Detection and collection of shiga toxin-producing Escherichia coli using foam concentration without membrane filtration

Information on Shiga toxin-producing Escherichia coli (STEC) in river water is scarce, and it is essential to understand its actual status in river water. This study investigated a method for the highly efficient recovery of STEC from river water in its active state by combining a coagulation and foam concentration and a selective medium. The method was applied to three rivers, and STEC-positive Escherichia coli (E. coli) were obtained from all rivers. Ten E. coli harboring one of the pathogenic genes (stx2, eae) were detected in the Oyodo River’s upstream and midstream and the Kaeda River’s midstream. Furthermore, antimicrobial agent susceptibility testing was performed on these ten strains using ten antimicrobial agents. Nine strains showed intermediate resistance to at least one antibiotic, and one was multidrug-resistant. This study’s coagulation and foam concentration and selective medium detection methods can efficiently collect STEC in river water and recover it in an active state without conventional membrane filtration. Isolating and cultivating this STEC strain will provide crucial information for antimicrobial agent susceptibility testing, target gene testing, and whole-genome analysis.Citation: Soichiro Tamai, Makoto Katafuchi, Xie Hui, Yoshihiro Suzuki, Detection and collection of shiga toxin-producing Escherichia coli using foam concentration without membrane filtration, Ecotoxicology and Environmental Safety, 291, 117797-117797, 2025-02, https://doi.org/10.1016/j.ecoenv.2025.11779

Genetic diversity of dissolved free extracellular DNA compared to intracellular DNA in wastewater treatment plants

Dissolved free extracellular DNA (free-exDNA) coexists with intracellular DNA (inDNA) in aquatic environments. Free-exDNA can be taken up by bacteria through transformation, and wastewater treatment plants (WWTPs) are positioned as potential hot spots for genetic contamination. However, studies comparing the composition of free-exDNA and inDNA is limited. This study employed colloidal adsorption and foam concentration method to recover free-exDNA from different WWTP stages and compared its diversity with inDNA via metagenomic analysis. Free-exDNA concentrations were observed to increase after chlorination. Genetic analysis revealed a higher abundance of specific genes following chlorination, suggesting that free-exDNA in effluent originated from bacterial death in secondary treated water. This result indicates that free-exDNA, which increases due to chlorination, is subsequently released into the catchment. Additionally, several high-risk antibiotic-resistance genes (ARGs) were detected that colocalized with mobile genetic elements. These ARGs were expected to have a high potential for gene transfer via transformation, and the risk was highlighted. Overall, these findings deepen our understanding of horizontal gene transfer risks in WWTPs.Citation: Soichiro Tamai, Miki Okuno, Yoshitoshi Ogura, Yoshihiro Suzuki, Genetic diversity of dissolved free extracellular DNA compared to intracellular DNA in wastewater treatment plants, Science of The Total Environment, 970, 178989-178989, 2025-03, https://doi.org/10.1016/j.scitotenv.2025.17898

Ballasted flocculation with powdered activated carbon adsorption for the simultaneous removal of odorous substances and suspended solids

Algal blooms in reservoirs can cause odor problems in tap water even after going through the coagulation–sedimentation process in water treatment plants. A common countermeasure is to introduce powdered activated carbon (PAC) in the coagulation–sedimentation process, but a long contact time is needed to ensure that odorous substances are adsorbed. In this study, PAC adsorption was combined with ballasted flocculation to realize the fast and simultaneous removal of suspended solids and odorous substances. Experiments were conducted using simulated raw water to determine the appropriate conditions for the proposed method and to compare the performance with that of conventional coagulation. The results showed that PAC adsorption and ballasted flocculation effectively reduced the concentrations of the representative odorous substances geosmin and 2-methylisoborneol to less than 1 ng/L and the turbidity to less than 1 TU (equivalent to 1 mg/L kaolin). Furthermore, the settling velocity of the ballasted flocculation was 22 times higher than that of the conventional coagulation. Thus, the proposed method can quickly and effectively remove suspended solids and odorous substances simultaneously. It is expected to be suitable for water treatment plants with limited space for retrofitting

The research on pursuing of estrogens in the coast urban area and development of its reduction technique

平成16年度~平成18年度科学研究費補助金(基盤研究(c))研究成果報告書research repor

Year-round monitoring of antibiotic-resistant bacteria in pristine uppermost stream and estimation of pollution sources

Citation: Emi Nishimura, Hui Xie, Soichiro Tamai, Masateru Nishiyama, Kei Nukazawa, Yuki Hoshiko, Yoshitoshi Ogura, Yoshihiro Suzuki, Year-round monitoring of antibiotic-resistant bacteria in pristine uppermost stream and estimation of pollution sources, Frontiers in Environmental Science, 12, 2024-09-09, https://doi.org/10.3389/fenvs.2024.143917

Performance recovery of proton exchange membrane electrolyzer degraded by metal cations contamination

Hydrogen production from renewable electricity offers an eco-friendly alternative to fossil fuels. Proton exchange membrane (PEM) electrolysis is a well-known method for this purpose. Studies have primarily focused on reducing costs of noble catalysts, improving efficiency, managing system degradation, and addressing membrane thinning caused by contaminated cations. However, techniques for PEM recovery post-degradation are still under development. This study investigated the effects of cations on PEM cells using artificial soft water, and analyzed two recovery methods to restore cell performance. Our findings indicate a significant rise in cell operating voltage and a decrease hydrogen production over 8 h of operation with soft water. After introducing both recovery methods, the initial operating value was reinstated in both cases. Only nitric acid treatment, however, achieved hydrogen production levels comparable to those of ultrapure water.Citation: PyaePyae Shwe Sin, SoeHtet Wai, Yasuyuki Ota, Kensuke Nishioka, Yoshihiro Suzuki, Performance recovery of proton exchange membrane electrolyzer degraded by metal cations contamination, International Journal of Hydrogen Energy, Volume 53, 2024, Pages 86-92, ISSN 0360-3199, https://doi.org/10.1016/j.ijhydene.2023.12.049

Antibiotic-resistant Escherichia coli isolated from dairy cows and their surrounding environment on a livestock farm practicing prudent antimicrobial use

application/pdfOn a livestock farm where antimicrobial administration and its history had been managed for prudent use of antimicrobials, we surveyed antibiotic-resistant Escherichia coli strains isolated from cow feces and the surrounding environment （i.e., rat and crow feces, and water samples from a drainage pit and wastewater processing tank） every month for 1 year. Two strains （1.7%） in cow feces were resistant to tetracycline, whereas all other strains were susceptible to all other antimicrobials. Among 136 strains isolated from cows and wild animals, only one ampicillin-resistant strain was identified. The antibiotic resistance rate in the drainage from the barn was 8.3% （10/120）, and all strains showed susceptibility for 8 months of the year. Tetracycline resistance was common in all resistant strains isolated from animal feces and water samples; all tetracycline-resistant strains carried tetA. These results strongly support the proper use and management of antibiotics on farms to minimize the outbreak and spread of antibiotic-resistant bacteria

タンパク質を用いた泡沫分離法による懸濁物除去に関する研究

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Monitoring of fecal bacteria and microbial source tracking in coastal urban area

平成19年度~平成22年度科学研究費補助金(基盤研究(c))研究成果報告書research repor

A study on removal and recovery of heavy metals from industrial wastewater by precipitation and foam separation

In this study, recovery of heavy metals from artificial wastewater containing Cr, Cu, Cd, Pb and Mo by precipitation and foam separation using lime and milk casein was investigated. In addition, to demonstrate the effectiveness of the proposed precipitation and foam separation method, it was applied to mining tailing water collected from an ore-mining facility in Mongolia. Lime was used as an alkaline agent for heavy-metal precipitation. Milk casein functioned as both a collector and a frother for foam separation. The removal efficiencies of heavy metals were determined by inductively plasma spectrometry. As results, the casein enabled the collection and recovery of the precipitation components of heavy metals within a total processing time of 10 min. Precipitation and foam separation using lime and casein is an effective and adaptable method for treating industrial effluents that contain heavy metals.othe