Development of a novel modified EGSB reactor for municipal sewage treatment at ambient temperatures

A novel modified expanded granular sludge bed(EGSBm) reactor was developed for anaerobic treatment of municipal sewage with mixed liquid recirculation instead of effluent recirculation commonly adopted by a conventional EGSB(EGSBc) reactor.Performances of these two reactors were compared in treating municipal sewage at ambient temperatures ranging from 8 to 26 ℃.At an upflow liquid velocity(Vup) of 10.3 m/h,the mean concentrations of filtrated COD(CODfilt) and COD of the EGSBm effluent were determined to be 59.4 and 95.9 mg/L,respectively,which were significantly lower than those of the EGSBc effluent operated under identical experimental conditions.When the organic loading rate was suddenly increased from 1.2 to 7.2 kg COD/(m3·d),the EGSBm regained the removal efficiency of previous operation phase in 10 d.Hydrodynamic characteristics of the reactors were compared using the residence time distribution(RTD) model.It was found that the treatment efficiency of EGSBm kept increasing as the Vup increased.The polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis(PCR-DGGE) technique was used to analyze the microbial diversity in EGSBm.Fingerprinting pattern indicated that some species in the inoculating sludge were still reserved in the granular sludge of EGSBm,moreover,several new species occurred.     

Analysis of effect of nicotine on microbial community structure in sediment using PCR-DGGE fingerprinting

Solid or liquid waste containing a high concentration of nicotine can pollute sediment in rivers and lakes, and may destroy the ecological balance if it is directly discharged into the environment without any treatment. In this study, the polymerase chain reaction(PCR) and denaturing gradient gel electrophoresis(DGGE) method was used to analyze the variation of the microbial community structure in the control and nicotinecontaminated sediment samples with nicotine concentration and time of exposure. The results demonstrated that the growth of some bacterial species in the nicotine-contaminated sediment samples was inhibited during the exposure. Some bacteria decreased in species diversity and in quantity with the increase of nicotine concentration or time of exposure, while other bacteria were enriched under the effect of nicotine, and their DGGE bands changed from undertones to deep colors. The microbial community structure, however, showed a wide variation in the nicotinecontaminated sediment samples, especially in the sediment samples treated with high-concentration nicotine. The Jaccard index was only 35.1%between the initial sediment sample and the sediment sample with a nicotine concentration of 0.030 mg/g after 28 d of exposure. Diversity indices showed that the contaminated groups had a similar trend over time. The diversity indices of contaminated groups all decreased in the first7 d after exposure, then increased until day 42. It has been found that nicotine decreased the diversity of the microbial community in the sediment.     

An introduction to the new degradation of polyvinyl chloride (PVC) shower hose

Recently, polyvinyl chloride (PVC) shower hoses have hardened throughout the eastern Shizuoka Prefecture, Japan. According to the elemental analysis results, the carbon and oxygen concentrations were much lower in the damaged hoses. These findings reveal that oxygen-containing, carbon-based plasticisers may leach from the damaged hose. As a result, the hoses lost flexibility after one year of use. The highest number of heterotrophic bacteria was detected by PCR-denaturing gradient gel electrophoresis in the shower water, and the bacterial DNA concentration was higher when hot water contacted the hose surface. I conclude that the plasticiser was leached from the stiffened hose through a bioaccumulation process.     

Characterization by culture-dependent and culture-independent methods of the bacterial population of suckling-lamb packaged in different atmospheres

This study offers insight into the dynamics of bacterial populations in fresh cuts of suckling lamb under four different atmospheric conditions: air (A), and three Modified Atmosphere Packaging (MAP) environments, 15%O₂/30%CO₂/55%N₂ (C, commercial), 70%O₂/30%CO₂ (O), and 15%O₂/85%CO₂ (H) for 18 days. Microbial analyses by both conventional methods and PCR-DGGE were performed. Controversial and surprising results emerged from comparing both methods in relation to the genus Pseudomonas. Thus, conventional methods detected the presence of high numbers of Pseudomonas colonies, although PCR-DGGE only detected this genus in air-packaged samples. PCR-DGGE detected higher microbial diversity in the control samples (A) than in the modified atmospheres (C, O, H), having atmosphere H the fewest number of species. Brochothrix thermosphacta, LAB (Carnobacterium divergens and Lactobacillus sakei), and Escherichia spp. were detected in all the atmospheres throughout storage. Moreover, previously undescribed bacteria from lamb meat such as Enterobacter hormaechei, Staphylococcus equorum and Jeotgalicoccus spp. were also isolated in this study by DGGE. Additionally, qPCR analysis was used to detect and characterize strains of Escherichia coli. Virulence genes (stx₁, stx₂ and eae) were detected throughout storage in 97% of the samples. A high CO₂ atmosphere was the most effective packaging combination doubling storage time in comparison with commercial atmosphere.     

The effects of lactic acid-based spray washing on bacterial profile and quality of chicken carcasses

Chicken products with high water and nutrient contents provide essential nutrients for microbial growth. This study was designed to determine the effect of lactic acid-based spray washing. First, the reduction of microbial counts on chicken carcasses was evaluated through lactic acid-based spray washing. Second, bacterial diversity on chicken carcasses in different steps in a chicken-slaughtering chain was investigated through polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The effect of spray washing on quick-frozen chicken quality was also examined. Results revealed that microbial counts decreased significantly after the chickens were spray-washed with 1.5% lactic acid at 50 °C for 15s. PCR-DGGE revealed a decrease in microbial counts of several bacterial species, such as uncultured bacterium, uncultured Clostridiales sp., Pseudomonas fluorescens, Ruminococcus sp., and uncultured Ruminococcus sp. The spray washing performed did not remarkably affect the pH and total volatile basic nitrogen of quick-frozen chicken during storage. Therefore, the proposed technique may be applied to chicken-slaughtering chains and may be used to investigate bacterial diversity on chicken carcasses.     

A PCR-DGGE method for the identification of histamine-producing bacteria in cheese

Histamine is the biogenic amine (BA) most frequently involved in food poisoning. Cheese is among the foods in which it is most commonly found, and in some of the highest concentrations. Its accumulation in cheese is mainly due to the presence of lactic acid bacteria (LAB) that produce histidine decarboxylase, an enzyme coded by the gene hdcA. This gene has been sequenced in several histamine-producing LAB. This paper reports a new culture-independent method based on PCR-DGGE for detecting and identifying, at the species level, the histaminogenic bacteria present in cheese. Primers were designed based on the hdcA gene sequences available for Gram positive bacteria, and PCR and DGGE optimized in order to differentiate between amplicons corresponding to different histamine-producing species. The proposed method provides a rapid and simple means of detecting and identifying histamine-producing Gram positive bacteria in foods with complex microbial communities, such as cheese.     

PCR-DGGE技术及其在环境工程生物处理中的应用

阐述了PCR-DGGE技术的原理及其优点,探讨了PCR-DGGE技术在环境工程废水生物处理、废气生物处理和污泥生物处理中的应用,分析了PCR-DGGE技术用于生物处理系统中微生物群落多样性和动态性研究的现状、前景和改进的策略.     

水体微生物多样性PCR-DGGE分析方法的比较研究

PCR-DGGE法是一种分析微生物群落和微生物多样性的分子生物学技术．阐述了在应用PCR-DGGE分析水体微生物多样性研究当中进行优化菌体收集、DNA提取、凝胶染色的方法，结果表明：用过滤法收集菌体更具完整性，用CTAB法提取环境总DNA最佳，用16h电泳更具可信度，银染法优于EB法．     

不同碳源强化生物除磷系统的PCR-DGGE分析

实验考察了不同碳源强化生物聚磷系统(EBPR)中的聚磷菌群,对3个不同碳源(1号实际生活污水、2号葡萄糖和3号乙酸钠)的序批式反应器(SBR)强化生物聚磷系统聚磷菌的16S rDNA特异性聚合酶链式反应(PCR)扩增产物进行了变形梯度凝胶电泳(DGGE)分析.结果表明,以生活污水为碳源的1号反应器具有数量最多的优势种群,而以葡萄糖和乙酸钠为碳源的2号、3号反应器的生物多样性较少.3个反应系统的微生物种群各有异同.具有除磷作用的未被培养细菌(条带3、4,AF527584、AF502204)为3个反应器所共有的生物量较多的优势种群,且其在以生活污水为碳源的1号反应系统中相对生物量最多.