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This paper studies the photocatalytic performance of graphene-based titanium dioxide (TiO2) on cementitious composites for the decomposition of Escherichia coli (E. coli) under visible light. Graphene-based TiO2 was first synthesized through a hydrothermal process. The composites were then evaluated in terms of adsorption capability and degradation of methylene blue dyes. The adsorption test shows a remarkable increase in the amount of dye adsorbed into the composite surface. GO-P25 could adsorb around 60% of the initial dye, while less than 10% of the initial dye was adsorbed by pristine TiO2-P25. The synthesized graphene-based TiO2 significantly enhanced the dye degradation activity (94%) compared to pristine P25 (36%) and Krono (52%), even with the longer irradiation time for P25 and Krono. This led to an increase in reaction rate that was almost 20 times that of P25. Considering the good adsorption capabilities and high photodegradation of dye under visible light for GO-P25, cement-based surfaces containing GO-P25 are expected to be improved for the decomposition of Escherichia coli (E. coli) under visible light. Graphene-based TiO2 on a cement-based surface showed high antibacterial activity with a 77% reduction in number of bacteria compared to a cement-based surface containing pristine TiO2. This study confirms the effectiveness of the composites for disinfection of E. coli under visible light. [ABSTRACT FROM AUTHOR]

Graphene oxide-titanium dioxide (GO-TiO2) composite was synthesized with one step hydrothermal process. The structure and morphology were characterized by field-emission-scanning-electron-microscopy, Thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Photocatalytic activity against Escherichia coli inactivation was carried out by GO-TiO2 mixed with cement composite under visible light. The result revealed no significant difference between morphology of GO-TiO2 and pristine TiO2. FESEM and FTIR results showed the presence of carbon component in the GO-TiO2 composites. TGA-IR confirmed that the GO content (3%) in the composite could be controlled during the synthesis process. The synthesized GO-TiO2 had stronger visible light absorption and narrower bandgap (3.11 eV) than TiO2 (3.21 eV). The bandgap reduction was also observed in cement sample with GO-TiO2 (3.08 eV) which could be beneficial for reducing the energy needed for photoexcitation. As a result, the specimen with GO-P25 outperformed specimens with others for Escherichia coli inactivation. [ABSTRACT FROM AUTHOR]

Here, multifunctional heterogeneous ion-exchange metal nanocomposite membranes were prepared for surface water desalination and bacterial inactivation under low-pressure (0.05 MPa) filtration conditions. Ultrafiltration (UF) heterogeneous ion exchange membranes (IEMs) were modified with different concentrations of AgNO3 and CuSO4 solutions using the intermatrix synthesis (IMS) technique to produce metal nanocomposite membranes. Scanning electron microscopy (SEM) images revealed that the metal nanoparticles (MNPs) (Ag and Cu) were uniformly distributed on the surface and the interior of the nanocomposite membranes. With increasing metal precursor solution concentration (0.01 to 0.05 mol·L−1), the metal content of Ag and Cu nanocomposite membranes increased from 0.020 to 0.084 mg·cm−2 and from 0.031 to 0.218 m·cm−2 respectively. Results showed that the hydrodynamic diameter diameters of Ag and Cu nanoparticles (NPs) increased from 62.42 to 121.10 nm and from 54.2 to 125.7 nm respectively, as the metal precursor concentration loaded increased. The leaching of metals from metal nanocomposite membranes was measured in a dead-end filtration system, and the highest leaching concentration levels were 8.72 ppb and 5.32 ppb for Ag and Cu, respectively. The salt rejection studies indicated that ionic selectivity was improved with increasing metal content. Bacterial filtration showed higher antibacterial activity for metal nanocomposite membranes, reaching 3.6 log bacterial inactivation. [ABSTRACT FROM AUTHOR]

The inactivation of Escherichia coli is one of the major issues in the food industry. The present study focuses on the application of a combined microwave-ultrasound system for the optimization of the inactivation of Escherichia coli ATCC 25922 in an orange juice drink. Using response surface methodology (RSM), trials were planned with a Box–Behnken Design (BBD) to maximize the impact of microwave power (A: 300–900 W), microwave treatment time (B: 15–35 s), and time of ultrasound (C: 10–30 min) on E. coli inactivation. Analysis of variance (ANOVA) was carried out and E. coli inactivation was expressed with a mathematical equation depending on the factors. The results showed that both the microwave treatment time and the time of ultrasound were effective as independent variables in eliminating the E. coli strain. However, the effect of these two variables, ultrasound and microwave exposure time, in combination was significantly greater than when examined separately. RSM modeling determined that optimal treatment conditions include 900 W microwave power, 33 s microwave treatment time, and 20 min time of ultrasound to achieve an 8-log reduction of E. coli, constituting total inactivation. The results of this study showed that ultrasound-microwave treatment is a potential alternative processing method for an orange juice beverage. [ABSTRACT FROM AUTHOR]

This paper studies the photocatalytic performance of graphene-based titanium dioxide (TiO2) on cementitious composites for the decomposition of Escherichia coli (E. coli) under visible light. Graphene-based TiO2 was first synthesized through a hydrothermal process. The composites were then evaluated in terms of adsorption capability and degradation of methylene blue dyes. The adsorption test shows a remarkable increase in the amount of dye adsorbed into the composite surface. GO-P25 could adsorb around 60% of the initial dye, while less than 10% of the initial dye was adsorbed by pristine TiO2-P25. The synthesized graphene-based TiO2 significantly enhanced the dye degradation activity (94%) compared to pristine P25 (36%) and Krono (52%), even with the longer irradiation time for P25 and Krono. This led to an increase in reaction rate that was almost 20 times that of P25. Considering the good adsorption capabilities and high photodegradation of dye under visible light for GO-P25, cement-based surfaces containing GO-P25 are expected to be improved for the decomposition of Escherichia coli (E. coli) under visible light. Graphene-based TiO2 on a cement-based surface showed high antibacterial activity with a 77% reduction in number of bacteria compared to a cement-based surface containing pristine TiO2. This study confirms the effectiveness of the composites for disinfection of E. coli under visible light.

[Display omitted] • ZnO 2 was used for visible-light-induced TC degradation and E. coli inactivation. • ZnO 2 had high adaptabilities to solution pH, matrix species and water sources. • TC sensitization caused •O 2 − generation responsible for self-promoted degradation. • The photoexcitation of the hydrolysates from ZnO 2 resulted in 1O 2 generation. In this study, zinc peroxide (ZnO 2) with broad energy gap was firstly used for visible-light-induced photocatalytic degradation of tetracycline (TC) and inactivation of Escherichia coli (E. coli). A small amount of ZnO 2 (10 mg) could efficiently degrade 100 mL of 50 mg/L TC in a wide pH range (4–12), and the degradation performance was rarely suppressed by common matrix species and natural water sources. Also, 100 mg/L ZnO 2 could inactivate around 7-log E. coli cells within 60 min under visible-light irradiation. Quenching experiments and electron paramagnetic resonance (EPR) results confirmed that superoxide radical (•O 2 −) and singlet oxygen (1O 2) were the main reactive oxygen species (ROS), which were attributed to the self-sensitization of TC and the photoexcitation of released H 2 O 2 under the catalysis of Zn(OH) 2 from the hydrolysis of partial ZnO 2 , respectively. The pathways of TC degradation and processes of visible-light-induced TC degradation and E. coli inactivation were proposed and deduced in detail. This work presented the enhanced visible-light photocatalytic activities of ZnO 2 for antibiotic degradation and bacterial inactivation, and provided a deep insight into the mechanisms of visible-light-induced TC degradation and E. coli inactivation over ZnO 2. [ABSTRACT FROM AUTHOR]

The inactivation of Escherichia coli is one of the major issues in the food industry. The present study focuses on the application of a combined microwave-ultrasound system for the optimization of the inactivation of Escherichia coli ATCC 25922 in an orange juice drink. Using response surface methodology (RSM), trials were planned with a Box–Behnken Design (BBD) to maximize the impact of microwave power (A: 300–900 W), microwave treatment time (B: 15–35 s), and time of ultrasound (C: 10–30 min) on E. coli inactivation. Analysis of variance (ANOVA) was carried out and E. coli inactivation was expressed with a mathematical equation depending on the factors. The results showed that both the microwave treatment time and the time of ultrasound were effective as independent variables in eliminating the E. coli strain. However, the effect of these two variables, ultrasound and microwave exposure time, in combination was significantly greater than when examined separately. RSM modeling determined that optimal treatment conditions include 900 W microwave power, 33 s microwave treatment time, and 20 min time of ultrasound to achieve an 8-log reduction of E. coli, constituting total inactivation. The results of this study showed that ultrasound-microwave treatment is a potential alternative processing method for an orange juice beverage.

• Fe-EC in-situ generated magnetite/green rust efficient for the inactivation of E. coli. • Unstable in-situ generated magnetite and GR was a prerequisite factor for inactivation. • Cell membrane damage was a key process for E. coli inactivation with magnetite. • Excess ROS and Fe2+ intracellular was a main reason for E. coli inactivation with GR. • Fe-EC in the absence of DO was efficient for E. coli inactivation in real wastewater. Electrocoagulation (EC) is promising for the removal of chemical and microbial contaminants. Although the removal of pathogens from wastewater is efficient by conventional Fe-EC in the presence of dissolved oxygen (DO), the non-inactivated pathogens in the sediment still have a risk. Herein, the inactivation of Escherichia coli (E. coli) with the mixed-valent iron nanoparticles, magnetite and green rust (GR), in-situ generated from Fe-EC process in the absence of DO was investigated. The inactivation efficiency was significantly higher with magnetite (4.7 log cells) and GR (3.2 log cells) compared with FeOOH (0.7–1.7 log cells) generated at 50 mA in 10 min. The unstable in-situ generated magnetite with positive charges was prone to adsorb onto E. coli , damaging the cell membrane, inactivating the bacteria. The unstable in-situ generated GR was prone to coagulate with E. coli , delivering Fe2+ into the cell and inducing the generation of endogenous ROS, inactivating the bacteria. Fe-EC in the absence of DO was proved to be efficient for the inactivation of E. coli (4.2–4.3 log cells) in real wastewater. These findings identified the ignored inactivation effect and mechanism of E. coli with magnetite and GR generated in situ from Fe-EC process, which will provide theoretical support for real applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Tris-Co(II) complex-H 2 O 2 could generate hydroxyl radicals continuously. • Tris-Co(II) complexes are apt to combine with E. Coli by electrostatic interactions. • High-efficiency inactivation of E. Coli was realized in the proposed system. Abstract Fenton/Fenton-like reaction is often used as an efficient method to generate hydroxyl radicals (HO) for bacteria inactivation in aqueous solution. However, inactivation efficiency of bacteria in aqueous solution using Fenton/Fenton-like reactions needs to further improve as a result of transient generation of HO. In this paper, we found that the formation of Tris-Co(II) complexes could decrease the redox potential of Co(III)/Co(II), facilitating the transformation of Tris-Co(III) complexes into Tris-Co(II) complexes. Therefore, HO could be generated continuously in the presence of H 2 O 2. Especially, Tris-Co(II) complexes are apt to combine with Escherichia Coli cells by electrostatic interactions, inducing a higher utilization ratio of the generated HO. Therefore, the proposed Tris-Co(II) complex-H 2 O 2 system could be employed as a high-efficiency sterilizing reagent for inactivation of E. Coli. This work provides a promising strategy for bacterial inactivation via an economic and eco-friendly manner. [ABSTRACT FROM AUTHOR]

Abstract The photocatalytic inactivation of Escherichia coli (E. coli) under light-emitting diode (LED) light irradiation was performed with P/Ag/Ag 2 O/Ag 3 PO 4 /TiO 2 photocatalyst to investigate the photocatalytic bactericidal activity. Our work showed that this composite photocatalyst possessed remarkable bacterial disinfection ability and could completely inactivate 108 cfu/mL of E. coli within just 40 min under the optimum catalyst loading of 0.5 g/L. The effects of different environmental factors, including light wavelength, light intensity, temperature, solution pH and inorganic ions, on the inactivation efficiency were evaluated. The results showed that bacteria inactivation by P/Ag/Ag 2 O/Ag 3 PO 4 /TiO 2 was more favorable with blue colored LED irradiation, light intensity at 750 W/m2, temperature in the range of 30–37 °C and pH values at natural or slightly alkaline condition. The existence of different inorganic ions under normal environmental level had no significant impact on the bactericidal performance. In addition, during the inactivation process, the morphology changes of E. coli cells were directly observed by scanning electron microscope (SEM) and further proved by the measurement of K+ leakage from the inactivated E. coli. The results demonstrated that the photocatalytic inactivation caused drastic damage on bacterial cells membrane. Furthermore, the mechanisms of photocatalytic bacterial inactivation were also systemically studied and the results confirmed that the excellent disinfection activity of P/Ag/Ag 2 O/Ag 3 PO 4 /TiO 2 resulted from the major reactive species: h+ and ·O 2 − from photocatalytic process instead of the leakage of Ag+ (≤0.085 ± 0.005 mg/L) from photocatalyst. These results indicate that P/Ag/Ag 2 O/Ag 3 PO 4 /TiO 2 photocatalyst has promising potential for real water sterilization application. Graphical abstract Image 1 Highlights • P/Ag/Ag 2 O/Ag 3 PO 4 /TiO 2 exhibited strong bactericidal activity under LED irradiation. • The effects of various environmental factors on disinfection were revealed. • The destruction process of E. coli cells was systemically studied. • Remarkable inactivation ascribed to photogenerated h+ and ·O 2 − instead of Ag+. • The photocatalyst holds enormous potential for actual water sterilization. Visible-light-driven photocatalyst with superior disinfection ability under various environmental conditions shows a great potential for actual water sterilization. [ABSTRACT FROM AUTHOR]

This study investigated the optimum conditions to maximize the inactivation of biofilms using both plasma-treated solutions and post-treatment storage conditions. Chemical properties of plasma-treated solutions were also analyzed to identify their possible biofilm inactivation mechanisms. Escherichia coli O157:H7 biofilms on stainless steel were prepared and immersed in distilled water (DW), 100 ppm of sodium chloride solution (NaCl), or 100 ppm of sodium hypochlorite solution (NaOCl), followed by container-type plasma treatment for 10 min (15 kHz and 250 W). After plasma discharge was switched off, biofilms immersed in the plasma-treated solution were stored for 10 min with the plasma apparatus closed or open. The log reduction of E. coli O157:H7 was NaOCl (3.58) > NaCl (2.06) = DW (1.95) in the closed storage condition. In addition, the bactericidal effect of NaOCl was higher in the closed condition than in the open condition. Concentrations of the hydroxyl radical (OH·) and peroxynitrite (ONOO−) were also the highest for NaOCl in the closed condition. Consequently, plasma treatment using NaOCl solution in the closed condition was found to be the optimum method for inactivation of E. coli O157:H7 biofilms, due to high hydroxyl radical and peroxynitrite concentrations. This method also has the merit of using a lower concentration of NaOCl than that used typically in industry. [ABSTRACT FROM AUTHOR]

BACKGROUND Inactivation of Escherichia coli, suspended in McIlvaine buffer, was investigated by the application of radio frequency electric field (RFEF) under single‐stage, multi‐stage and recirculation flow configurations using a parallel‐plate treatment chamber. Changes in the survival fraction were correlated, through predictive microbiology, as a function of key process parameters: electric field strength, temperature, time and flow rate, as well as the intrinsic media properties: pH and electrical conductivity. Various empirical models, including Hülsheger, Peleg, Geeraerd and Weibull were compared with mechanistic models, such as the first‐order exponential decay and the two‐term exponential models. Mechanistic models were employed to formulate reactor models by performing differential mass balances over the inactivation chambers, with plug‐flow‐reactor (PFR) assumption for single‐ and multi‐stage configurations, and differential PFR for recirculation configuration. RESULTS: The single‐stage configuration with variable flow rate was proven unsuitable for kinetic studies. Nonlinear logarithmic inactivation profiles were observed with multi‐stage and recirculation. The two‐term exponential mechanistic model effectively explained the kinetics of inactivation. Treatment chambers were successfully modelled mechanistically with reaction engineering principles. Common kinetic constants fitted the experimental data for all flow configurations. The intrinsic properties of media also influenced process kinetics. CONCLUSIONS: The presence of variable resistances amongst microbial population adds nonlinearity in RFEF processing with the extension of the treatment time. The research showed that unlike empirical models, the mechanistic approach can explain the complex inactivation behaviour for all flow configurations. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The objectives of this study were to assess the effectiveness of an ultraviolet (UV‐C, 254 nm) irradiation system and the spray‐drying method as two independent safety steps on inactivation of Escherichia coli K88 and K99 spiked in porcine plasma at 6·46 ± 0·04 log10 ml−1 and 6·78 ± 0·67 log10 ml−1 respectively for UV‐C method, and at 7·31 ± 0·39 log10 ml−1 and 7·66 ± 0·11 log10 ml−1, respectively for the spray‐drying method. The UV‐C method was performed at different UV light doses (from 750 to 9000 J l−1) using a pilot plant UV‐C device working under turbulent flow. Spray‐drying treatment was done at inlet temperature 220 ± 1°C and two different outlet temperatures, 80 ± 1°C or 70 ± 1°C. Results indicated that UV‐C treatment induced a 4 log10 viability reduction for both E. coli at 3000 J l−1. Full inactivation of both E. coli strains was achieved in all spray‐dried samples dehydrated at both outlet temperatures. The special UV‐C system design for turbid liquid porcine plasma is a novel treatment that can provide an additional redundant biosafety feature that can be incorporated into the manufacturing process for spray‐dried animal plasma. Significance and Impact of the Study: The safety of raw materials from animal origin such as spray‐dried porcine plasma (SDPP) may be a concern for the swine industry. Ultraviolet treatment at 254 nm (UV‐C) of liquid plasma has been proposed as an additional biosafety feature in the manufacturing process of SDPP. We found that UV‐C exposure in the liquid plasma at 3000 J l−1 reduces about 4 log10 ml−1 for E. coli K88 and K99. Full inactivation of both E. coli strains was achieved in all spray‐dried samples. The incorporation of UV‐C treatment to liquid plasma improves the robustness of the SDPP manufacturing process. Significance and Impact of the Study: The safety of raw materials from animal origin such as spray‐dried porcine plasma (SDPP) may be a concern for the swine industry. Ultraviolet treatment at 254 nm (UV‐C) of liquid plasma has been proposed as an additional biosafety feature in the manufacturing process of SDPP. We found that UV‐C exposure in the liquid plasma at 3000 J l−1 reduces about 4 log10 ml−1 for E. coli K88 and K99. Full inactivation of both E. coli strains was achieved in all spray‐dried samples. The incorporation of UV‐C treatment to liquid plasma improves the robustness of the SDPP manufacturing process. [ABSTRACT FROM AUTHOR]

This study addresses inactivation of E. coli in either 5- or 10-mL volumes, which were 50- to 100-fold greater than used in an earlier study (Brayman et al. 2017). Cells were treated with 1-MHz pulsed high-intensity focused ultrasound (10 cycles, 2-kHz repetition frequency, +65/-12.8 MPa focal pressures). The surviving fraction was assessed by coliform assay, and inactivation demonstrated curvilinear kinetics. The reduction of surviving fraction to 50% required 2.5 or 6 min in 5- or 10-mL samples, respectively. Exposure of 5 mL for 20 min reduced the surviving fraction to ∼1%; a similar exposure of 10-mL samples reduced the surviving fraction to ∼10%. Surviving cells from 5-min exposures appeared normal under light microscopy, with minimal debris; after 20 min, debris dominated. Transmission electron microscopy images of insonated samples showed some undamaged cells, a few damaged but largely intact cells and comminuted debris. Cellular damage associated with substantive but incomplete levels of inactivation can be variable, ranging from membrane holes tens of nanometers in diameter to nearly complete comminution. [ABSTRACT FROM AUTHOR]

The disinfection of synthetic fresh-cut wastewater (SFCWW) by several solar processes has been investigated as an alternative to the commonly used chlorination in this industry. To this end, a SFCWW recipe was developed based on real sample analysis from the fresh-cut industry and literature data. It is characterized mainly by the presence of organic matter in solution (25 mg/L DOC) and turbidity (100 NTU). The inactivation kinetics of human pathogenic bacteria ( E. coli O157:H7 and Salmonella enteritidis ) in SFCWW was assessed by solar photo-inactivation, H 2 O 2 /solar, iron/solar and solar photo-Fenton processes. Excellent inactivation performance was achieved in all cases demonstrating the capability of solar processes to disinfect water even at high levels of turbidity. The best bacterial inactivation rates were obtained with the H 2 O 2 /solar process (20 mg/L) in less than 60 min for both E. coli and S. enteriditis . Moreover, the influence of UVA irradiance (10–50 W/m 2 ) on the inactivation of both pathogens by the H 2 O 2 /solar process at several H 2 O 2 concentrations was investigated. These results showed a slightly different response for both pathogens against UVA irradiance and H 2 O 2 concentration: photo-limitation for both types of bacteria; while only E. coli was limited by the H 2 O 2 concentrations investigated in this work. [ABSTRACT FROM AUTHOR]

Three different methods of bacterial viability monitoring were compared to detect chemically or thermally inactivated Escherichia coli. Direct colony enumeration, live/dead bacterial cell staining with a fluorescent dye, and the dehydrogenase activity assay were compared with respect to their ease of use and time required to perform the three different tests. The green (live cell)/red (dead cell) ratio obtained from the fluorescent bacterial cell staining approach showed a linear relationship with the colony forming units; the result obtained with dehydrogenase was similar to those. The sensitivity of the monitoring methods to detect bacterial deactivation varied with different disinfection conditions. After thermal treatment, the sensitivity of the staining approach was lower, while that of the dehydrogenase activity assay was the highest. After chemical treatment, the sensitivity of detection for both methods was similar. [ABSTRACT FROM AUTHOR]

Non-thermal processes are in demand in the meat industry due to their ability to inactivate foodborne pathogens, such as Escherichia coli O157:H7, at room temperatures. Although ultraviolet-light (UV-C) is a potential process for eliminating pathogens while preserving the quality of foods, its inefficiency in penetrating solid foods might result in a lower log reduction of pathogens in meat. Thus, it is necessary to look at hurdle technologies. Lemongrass oil (LG), with its antimicrobial, antifungal and antioxidant properties, can be an ideal alternative. Therefore, the objective of this study was to evaluate the efficacy of UV-C, LG, and their combination on E. coli K12 inoculated goat meat. Lemongrass oil at 0.25%, 0.5%, and 1% concentrations (w/v) with intensities of 100 and 200 μW cm −2 , which provided an energy dose of 0.2–2.4 mJ cm −2 of UV-C, was used to treat goat meat for 2, 4, 6, 8, 10, and 12 min. The top surfaces of LG treated goat meat samples were treated with UV-C by these combinations of treatments. The combination of 1% LG + UV-C with 200 μW cm −2 treatment for 2 min resulted in a synergistic microbial reduction of 6.66 log 10  CFU mL −1 (below detection levels) of E. coli K12 compared to the control, the level of which was significantly higher than individual and other hurdle treatments ( P ≤ 0.05). No significant effect on the texture, whereas, changes in color and oxidative stability of goat meat was observed with LG + UV-C treatments. Although this combination seems to be a better option, treatment conditions need to be optimized and further studies are required to validate hurdle mechanisms for commercial applications. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate how treatment temperature influences the solubility of ClO 2 gas and the antimicrobial effect of ClO 2 gas against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on produce and food contact surfaces. Produce and food contact surfaces inoculated with a combined culture cocktail of three strains each of the three foodborne pathogens were processed in a treatment chamber with 20 ppmv ClO 2 gas at 15 or 25 °C under the same conditions of absolute humidity (11.2–12.3 g/m 3 ) for up to 30 min. As treatment time increased, ClO 2 gas treatment at 15 °C caused significantly more ( p  < 0.05) inactivation of the three pathogens than treatment at 25 °C. ClO 2 gas treatment at 25 °C for 30 min resulted in 1.15 to 1.54, 1.53 to 1.88, and 1.00 to 1.78 log reductions of the three pathogens on spinach leaves, tomatoes, and stainless steel No.4, respectively. ClO 2 gas treatment at 15 °C for 30 min caused 2.53 to 2.88, 2.82 to 3.23, and 2.37 to 3.03 log reductions of the three pathogens on spinach leaves, tomatoes, and stainless steel No.4, respectively. Treatment with ClO 2 gas at 25 °C for 20 min resulted in 1.88 to 2.31 log reductions of the three pathogens on glass while >5.91 to 6.82 log reductions of these pathogens occurred after 20 min when treated at 15 °C. Residual ClO 2 levels after gas treatment at 15 °C were significantly ( p  < 0.05) higher than those at 25 °C. The results of this study can help the food processing industry establish optimum ClO 2 gas treatment conditions for maximizing the antimicrobial efficacy of ClO 2 gas. [ABSTRACT FROM AUTHOR]

A dielectric barrier discharge reactor with plane-parallel electrode was utilized to disinfect the bacterium Escherichia coli ($E. coli$) to figure out the efficiency and mechanism of inactivation. During the treatment, a satisfactory potential for inactivation was observed. The inactivation rate reached 100% without any gases ventilated after 15 min of treatment and 100% with 0.6 L/min air after 9 min of treatment. The plasma was generated by a high-voltage alternating current regulator. The output power was around 33.8 W per cycle and the power utilization efficiency was 57.6%. The atmospheric sources of sole nitrogen or sole oxygen were not favorable for the bacterial inactivation, while air plasma presented better inactivation results. It indicates that the presence of active species containing nitrogen and oxygen, generated from the air plasma, or other active species derived from NO $x$ , such as ONOOH, which is produced by NO2 and OH, plays a more important role on bacterial inactivation. The ventilation result is different from others’ studies. Moreover, scanning electron microscopy was used to observe the $E.~coli$ cell topography alternation. After discharge, $E.~coli$ seemed to be more shrunken and blurred. Cells finally collapsed and part of them got stuck to each other. [ABSTRACT FROM AUTHOR]

The direct inactivation effects of an atmospheric pressure direct current (DC) air plasma against planktonic Staphylococcus aureus ( S . aureus ) and Escherichia coli ( E . coli ) in aqueous solution are investigated in vitro. Upon plasma treatment, extensively analyses on cell culturability, metabolic capacity, membrane integrity, surface morphology, cellular proteins, nucleic acids and intracellular reactive oxygen species (ROS) for both bacterial species were carried out and significant antimicrobial effects observed. Compared with the cellular culturability, a sub-lethal viable but non-culturable (VBNC) state was induced while more S . aureus entered this state than E . coli . Damaged bacterial outer structures were observed and the total concentrations of cellular protein and nucleic acid decreased for both bacteria after plasma treatment. The plasma-induced aqueous reactive species (RS) and intracellular ROS might produce detrimental effects to the bacteria, while S . aureus was less susceptible to the discharge after a 20-min exposure compared to E . coli . [ABSTRACT FROM AUTHOR]

Food preservation by the use of essential oils (EOs) is being extensively studied because of the antimicrobial properties of their individual constituents (ICs). Three resistant mutants (termed CAR, CIT, and LIM) of Escherichia coli MG1655 were selected by subculturing with the ICs carvacrol, citral, and (+)-limonene oxide, respectively. These derivative strains showed increased MIC values of ICs and concomitantly enhanced resistance to various antibiotics (ampicillin, trimethoprim, chloramphenicol, tetracycline, kanamycin, novobiocin, norfloxacin, cephalexin, and nalidixic acid) compared to those for the parental strain (wild type [WT]). Whole-genome sequencing (WGS) of these hyperresistant strains permitted the identification of single nucleotide polymorphisms (SNPs) and deletions in comparison to the WT. In order to analyze the contribution of these mutations to the increased antimicrobial resistance detected in hyperresistant strains, derivative strains were constructed by allelic reversion. A role of the SoxR D137Y missense mutation in CAR was confirmed by growth in the presence of some ICs and antibiotics and by its tolerance to ICs but not to lethal heat treatments. In CIT, increased resistance relied on contributions by several detected SNPs, resulting in a frameshift in MarR and an in-frame GyrB ΔG157 mutation. Finally, both the insertion resulting in an AcrR frameshift and large chromosomal deletions found in LIM were correlated with the hyperresistant phenotype of this strain. The nature of the obtained mutants suggests intriguing links to cellular defense mechanisms previously implicated in antibiotic resistance. IMPORTANCE The antimicrobial efficacy of ICs has been proven over the years, together with their potential to improve traditional heat treatments by reducing treatment intensity and, consequently, adverse effects on food quality. However, the mechanisms of bacterial inactivation by ICs are still not well understood, in contrast to antibiotics. We performed WGS of three E. coli strains that are hyperresistant to ICs. The information provided detailed insight into the mechanisms of bacterial resistance arising from exposure to carvacrol, citral, and (+)-limonene oxide. Future experiments will undoubtedly yield additional insights into genes and pathways contributing to the acquisition of endogenous resistance to ICs. [ABSTRACT FROM AUTHOR]

A visible light active structured photocatalyst consisting of Nitrogen-doped TiO 2 particles immobilized on polystyrene spheres by solvent cast method was developed for possible application as tertiary treatment in small municipal wastewater treatment plants. The structured catalyst was characterized by spectroscopic and morphological techniques evidencing that the preparation method was able to disperse evenly anatase Nitrogen-doped TiO 2 particles on polystyrene spheres and that the structured catalyst can be activated by visible light. The photocatalytic tests were driven first in a laboratory scale reactor configuration irradiated through visible light emitted by light emitting diodes and then using a solar compound triangular collector based reactor for outdoor experiments. The results from laboratory scale experiments did not show any photocatalyst deactivation after several treatment cycles; the photocatalytic process was effective in methylene blue degradation experiments and real wastewater disinfection (92.6% indigenous Escherichia coli inactivation after 120 min of irradiation time). In outdoor experiments under direct solar light, the structured photocatalyst confirmed its efficiency in the inactivation of indigenous Escherichia coli present in a municipal wastewater (87% inactivation after 120 min treatment and 2 kJ/L of cumulative energy per unit of volume) because the residual bacterial count met the limit (50 CFU/mL) established by Italian law for wastewater disposal in surface water. [ABSTRACT FROM AUTHOR]

Gloves are worn by workers harvesting ready-to-eat produce as a deterrent for contaminating the produce with enteric pathogens that may reside on their hands. As fields are not sterile environments, the probability for gloves to become contaminated still exists and therefore it is critical to understand the conditions that affect the survival of pathogens on gloves. Both Escherichia coli O157:H7 and Salmonella deposited on glove surfaces in a liquid state survived longer when the pathogen had been suspended in lettuce sap than when suspended in water. Despite this protection, pathogens deposited on clean single-use gloves were more likely to survive during drying than pathogens deposited on dirty gloves (a film of lettuce sap had been applied to the surface prior to pathogen application and soil had been ground into the gloves). Survival of both E . coli O157:H7 and Salmonella was biphasic with the greatest losses occurring during the first hour of drying followed by much slower losses in the ensuing hours. Pathogens grown in rich media (tryptic soy broth) versus minimal media (M9) as well as those cultured on solid agar versus liquid broth were also more likely to be resistant to desiccation when deposited onto gloves. Although survival of E . coli O157:H7 on nitrile gloves was in general greater than it was on latex gloves, the relative survival of Salmonella on the two glove types was inconsistent. Due to these inconsistencies, no one glove type is considered better than another in reducing the risk for contamination with enteric pathogens. In addition, the extended survival of what are generally referred to as stress-resistant pathogens suggests that gloves either be changed frequently during the day or washed in a disinfectant to reduce the risk of glove contamination that could otherwise contaminate product handled with the contaminated gloves. [ABSTRACT FROM AUTHOR]

In the present work, the synergistic SODIS-thermal model , describing the E. coli inactivation by solar exposure (SODIS) considering the synergistic effect of solar UV photons and solar heating of water under controlled conditions of irradiance and temperature, is validated under real field conditions. The main objective of this work is to demonstrate its capability to predict the solar bacterial inactivation in several solar reactor designs, different scales, and under real field conditions, i.e. variable solar irradiation, water turbidity and temperature. The model was proven to be able to predict satisfactorily the E. coli inactivation under different climate conditions in plastic 2-L PET (polyethylene terephthalate) bottles, the most widely used for SODIS application, in isotonic and natural well water. This model predicts also, with a high acceptance level (NRMSLE <20%), the E. coli inactivation in turbid water, experimentally studied with an artificial turbidity agent (kaolin) and natural red soils to simulate the turbidity between 5 and 300 NTU. The simulation results for turbid water were performed using the Radiative Transfer Equation for the incident irradiance. In addition, the model was applied for different reactor designs (volumes ranged 2.5–22.5 L) and materials (polycarbonate, borosilicate and methacrylate) concluding that transmittance affects significantly to the incident radiation and hence to the bacterial inactivation. The predicted water disinfection of the synergistic SODIS-thermal model has important implications in photo-reactor design as a potential tool for comparing the efficiency of new prototypes and for automatized control systems for SODIS reactors. A ‘safe time’ and ‘safe UV-A dose’ were defined as the minimal time or UV-A dose necessary to achieve a certain bacterial reduction. [ABSTRACT FROM AUTHOR]

Photodynamic inactivation (PDI) of bacteria may play a major role in facing the challenge of the ever expanding antibiotic resistances. Here we report about the direct correlation of singlet oxygen luminescence kinetics and phototoxicity in E. coli cell suspension under PDI using the widely applied cationic photosensitizer TMPyP. Through direct access to the microenvironment, the time resolved investigation of singlet oxygen luminescence plays a key role in understanding the photosensitization mechanism and inactivation pathway. Using the homemade set-up for highly sensitive time resolved singlet oxygen luminescence detection, we show that the cationic TMPyP is localized predominantly outside the bacterial cells but in their immediate vicinity prior to photodynamic inactivation. Throughout following light exposure, a clear change in singlet oxygen kinetics indicates a redistribution of photosensitizer molecules to at least one additional microenvironment. We found the signal kinetics mirrored in cell viability measurements of equally treated samples from same overnight cultures conducted in parallel: A significant drop in cell viability of the illuminated samples and stationary viability of dark controls. Thus, for the system investigated in this work – a Gram-negative model bacteria and a well-known PS for its PDI – singlet oxygen kinetics correlates with phototoxicity. This finding suggests that it is well possible to evaluate PDI efficiency directly via time resolved singlet oxygen detection. [ABSTRACT FROM AUTHOR]

In this paper, the antibacterial activity of titanium dioxide modified with reduced graphene oxide (rGO) was presented. TiO 2 /rGO photocatalysts were prepared by the hydrothermal method under elevated pressure at 180 °C and heated at 100 °C in Ar flow. The obtained photocatalysts were characterized by means of XRD, FTIR/DRS, UV–vis/DR, Raman spectroscopy and scanning electron microscopy (SEM). The carbon content was also examined. FTIR/DRS and Raman analysis confirmed the presence of rGO in the TiO 2 structure, suggesting a successful modification. The antimicrobial photoactivity of photocatalysts was conducted against E. coli under an artificial solar light. The results show that all TiO 2 /rGO photocatalysts exhibited an antibacterial activity higher than unmodified TiO 2 . The best result was found for sample with 1.5 wt% additive of reduced graphene oxide. In this case, total inactivation of E. coli was noticed after 75 min of irradiation. It was found that the presence of rGO in sample improves the antimicrobial activity. [ABSTRACT FROM AUTHOR]

Atmospheric pressure plasmas have achieved great scientific and technological advances for a wide range of applications including the field of antimicrobial treatment. In this paper, a home-made atmospheric pressure plasma jet device was built and the effects of air plasma treatments on the inactivation of pure bacterial culture (Escherichia coli ATCC 8739) deposited onto the surface of agar plates were investigated. Plasmas were generated using high voltage discharge for 30, 60 and 90 s. The number of viable microorganisms was determined using a plate count method. Microbial Log10 reduction depended on the time of exposure and feed gas flow. A significant reduction of about 2.5 Log10 for E. coli was achieved within 60 s of plasma treatment. This result can be related to the presence of reactive species in the plasma volume, in particular, O radicals. [ABSTRACT FROM AUTHOR]

In this investigation, a new, green photo-Fenton process for wastewater treatment is proposed, involving the use of a natural iron source and natural additives, deriving from wastes, acting as iron chelators. The use of mineral iron as precursor in the photo-Fenton process, instead of iron salts, was still able to promote E. coli inactivation. Furthermore, the addition of four low weight organic acids (citric, tartaric, ascorbic and caffeic) showed a significant enhancement of the process, reaching total inactivation except for caffeic acid, which showed no significant effects. Two natural products, rich in the promising organic acids were tested as additives, lime and orange juice, plus their infusion. Lime-based additives showed better results compared to orange-based ones, which could be attributed to the excessive addition of organic matter in the orange systems. The formation of photoactive complexes with the mineral iron and the organic acids from the natural products induced the production of reactive species and ferrous ion, sustaining a homogeneous Fenton reaction. Finally, the proposed modified process was tested against different secondary effluents from a municipal wastewater treatment plant. Total bacterial inactivation was reached in the lime-based system, with no visible microorganism regrowth after 48 h. Additionally, the process was able to eliminate 40% of the total identified micropollutants of the secondary effluent reaching almost 50% of removal of the total effluent organic matter. [ABSTRACT FROM AUTHOR]

The antibacterial activity of concrete plates loaded with various titania photocatalysts was investigated. The target in bacteria testing was Escherichia coli K12. The presence of photocatalysts in the concrete matrix at a dose of 10 wt.% improved the antibacterial properties, which became significant depending on the type of the added photocatalyst. Total inactivation of E. coli irradiated under artificial solar light was observed on the concrete plates loaded with the following photocatalysts: TiO2/N,CMeOH-300, TiO2/N,CEtOH-100, TiO2/N,CisoPrOH-100 and TiO2/N-300. The modified Hom disinfection kinetic model was found as a best-fit model for the obtained results. The presence of nitrogen and carbon in the photocatalysts structure, as well as crystallite size, surface area and porosity, contributed to the increase of antibacterial properties of concrete plates.

Irrigation water has been highlighted as a potential contamination source of fresh produce with foodborne pathogens. Water disinfection treatments can be used to improve its microbiological safety. Growers should ascertain the minimum effective disinfectant doses able to achieve the desired microbiological goals. Furthermore, potential unwanted effects both on crop health and on chemical risks associated with the accumulation of disinfection by-products (DBPs) on the crop must be taken into account. The minimum effective doses vary depending on intrinsic factors (e.g. physicochemical characteristics of the irrigation water, concentration of the target microorganism) and also extrinsic factors (e.g. geographical and weather conditions). In the present study, different types of surface irrigation water were treated with various doses of a stable solution of chlorine dioxide (ClO 2 ) (0.1–2.5 mg/L) at 21 ± 2 °C for a contact time of 1 min. Escherichia coli concentration (before and after treatment) and the residual ClO 2 (after treatment) were analyzed. Several water physicochemical parameters were measured (chemical oxygen demand (COD), turbidity, pH, oxidation-reduction potential (ORP), conductivity and absorbance of filtered water samples at 254 nm (UV254)). Data obtained was used to develop a model for ClO 2 decay and a model for E. coli inactivation by linear regression. The ClO 2 decay model (adjusted R 2 = 0.93) included the initial ClO 2 concentration and the UV254 as explanatory variables. The E. coli inactivation model (adjusted R 2 = 0.77) included the initial ClO 2 concentration, the initial E. coli concentration, and the UV254 as explanatory variables. The development of these models would help growers in making decisions regarding the minimum effective doses they might use to treat their irrigation water when using a stable solution of ClO 2 to reduce microbial risk of fresh produce. [ABSTRACT FROM AUTHOR]

Ag 2 WO 4 /g-C 3 N 4 composite photocatalyst was synthesized by polymerization of thiourea and ammonia chloride combined with the deposition-precipitation method, which was applied as an efficient visible-light driven photocatalyst for inactivating Escherichia coli ( E. coli ). The physicochemical properties of these photocatalysts were systematically characterized by various techniques such as SEM, TEM, XRD, FT-IR, BET, UV–vis DRS and PL. The synthesized photocatalysts exhibited outstandingly enhanced photocatalytic disinfection efficiency compared with that of pure g-C 3 N 4 and Ag 2 WO 4 under visible light. Furthermore, the optimal mass ratio of the Ag 2 WO 4 to g-C 3 N 4 was 5 wt%, and a number of live bacteria could be completely inactivated with Ag 2 WO 4 (5%)/g-C 3 N 4 (100 μg/mL) after 90 min under visible light irradiation. The high disinfection efficiency is due to the synergetic effect between g-C 3 N 4 and Ag 2 WO 4 , including a good distribution of Ag 2 WO 4 particles on the surface of g-C 3 N 4 and an improved separation rate of photogenerated electron-hole pairs. The enhanced disinfection mechanism was also investigated using photogenerated current densities and electrochemical impedance spectroscopy (EIS). Considering the bulk availability and excellent disinfection activity of Ag 2 WO 4 /g-C 3 N 4 composite, it is a promising solar-driven photocatalyst for cleaning the microbial contaminated water. [ABSTRACT FROM AUTHOR]

Dielectric barrier discharge atmospheric cold plasma (DACP) treatment was evaluated for the inactivation of Escherichia coli O157:H7, surface morphology, color, carbon dioxide generation, and weight loss of bulk Romaine lettuce in a commercial plastic clamshell container. The lettuce samples were packed in a model bulk packaging configuration (three rows with either 1, 3, 5, or 7 layers) in the container and treated by DACP (42.6 kV, 10 min). DACP treatment reduced the number of E. coli O157:H7 in the leaf samples in the 1-, 3-, and 5-layer configurations by 0.4–0.8 log CFU/g lettuce, with no significant correlation to the sample location ( P > 0.05). In the largest bulk stacking with 7 layers, a greater degree of reduction (1.1 log CFU/g lettuce) was observed at the top layer, but shaking the container increased the uniformity of the inhibition. DACP did not significantly change the surface morphology, color, respiration rate, or weight loss of the samples, nor did these properties differ significantly according to their location in the bulk stack. DACP treatment inhibited E. coli O157:H7 on bulk lettuce in clamshell containers in a uniform manner, without affecting the physical and biological properties and thus holds promise as a post-packaging process for fresh and fresh-cut fruits and vegetables. [ABSTRACT FROM AUTHOR]

Aims The aim of this study was to investigate the antibiofilm potential of five essential oil ( EO) components with cyclic (sabinene- SAB, carveol-C1, carvone-C2) and acyclic (citronellol-C3 and citronellal-C4) structures against Escherichia coli and Staphylococcus aureus. Methods and Results The selected EO components prevented biofilm set-up, with C3 and C4 causing remarkable effects. When applied against pre-established biofilms, they promoted high biomass removal and inactivation of biofilm cells. Moreover, no viable E. coli biofilm cells were detected after exposure to SAB at 5 × MIC and 10 × MIC, and a significant viability decrease was observed for both bacteria with the other EO components. SAB, C3 and C4 caused the most prominent effects apparently due to their octanol-water partition coefficient ( Po/w), the number of rotatable bonds ( n- ROTB) and the free hydroxyl groups. Conclusions The overall results demonstrated that the selected EO components, particularly SAB, C3 and C4 are of interest as new lead molecules to both prevent biofilm set-up and to control pre-established biofilms of E. coli and S. aureus. Significance and Impact of the Study The tested EO components exhibited prominent antibiofilm properties against E. coli and S. aureus providing a novel and effective alternative/complementary approach to counteract chronic infections and the transmission of diseases in clinical settings. [ABSTRACT FROM AUTHOR]

Aims To evaluate the effect of ultraviolet ( UV) disinfection on antibiotic-resistant Escherichia coli. Methods and Results Antibiotic-resistant E. coli strains were isolated from a wastewater treatment plant and subjected to UV disinfection. The effect of UV disinfection on the antibiotic resistance profiles and the antibiotic resistance genes ( ARGs) of antibiotic-resistant E. coli was evaluated by a combination of antibiotic susceptibility analysis and molecular methods. Results indicated that multiple-antibiotic-resistant ( MAR) E. coli were more resistant at low UV doses and required a higher UV dose (20 mJ cm−2) to enter the tailing phase compared with those of antibiotic-sensitive E. coli (8 mJ cm−2). UV disinfection caused a selective change in the inhibition zone diameters of surviving antibiotic-resistant E. coli and a slight damage to ARGs. The inhibition zone diameters of the strains resistant to antibiotics were more difficult to alter than those susceptible to antibiotics because of the existence and persistence of corresponding ARGs. Conclusions The resistance of MAR bacteria to UV disinfection at low UV doses and the changes in inhibition zone diameters could potentially contribute to the selection of antibiotic-resistant bacteria in wastewater treatment after UV disinfection. The risk of spread of antibiotic resistance still exists owing to the persistence of ARGs. Significance and Impact of the Study Our study highlights the acquisition of other methods to control the spread of ARGs. [ABSTRACT FROM AUTHOR]

This study was motivated by the desire to develop a non-invasive means to treat abscesses, and represents the first steps toward that goal. Non-thermal, high-intensity focused ultrasound (HIFU) was used to inactivate Escherichia coli (∼1 × 109 cells/mL) in suspension. Cells were treated in 96-well culture plate wells using 1.95-MHz ultrasound and incident focal acoustic pressures as high as 16 MPa peak positive and 9.9 MPa peak negative (free field measurements). The surviving fraction was assessed by coliform culture and the alamarBlue assay. No biologically significant heating was associated with ultrasound exposure. Bacterial inactivation kinetics were well described by a half-life model, with a half-time of 1.2 min. At the highest exposure levels, a 2log inactivation was typically achieved within 10 min. The free field-equivalent peak negative acoustic pressure threshold for inactivation was ∼7 MPa. At the highest acoustic pressures used, inactivation efficacy was insensitive to reciprocal changes in pulse length and pulse repetition frequency at constant duty factor. Although treated volumes were very small, proof of principle was provided by these experiments. [ABSTRACT FROM AUTHOR]

The effect of reactor material (borosilicate and polyethylene terephthalate-PET) and its reuse on the microbiological and chemical decontamination of water by the photo-Fenton reaction at near-neutral pH was assessed. Escherichia coli was used as an indicator of faecal contamination and resorcinol was employed as a model organic pollutant in water. Total E. coli removal was achieved using 0.3/20 mg L −1 (5.4 × 10 −3 /0.6 mM) of Fe 2+ /H 2 O 2 after 120 and 180 min in commercial borosilicate (R1) and PET (R2) bottles, respectively. Likewise, under the same conditions, total degradation of resorcinol was reached at 120 min of treatment in both R1 and R2 reactors. Despite the UV transmittance level is higher in borosilicate reactors than in PET, no significant differences in removal kinetics were observed in the new reactors. However, the reuse of the R1 reactors showed a detrimental effect on optical properties of the material, leading to a reduction in the E. coli removal and resorcinol degradation by the photo-Fenton process. Conversely, when reused R2 was employed the removal of such contaminants was slightly faster than that observed in new reactors. This fact was attributed to the additional reactive oxygen species (ROS) produced from the oxidation of polymeric material during the photo-Fenton reaction. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) synthesized by the catalytic decomposition of methane were used as the support for magnetic Fenton and photo-Fenton catalysts to treat real wastewater contaminated with dyes and Escherichia coli. The effect of methane flow, the use of diluent (N), and the reaction time in the production of CNTs were studied. An increase in the production of CNTs with increased CH flow and a decrease over the reaction time were recorded. Catalysts with 1, 3, and 5% w/ w Fe were obtained and characterized by several spectroscopic and microscopic techniques. Multi-walled CNTs and bamboo-like carbon nanofibers with average diameters of 44.0 nm and average lengths of 237.0 nm were obtained. The catalysts had FeO (oxide species) crystallite sizes between 10 and 18 nm and soft ferromagnetic properties. A factorial 3 design was used for selecting variables for the catalytic tests, wherein the concentration of HO, the catalyst mass, and the percentage of iron were evaluated. Subsequently, kinetic experiments were performed. The photo-Fenton process (5% Fe, 200 mg, and 0.4 M HO) showed the best results in terms of total organic carbon (TOC) abatement, discoloration, and E. coli inactivation without leaching of Fe. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the efficacy of gamma and electron beam irradiation to inactivate foodborne pathogens in ready-to-bake cookie dough and to determine the effect on quality by measuring color and texture changes. Cookie dough inoculated with Escherichia coli O157:H7, Salmonella Typhimurium, or Listeria monocytogenes was subjected to gamma and electron beam irradiation, with doses ranging from 0 to 3 kGy. As the radiation dose increased, the inactivation effect increased among all tested pathogens. After 3.0 kGy of gamma and electron beam irradiation, numbers of inoculated pathogens were reduced to below the detection limit (1 log CFU/g). The D 10 -values of E. coli O157:H7, S. Typhimurium, and L. monocytogenes in cookie dough treated with gamma rays were 0.53, 0.51, and 0.71 kGy, respectively, which were similar to those treated by electron beam with the same dose. Based on the D 10 -value of pathogens in cookie dough, L. monocytogenes showed more resistance to both treatments than did E. coli O157:H7 and S. Typhimurium. Color values and textural characteristics of irradiated cookie dough were not significantly ( P > 0.05) different from the control. These results suggest that irradiation can be applied to control pathogens in ready-to-bake cookie dough products without affecting quality. [ABSTRACT FROM AUTHOR]

One-dimensional titanate nanotubes (H2Ti2O5·H2O) functionalized with silver nanoparticles (AgNPs) exhibited unique properties for the effective inactivation of the Gram-negative Escherichia coli within 45 minutes under irradiation using a 65 W halogen lamp. The pathway of the photo-assisted catalytic inactivation was examined by SEM and TEM using a reproducible biological protocol for sample preparations. The membrane integrity of the bacteria was damaged due to the oxidative stress caused by the reactive oxygen species, the bacteriostatic effect of the highly-dispersed-surface AgNPs (∼5 nm) and the sharp nanotube penetration that induced the cell death. [ABSTRACT FROM AUTHOR]

We report two BODIPY based photosensitizers (Br2BOAc and I2BOAc) featuring an acetoxymethyl substituent at the meso-position. These photosensitizers show improved photostability against singlet oxygen, when compared to a BODIPY photosensitizer lacking the acetoxymethyl group. Both compounds were evaluated for photodynamic therapy against HeLa cells and photodynamic inactivation against E. coli bacteria. We show that the compounds readily embed in the lipid membranes of HeLa cervical cancer cells and efficiently induced light-dependent apoptosis at nanomolar concentration. Also, both compounds showed a substantial degree of photoinactivation of E. coli bacteria when used at low micromolar concentrations. [ABSTRACT FROM AUTHOR]

Combined non-thermal treatment with chlorine dioxide (ClO 2 ) gas, ultraviolet-C (UV-C) light, and fumaric acid was performed to inactivate Listeria monocytogenes and Escherichia coli O157:H7 inoculated on plums. Plums were treated with ClO 2 gas (15 and 30 ppmv), fumaric acid (0.1, 0.3, and 0.5%), and by UV-C irradiation (3, 5, and 10 kJ/m 2 ). The single treatments with 15 or 30 ppmv ClO 2 gas, 0.5% fumaric acid, and 10 kJ/m 2 UV-C decreased the population of L. monocytogenes by 1.78, 2.00, 1.65, and 1.62 log CFU/g, respectively, and the population of E. coli O157:H7 by 1.73, 1.81, 1.34, and 2.07 log CFU/g, respectively. In addition, combined treatments reduced the populations of the pathogenic bacteria more than each treatment alone. In particular, the combined treatment with ClO 2 gas (30 ppmv) for 20 min, fumaric acid (0.5%), and UV-C (10 kJ/m 2 ) decreased the populations of L. monocytogenes and E. coli O157:H7 by 6.26 and 5.48 log CFU/g, respectively. These results suggest that combined treatment with ClO 2 gas, UV-C light, and fumaric acid may be a useful hurdle technology to enhance the microbiological safety of plums. [ABSTRACT FROM AUTHOR]

This study investigated the use of a sub-stoichiometric TiO 2 reactive electrochemical membrane (REM) for the inactivation of a model Escherichia coli ( E. coli ) pathogen in chloride-free solutions. The filtration system was operated in dead-end, outside-in filtration model, using the REM as anode and a stainless steel mesh as cathode. A 1-log removal of E. coli was achieved when the electrochemical cell was operated at the open circuit potential, due to a simple bacteria-sieving mechanism. At applied cell potentials of 1.3 and 3.5 V neither live nor dead E. coli cells were detected in the permeate stream (detection limit of 1.0 cell mL −1 ), which was attributed to enhanced electrostatic bacteria adsorption at the REM anode. Bacteria inactivation in the retentate solution increased as a function of the applied cell potential, which was attributed to transport of E. coli to the REM and stainless steel cathode surfaces, and direct contact with the local acidic and alkaline environment produced by water oxidation at the anode and cathode, respectively. Clear evidence for an E. coli inactivation mechanism mediated by either direct or indirect oxidation was not found. The low energy requirement of the process (2.0–88 W h m −3 ) makes the REM an attractive method for potable water disinfection. [ABSTRACT FROM AUTHOR]

Disinfection of hot water systems is critical in reducing the incidence of disease outbreaks caused by pathogenic bacteria. Electrochemical disinfection (ED) has been identified as an economical, low-maintenance, and chemical-free alternative in the fight against waterborne pathogenic microorganisms. It also provides the residual disinfection needed to inactivate the planktonic bacteria released by the biofilm. The work presented here includes fundamental small-scale laboratory optimization experiments in a flask where platinum-coated electrodes were immersed in 3.5 L of tap water contaminated with Escherichia coli (NCT10418) with an initial population density between 3 × 105 and 1.6 × 105 colony forming units=mL (CFU=mL) or Legionella pneumophila serogroup 1 (NCTC12821) ranging from 180 to 244 CFU=mL. Voltage, electrode area, interelectrode distance, spiking time, volume of contaminated water, and mixer speed were varied to determine the optimal geometrical and operational requirements needed to kill bacteria. Experimental results indicate ED to be an effective control method, with a >4-log inactivation of E. coli and a >5-log inactivation of Legionella in 10 and 45 min, respectively, at a current density of ≈4 mA=cm2. The findings of the flask experiments were translated into real-world conditions by evaluating the long-term performance of an optimized ED prototype device installed in the hot water recirculation system of a small-size healthcare center building. The results showed that ED is effective at minimizing pathogen contamination of the hot water distribution system from initial values, with total bacteria levels and Pseudomonas species being reduced in all of the samples over a 15-month period following activation of the ED device. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZnO 2 /CQD composites were firstly used as visible-light photocatalysts. • •O 2 and 1O 2 were the dominant ROSs generated in the photocatalytic processes. • The self-oxygenated composites possessed high adaptability and broad application. • CQD played key roles in boosting visible-light photocatalytic performance of ZnO 2. • Multifunctional roles of CQD in the composites were revealed in detail. Herein, the novel zinc peroxide/carbon quantum dots (ZnO 2 /CQD) composites were synthesized by an in-situ composite process for visible-light photocatalytic tetracycline (TC) degradation and Escherichia coli (E. coli) inactivation. It was found that 0.1 g/L ZnO 2 /CQD composite could degrade over 80 % of 50 mg/L TC and inactivate around 7-log E. coli cells after 2 h and 50 min of irradiation, respectively. The as-obtained ZnO 2 /CQD composites exhibited superior visible-light photocatalytic performance to individual ZnO 2 , and superoxide radical (•O 2 −) and singlet oxygen (1O 2) were identified to be the main reactive oxygen species (ROSs) for TC degradation and E. coli inactivation. The introduction of CQD reduced the particle size and increased specific surface area, benefiting for adsorption. Meanwhile, it promoted visible-light absorption and accelerated the separation of photogenerated electron-hole pairs with a 3-fold increase in photocurrent, thus producing more ROSs under visible-light irradiation. Moreover, the ZnO 2 /CQD composites exhibited a high adaptability towards initial solution pH, common coexisting anions, oxygen-deficient environment, diverse water sources and organic pollutants. This study not only provided highly adaptable visible-light-driven photocatalysts for organic degradation and bacterial inactivation, but also shed light on the multifunctional roles of CQD in boosting visible-light photocatalytic performance. [ABSTRACT FROM AUTHOR]

Ozone, a strong oxidant and disinfectant, seems ideal to cope with future challenges of water treatment, such as micropollutants, multiresistant bacteria (MRB) and even intracellular antibiotic resistance genes (ARG), but information on the latter is scarce. In ozonation experiments we simultaneously determined kinetics and dose-dependent inactivation of Escherichia coli and its plasmid-encoded sulfonamide resistance gene sul1 in different water matrixes. Effects in E. coli were compared to an autochthonous wastewater community. Furthermore, resistance elimination by ozonation and post-treatment were studied in full-scale at a wastewater treatment plant (WWTP). Bacterial inactivation (cultivability, membrane damage) and degradation of sul1 were investigated using plate counts, flow cytometry and quantitative real-time PCR. In experiments with E. coli and the more ozone tolerant wastewater community disruption of intracellular genes was observed at specific ozone doses feasible for full-scale application, but flocs seemed to interfere with this effect. At the WWTP, regrowth during postozonation treatment partly compensated inactivation of MRB, and intracellular sul1 seemed unaffected by ozonation. Our findings indicate that ozone doses relevant for micropollutant abatement from wastewater do not eliminate intracellular ARG. [ABSTRACT FROM AUTHOR]

We investigated the survival kinetics of Salmonella enterica and enterohemorrhagic Escherichia coli under various water activity (aw) conditions to elucidate the net effect of aw on pathogen survival kinetics and to pursue the development of a predictive model of pathogen survival as a function of aw. Four serotypes of S. enterica (Stanley, Typhimurium, Chester, and Oranienburg) and three serotypes of enterohemorrhagic E. coli (E. coli 026, E. coli 0111, and E. coli 0157:H7) were examined. These bacterial strains were inoculated on a plastic plate surface at a constant relative humidity (RH) (22, 43, 58, 68, or 93% RH, corresponding to the aw) or on a surface of almond kernels (aw 0.58), chocolate (aw 0.43), radish sprout seeds (aw 0.58), or Cheddar cheese (aw 0.93) at 5, 15, or 25°C for up to 11 months. Under most conditions, the survival kinetics were nonlinear with tailing regardless of the storage aw, temperature, and bacterial strain. For all bacterial serotypes, there were no apparent differences in pathogen survival kinetics on the plastic surface at a given storage temperature among the tested RH conditions, except for the 93% RH condition. Most bacterial serotypes were rapidly inactivated on Cheddar cheese when stored at 5°C compared with their inactivation on chocolate, almonds, and radish sprout seeds. Distinct trends in bacterial survival kinetics were also observed between almond kernels and radish sprout seeds, even though the aws of these two foods were not significantly different. The survival kinetics of bacteria inoculated on the plastic plate surface showed little correspondence to those of bacteria inoculated on food matrices at an identical aw. Thus, these results demonstrated that, for low-aw foods and/or environments, aw alone is insufficient to account for the survival kinetics of S. enterica and enterohemorrhagic E. coli. [ABSTRACT FROM AUTHOR]

Boron (B) doped bismuth oxybromide (B-BiOBr) nanosheets were synthesized using a hydrothermal method and their photocatalytic activities were investigated through inactivating a typical bacterium, Escherichia coli K-12 using fluorescence tubes as visible light (VL) sources. B atoms are successfully doped into the crystal lattice of BiOBr. However, the morphology, crystal structure, and {001}-facet exposed feature of B-BiOBr nanosheets remains unchanged compared with pure BiOBr nanosheets. Significantly, the as-prepared B-BiOBr nanosheets show superior activity in the photocatalytic inactivation of E. coli K-12 over pure BiOBr nanosheets under VL irradiation. Photogenerated h + is evidenced to be the major reactive species accounting for the inactivation process of B-BiOBr. With its electron-deficient characteristics, the B dopant is favorable to accept extra e − from VB of BiOBr, leading to improved charge carrier separation efficiency. The greatly enhanced bacterial inactivation efficiency was attributed to the synergic advantages of enhanced VL adsorption capability and more amount of photogenerated h + with higher oxidative ability. In addition, the destruction process of bacterial cell was also observed from the destruction of cell membrane to the intracellular components. [ABSTRACT FROM AUTHOR]