Modeling heterogeneous photocatalytic inactivation of E. coli using suspended and immobilized TiO2 reactors

A study was carried out to develop a kinetic model of the photocatalytic inactivation of Escherichia coli using different TiO₂ catalysts. The model developed is based on a reaction scheme that involves effectively coupling mass‐transfer fluxes between bacteria and catalyst surface on one hand and bacterial degradation reaction on the other. The photocatalytic results were derived from experiments led in a batch reactor under both dark and Ultra Violet (UV) irradiation conditions. Using a reference catalyst, the robustness of the developed model was tested under solar conditions. The experimental data validated the model as successfully able to reproduce evolutions in the viable bacteria concentration in the range of parameters studied without any further adjustment of the kinetic parameters. The model was used to simulate the bacterial degradation kinetics under different working conditions to describe the partitioning of both bacterial adhesion and photocatalytic reaction in the solution to be treated © 2015 American Institute of Chemical Engineers AIChE J, 61: 2532–2542, 2015     

Detection of pathogenic Escherichia coli strains in groundwater in the Yaoundé region (Cameroon,Central Africa)

This study was aimed at assessing the prevalence of pathogenic Escherichia coli strains, relative to the total count of E. coli, faecal coliforms and other heterotrophic mesophilic aerobic bacteria (HMAB) isolated in groundwater in the equatorial region of Cameroon (Central Africa). Bacteria were isolated using standard methods. Pathogenic E. coli strains were then identified using haemagglutination and antisera tests. The maximum abundance of HMAB, faecal coliforms and E. coli strains were 4.9 × 10⁶, 5.6 × 10³ and 1 × 10³ colony‐forming units (CFU)/100 mL, respectively. The count of pathogenic E. coli strains reached 3 CFU/100 mL. The counts of commensal and pathogenic E. coli strains underwent temporal and spatial fluctuations. In 21% of sampling sites, the abundance of faecal coliforms was significantly correlated to that of E. coli (P < 0.05). However, the isolated bacterial count was not significantly correlated to that of the pathogenic E. coli strains (P > 0.05). The bacteria abundance dynamics may be impacted by many interacting factors.     

Bacterial contamination due to point and nonpoint source pollution in a rapidly growing urban center in an arid region

The distribution of bacterial contaminants (Escherichia coli and total coliforms) and nutrients (nitrogen and phosphorus) in a rapidly growing metropolitan area, the Las Vegas Valley, were studied to assess the contributions of point and nonpoint pollution sources under dry weather flow (pre rainfall) and wet weather flow (post rainfall) events. Nonpoint sources emanating from urban centers and septic seepage were found to be a primary source of bacterial contamination in the Las Vegas Wash, a mainstream wash channel where the Las Vegas Valley watershed drains. Contribution of point sources (wastewater treatment plants) to E. coli and total coliforms were found to be negligible. However, data in the Tropicana/Flamingo Wash, a tributary of the Las Vegas Wash, showed high bacterial activities in the wet antecedent rainfall condition as compared to the pre-rain dry antecedent condition suggesting that the rainfall increased bacterial activities.     

Antivirulence Isoquinolone Mannosides: Optimization of the Biaryl Aglycone for FimH Lectin Binding Affinity and Efficacy in the Treatment of Chronic UTI

Uropathogenic E. coli (UPEC) employ the mannose‐binding adhesin FimH to colonize the bladder epithelium during urinary tract infection (UTI). Previously reported FimH antagonists exhibit good potency and efficacy, but low bioavailability and a short half‐life in vivo. In a rational design strategy, we obtained an X‐ray structure of lead mannosides and then designed mannosides with improved drug‐like properties. We show that cyclizing the carboxamide onto the biphenyl B‐ring aglycone of biphenyl mannosides into a fused heterocyclic ring, generates new biaryl mannosides such as isoquinolone 22 (2‐methyl‐4‐(1‐oxo‐1,2‐dihydroisoquinolin‐7‐yl)phenyl α‐d ‐mannopyranoside) with enhanced potency and in vivo efficacy resulting from increased oral bioavailability. N‐Substitution of the isoquinolone aglycone with various functionalities produced a new potent subseries of FimH antagonists. All analogues of the subseries have higher FimH binding affinity than unsubstituted lead 22 , as determined by thermal shift differential scanning fluorimetry assay. Mannosides with pyridyl substitution on the isoquinolone group inhibit bacteria‐mediated hemagglutination and prevent biofilm formation by UPEC with single‐digit nanomolar potency, which is unprecedented for any FimH antagonists or any other antivirulence compounds reported to date.     

微生物固定化吸附剂吸附Pd(II)的研究

微生物法在吸附处理重金属污染和回收贵金属方面具有广阔的发展前景。利用载体A固定化大肠杆菌开发了一种高效微生物固定化吸附剂,研究其对Pd(II)的吸附特性,构建其对Pd(II)的动态吸附模型,并开展了循环再生实验。结果表明,吸附柱的穿透时间和耗竭时间与大肠杆菌的浓度、微生物固定化吸附剂的填充量成正相关,与溶液流速成负相关;载体A:粘结剂:大肠杆菌的质量比为4:1:3,固定化吸附剂添加量为15 g、溶液流速3 mL/min时,吸附柱对Pd(II)有较好的吸附效率,穿透时间和耗竭时间分别为60 min和360 min;使用2 mol/L的HCl对负载Pd(II)后吸附剂进行解吸处理,解吸率达到99.32%;吸附-解吸循环5次后,固定化吸附剂对Pd(II)的吸附量基本保持不变。     

大肠杆菌FMME-N-26生产琥珀酸的发酵条件优化和放大

琥珀酸(Succinic acid)被认为是白色生物技术生产的最具潜力的大宗化学品之一,在工业上具有广泛的应用。微生物发酵生产琥珀酸具有环境友好和可持续发展等优点,展现出良好的发展前景,但是存在得率低、副产物积累、生产强度低等问题。为了实现琥珀酸的高效生产,在3.6 L发酵罐中对E. coli FMME-N-26生产琥珀酸发酵条件和补料策略进行了优化,建立了好氧-厌氧两阶段发酵工艺,最终确定发酵策略为：有氧发酵8 h后转为厌氧发酵,MgCO3为pH中和剂,发酵72 h补加抗渗透压保护剂2 mmol/L甜菜碱,厌氧阶段控制葡萄糖浓度为1~5 g/L。优化后发酵72 h,琥珀酸的产量和厌氧阶段得率分别达到119.2 g/L和1.08 g/g葡萄糖(理论得率97%),分别比优化前提高了46.4%和4.8%,副产物乙酸和乳酸仅积累2.37和0.94 g/L,分别比优化前降低了37.1%和49.2%。在1000 L发酵罐中实现中试放大生产,E. coli FMME-N-26生产琥珀酸的产量、得率和生产强度在国内外属于领先水平,为琥珀酸工业化生产奠定了坚实的基础,同时也为其他高价值化学品的生产提供了借鉴。     

壳聚糖在抗菌PP中的应用

通过热重分析、差示扫描量热法对壳聚糖的热稳定性进行了研究,考察了其在抗菌聚丙烯(PP)中应用的可行性。壳聚糖在氧气中起始分解温度为252.0℃,可满足加工PP时对耐热性能的要求。壳聚糖改性PP的流动性和力学性能变化不大,黄色指数增加。随着壳聚糖添加量的增加,抗菌率逐渐提高,当壳聚糖质量分数达3%时,抗菌PP对大肠杆菌和金黄葡萄球菌的杀菌率均可达99%。     

Magnetic polymeric nanoparticles functionalized by mannose‐rhodamine conjugate for detection of E. coli

Mannose‐rhodamine (Rh) conjugate (80% yield) was synthesized in a one‐pot reaction and immobilized onto magnetic polymeric nanoparticles (MPNP; 43% magnetic content) of poly(styrene/divinyl benzene/acrylic acid). The resulting nanoparticles contained MPNP as a substrate, mannose as an E. coli receptor and Rh as a fluorescent signaling unit. TEM imaging clearly demonstrated that multiple mannose‐Rh MPNPs could be captured by E. coli strain ORN178. The fluorescent signal from captured nanoparticles was emitted at 580 nm. These results indicate that mannose‐Rh MPNP offers a simple and rapid strategy for bacterial detection. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40012.