Mass balance and kinetic analysis of anaerobic microbial dechlorination of pentachlorophenol in a continuous flow column

A mass balance and kinetic investigation of anaerobic dechlorination of pentachlorophenol (PCP) was undertaken using an enriched microbial consortium in a laboratory scale continuous flow column, as a model microbial permeable reactive barrier. The chlorine balance showed that 50 µM PCP was largely dechlorinated to phenol with the formation of a small quantity of 3-chlorophenol as an intermediate metabolite (hydraulic retention time 7.6 days), and the chlorine removal efficiency reached 36 µM d^-1. When the initial PCP concentration was increased to 100 µM the chlorine removal efficiency increased 1.5 times. However, the dechlorination activity disappeared after 7.4 pore volumes (58 days), demonstrating the susceptibility of the dechlorination culture to high concentrations of PCP. Lactate released hydrogen as an electron donor during PCP dechlorination, with acetate, propionate, CO₂ and CH₄ as byproducts. The carbon balance showed that some of the organic carbon source (PCP, lactate) in the influent was converted to gas and utilized for biomass growth in addition to organic metabolites. The kinetic study was conducted in a batch culture and yielded 1.99 mg l^-1 biomass growth per unit of chlorine consumption (µM). The Monod equation was well fitted to the specific growth rate of 1.38 d^-1 and a half saturation constant of 0.29 µM. The organic chlorine removal rate in the batch culture was consistent with the results in the flow column, indicating the feasibility of and potential for in situ estimation and prediction through batch culture studies.     

Evaluation of various salt levels and different dairy proteins in combination with microbial transglutaminase on the quality characteristics of restructured pork ham

The objective of this study was to evaluate the quality characteristics of restructured pork hams (RH) manufactured with various salt levels (0.5%, 1.0%, and 1.5%) and different dairy proteins (sodium caseinate, SC and whey protein isolate, WPI; 1.0%) in combination with microbial transglutaminase (MTGase; 0.3%). Reduced‐salt (0.5% and 1.0%) RH resulted in reductions of moisture contents (%), textural springiness, cooking yield and most sensory preferences (P < 0.05). When dairy proteins in combination with MTGase were incorporated into the manufacture of RH, SC with MTGase was shown to reduce cooking loss (CL, %) and to increase the textural springiness and chewiness of RH, whereas WPI with MTGase increased textural springiness and chewiness, as well as the shear value of RH (P < 0.05). On the contrary, MTGase with dairy proteins improved the sensory preferences of reduced‐salt (1.0%) RH to give it similar sensory properties to those of the regular‐salt (1.5%) RH controls (CTL) (P > 0.05). The findings of this study demonstrated that the combination of 1.0% dairy proteins and 0.3% MTGase could affect improvements in the functional, textural and sensory properties of reduced‐salt (1.0%) RH.     

无介体微生物燃料电池阳极生物膜传质分析

针对无介体微生物燃料电池阳极侧生物膜内的传递过程建立了一维稳态扩散传输模型,模型认为底物氧化产生的电子以直接方式传递至阳极,并考虑了生物膜内电势及pH的变化,计算获得了微生物燃料电池生物膜内的底物浓度、电势、电流密度以及pH值分布,讨论了生物膜的电导率、阳极电势和缓冲液浓度对生物膜内传质特性及产电性能的影响。计算结果表明随着生物膜电导率和阳极电势的增大,生物膜内底物浓度及pH值均降低,电池电流密度升高;进口缓冲液浓度越大,生物膜内pH值越高,有利于维持阳极生物膜内微生物的活性。     

The Effect of Active Packaging on Microbial Stability and Quality of Chinese Steamed Bread

The present study was conducted to evaluate the effect of active packaging [oxygen absorber (OA) or oxygen absorber combined with ethanol emitter (OA + EE)] on microbial stability and quality of Chinese steamed bread (CSB) stored at 25 °C. Air‐packaged CSB was taken as control. Microbiological, sensory, physical, thermal and mechanical changes were monitored as a function of treatment and storage time. On day 2 of storage total plate count was reduced by 3.1, 3.7 and 4.4 cfu/g by OA, OA + EE (1% v/v) and OA + EE (3% v/v), respectively (p < 0.05). Yeasts and moulds were inhibited during the entire storage period. No detrimental effects of OA + EE (1% v/v) were observed on organoleptic parameters, whereas OA + EE (3% v/v) gave a strong objectionable flavour and taste. Active packaging significantly (p < 0.05) delayed the increase of potential of hydrogen as compared to the control. No significant effect of active packaging was found on moisture content, water activity, colour and specific volume. An increase in the melting enthalpy of amylopectin crystallite was observed in all samples during storage. The stored CSB samples packaged with OA showed higher values of hardness compared to samples packaged with OA + EE (1% v/v), indicating the potential of ethanol as plasticizer of the protein network. The results indicate the potential application of OA and OA + EE (1% v/v) as an antimicrobial packaging system for CSB preservation. Copyright © 2015 John Wiley & Sons, Ltd.     

Combined permeable pavement and photocatalytic titanium dioxide oxidation system for urban run‐off treatment and disinfection

Permeable pavement systems (PPS) are frequently associated with high removal efficiencies for water quality parameters. Their effluent can, therefore, be recycled, for example, for sprinkling onto gardens. Nevertheless, some stakeholders fear that potentially pathogenic organisms within the treated run‐off could be too high, and therefore they request disinfection before recycling. The aim of this paper is, therefore, to assess the efficiency of a batch flow combined titanium dioxide (TiO₂) and ultraviolet (UV) light photocatalytic reactor in removing water‐borne microbial contaminants from the effluent of PPS. Combined TiO₂ and UV photocatalytic reaction times between 80 and 100 min were required for the complete removal of Escherichia coli, total coliforms and faecal Streptococci, which had mean initial counts of 1.5 × 10⁷, 4.4 × 10⁶ and 6.9 × 10⁵ colony‐forming units (CFU) per 100 mL, respectively. In comparison, UV disinfection alone resulted in insignificant microbial removal. Suspended TiO₂ powder was more effective than small immobilised TiO₂ crystals.     

Drivers of microbial community composition in mesophilic and thermophilic temperature-phased anaerobic digestion pre-treatment reactors

Temperature-phased anaerobic digestion (TPAD) is an emerging technology that facilitates improved performance and pathogen destruction in anaerobic sewage sludge digestion by optimising conditions for 1) hydrolytic and acidogenic organisms in a first-stage/pre-treatment reactor and then 2) methogenic populations in a second stage reactor. Pre-treatment reactors are typically operated at 55–65 °C and as such select for thermophilic bacterial communities. However, details of key microbial populations in hydrolytic communities and links to functionality are very limited. In this study, experimental thermophilic pre-treatment (TP) and control mesophilic pre-treatment (MP) reactors were operated as first-stages of TPAD systems treating activated sludge for 340 days. The TP system was operated sequentially at 50, 60 and 65 °C, while the MP rector was held at 35 °C for the entire period. The composition of microbial communities associated with the MP and TP pre-treatment reactors was characterised weekly using terminal-restriction fragment length polymorphism (T-RFLP) supported by clone library sequencing of 16S rRNA gene amplicons. The outcomes of this approach were confirmed using 454 pyrosequencing of gene amplicons and fluorescence in-situ hybridisation (FISH). TP associated bacterial communities were dominated by populations affiliated to the Firmicutes, Thermotogae, Proteobacteria and Chloroflexi. In particular there was a progression from Thermotogae to Lutispora and Coprothermobacter and diversity decreased as temperature and hydrolysis performance increased. While change in the composition of TP associated bacterial communities was attributable to temperature, that of MP associated bacterial communities was related to the composition of the incoming feed. This study determined processes driving the dynamics of key microbial populations that are correlated with an enhanced hydrolytic functionality of the TPAD system.     

Mn(Ⅱ)对好氧颗粒污泥微生物活性的影响

针对城市污水中重金属离子短期超标影响污水生物处理系统正常运行的问题,采用好氧颗粒污泥SBR反应器,研究了不同浓度Mn(Ⅱ)短期冲击下对好氧颗粒污泥污染物去除性能、外观结构和微生物活性的影响。试验结果表明,好氧颗粒污泥受不同浓度Mn(Ⅱ)10 d的冲击后,COD去除率受Mn(Ⅱ)影响较小,Mn(Ⅱ)会轻微促进AGS对TN的去除。Mn(Ⅱ)分别为0.5、1.0、3.0 mg/L可提高好氧颗粒污泥的活性,在相应浓度的冲击下SOUR分别提高16.0%、108.5%、51.8%,TTC-ETS分别提高了7.7%、112.4%、45.7%。5.0 mg/L Mn(Ⅱ)对SOUR和TTC-ETS的抑制率分别为13.8%和33.5%。     

Ni-P-PTFE镀层表面黏液形成菌的污垢特性

目的 研究Ni-P-PTFE镀层改性换热面对微生物污垢的抑制作用.方法 调整化学镀工艺,在换热器常用的低碳钢表面制备不同性能的复合镀层,获取镀层厚度、镀速和表面能等参数.对低碳钢和Ni-P-PTFE复合镀层进行微观形貌对比,并进行黏液形成菌污垢静置实验,测量菌悬液中的细菌数量变化及试样质量变化.分析复合镀层表面在黏液形成菌污垢实验前后的宏观和微观形貌,与低碳钢试样进行对比,研究复合镀层试样表面能和镀层表面污垢沉积的关联性.结果 Ni-P-PTFE复合镀层改变了换热面的表面性能,接触角明显增大,表面能由改性前的49.16 mJ/m2降低到7.54 mJ/m2.与低碳钢的静置结果 相比,悬挂复合镀层试样的菌悬液中黏液形成菌数量显著减少,复合镀层试样表面平均污垢沉积量减少到2.3 g/m2(低碳钢表面为12.1 g/m2).结论 Ni-P-PTFE镀层可以有效抑制黏液形成菌的生长,低表面能有效减少了微生物污垢的沉积,使其表现出良好的耐蚀性和抗垢性.     

3-羟基丙酸的绿色合成法

3-羟基丙酸是一种重要的化工产品,既可以作为精细化工中间体,也可以合成高聚物。综述采用微生物发酵法和化学转化法制备3-羟基丙酸的研究进展,着重介绍化学转化法,通过比较认为化学转化法更具竞争力,具有广阔的发展前景。