质和酿酒工艺对乳酸菌的作用等方面进行了综述,讨论了葡萄酒生态环境对乳酸菌代谢的影响,为苹果酸一乳酸发酵的有效控制提供一些参考.     

22株中国优良酒酒球菌代谢生物胺的检测

葡萄酒苹果酸-乳酸菌在葡萄酒苹果酸-乳酸发酵中对氨基酸进行脱羧反应产生具有毒性作用的生物胺.利用PCR技术及HPLC检测方法对22株中国优良酒酒球菌的生物胺代谢安全性进行研究.结果表明,PCR检测结果与HPLC测定结果一致,从我国葡萄产区筛选的优良酒酒球菌均不产生组胺、酪胺和腐胺,从生物胺角度.我国筛选的22株优良酒酒球菌具有较高的生物胺代谢安全性.     

苹果酸-乳酸发酵能量产生机理

苹果酸乳酸发酵(MLF)是现代葡萄酒酿造工艺中重要的生物降酸手段。MLF是L苹果酸在乳酸菌的苹果酸乳酸酶催化下转变成L乳酸的酶促反应过程,该过程没有底物水平的磷酸化,但在MLF过程中苹果酸确实能够刺激细菌的比生长速率,增加细菌生物量。进一步的研究表明,代谢能的产生并非由于苹果酸的脱羧反应,而主要源于跨膜的L苹果酸摄入和(或)L乳酸的流出,从而产生跨膜质子电动势(pmf)(一小部分能量可能由L苹果酸的代谢中间产物丙酮酸产生)。按照化学渗透理论,pmf驱动F0F1ATPase合成ATP用于细菌生长。本文还对苹果酸的运输机制进行了综述。     

苹果酸—乳酸发酵能量产生机理

苹果酸－乳酸发酵（MLF）是现代葡萄酒酿造工艺中重要的生物降酸手段。MLF是L－苹果酸在乳酸菌的苹果酸－乳酸酶催化下转变成L－乳酸的酶促反应过程,该过程没有底物水平的磷酸化,但在MLF过程中苹果酸确实能够刺激细菌的比生长速率,增加细菌生物量。进一步的研究表明,代谢能的产生并非由于苹果酸的脱羧反应,而主要源于跨膜的L－苹果酸摄入和（或）L－乳酸的流出,从而产生跨膜质子电动势（pmf)(一小部分能量可能由L－苹果酸的代谢中间产物丙酮酸产生）。按照化学渗透理论,pmf驱动F0F1-ATPase合成ATP用于细菌生长。本文还对苹果酸的运输机制进行了综述。     

酒酒球菌苹果酸-乳酸酶基因的测序及分析

苹果酸乳酸酶是乳酸菌进行苹果酸乳酸发酵(MLF)的关键酶。以携带酒酒球菌(Oenococcusoeni)优良菌系OenococcusoeniSD2a的苹果酸乳酸酶基因mleA的重组质粒pLmleA作为测序质粒,进行测序分析。测序结果表明,克隆到的mleA基因序列与已报道的序列同源性为99%。mleA基因序列中有2个碱基与报道不同,其中1614碱基的改变导致错意突变,编码的氨基酸由报道的Asp变为Glu,这一改变使得原有的BamHI位点不再存在。     

乳酸菌基因组学研究进展

乳酸菌（Lactic acid bacteria LAB）是指一类能够通过同型发酵或异型发酵而产生乳酸的细菌。它们一般呈革兰阳性,厌氧,无芽孢,耐酸。根据发酵形式的不同,乳酸菌可以分为两类：同型发酵的菌主要产物为乳酸,而异型发酵的菌除了乳酸还同时产生乙酸、乙醇、二氧化碳及甲酸等。乳酸菌广泛分布于自然界,与人类生活关系密切。在人类的胃肠道、口腔以及生殖道都能够找到一些正常生存的乳酸菌,它们被认为是胃肠道的正常菌群,对于维持肠道的完整性、免疫调节及抑制致病菌、抗感染方面具有重要作用。最近有证据显示乳酸菌还能够加强特异性及非特异性免疫。目前乳酸菌广泛应用于食品发酵、工业乳酸发酵以及医疗保健领域。对于乳酸菌的研究已经从最初的形态学研究发展为细胞水平和分子水平的研究。     

苹果酸降解相关基因在酿酒酵母中的表达

微生物降酸是现代葡萄酒酿造重要工艺。将裂殖酵母苹果酸通透酶基因(mae1)和苹果酸酶基因(mae2)克隆到酿酒酵母中,构建了苹果酸酒精酵母;将mae1基因和乳酸乳球菌的苹果酸乳酸酶基因(mleS)克隆到酿酒酵母中,构建了苹果酸乳酸酵母。构建的酵母重组子能够有效地分解发酵基质中的苹果酸。     

苹果酸-乳酸发酵相关基因克隆及其在酵母中的表达

苹果酸乳酸发酵是不同葡萄酒酿造过程中至关重要的降酸步骤。近20年来,围绕苹果酸乳酸发酵相关基因的克隆以及在酿酒酵母中表达的研究取得了一些进展,就该研究进展和存在的问题进行了综述。此外,也论及了苹果酸-乙醇发酵相关基因的研究,这对于一些不适合苹果酸-乳酸发酵的葡萄酒具有重要意义 。     

L-乳酸调控乳酸产生菌产物光学纯度的分析

发酵初期在米根霉菌发酵培养基中添加L-乳酸可以调控发酵产物乳酸的光学纯度。随着L-乳酸添加量的增加,所产L-乳酸的光学纯度随之增加,当L-乳酸的添加量≥1.5g/L时,D-乳酸不再产生。同时,L-乳酸的产量、生物量、糖转化率也随之降低。该调控方法对乳酸菌调控产L-乳酸光学纯度影响不大,对大肠杆菌发酵调控产D-乳酸光学纯度没有效果。     

乳酸粪链球菌的营养要求

乳酸菌是一类能发酵糖产生乳酸而多数不能分解蛋白质的细菌的总称。1868年,Schulzc发现酒精厂的酵母醪中混有乳酸菌。1877年,Lister分离出乳酸链球菌。迄今为止,已知的乳酸细菌有40多种。按Bergey的细菌分类法,乳酸菌可分为五个属,其中乳杆菌属和链球菌属使用最广。它们与人类的关系十分     

Separation and simultaneous determination of nalidixic acid, hydroxynalidixic acid and carboxynalidixic acid in serum and urine by micellar electrokinetic capillary chromatography

Separation in capillary electrophoresis is governed by various factors, including buffer type, buffer concentration, pH, temperature, voltage and micelles. Through proper adjustment of these parameters, nalidixic acid and its two major metabolites, 7-hydroxynalidixic and 7-carboxynalidixic, could be separated by micellar electrokinetic capillary chromatography using an electrophoretic electrolyte consisting of 50 mM borate buffer (pH 9) containing 25 mM sodium dodecyl sulphate and 10% acetonitrile. A linear relationship between concentration and peak area for each compound was obtained in the concentration range 0.15–100 μg ml⁻¹, with a correlation coefficient greater than 0.999 and detection limits in the 0.2–0.7 ng ml⁻¹ range. Intra- and inter-day precision values of about 0.8–1.2% RSD (n=11) and 1.3–2.0% RSD (n=30), respectively, were obtained. The method has been applied to the analysis of nalidixic acid and its two major metabolites in serum and urine with limits of sensitivity lower than 0.8 ng ml⁻¹.     

酚酸类物质对三七幼苗的化感影响

该文研究了不同浓度的阿魏酸、对香豆酸、丁香酸、对羟基苯甲酸、香草酸5种酚酸类物质对三七幼苗生长和生理的影响。结果表明:处理后,三七幼苗的苗高、根长、可溶性蛋白质含量、根系活力、CAT以及POD活性均有所降低。其中,阿魏酸各处理组幼苗的苗高及POD活性均显著降低,50、100 mg·L~(-1)的对香豆酸以及100 mg·L~(-1)的香草酸处理组幼苗苗高也分别比对照显著降低16.19%、16.67%和29.29%;对香豆酸、丁香酸以及对羟基苯甲酸各处理组幼苗根长均显著低于对照;香草酸处理组幼苗的根系活力也显著低于对照,且幼苗的CAT活性在10、50、100 mg·L~(-1)丁香酸、对羟基苯甲酸以及香草酸处理下也达到了显著降低水平。此外,1 mg·L~(-1)阿魏酸以及100 mg·L~(-1)香草酸处理组幼苗的叶绿素含量也均显著降低;中高浓度的阿魏酸、对香豆酸、丁香酸、对羟基苯甲酸增加了三七幼苗的MDA含量,而香草酸在0.1、1、10、100 mg·L~(-1)浓度下显著降低幼苗的MDA含量;丁香酸、香草酸、对羟基苯甲酸以及中高浓度的对香豆酸增加了三七幼苗的SOD活性,且香草酸各处理组均达到了显著性水平。综上结果表明,5种酚酸类物质对三七幼苗均具有一定的化感抑制作用,但各酚酸物质的作用方式及强度并不完全一致,阿魏酸的化感影响较大,这为进一步研究三七的化感自毒作用提供了一定的理论参考。     

Comparative acid stress response of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella Typhimurium after habituation at different pH conditions

AIMS: The aim of the study was to evaluate the effect of habituation at different pH conditions on the acid resistance of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella enterica serotype Typhimurium, and to identify potential differences between the adaptive responses of the three pathogens. METHODS: Stationary phase cells of L. monocytogenes, E. coli O157:H7 and S. Typhimurium, grown in glucose-free media, were exposed to pH 3.5 broth directly or after habituation for 90 min at various pH conditions from 4.0 to 6.0. Survivors at pH 3.5 were determined by plating on tryptic soy agar and incubating at 30 degrees C for 48 h. The kinetics (death rate) of the pathogens at pH 3.5 was calculated by fitting the data to an exponential model. RESULTS: Habituation to acidic environments provided protection of the pathogens against lethal acid conditions. This acid protection, however, was found to be pH dependent. For example, for E. coli O157:H7 an increased acid resistance was observed after habituation at a pH range from 4.0 to 5.5, while the maximum acid tolerance was induced at pH 5.0. Furthermore, the effect of low pH habituation was different among pathogens. For L. monocytogenes, E. coli O157:H7 and S. Typhimurium, the pH range within which habituation resulted to increased acid resistance was 5.0-6.0, 4.0-5.5 and 4.0-5.0, respectively, while the maximum acid tolerance was induced after habituation at pH 5.5, 5.0 and 4.5, respectively. SIGNIFICANCE: Acid stress conditions are common within current food processing technologies. The information on adaptive responses of L. monocytogenes, E. coli O157:H7 and S. Typhimurium after habituation to different pH environments provided in the present study, could lead to a more realistic evaluation of food safety concerns and to a better selection of processes in order to avoid adaptation phenomena and to minimize the potential for food safety risks.     

Triterpene acids from Salvia and Teucrium species

The pentacyclic triterpene acids ursolic acid, oleanolic acid, micromeric acid, maslinic acid and 3-epi-maslinic acid have been isolated from several Salvia and Teucrium species.     

氨基酸分析仪测定饲料添加剂——叶酸的方法

用６ｍｏｌ／Ｌ盐酸于１１０℃条件下水解饲料添加剂——叶酸,使之游离出谷氨酸,用氢氧化钠中和调节ｐＨ到２,氨基酸分析仪测定谷氨酸含量,经与标准叶酸水解样品比较,计算出叶酸的纯度。该方法重现性好,变异系数ＣＶ＝０．０８％,平均回收率为９８．３４％,浓度与峰面积呈线性相关,相关系数ｒ＝０．９９８７,可随氨基酸分析同时进行,不需改变任何分析条件。     

Temperature regulates tuber-inducing lipoxygenase-derived metabolites in potato (Solanum tuberosum)

Temperature is one of the major environmental factors affecting potato tuberization. It has been suggested that lipoxygenase (LOX) mediates between temperature and tuber induction. In this study, the contents of the LOX-derived metabolites hydroperoxylinolenic acid (HPOT), jasmonic acid (JA), tuberonic acid (TA) and tuberonic acid glucoside (TAG) were analyzed in leaves of potatoes growing at different temperatures. At low, tuber-inducing temperature, endogenous levels of JA, TA and TAG rise, indicating their crucial role in tuber induction. The concentration of 13(S)-HPOT seems not to be directly affected by temperature. Instead, the molecule has only a short half-life in leaves and is readily metabolized.     

硬枝树花中抑制H_22荷瘤小鼠肿瘤的活性成分研究

研究了从硬枝树花中提取得到的4个单体化合物松萝酸(usnic acid)、去甲环萝酸(evernic acid)、巴尔巴地衣酸(barbatic acid)和水杨嗪酸(salazinic acid)对H22荷瘤小鼠的抑瘤作用,并且对抑瘤率、胸腺指数、脾指数及小鼠白介素-2含量等各个指标的进行检测,以说明此4种化合物对小鼠肿瘤生长的抑制效果。结果表明,松萝酸高、中剂量组,去甲环萝酸高、中剂量组,巴尔巴地衣酸低剂量组,水杨嗪酸高剂量组对小鼠肿瘤有较好的抑制效果,与阴性对照组比较有极显著差异(P0.01),并且这些组的H22荷瘤小鼠血清中白介素-2的含量显著增加,与抑制肿瘤活性具有相关性。