Effects of temperature,storage time and pH on survival of Escherichia coli in source‐separated yellowwater

Laboratory‐scale experiments on the survival of Escherichia coli in raw, undiluted, freshly collected, source‐separated yellowwater were performed. Concentrations of E. coli and its survival at different temperature regimes and storage times were measured in yellowwater originally cross‐contaminated with faeces and yellowwater purposely contaminated (deliberately spiked) with faecal material. The temperature regimes of cold (4°C), mild (10°C) and warm (22°C) were the limited factors, whereas the storage time of the contaminated yellowwater was unlimited and lasted until the E. coli concentrations reached the limit of detection of < 1 Most Probable Number (MPN)/100 mL. Temperature and pH played the main role in the inactivation and longevity of E. coli in source‐separated yellowwater. The mild storage conditions were the most favourable for the persistence of E. coli, which reached 40 days with a concentration of 2.0 E+03 MPN in 100 mL of undiluted yellowwater.     

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     

Ozone-Bromine Treatment – Water Treatment in Public Pools without Chlorine: A New Standard?

The central task of the rules and regulations governing water treatment in public swimming pools is to provide guidelines, the compliance with which leads to completely hygienic water. For this purpose, DIN 19643 “Treatment of Water of Swimming Pools and Baths” applies in Germany. To date, this standard has prescribed the chlorination of water. In a therapeutic pool introduced here, water was treated without chlorine. The water quality was observed as part of a long-term study over the course of three years. During the entire period, no germs were detected in the filtrate of the system, not even unspecific CFU germs. The treatment presented here is detailed from both theoretical and practical viewpoints. The treatment uses the oxidation power of ozone to form hypobromous acid as a disinfectant in water containing bromide. A crucial aspect of the treatment is the possible formation of bromate. It is shown that the formation of bromate can be suppressed very effectively. Further bromine-based by-products were monitored. Unpleasant by-products as known from the chlorination were not found. The treatment, known as ozone-bromine Treatment, demonstrates new ways to treat water in public swimming pools and should now be incorporated into the German DIN 19643. It is to be expected that this will also be reflected in the national standards of other countries.     

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。     

Microbial Upgrading of Acetate into Value-Added Products—Examining Microbial Diversity,Bioenergetic Constraints and Metabolic Engineering Approaches

Ecological concerns have recently led to the increasing trend to upgrade carbon contained in waste streams into valuable chemicals. One of these components is acetate. Its microbial upgrading is possible in various species, with Escherichia coli being the best-studied. Several chemicals derived from acetate have already been successfully produced in E. coli on a laboratory scale, including acetone, itaconic acid, mevalonate, and tyrosine. As acetate is a carbon source with a low energy content compared to glucose or glycerol, energy- and redox-balancing plays an important role in acetate-based growth and production. In addition to the energetic challenges, acetate has an inhibitory effect on microorganisms, reducing growth rates, and limiting product concentrations. Moreover, extensive metabolic engineering is necessary to obtain a broad range of acetate-based products. In this review, we illustrate some of the necessary energetic considerations to establish robust production processes by presenting calculations of maximum theoretical product and carbon yields. Moreover, different strategies to deal with energetic and metabolic challenges are presented. Finally, we summarize ways to alleviate acetate toxicity and give an overview of process engineering measures that enable sustainable acetate-based production of value-added chemicals.     

Modelling concentration gradients in fed-batch cultivations of E. coli – towards the flexible design of scale-down experiments

The cover image is based on the Research Article Modelling concentration gradients in fed-batch cultivations of E. coli - towards the flexible design of scale-down experiments by Emmanuel Anane et al., DOI: 10.1002/jctb.5798 .

     

Functional expression of recombinant sweet-tasting protein brazzein by Escherichia coli and Bacillus licheniformis

Brazzein is an attractive sweetener candidate because of its sugar-like taste, high sweetness, and good stability at high temperature and wide pH range. This study was aimed to express and purify bioactive recombinant brazzein (rBrazzein). The rBrazzein gene was synthesized according to the preferred codons of Bacillus subtilis and successfully expressed in Escherichia coli and Bacillus licheniformis. In E. coli host, lower induction temperature of 30°C increased soluble rBrazzein (Ebrazzein) at high level. In B. licheniformis host, two signal peptides (Sec type and Tat type) were evaluated for the expression of rBarzzein in B. subtilis and B. licheniformis. However, only the Sec-type signal peptide guided the secretion expression of rBrazzein in B. licheniformis. The rBrazzein was expressed steadily and the highest yield reached about 57 mg/L at 36 h by small-scale fermentation. The purification procedure of rBrazzein by B. licheniformis (Bbrazzein) was thus established. Approximately 5 mg/L purified rBrazzein was obtained and the purity was 85%. The conformational state of rBrazzeins was confirmed by circular dichroism. The bioactivities of rBrazzeins were evaluated by sweet taste testing. The Bbrazzein and Ebrazzein were 266 times and 400 times sweeter than sucrose on a weight basis, respectively. The formation of disulfide bonds were both confirmed by LC/MS/MS and MALDI-TOF. The CD analysis indicated that Ebrazzein has a similar secondary structure with natural brazzein, which explained why Ebrazzein had a higher intensity of sweetness. This study demonstrated that B. licheniformis system is useful to produce active recombinant brazzein, and has potential food industry applications.