Susceptibility of pESI positive Salmonella to treatment with biocide chemicals approved for use in poultry meat processing as compared to Salmonella without the pESI plasmid.

Salmonella is a common cause of human foodborne illness, which is frequently associated with consumption of contaminated or undercooked poultry meat. Serotype Infantis is among the most common serotypes isolated from poultry meat products globally. Isolates of serotype Infantis carrying the pESI plasmid, the most dominant strain of Infantis, have been shown to exhibit oxidizer tolerance. Therefore, 16 strains of Salmonella with and without pESI carriage were investigated for susceptibility to biocide chemical processing aids approved for use in US poultry meat processing: peracetic acid (PAA), cetylpyridinium chloride (CPC), calcium hypochlorite, and sodium hypochlorite. Strains were exposed for 15 s to simulate spray application and 90 min to simulate application in an immersion chiller. All strains tested were susceptible to all concentrations of PAA, CPC, and sodium hypochlorite when applied for 90 min. When CPC, calcium hypochlorite, and sodium hypochlorite were applied for 15 s to simulate spray time, strains responded similarly to each other. However, strains responded variably to exposure to PAA. The variation was not statistically significant and appears unrelated to pESI carriage. Results highlight the necessity of testing biocide susceptibility in the presence of organic material and in relevant in situ applications.

Exploring the viability of peracetic acid-mediated antibiotic degradation in wastewater through activation with electrogenerated HClO.

Electrochemical advanced oxidation processes (EAOPs) face challenging conditions in chloride media, owing to the co-generation of undesirable Cl-disinfection byproducts (Cl-DBPs). Herein, the synergistic activation between in-situ electrogenerated HClO and peracetic acid (PAA)-based reactive species in actual wastewater is discussed. A metal-free graphene-modified graphite felt (graphene/GF) cathode is used for the first time to achieve the electrochemically-mediated activation of PAA. The PAA/Cl- system allowed a near-complete sulfamethoxazole (SMX) degradation (kobs =0.49 min-1) in only 5 min in a model solution, inducing 32.7- and 8.2-fold rise in kobs as compared to single PAA and Cl- systems, respectively. Such enhancement is attributed to the occurrence of 1O2 (25.5 µmol L-1 after 5 min of electrolysis) from the thermodynamically favored reaction between HClO and PAA-based reactive species. The antibiotic degradation in a complex water matrix was further considered. The SMX removal is slightly susceptible to the coexisting natural organic matter, with both the acute cytotoxicity (ACT) and the yield of 12 DBPs decreasing by 29.4 % and 37.3 %, respectively. According to calculations, HClO accumulation and organic Cl-addition reactions are thermodynamically unfavored. This study provides a scenario-oriented paradigm for PAA-based electrochemical treatment technology, being particularly appealing for treating wastewater rich in Cl- ion, which may derive in toxic Cl-DBPs.

Activation of peracetic acid by electrodes using biogenic electrons: A novel energy- and catalyst-free process to eliminate pharmaceuticals.

Peracetic acid (PAA) has received increasing attention as an alternative oxidant for wastewater treatment. However, existing processes for PAA activation to generate reactive species typically require external energy input (e.g., electrically and UV-mediated activation) or catalysts (e.g., Co2+), inevitably increasing treatment costs or introducing potential new contaminants that necessitate additional removal. In this work, we developed a catalyst-free, self-sustaining bioelectrochemical approach within a two-chamber bioelectrochemical system (BES), where a cathode electrode in-situ activates PAA using renewable biogenic electrons generated by anodic exoelectrogens (e.g., Geobacter) degrading biodegradable organic matter (e.g., acetic acid) in wastewater at the anode. This innovative BES-PAA technique achieved 98 % and 81 % removal of 2 µM sulfamethoxazole (SMX) in two hours at pH 2 (cation exchange membrane) and pH 6 (bipolar membrane) using 100 µM PAA without external voltage. Mechanistic studies, including radical quenching, molecular probe validation, electron spin resonance (ESR) experiments, and density functional theory (DFT) calculations, revealed that SMX degradation was driven by reactive species generated via biogenic electron-mediated OO cleavage of PAA, with CH3C(O)OO• contributing 68.1 %, •OH of 18.4 %, and CH3C(O)O• of 9.4 %, where initial formation of •OH and CH3C(O)O• rapidly reacts with PAA to produce CH3C(O)OO•. The presence of common water constituents such as anions (e.g., Cl-, NO3-, and H2PO4-) and humic acid (HA) significantly hinders SMX removal via the BES-PAA technique, whereas CO32- and HCO3- ions have a comparatively minor impact. Additionally, the study investigated the removal of various pharmaceuticals present in secondary treated municipal wastewater, attributing differences in removal efficiency to the selective action of CH3C(O)OO•. This research demonstrates a novel PAA activation method that is ecologically benign, inexpensive, and capable of overcoming catalyst deactivation and secondary pollution issues.

Efficient degradation of sulfadiazine by UV-triggered electron transfer on oxalic acid-functionalized corn straw biochar for activating peroxyacetic acid: Performance, mechanism, and theoretical calculation.

A novel UV/oxalic acid functionalized corn straw biochar (OCBC)/peroxyacetic acid (PAA) system was built to degrade sulfadiazine from waters. 94.7 % of SDZ was removed within 30 min by UV/OCBC/PAA. The abundant surface functional groups and persistent free radicals (PFRs) on OCBC were responsible for these performances. Cyclic voltammetry (CV) and other characterization analysis revealed, under UV irradiation, the addition of OCBC served as electron donor, which might promote the reaction of electrons with PAA. The quenching and electron paramagnetic resonance (EPR) tests indicated that R-O•, 1O2 and •OH were generated. Theoretical calculations indicated sulfonamide bridge was vulnerable under the attacks of reactive species. In addition, high removal effect achieved by 5 reuse cycles and different real waters also suggested the sustainability of UV/OCBC/PAA. Overall, this study provided a feasible approach to remove SDZ with high mineralization efficiency, in addition to a potential strategy for resource utilization of corn straw.

Assessing the efficacy of sanitizer sprays during brush or polyvinyl chloride (PVC) roller treatment to reduce Salmonella populations on whole mangoes.

Sanitizer spray and brush roller treatments have been documented as an effective means of reducing Salmonella on the surface of produce. The purpose of this study was to evaluate the efficacy of chlorine (NaOCl), peroxyacetic acid (PAA), and chlorine dioxide (ClO2) sprays to reduce Salmonella populations on the surface of mangoes during washing with brush or polyvinyl chloride (PVC) rollers. Whole mangoes were spot inoculated with 100 µL of a rifampicin-resistant Salmonella (8 log CFU/mL) cocktail at the equator and dried for 1 h. Mangoes were washed with a lab-scale roller system with either ground water (control), or sanitizers (100 ppm NaOCl, 80 ppm PAA, or 5 ppm ClO2) for 0, 5, 15, 30, or 60 s (n = 15 mangoes). Dey/Engley buffer (100 mL) was used to rinse mangoes before plating on media supplemented with rifampicin. NaOCl, PAA, and ClO2 spray (except for ClO2 at 30 s) had significantly higher reduction on Salmonella population than water spray at all treatment times (P ≤ 0.05) when brush rollers were used. All tested sanitizers also achieved a significantly higher reduction than water at 5 s when PVC rollers were used (P ≤ 0.05). Salmonella reductions achieved by brush and PVC rollers was not statistically different (P > 0.05). After a 5 s treatment on brush and PVC rollers, NaOCl, PAA, and ClO2 spray had ca. 3.03 and 3.45 log, 3.96 and 3.28 log, and 2.54 and 2.00 log CFU/mango reductions, respectively, whereas water spray achieved 1.75 and 0.98 log CFU/mango reduction. Addition of sanitizers to spray water used during brush or PVC washing in mango packinghouses can reduce Salmonella on mango surfaces.

Modelling the colony growth dynamics of Listeria monocytogenes single cells after exposure to peracetic acid and acidic conditions.

Studies of classical microbiology rely on the average behaviour of large cell populations without considering that clonal bacterial populations may bifurcate into phenotypic distinct sub-populations by random switching mechanisms.Listeria monocytogenes exposure to sublethal stresses may induce different physiological states that co-exist (i.e., sublethal injury or dormancy) and present variable resuscitation capacity. Exposures to peracetic acid (PAA; 10-30 ppm; for 3 h), acetic acid and hydrochloric acid (AA and HCl; pH 3.0-2.5; for 5 h) at 20 °C were used to induce different physiological states in L. monocytogenes, Scott A strain. After stress exposure, colony growth of single cells was monitored, on Tryptic Soy Agar supplemented with 0.6 % Yeast Extract, using time-lapse microscopy, at 37 °C. Images were acquired every 5 min and were analyzed using BaSCA framework. Most of the obtained growth curves of the colonies were fitted to the model of Baranyi and Roberts for the estimation of lag time (λ) and maximum specific growth rate (µmax), except the ones obtained after exposure to AA pH 2.7 and 2.5 that were fitted to the Trilinear model. The data of λ and µmax that followed a multivariate normal distribution were used to predict growth variability using Monte Carlo simulations. Outgrowth kinetics after treatment with AA (pH 2.7 and 2.5; for 5 h at 20 °C), PAA (30 ppm; for 3 h at 20 °C) revealed that these stress conditions increase the skewness of the variability distributions to the right, meaning that the variability in lag times increases in favour of longer outgrowth. Exposures to AA pH 2.5 and 30 ppm PAA resulted in two distinct subpopulations per generation with different growth dynamics. This switching mechanism may have evolved as a survival strategy for L. monocytogenes cells, maximizing the chances of survival. Simulation of microbial growth showed that heterogeneity in growth dynamics is increased when cells are recovering from exposure to sublethal stresses (i.e. PAA and acidic conditions) that may induce injury or dormancy.

Effect of microwaves combined with peracetic acid to improve the dewatering performance of residual sludge.

The activated sludge process plays a crucial role in modern wastewater treatment plants. During the treatment of daily sewage, a large amount of residual sludge is generated, which, if improperly managed, can pose burdens on the environment and human health. Additionally, the highly hydrated colloidal structure of biopolymers limits the rate and degree of dewatering, making mechanical dewatering challenging. This study investigates the impact and mechanism of microwave irradiation (MW) in conjunction with peracetic acid (PAA) on the dewatering efficiency of sludge. Sludge dewatering effectiveness was assessed through capillary suction time (CST) and specific resistance to filtration (SRF). Examination of the impact of MW-PAA treatment on sludge dewatering performance involved assessing the levels of extracellular polymeric substances (EPS), employing three-dimensional excitation-emission matrix (3D-EEM), Fourier transform-infrared spectroscopy (FT-IR), and scanning electron microscopy. Findings reveal that optimal dewatering performance, with respective reductions of 91.22% for SRF and 84.22% for CST, was attained under the following conditions: microwave power of 600 W, reaction time of 120 s, and PAA dosage of 0.25 g/g MLSS. Additionally, alterations in both sludge EPS composition and floc morphology pre- and post-MW-PAA treatment underwent examination. The findings demonstrate that microwaves additionally boost the breakdown of PAA into •OH radicals, suggesting a synergistic effect upon combining MW-PAA treatment. These pertinent research findings offer insights into employing MW-PAA technology for residual sludge treatment.

A systematic investigation of peracetic acid oxidation and polymeric coagulants re-flocculation to enhance activated sludge dewatering: Multi-porous skeleton structures.

In this research, the effects of peracetic acid (PAA), polymeric flocculants, and their combined conditioning on improving the dewatering performance were comprehensively evaluated. The results showed that sludge cake moisture content, capillary suction time (CST), and specific resistance to filtration (SRF) were 70.6%, 48.1 s, and 3.42 × 1012 m/kg after adding 0.10 g/gMLSS PAA for 50 min, representing reductions of 12.60%, 40.32%, and 33.98%, respectively. Additionally, conditioning of sludge with polyferric sulfate (PFS), polyaluminum chloride (PAC), and cationic polyacrylamide (CPAM) enhanced sludge properties in the following order: CPAM > PAC > PFS. After the PAA oxidation and re-flocculation process, the optimal dosages of PFS, PAC, and CPAM were reduced to 1.5 g/L, 0.9 g/L, and 0.04 g/L, respectively. The sludge dewatering performance significantly improved, with sludge cake moisture content measuring 65.8%, 66.3%, and 61.7%, respectively. Moreover, the spatial multi-porous skeleton structures were formed via re-flocculation to improve the sludge dewatering. Furthermore, economic evaluation validated that the pre-oxidation and re-flocculation process could be considered an economically viable option. These research findings could serve as a valuable reference for practical engineering applications.

Peracetic acid treatment of squid eggs infected with parasitic copepod (Ikanecator primus gen. et sp. nov.).

Having been successfully bred in semi-intensive and intensive aquaculture systems, oval squids of the Sepioteuthis lessoniana species complex are emerging as promising candidates for research and industry. Nevertheless, information about pathogens and diseases that may affect squid aquaculture remains sparse. In this study, we identify new parasitic copepod species that causes squid mortality and decreases squid hatching rates, and we also offer a solution to eliminate the pathogen during incubation of squid eggs. The newly discovered copepod Ikanecator primus gen. et sp. nov. was identified on oval squid eggs for the first time using both morphological and molecular diagnostic markers. In the genomes of the copepod and associated microbiome, we identified multiple genes for enzymes involved in cephalopod eggshell degradation in genomes of the copepod and associated microbiome. Furthermore, we conducted experiments to assess efficacy of peracetic acid in inhibiting the I. primus gen. et sp. nov. both in vitro and in vivo using immersion treatment. We established that a 2-min exposure to a concentration of 250 µl/L of peracetic acid containing product (PAA-product; 35 mg/L PAA and 15 mg/L H2O2) inhibited the development of nauplii in vitro. All parasites exposed to a concentration of 500 µl/L of PAA-product (70 mg/L PAA and 30 mg/L H2O2) were eliminated within two minutes. On top of this, the immersion treatment with 500 µl/L of PAA-product (70 mg/L PAA and 30 mg/L H2O2) improved survival of squid embryos and increased size of squid hatchlings compared with control and the immersion treatment with 125 µl/L of PAA-product (17.5 mg/L PAA and 7.5 mg/L H2O2) and the immersion treatment with 250 µl/L of PAA-product (35 mg/L PAA and 15 mg/L H2O2). These findings suggest that PAA holds a great potential as inhibitor and controller of parasitic copepod infections and for overall health management in cephalopod culture.

Effects of prolonged application of peracetic acid-based disinfectant on recirculating aquaculture systems stocked with Atlantic salmon parr.

The use of recirculating aquaculture systems (RAS) for Atlantic salmon (Salmo salar) production has become increasingly common. RAS water disinfection plays a crucial role on its biosecurity. Peracetic acid (PAA) is a promising disinfectant due to its powerful oxidative properties, broad antimicrobial spectrum, and rapid degradation into no harmful compounds. This study focused on assessing the consequences of prolonged application of a PAA-based disinfectant in a RAS stocked with salmon parr. The experiment included three treatment groups in triplicate: 0 mg/L PAA (control), 0.1 mg/L PAA, and 1 mg/L PAA, using nine-replicated RAS with a total of 360 fish (14.8 ± 2.3 g; N = 40/RAS). The study spanned 28 days, with samples collected on days 0, 14, and 28. The analyzed parameters were water quality, and fish parameters, including external welfare indicators, gill histology, total antioxidant capacity (TAC), reactive oxygen species/reactive nitrogen species (ROC/RNC), oxidative stress biomarkers related to DNA and protein, cellular DNA damage, and global gene expression. While water quality remained relatively stable, there was an increase in bacterial populations in the groups exposed to PAA, particularly 1 mg/L PAA. Fish weight did not differ between the control and PAA-exposed groups. TAC, ROC/RNC, and oxidative stress biomarkers exhibited similar trends. The study identified >400 differentially expressed genes (DEGs) in the skin, gill, and olfactory organ, with many of these DEGs associated with immune responses. Comparing the transcriptomic profiles of the three tissue organs revealed that the olfactory organ was the most reactive to PAA treatment. This study shows that calculated PAA concentrations of 0.1 mg/L and 1 mg/L in the pump-sump, contributed to an increase of bacteria whereas no detectable differences in health and welfare of salmon parr were found. These findings are promising for the implementation of PAA-based disinfectants in RAS stoked with Atlantic salmon parr.

Prehydrated Electrons Activated by Continuous Electron Transfer Stemmed from Peracetic Acid Homolysis Mediated by Diamond Surface Defects for Enhanced PFOA Destruction.

Research on the use of peracetic acid (PAA) activated by nonmetal solid catalysts for the removal of dissolved refractory organic compounds has gained attention recently due to its improved efficiency and suitability for advanced water treatment (AWT). Among these catalysts, nanocarbon (NC) stands out as an exceptional example. In the NC-based peroxide AWT studies, the focus on the mechanism involving multimedia coordination on the NC surface (reactive species (RS) path, electron reduction non-RS pathway, and singlet oxygen non-RS path) has been confined to the one-step electron reaction, leaving the mechanisms of multichannel or continuous electron transfer paths unexplored. Moreover, there are very few studies that have identified the nonfree radical pathway initiated by electron transfer within PAA AWT. In this study, the complete decomposition (kobs = 0.1995) and significant defluorination of perfluorooctanoic acid (PFOA, deF% = 72%) through PAA/NC has been confirmed. Through the use of multiple electrochemical monitors and the exploration of current diffusion effects, the process of electron reception and conduction stimulated by PAA activation was examined, leading to the discovery of the dynamic process from the PAA molecule → NC solid surface → target object. The vital role of prehydrated electrons (epre-) before the entry of resolvable electrons into the aqueous phase was also detailed. To the best of our knowledge, this is the first instance of identifying the nonradical mechanism of continuous electron transfer in PAA-based AWT, which deviates from the previously identified mechanisms of singlet oxygen, single-electron, or double-electron single-path transfer. The pathway, along with the strong reducibility of epre- initiated by this pathway, has been proven to be essential in reducing the need for catalysts and chemicals in AWT.

Induction into viable but non culturable state and outgrowth heterogeneity of Listeria monocytogenes is affected by stress history and type of growth.

Exposure to sublethal stresses related to food-processing may induce a heterogenous mixture of cells that co-exist, comprising healthy, sublethally injured, dormant and dead cells. Heterogeneity in survival capacity and dormancy of single cells may impede the detection of foodborne pathogens. In this study, we exposed Listeria monocytogenes Scott A strain, to peracetic acid (PAA; 20-40 ppm) and to acidic conditions (hydrochloric (HCl) and acetic (AA) acid, adjusted to pH 2.7-3.0, to evaluate the resuscitation capacity and outgrowth kinetics of metabolically active cells in two different media. Injury and the viable-but-non-culturable (VBNC) status of cells were assessed by flow cytometry using CFDA (metabolically active) and PI (dead) staining. Stressed CFDA+PI- cells were sorted on Tryptic Soy (TS) Agar or in TS broth, both supplemented with 0.6 % Yeast Extract (TSAYE or TSBYE), to evaluate culturability. Resuscitation capacity of CFDA+PI-sorted cells (10 events/well) was monitored by visual inspection on TSAYE and by optical density measurement in TSBYE for 5 days. Sorting of L. monocytogenes viable cells (CFDA+PI-) in Ringer's solution on TSAYE and TSBYE showed 100 % recovery in both media (control condition), while the mean lag time in TSBYE was 9.6 h. Treatment with 20 ppm PAA for 90 and 180 min resulted in 74.79 % and 85.82 % of non-culturable cells in TSBYE and increased the average lag time to 41.7 h and 43.8 h, respectively, compared to the control (9.6 h). The longest average lag time (79.5 h) was detected after treatment with 30 ppm PAA for 90 min, while at the same condition sorting of CFDA+PI- cells resulted in 95.05 % and 93.94 % non-culturable cells on TSAYE and TSBYE, respectively. The highest percentage of wells with non-culturable cells (96.17 %) was detected on TSAYE after treatment with 40 ppm PAA for 30 min. Fractions of VBNC cells were detected in TSBYE after treatment with HCl pH 3.0 for 60 and 240 min, and in TSAYE and TSBYE after exposure to AA pH 2.7. Treatment with AA pH 2.7 for 150-300 min increased the range of recorded lag time values compared to 60 min, from 8.6 h up to 13.3 h, as well as the mean lag times in TSBYE. Modelling of the outgrowth kinetics comparing the two types of stress (oxidative vs acid) and the two systems of growth (colonial vs planktonic) revealed that low starting concentrations hindered the detection of viable L. monocytogenes cells, either due to VBNC induction or cell heterogeneity.

Efficient disinfection of combined sewer overflows by ultraviolet/peracetic acid through intracellular oxidation with preserving cell integrity.

Combined sewer overflows (CSOs) introduce microbial contaminants into the receiving water bodies, thereby posing risks to public health. This study systematically investigated the disinfection performance and mechanisms of the combined process of ultraviolet and peracetic acid (UV/PAA) in CSOs with selecting Escherichia coli (E. coli) as a target microbial contaminant. The UV/PAA process exhibited superior performance in inactivating E. coli in simulated CSOs compared with UV, PAA, and UV/H2O2 processes. Increasing the PAA dosage greatly enhanced the disinfection efficiency, while turbidity and organic matter hindered the inactivation performance. Singlet oxygen (1O2), hydroxyl (•OH) and organic radicals (RO•) contributed to the inactivation of E. coli, with •OH and RO• playing the prominent role. Variations of intracellular reactive oxygen species, malondialdehyde, enzymes activities, DNA contents and biochemical compositions of E. coli cells suggested that UV/PAA primarily caused oxidative damage to intracellular molecules rather than the damage to the lipids of the cell membrane, therefore effectively limited the regrowth of E. coli. Additionally, the UV/PAA process displayed an outstanding performance in disinfecting actual raw CSOs, achieving a 2.90-log inactivation of total bacteria after reaction for 4 min. These results highlighted the practical applicability and effectiveness of the UV/PAA process in the disinfection of CSOs.

Enhanced degradation of emerging contaminants by Far-UVC photolysis of peracetic acid: Synergistic effect and mechanisms.

Krypton chloride (KrCl*) excimer lamps (222 nm) are used as a promising irradiation source to drive ultraviolet-based advanced oxidation processes (UV-AOPs) in water treatment. In this study, the UV222/peracetic acid (PAA) process is implemented as a novel UV-AOPs for the degradation of emerging contaminants (ECs) in water. The results demonstrate that UV222/PAA process exhibits excellent degradation performance for carbamazepine (CBZ), with a removal rate of 90.8 % within 45 min. Notably, the degradation of CBZ in the UV222/PAA process (90.8 %) was significantly higher than that in the UV254/PAA process (15.1 %) at the same UV dose. The UV222/PAA process exhibits superior electrical energy per order (EE/O) performance while reducing resource consumption associated with the high-energy UV254/PAA process. Quenching experiments and electron paramagnetic resonance (EPR) detection confirm that HO• play a dominant role in the reaction. The contributions of direct photolysis, HO•, and other active species (RO• and 1O2) are estimated to be 5 %, 88 %, and 7 %, respectively. In addition, the effects of Cl-, HCO3-, and humic acid (HA) on the degradation of CBZ are evaluated. The presence of relatively low concentrations of Cl-, HCO3-, and HA can inhibit CBZ degradation. The UV222/PAA oxidation process could also effectively degrade several other ECs (i.e., iohexol, sulfamethoxazole, acetochlor, ibuprofen), indicating the potential application of this process in pollutant removal. These findings will propel the development of the UV222/PAA process and provide valuable insights for its application in water treatment.

Relative resistance of Salmonella serotypes (Typhimurium, Infantis, and Reading) to peroxyacetic acid on chicken wings.

Peroxyacetic acid (PAA) is widely used as an antimicrobial in poultry processing. Recent salmonellosis outbreaks caused by Salmonella Infantis (SI) from chicken products and Salmonella Reading (SR) from turkey products have raised concerns about their enhanced resistance (compared to Salmonella Typhimurium [ST]) to commonly used antimicrobial interventions such as PAA. The objective of this research was to evaluate the efficacy of PAA against Salmonella serotypes (Typhimurium, Infantis and Reading), effect on product color and decomposition of PAA at different pH levels. Fresh chicken wings (0.45 kg) were inoculated with a cocktail (ca. 6 log CFU/mL) of nalidixic acid resistant ST, rifampicin resistant SI and kanamycin resistant SR. Inoculated chicken wings were immersed in PAA solutions (100 or 500 ppm; adjusted to either pH 8.5 or unadjusted natural pH) for either 10 s or 60 min to replicate treatments for chicken parts or whole carcasses, respectively. Treated chicken wings were rinsed in buffered peptone water (100 mL) containing sodium thiosulfate (0.1 %), serially diluted in peptone water supplemented with 200 ppm of nalidixic acid, rifampicin or kanamycin for enumeration of ST, SI, and SR respectively, and plated on APC Petrifilm. Immersion of chicken wings in 500 ppm PAA for 60 min resulted in greater microbial reductions (P ≤ 0.05) of ST, SI, SR of ca. Two log CFU/mL each, compared to 10 s treatment. Regardless of concentration and pH of PAA, increased exposure time (60 min vs. 10 s) resulted in greater reductions (P ≤ 0.05) of ST, SI, SR. ST was slightly more resistant to PAA solutions than S. Infantis and S. Reading (P ≤ 0.05) for all experimental conditions (PAA conc, pH, and exposure times). Faster decomposition of PAA (100 and 500 ppm) was observed at pH 8.5 compared to unadjusted, natural pH (P ≤ 0.05). Product color (lightness, L*) was not affected regardless of the PAA concentration, exposure time or the pH.

Enhanced Degradation of Micropollutants in a Peracetic Acid/Mn(II) System with EDDS: An Investigation of the Role of Mn Species.

Extensive research has been conducted on the utilization of a metal-based catalyst to activate peracetic acid (PAA) for the degradation of micropollutants (MPs) in water. Mn(II) is a commonly employed catalyst for homogeneous advanced oxidation processes (AOPs), but its catalytic performance with PAA is poor. This study showed that the environmentally friendly chelator ethylenediamine-N,N'-disuccinic acid (EDDS) could greatly facilitate the activation of Mn(II) in PAA for complete atrazine (ATZ) degradation. In this process, the EDDS enhanced the catalytic activity of manganese (Mn) and prevented disproportionation of transient Mn species, thus facilitating the decay of PAA and mineralization of ATZ. By employing electron spin resonance detection, quenching and probe tests, and 18O isotope-tracing experiments, the significance of high-valent Mn-oxo species (Mn(V)) in the Mn(II)-EDDS/PAA system was revealed. In particular, the involvement of the Mn(III) species was essential for the formation of Mn(V). Mn(III) species, along with singlet oxygen (1O2) and acetyl(per)oxyl radicals (CH3C(O)O•/CH3C(O)OO•), also contributed partially to ATZ degradation. Mass spectrometry and density functional theory methods were used to study the transformation pathway and mechanism of ATZ. The toxicity assessment of the oxidative products indicated that the toxicity of ATZ decreased after the degradation reaction. Moreover, the system exhibited excellent interference resistance toward various anions and humid acid (HA), and it could selectively degrade multiple MPs.

Effective of different industrial disinfection in subzero cold-chain environment.

Effective disinfection methods are crucial in the cold chain transportation process of food due to the specificity of temperature and the diversity of contaminated flora. The objective of this study was to investigate the sanitizing effect of different disinfectants on various fungi at - 20 °C to achieve accurate disinfection of diverse bacterial populations. Peracetic acid, hydrogen peroxide, and potassium bisulfate were selected as low-temperature disinfectants and were combined with antifreeze. The sanitizing effect of these cryogenic disinfectants on pathogens such as Bacillus subtilis black variant spores (ATCC9372), Staphylococcus aureus (ATCC 6538), Candida albicans (ATCC 10231), Escherichia coli (8099), and poliovirus (PV-1) was sequentially verified by bactericidal and virus inactivation experiments. After a specified time of disinfection, a neutralizing agent was used to halt the sanitizing process. The study demonstrates that different disinfectants exhibit selective effects during the low-temperature disinfection process. Peracetic acid, hydrogen peroxide, and potassium monopersulfate are suitable for the low-temperature environmental disinfection of bacterial propagules, viruses, and fungal contaminants. However, for microorganisms with strong resistance to spores, a low-temperature disinfectant based on peracetic acid should be chosen for effective disinfection treatment. Our results provide a valuable reference for selecting appropriate disinfectants to sanitize various potential pathogens in the future.

Assessing the stability and sporicidal efficacy of oxidizing disinfectants.

BACKGROUND: The role of the healthcare environment in the transmission of clinical pathogens is well established. EN 17126:2018 was developed to address the need for regulated sporicidal product testing and includes a realistic medical soil to enable validation of products that claim combined cleaning and disinfection efficacy. AIM: To investigate the chemical stability and sporicidal efficacy of oxidizing disinfectant products in the presence of simulated clean and medical dirty conditions. METHODS: Disinfectant stability and sporicidal efficacy were evaluated in like-for-like ratios of soil:product. Disinfectants were exposed to simulated test soils and free chlorine, chlorine dioxide or peracetic acid concentrations were measured using standard colorimetric methods. Efficacy of disinfectants against C. difficile R027 endospores was assessed as per EN 17126:2018. Comparisons of performance between clean and medical dirty conditions were performed using one-way analysis of variance. Correlation analysis was performed using Pearson product-moment correlation. FINDINGS: Performance of chlorine-releasing agents (sodium dichloroisocyanurate, chlorine dioxide and hypochlorous acid) was concentration dependent, with 1000 ppm chlorine showing reduced stability and efficacy in dirty conditions. By contrast, peracetic acid product demonstrated stability and consistently achieved efficacy in dirty conditions. CONCLUSION: These results have implications for clinical practice, as ineffective environmental decontamination may increase the risk of transmission of pathogens that can cause healthcare-associated infections.

Inactivation of Desiccation-Resistant Salmonella on Apple Slices Following Treatment with ε-Polylysine, Sodium Bisulfate, or Peracetic Acid and Subsequent Dehydration.

Salmonella is capable of surviving dehydration within various foods, such as dried fruit. Dried fruit, including apple slices, have been the subject of product recalls due to contamination with Salmonella. A study was conducted to determine the fate of Salmonella on apple slices, following immersion in three antimicrobial solutions (viz., ε-polylysine [epsilon-polylysine or EP], sodium bisulfate [SBS], or peracetic acid [PAA]), and subsequent hot air dehydration. Gala apples were aseptically cored and sliced into 0.4 cm thick rings, bisected, and inoculated with a five-strain composite of desiccation-resistant Salmonella, to a population of 8.28 log CFU/slice. Slices were then immersed for 2 min in various concentrations of antimicrobial solutions, including EP (0.005, 0.02, 0.05, and 0.1%), SBS (0.05, 0.1, 0.2, and 0.3%), PAA (18 or 42 ppm), or varying concentrations of PAA + EP, and then dehydrated at 60°C for 5 h. Salmonella populations in positive control samples (inoculated apple slices washed in sterile water) declined by 2.64 log after drying. In the present study, the inactivation of Salmonella, following EP and SBS treatments, increased with increasing concentrations, with maximum reductions of 3.87 and 6.20 log (with 0.1 and 0.3% of the two compounds, respectively). Based on preliminary studies, EP concentrations greater than 0.1% did not result in lower populations of Salmonella. Pretreatment washes with either 18 or 42 ppm of PAA inactivated Salmonella populations by 4.62 and 5.63 log, respectively, following desiccation. Combining PAA with up to 0.1% EP induced no greater population reductions of Salmonella than washing with PAA alone. The addition of EP to PAA solutions appeared to destabilize PAA concentrations, reducing its biocidal efficacy. These results may provide antimicrobial predrying treatment alternatives to promote the reduction of Salmonella during commercial or consumer hot air drying of apple slices.

Photo-assisted natural chalcopyrite activated peracetic acid for efficient micropollutant degradation.

The effective activation of natural chalcopyrite (CuFeS2) on peracetic acid (PAA) to remove organic micropollutants was studied under visible light irradiation. Results showed than an effective sulfamethoxazole (SMX) degradation (95.0 %) was achieved under visible light irradiation for 30 min at pH 7.0. Quenching experiments, electron spin resonance analysis, and LC/MS spectrum demonstrated that HO• and CH3C(O)OO• were the main reactive species for SMX degradation, accounting for 43.3 % and 56.7 % of the contributions, respectively. Combined with X-ray photoelectron spectroscopy analysis, the photoelectrons generated on CuFeS2 activated by visible light enhanced the Fe3+/Fe2+ and Cu2+/Cu+ cycles on the surface, thereby activating PAA to generate HO•/CH3C(O)OO•. The removal rate of SMX decreased with the increase in wavelengths, due to the formation of low energy photons at longer wavelengths. Besides, the optimal pH for degradation of SMX by CuFeS2/PAA/Vis-LED process was neutral, which was attributed to the increasing easily activated anionic form of PAA during the increase in pH and the depletion of Fe species at alkaline conditions. Cl-, HCO3-, and HA slightly inhibited SMX degradation because of reactive species being quenched and/or shielding effect. Furthermore, the degradation efficiency of different pollutants by CuFeS2/PAA/Vis-LED was also measured, and the removal efficiency was different owing to the selectivity of CH3C(O)OO•. Finally, the process exhibited good applicability in real waters. Overall, this study provides new insight into visible light-catalyzed activation of PAA and suggests on further exploration of the intrinsic activation mechanism of PAA.