Effect of high shear stress on microbial viability

Escherichia coli and Saccharomyces cerevisiae suspensions were submitted to controlled shear stress. Above a threshold value shear stress induced a decrease in micro‐organism viability. The threshold of shear stress efficiency depended on the micro‐organisms, being between 1292 Pa and 2770 Pa for S cerevisiae, and about 1250 Pa for E coli. Above 1810 Pa, E coli cells were disrupted whereas the S cerevisiae cells remained intact. The higher the cellular concentration, the greater the rate of decrease in viability. Viability loss was influenced by the number of passages through the experimental shear stress device and by exposure time. © 2001 Society of Chemical Industry     

嵊泗县贝类生产海域贻贝和环境监测的研究

实验研究了嵊泗三个海域的贻贝中大肠杆菌、菌落总数、铅和镉的含量情况,并对贻贝的生长环境的水质进行了检测。结果表明,抽检的贻贝大肠杆菌、菌落总数符合农业部一类贝类生产养殖区标准。其铅、镉含量也符合《食品中污染物限量》(GB 2762-2012)要求。同时,水质样品铅和镉的含量符合《中华人民共和国渔业水质标准(GB 11607-1989)》的限量要求。     

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     

β-葡萄糖苷酶高产菌株的筛选及其基因的克隆与表达

利用栀子苷培养基从滨海新区盐碱地土样中筛选得到一株高产β-葡萄糖苷酶菌株,酶活力达到14.82U·mL-1,经16SrDNA鉴定,命名为短小芽孢杆菌B-4。克隆获得B-4β-葡萄糖苷酶基因,测序结果表明,其大小为1437bp,与GenBank中短小芽孢杆菌SAFR-032β-葡萄糖苷酶基因YP_001488769.1序列比对,核苷酸序列同源性达97%,氨基酸序列同源性达99%。进一步利用表达载体pET-22b（＋）,实现β-葡萄糖苷酶基因bglB在大肠杆菌BL21（DE3）中的高效表达,酶活力达46.85U·mL-1。     

大肠杆菌乙酰辅酶A代谢调控及其应用研究进展

利用生物法合成生物基化学品具有高效、绿色、可持续发展等优势。乙酰辅酶A作为细胞内物质代谢的重要中间产物,是利用生物转化法合成许多生物基化学品的重要前体,在微生物碳代谢过程中发挥着枢纽作用。本文综述了大肠杆菌乙酰辅酶A的合成、代谢调控策略及其重要应用,重点总结了乙酰辅酶A的合成途径及近期发展的提高乙酰辅酶A胞内通量的代谢调控策略,包括乙酸途径的代谢调控、丙酮酸合成乙酰辅酶A途径的代谢调控、中心碳代谢途径的代谢调控、β氧化合成乙酰辅酶A途径的代谢调控和乙酰辅酶A合成新途径的发掘,进一步展望了提高乙酰辅酶A供给的策略,利用基因组编辑技术构建合成乙酰辅酶A为前体化学品细胞工厂的方法。     

Improvement of Aglycone π-Stacking Yields Nanomolar to Sub-nanomolar FimH Antagonists

Antimicrobial resistance has become a serious concern for the treatment of urinary tract infections. In this context, an anti-adhesive approach targeting FimH, a bacterial lectin enabling the attachment of E. coli to host cells, has attracted considerable interest. FimH can adopt a low/medium-affinity state in the absence and a high-affinity state in the presence of shear forces. Until recently, mostly the high-affinity state has been investigated, despite the fact that a therapeutic antagonist should bind predominantly to the low-affinity state. In this communication, we demonstrate that fluorination of biphenyl α-d -mannosides leads to compounds with perfect π–π stacking interactions with the tyrosine gate of FimH, yielding low nanomolar to sub-nanomolar K_D values for the low- and high-affinity states, respectively. The face-to-face alignment of the perfluorinated biphenyl group of FimH ligands and Tyr48 was confirmed by crystal structures as well as ¹H,¹⁵N-HSQC NMR analysis. Finally, fluorination improves pharmacokinetic parameters predictive for oral availability.     

青蒿琥酯增加小鼠腹腔巨噬细胞内化内毒素、大肠埃希菌的作用及可能机制

目的: 观察青蒿琥酯(artesunate, AS)对小鼠腹腔巨噬细胞内化清除脂多糖/内毒素(lipopolysaccharide/endotoxin, LPS)和吞噬大肠埃希菌的影响,并初步探讨其可能的作用机制。方法: MTT法检测不同浓度网格蛋白抑制剂(monodansylcadaverine, MDC)、内体酸化抑制剂氯喹(chloroquine, CQ)对小鼠腹腔巨噬细胞活力的影响,以选择恰当的药物工作浓度;激光共聚焦法检测青蒿琥酯及MDC、CQ对小鼠腹腔巨噬细胞内化FITC-LPS的影响;分别采用激光共聚焦和菌落集落形成计数实验观察青蒿琥酯对小鼠腹腔巨噬细胞内化大肠埃希菌的影响;逆转录PCR检测青蒿琥酯对小鼠腹腔巨噬细胞清道夫受体A(class A scavenger receptor,SR-A) mRNA表达的影响。结果: MDC和CQ浓度分别小于 25 μg/mL 和 20 μg/mL 时对小鼠腹腔巨噬细胞活力无影响;MDC、CQ可抑制小鼠腹腔巨噬细胞内化LPS,青蒿琥酯可增加小鼠腹腔巨噬细胞对LPS的内化,而且青蒿琥酯可增加MDC和CQ处理的巨噬细胞内化LPS的功能。激光共聚焦和菌落集落形成计数实验均显示青蒿琥酯可增加小鼠腹腔巨噬细胞对大肠埃希菌的内化能力。逆转录PCR结果显示青蒿琥酯可增强LPS处理或未处理的小鼠腹腔巨噬细胞SR-A mRNA的表达。结论: 青蒿琥酯可增强小鼠腹腔巨噬细胞内化LPS、大肠埃希菌的能力,该作用可能与SR-A mRNA表达升高有关。