高锰酸钾预氧化对大肠杆菌DBPsFP的去除

以大肠杆菌为试验对象,采用高锰酸钾（KMnO₄）预氧化法,研究了不同的高锰酸钾浓度、氯化时间、pH值、预氧化时间及反应温度在氯化消毒过程中对大肠杆菌消毒副产物生成潜能（DBPsFP）的去除影响.研究表明：随着KMnO₄浓度的增加,二氯乙腈（DCAN）、三氯乙腈（TCAN）、1,1,1-三氯丙酮（1,1,1-TCP）及三氯乙醛（CH）浓度先降低,后升高,1,1-二氯丙酮（1,1-DCP）浓度先升高,后降低;三氯甲烷（TCM）浓度逐渐降低.在KMnO₄浓度2mg/L时,DCAN、TCAN、1,1,1-TCP浓度降至最低,对大肠杆菌DBPsFP的氧化去除效果最好;延长氯化时间,TCAN,1,1-DCP浓度逐渐升高,而DCAN,CH和1,1,1-TCP浓度先升高后降低.TCM浓度先升高后趋于稳定;pH值由5升高到9时,1,1,1-TCP、TCAN浓度不断地降低;DCAN浓度先降低,再升高;而1,1-DCP、CH浓度先升高,再降低;延长预氧化时间,TCAN、DCAN、TCM的浓度逐渐降低;1,1-DCP、1,1,1-TCP的浓度先升高,再降低;CH的浓度先升高,之后趋于稳定;随着反应温度的升高,1,1-DCP、DCAN的浓度逐渐升高;1,1,1-TCP浓度则逐渐降低;TCAN、TCM的浓度先升高再降低,而CH浓度则先降低再升高.综上,在KMnO₄浓度2mg/L,氯化时间48h,碱性条件（pH > 8）,预氧化时间30min时最有利于大肠杆菌DBPsFP的去除.     

大肠杆菌JM105中硝酸盐还原酶的制备及其性质

近年来,硝酸盐和亚硝酸盐的污染已引起普遍关注。目前,蔬菜和粮食的NO3-含量过高主要由于农药和化肥的使用、工业废水或生活污水灌溉等,食品类主要来自腌制食品和食品添加剂或防腐剂等。另外,向乳制品或食品中参碱、食盐、化肥、脏水、碱性水等也是硝酸盐污染的来源之一。因此,迫切需要快速、简便、可用于现场的硝酸盐检测方法。这就需仰赖生物酶方法,而生物酶方法的关键是酶制剂的制备和检测方法的建立。本研究通过筛选、厌氧和硝酸盐诱导培养、超声波细胞破碎和差速离心提取等方法,从大肠杆菌(Escherichia coli)JM105细胞膜中制备了硝酸盐还原酶并对其性质进行了研究。结果表明:从大肠杆菌JM105中制得的酶制剂活力很高,且在酶过量的情况下可将NO3-完全转化为NO2-,在用磷酸缓冲液清洗并冷冻保藏过夜后不含有亚硝酸盐还原酶。在加入黄素单核苷酸辅酶(FMN)后,该酶的活力可提高64%,比活力达0.42U·mg-1蛋白。该酶十分稳定,在40℃下24h活力无影响,在浓度为1mmol·L-1的Cu2 、Fe3 、Ca2 、Zn2 、Mg2 和Mo6 存在下,其活力亦不改变。因此,该酶可用于测定食品、蔬菜和环境中硝酸盐的含量。     

微直流电场对大肠杆菌生长代谢活性的作用

对大肠杆菌（Escherichia coli,DH5α）培养液在连续培养时分别通入不同强度的直流电场,研究了其在持续直流电刺激下的生长曲线、pH曲线、ATP酶活性、胞内总蛋白含量、细胞膜通透性以及细菌微观形态变化.结果表明,适宜的直流电能够促进大肠杆菌增殖;大肠杆菌的ATP酶活在25 mA电流作用下在对数生长前期、对数...     

介质阻挡气液两相放电灭活大肠杆菌

采用双向窄脉冲介质阻挡气液两相放电技术,对大肠杆菌灭活效果进行了试验.研究了曝气量、初始含菌量、处理时间、电场强度及电导率与大肠杆菌灭活率的关系.结果表明,菌体灭活率随初始含菌量、电场强度、处理时间的增加而增大,但随电导率的增加而减小.较佳的曝气量为0.75m³/h.     

UV系统净化贝类中大肠杆菌的研究

经人工方法使菲律宾蛤仔(Ruditapes philippinarum)体内积累埃希氏大肠菌(Escherichia coli)达到5个对数值后,放入小型紫外线(UV)循环净化系统中,通过正交试验来研究各种环境因子对贝类自身净化能力的影响。经56h净化处理后,贝肉中的E．coli减小约3个对数值。方差分析结果表明影响菲律宾蛤仔净化效果的因子依次为水交换率、贝水比和温度,其最佳的净化条件为：换水率3次／h、贝水比为1：4、温度15℃。证明紫外线系统用于净化菲律宾蛤仔是有效的。     

微生物絮凝剂产生菌的培养条件研究

从活性污泥中分离筛选到1株高效絮凝剂产生菌E 9,初步鉴定其为大肠杆菌。首次发现大肠杆菌能产生微生物絮凝剂。该菌产生絮凝剂的适宜培养条件为:乙醇为碳源,大豆粉为氮源,初始pH值为6. 5~7 .2、温度为30℃。絮凝实验结果表明,该菌产絮凝剂对高岭土悬浊液的絮凝率可达97% ~99. 5%,而絮凝剂投加量仅为通用发酵培养基的1 /15,絮凝效果优于聚丙烯酰胺等常用絮凝剂。     

FECAL‐INDICATOR BACTERIA IN STREAMS ALONG A GRADIENT OF RESIDENTIAL DEVELOPMENT1

ABSTRACT: Fecal‐indicator bacteria were sampled at 14 stream sites in Anchorage, Alaska, USA, as part of a study to determine the effects of urbanization on water quality. Population density in the subbasins sampled ranged from zero to 1,750 persons per square kilometer. Higher concentrations of fecal‐coliform, E. coli, and enterococci bacteria were measured at the most urbanized sites. Although fecal‐indicator bacteria concentrations were higher in summer than in winter, seasonal differences in bacteria concentrations generally were not significant. Areas served by sewer systems had significantly higher fecal‐indicator bacteria concentrations than did areas served by septic systems. The areas served by sewer systems also had storm drains that discharged directly to the streams, whereas storm sewers were not present in the areas served by septic systems. Fecal‐indicator bacteria concentrations were highly variable over a two‐day period of stable streamflow, which may have implications for testing of compliance to water‐quality standards.     

Modeling of Escherichia coli Fluxes on a Catchment and the Impact on Coastal Water and Shellfish Quality1

Bougeard, Morgane, Jean‐Claude Le Saux, Nicolas Pérenne, Claire Baffaut, Marc Robin, and Monique Pommepuy, 2011. Modeling of Escherichia coli Fluxes on a Catchment and the Impact on Coastal Water and Shellfish Quality. Journal of the American Water Resources Association (JAWRA) 1‐17. DOI: 10.1111/j.1752‐1688.2011.00520.x Abstract: The simulation of the impact of Escherichia coli loads from watersheds is of great interest for assessing estuarine water quality, especially in areas with shellfish aquaculture or bathing activities. For this purpose, this study investigates a model association based on the Soil and Water Assessment Tool (SWAT) coupled with a hydrodynamic model (MARS 2D; IFREMER). Application was performed on the catchment and estuary of Daoulas area (France). The daily E. coli fluxes simulated by SWAT are taken as an input in the MARS 2D model to calculate E. coli concentrations in estuarine water and shellfish. Model validation is based on comparison of frequencies: a strong relationship was found between calculated and measured E. coli concentrations for river quality (r² = 0.99) and shellfish quality (r² = 0.89). The important influence of agricultural practices and rainfall events on the rapid and large fluctuations in E. coli fluxes from the watershed (reaching three orders of magnitude in <24 hours) is one main result of the study. Response time in terms of seawater quality degradation ranges from one to two days after any important rainfall event (greater than 10 mm/day) and the time for estuary to recover good water quality also mainly depends on the duration of the rainfall. In the estuary, three effects (rainfall, tidal dilution, and manure spreading) have been identified as important influences.     

拟南芥硫酯酶基因(atfata)在大肠杆菌中的表达及其对游离脂肪酸合成的影响

硫酯酶催化脂酰ACP(酰基载体蛋白)水解生成游离脂肪酸和ACP载体蛋白,能够解除脂肪酸合成与磷脂合成的偶联,是获得游离脂肪酸的关键基因.将拟南芥的硫酯酶基因atfata克隆到原核表达载体pET30a上,在大肠杆菌BL21(DE3)中成功表达了His-tag融合蛋白,经SDS-PAGE检测获得特异性表达条带.对该重组菌株进行摇瓶发酵实验,GC-MS检测表明其与对照菌株脂肪酸组成并未发生变化;但其脂肪酸产量达到232.06 mg/L,比对照菌株提高了70%;同时胞外游离脂肪酸产量达到了33 mg/L,占总脂肪酸含量的15%,是野生菌株胞外脂肪酸产量的7倍.图3表2参17     

Photo- and electro-catalysis for solar disinfection of Escherichia coli-contaminated water using Ag–TiO2/graphite

A titanium dioxide film on a graphite substrate was synthesized by chemical bath deposition from TiCl₄ as precursor and with the surfactant cetyl trimethyl ammonium bromide as a linking and assembling agent. Silver was loaded on the TiO₂ film by electrodeposition at 0.025?A. Water contaminated with Escherichia coli was disinfected under sunlight irradiation by photolysis (Lys), photocatalysis (PC), photoelectrocatalysis (PEC), and electrocatalysis (EC). The highest rate constant, k, was achieved with EC; k was 5.1?×?10^?2 colony forming units (CFU) mL^?1?min^?1. However, auto-oxidation of Ag occurred during EC and PEC. Meanwhile, the rate constant of disinfection by means of PC was lower than EC and PEC, and k was 3.82?×?10^?2 CFU?mL^?1?min^?1. Nevertheless, the auto-oxidation of Ag in the Ag–TiO₂/graphite tablet did not occur during the disinfection process.