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Obe T, Kiess AS, Nannapaneni R. Antimicrobial Tolerance in Salmonella: Contributions to Survival and Persistence in Processing Environments. Animals (Basel) 2024; 14:578. [PMID: 38396546 PMCID: PMC10886206 DOI: 10.3390/ani14040578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 02/01/2024] [Accepted: 02/07/2024] [Indexed: 02/25/2024] Open
Abstract
Salmonella remains a top bacterial pathogen implicated in several food-borne outbreaks, despite the use of antimicrobials and sanitizers during production and processing. While these chemicals have been effective, Salmonella has shown the ability to survive and persist in poultry processing environments. This can be credited to its microbial ability to adapt and develop/acquire tolerance and/or resistance to different antimicrobial agents including oxidizers, acids (organic and inorganic), phenols, and surfactants. Moreover, there are several factors in processing environments that can limit the efficacy of these antimicrobials, thus allowing survival and persistence. This mini-review examines the antimicrobial activity of common disinfectants/sanitizers used in poultry processing environments and the ability of Salmonella to respond with innate or acquired tolerance and survive exposure to persists in such environments. Instead of relying on a single antimicrobial agent, the right combination of different disinfectants needs to be developed to target multiple pathways within Salmonella.
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Affiliation(s)
- Tomi Obe
- Department of Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA
| | - Aaron S. Kiess
- Prestage Department of Poultry Science, College of Agriculture and Life Sciences, North Carolina State University, Raleigh, NC 27695, USA;
| | - Ramakrishna Nannapaneni
- Department of Food Science, Nutrition and Health Promotion, Mississippi State University, Mississippi, MS 39762, USA;
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Zhang H, Chen L, Du P, Li F, Liu W. Unraveling Different Reaction Characteristics of Alkoxy Radicals in a Co(II)-Activated Peracetic Acid System Based on Dynamic Analysis of Electron Distribution. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024. [PMID: 38315813 DOI: 10.1021/acs.est.3c07977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have shown broad application prospects in organic wastewater treatment. Alkoxy radicals including CH3COO• and CH3COOO• are primary reactive species in PAA-AOP systems; however, their reaction mechanism on attacking organic pollutants still remains controversial. In this study, a Co(II)/PAA homogeneous AOP system at neutral pH was constructed to generate these two alkoxy radicals, and their different reaction mechanisms with a typical emerging contaminant (sulfacetamide) were explored. Dynamic electron distribution analysis was applied to deeply reveal the radical-meditated reaction mechanism based on molecular orbital analysis. Results indicate that hydrogen atom abstraction is the most favorable route for both CH3COO• and CH3COOO• attacking sulfacetamide. However, both radicals cannot react with sulfacetamide via the radical adduct formation route. Interestingly, the single-electron transfer reaction is only favorable for CH3COO• due to its lower ESUMO. In comparison, CH3COOO• can react with sulfacetamide via a similar radical self-sacrificing bimolecular nucleophilic substitution (SN2) route owing to its high ESOMO and easy escape of unpaired electrons from n orbitals of O atoms in the peroxy bond. These findings can significantly improve the knowledge of reactivity of CH3COO• and CH3COOO• on attacking organic pollutants at the molecular orbital level.
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Affiliation(s)
- Huixuan Zhang
- College of Environmental Sciences and Engineering, Peking University, Beijing 100871, P.R. China
| | - Long Chen
- College of Environmental Sciences and Engineering, Peking University, Beijing 100871, P.R. China
| | - Penghui Du
- College of Environmental Sciences and Engineering, Peking University, Beijing 100871, P.R. China
| | - Fan Li
- College of Environmental Sciences and Engineering, Peking University, Beijing 100871, P.R. China
- The Key Laboratory of Water and Sediment Sciences (Ministry of Education), Peking University, Beijing 100871, P.R. China
| | - Wen Liu
- College of Environmental Sciences and Engineering, Peking University, Beijing 100871, P.R. China
- The Key Laboratory of Water and Sediment Sciences (Ministry of Education), Peking University, Beijing 100871, P.R. China
- International Joint Laboratory for Regional Pollution Control (Ministry of Education), Peking University, Beijing 100871, P.R. China
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Wang D, Palmer JS, Fletcher GC, On SLW, Gagic D, Flint SH. Efficacy of commercial peroxyacetic acid on Vibrio parahaemolyticus planktonic cells and biofilms on stainless steel and Greenshell™ mussel (Perna canaliculus) surfaces. Int J Food Microbiol 2023; 405:110372. [PMID: 37672942 DOI: 10.1016/j.ijfoodmicro.2023.110372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 08/07/2023] [Accepted: 08/26/2023] [Indexed: 09/08/2023]
Abstract
The potential of using commercial peroxyacetic acid (PAA) for Vibrio parahaemolyticus sanitization was evaluated. Commercial PAA of 0.005 % (v/v, PAA: 2.24 mg/L, hydrogen peroxide: 11.79 mg/L) resulted in a planktonic cell reduction of >7.00 log10 CFU/mL when initial V. parahaemolyticus cells averaged 7.64 log10 CFU/mL. For cells on stainless steel coupons, treatment of 0.02 % PAA (v/v, PAA: 8.96 mg/L, hydrogen peroxide: 47.16 mg/L) achieved >5.00 log10 CFU/cm2 reductions in biofilm cells for eight strains but not for the two strongest biofilm formers. PAA of 0.05 % (v/v, PAA: 22.39 mg/L, hydrogen peroxide: 117.91 mg/L) was required to inactivate >5.00 log10 CFU/cm2 biofilm cells from mussel shell surfaces. The detection of PAA residues after biofilm treatment demonstrated that higher biofilm production resulted in higher PAA residues (p < 0.05), suggesting biofilm is acting as a barrier interfering with PAA diffusing into the matrices. Based on the comparative analysis of genomes, robust biofilm formation and metabolic heterogeneity within niches might have contributed to the variations in PAA resistance of V. parahaemolyticus biofilms.
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Affiliation(s)
- Dan Wang
- School of Food and Advanced Technology, Massey University, Private Bag 11222, Palmerston North, New Zealand.
| | - Jon S Palmer
- School of Food and Advanced Technology, Massey University, Private Bag 11222, Palmerston North, New Zealand
| | - Graham C Fletcher
- The New Zealand Institute for Plant & Food Research Limited, Private Bag 92169, Auckland 1142, New Zealand
| | - Stephen L W On
- Faculty of Agriculture and Life Sciences, Lincoln University, Private Bag 85084, Canterbury, New Zealand
| | - Dragana Gagic
- School of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
| | - Steve H Flint
- School of Food and Advanced Technology, Massey University, Private Bag 11222, Palmerston North, New Zealand
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György É, Unguran KA, Laslo É. Biocide Tolerance and Impact of Sanitizer Concentrations on the Antibiotic Resistance of Bacteria Originating from Cheese. Foods 2023; 12:3937. [PMID: 37959056 PMCID: PMC10648639 DOI: 10.3390/foods12213937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/13/2023] [Accepted: 10/20/2023] [Indexed: 11/15/2023] Open
Abstract
In this study, we determined and identified the bacterial diversity of different types of artisanal and industrially produced cheese. The antibiotic (erythromycin, chloramphenicol, kanamycin, ampicillin, clindamycin, streptomycin, tetracycline, and gentamicin) and biocide (peracetic acid, sodium hypochlorite, and benzalkonium chloride) resistance of clinically relevant bacteria was determined as follows: Staphylococcus aureus, Macrococcus caseolyticus, Bacillus sp., Kocuria varians, Escherichia coli, Enterococcus faecalis, Citrobacter freundii, Citrobacter pasteurii, Klebsiella oxytoca, Klebsiella michiganensis, Enterobacter sp., Enterobacter cloacae, Enterobacter sichuanensis, Raoultella ornithinolytica, Shigella flexneri, and Salmonella enterica. Also, the effect of the sub-inhibitory concentration of three biocides on antibiotic resistance was determined. The microbiota of evaluated dairy products comprise diverse and heterogeneous groups of bacteria with respect to antibiotic and disinfectant tolerance. The results indicated that resistance was common in the case of ampicillin, chloramphenicol, erythromycin, and streptomycin. Bacillus sp. SCSSZT2/3, Enterococcus faecalis SRGT/1, E. coli SAT/1, Raoultella ornithinolytica MTT/5, and S. aureus SIJ/2 showed resistance to most antibiotics. The tested bacteria showed sensitivity to peracetic acid and a different level of tolerance to benzalkonium chloride and sodium hypochlorite. The inhibition zone diameter of antibiotics against Enterococcus faecalis SZT/2, S. aureus JS11, E. coli CSKO2, and Kocuria varians GRT/10 was affected only by the sub-inhibitory concentration of peracetic acid.
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Affiliation(s)
- Éva György
- Department of Food Science, Faculty of Economics, Socio-Human Sciences and Engineering, Sapientia Hungarian University of Transylvania, 530104 Miercurea Ciuc, Romania; (K.A.U.); (É.L.)
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Castro VS, Fang Y, Yang X, Stanford K. Association of resistance to quaternary ammonium compounds and organic acids with genetic markers and their relationship to Escherichia coli serogroup. Food Microbiol 2023; 113:104267. [PMID: 37098428 DOI: 10.1016/j.fm.2023.104267] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 03/17/2023] [Indexed: 03/31/2023]
Abstract
Sanitizer resistance is being extensively investigated due to the potential for bacterial survival and cross-resistance with other antimicrobials. Similarly, organic acids are being used due to their microbial inactivation potential as well as being generally recognized as safe (GRAS). However, little is known about associations of genetic and phenotypic factors in Escherichia coli related to resistance to sanitizers and organic acids as well as differences between "Top 7" serogroups. Therefore, we investigated 746 E. coli isolates for resistance to lactic acid and two commercial sanitizers based on quaternary ammonium and peracetic acid. Furthermore, we correlated resistance to several genetic markers and investigated 44 isolates using Whole Genome Sequencing. Results indicate that factors related to motility, biofilm formation, and Locus of Heat Resistance played a role in resistance to sanitizers and lactic acid. In addition, Top 7 serogroups significantly differed in sanitizer and acid resistance, with O157 being the most consistently resistant to all treatments. Finally, mutations in rpoA, rpoC, and rpoS genes were observed, in addition to presence of a Gad gene with alpha-toxin formation in all O121 and O145 isolates, which may be related to increased resistance of these serogroups to the acids used in the present study.
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Luukkonen T, von Gunten U. Oxidation of organic micropollutant surrogate functional groups with peracetic acid activated by aqueous Co(II), Cu(II), or Ag(I) and geopolymer-supported Co(II). WATER RESEARCH 2022; 223:118984. [PMID: 36027766 DOI: 10.1016/j.watres.2022.118984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 07/25/2022] [Accepted: 08/13/2022] [Indexed: 06/15/2023]
Abstract
Peracetic acid (PAA) in combination with transition metals has recently gained increasing attention for organic micropollutant abatement. In this study, aqueous Co(II), Cu(II), and Ag(I) were compared for their capacity to activate PAA. Co(II) outperformed Cu(II) or Ag(I) and the optimum conditions were 0.05 mM of Co(II), 0.4 mM of PAA, and pH 3. However, due to a wider applicability in water treatment, pH 7 (i.e., bicarbonate buffer) was selected for detailed investigations. The abatement of different micropollutant surrogates could be described with a second-order rate equation (observed second-order rate constants, kobs were in the range of 42-132 M-1 s-1). For the para-substituted phenols, there was a correlation between the observed second-order rate constants of the corresponding phenolates and the Hammett constants (R2 = 0.949). In all oxidation experiments, the reaction rate decreased significantly after 1-2 min, which coincided with the depletion of PAA but also with the deactivation of the Co(II) catalyst by oxidation to Co(III) and subsequent precipitation. It was demonstrated that Co(II) immobilized on a geopolymer-foam performed approximately similarly as aqueous Co(II) but without deactivation due to Co(III) precipitation. This provides a potential option for the further development of heterogeneous catalytic Co(II)/PAA advanced oxidation processes utilizing geopolymers as a catalyst support material.
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Affiliation(s)
- Tero Luukkonen
- University of Oulu, Fibre and Particle Engineering Research Unit, P.O. Box 8000, FI-90014, Finland; Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, Dübendorf CH-8600, Switzerland.
| | - Urs von Gunten
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, Dübendorf CH-8600, Switzerland; School of Architecture, Civil and Environmental Engineering (ENAC), Ecole Polytechnique Lausanne (EPFL), Lausanne 1015, Switzerland.
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Surface Decontamination and Shelf-Life Extension of Gilthead Sea Bream by Alternative Washing Treatments. SUSTAINABILITY 2022. [DOI: 10.3390/su14105887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The efficacy of washing and the investigation of alternative sanitizing treatments for the reduction of microbial population are major issues for fresh fish and seafood. Limited work on the effect of alternative washing media on fish, particularly gilthead sea bream, one of the important popular fish species, has been published and no industrial scaling-up has been reported. The objective of this study was to systematically evaluate the effect of surface decontamination treatments on the microbial load of fish and the quality and shelf life during subsequent chilled storage. Citric acid (200 ppm for 0–10 min), lactic acid (200 ppm for 0–10 min), and peracetic acid (0–200 ppm for 0–4 min) were tested as alternative washing media by immersion of gutted gilthead sea bream by evaluating their effect on microbial growth and physicochemical and organoleptic degradation of fish. The results of the study indicated that washing with citric (200 ppm, 10 min) and peracetic acid (200 ppm, 4 min) significantly delayed the growth of spoilage microorganisms (total viable count, Pseudomonas spp., Enterobacteriaceae spp., and H2S-producting bacteria) in gutted fish and extended the shelf life to 18 days at 0 °C, compared to 11 days without washing treatment. Appropriate handling and processing of fish and shelf-life extension may enable longer transportation and thus open new distant markets, as well as contribute to reduce food waste during transportation and storage.
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Wang J, Wu Z, Wang H. Combination of ultrasound-peracetic acid washing and ultrasound-assisted aerosolized ascorbic acid: A novel rinsing-free disinfection method that improves the antibacterial and antioxidant activities in cherry tomato. ULTRASONICS SONOCHEMISTRY 2022; 86:106001. [PMID: 35405541 PMCID: PMC9011114 DOI: 10.1016/j.ultsonch.2022.106001] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 03/19/2022] [Accepted: 04/03/2022] [Indexed: 05/15/2023]
Abstract
Traditional ultrasound (US)-assisted disinfection is only effective during washing. Coating is an effective method to control microbial growth after washing; however, cross-contamination can occur during immersion in the coating aqueous solution. Tap water (TW) rinsing is generally used to remove sanitizer residues after US-assisted washing; however, the Food and Drug Administration stated that rinsing is unnecessary when the peracetic acid (PAA) concentration does not exceed 80 ppm. In this study, we proposed a novel US-assisted hurdle technology of 80 ppm PAA combined with low-frequency US (25 kHz) during washing, followed by US-assisted aerosolization processing (nonimmersion coating). Ascorbic acid (AA), a safe and low-cost agent, was selected as the aerosolization solution. Cherry tomatoes were selected as the model, and the proposed method was compared with traditional US-assisted disinfection methods (US-10 ppm free chlorine washing + TW rinsing and US-5 ppm chlorine dioxide washing + TW rinsing) to analyze the disinfection efficacy and quality changes. During storage, US-PAA + 1%AA facilitated additional 0.7-0.9, 0.6-0.8, 0.7-1.0, and 0.5-1.0 log CFU/g reductions in the counts of Escherichia coli O157:H7, Salmonella Typhimurium, aerobic mesophilic counts, and molds and yeasts, respectively, as compared with traditional US-assisted methods. Sensory properties, color index, total soluble solids, titratable acidity, and weight loss were not negatively affected by any of the treatments. Firmness was slightly reduced after all treatments; however, the firmness of the samples was maintained during storage, in contrast with the decreased firmness observed in the control. Phenolic content and antioxidant activity significantly increased after all treatments. Further analysis of two key enzymes (phenylalanine ammonia-lyase and 4-coumarate-CoA ligase) involved in phenolic synthesis showed that their levels significantly increased following all treatments, leading to an increase in phenolic content and antioxidant activity. This result also indicated that US-assisted washing could act as an abiotic elicitor to increase nutritional content. Overall, US-PAA + 1%AA treatment served as an effective method for disinfecting produce during washing and for controlling microbial growth after washing without prolonging the processing time, which is an advantage over traditional US-assisted washing.
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Affiliation(s)
- Jiayi Wang
- College of Food and Chemical Engineering, Shaoyang University, Shaoyang 422000, China.
| | - Zhaoxia Wu
- College of Food Science, Shenyang Agricultural University, Shenyang 110000, China
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Wang J, Wu Z. Combined use of ultrasound-assisted washing with in-package atmospheric cold plasma processing as a novel non-thermal hurdle technology for ready-to-eat blueberry disinfection. ULTRASONICS SONOCHEMISTRY 2022; 84:105960. [PMID: 35240411 PMCID: PMC8891714 DOI: 10.1016/j.ultsonch.2022.105960] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 02/14/2022] [Accepted: 02/23/2022] [Indexed: 06/14/2023]
Abstract
Ultrasound (US) has limited disinfection efficacy, and it has been recommended to combine it with chemical disinfectants during fresh produce washing. After washing and before packaging, the disinfection effect of US-assisted washing can be weakened; thus, in-package disinfection is important. As a nutritious fruit, there are no packaged blueberries can be directly eaten. Therefore, in this study, blueberry was selected as the model, and the two most commonly used disinfectants (free chlorine [FC] at 10 ppm and peracetic acid [PAA] at 80 ppm) were combined with low-frequency US (25 kHz) during washing, followed by in-package disinfection using dielectric barrier discharge cold plasma (CP). The disinfection efficacy of US-FC and US-PAA against Escherichia coli O157:H7 and Salmonella Typhimurium was significantly higher than that of US, PAA, or FC alone. The highest disinfection efficacy of CP was observed at the pulse frequency range of 400-800 Hz. For US-FC (1 min) + CP (1 min), an additional 0.86, 0.71, 0.42, and 0.29 log CFU/g of reduction for E. coli O157:H7, S. Typhimurium, aerobic mesophilic counts, and mold and yeast was achieved, respectively, compared with US-FC (2 min) alone. For US-PAA (1 min) + CP (1 min) an additional 0.71, 0.59, 0.32, and 0.21 log CFU/g of reduction was achieved for the above organisms, respectively, compared with US-PAA (2 min) alone. Quality loss (in total color difference, firmness, and anthocyanin content) was not observed after treatment with US-FC + CP, US-PAA + CP, US-FC, or US-PAA. After treatment with US-FC + CP or US-PAA + CP, the reactive oxygen species (ROS) content was significantly lower than that in the other groups, and antioxidant enzyme activity was significantly higher than that in the other groups, suggesting that in-package CP can activate the blueberry antioxidant system to scavenge ROS, thereby lowering the risk of quality loss. US-CP combination not only improves the disinfection efficacy but also lowers quality loss caused by ROS, without prolonging the processing time.
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Affiliation(s)
- Jiayi Wang
- College of Food and Chemical Engineering, Shaoyang University, Shaoyang 422000, China.
| | - Zhaoxia Wu
- College of Food Science, Shenyang Agricultural University, Shenyang 110000, China
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Almuhtaram H, Hofmann R. Evaluation of ultraviolet/peracetic acid to degrade M. aeruginosa and microcystins -LR and -RR. JOURNAL OF HAZARDOUS MATERIALS 2022; 424:127357. [PMID: 34687995 DOI: 10.1016/j.jhazmat.2021.127357] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/23/2021] [Accepted: 09/24/2021] [Indexed: 06/13/2023]
Abstract
The reactivity of peracetic acid (PAA) alone, and PAA exposed to ultraviolet radiation (UV), was investigated on Microcystis aeruginosa cells, and on microcystin-LR and -RR. Reaction rates between PAA and MC-LR (k = 3.46 M-1 s-1) and MC-RR (k = 2.67 M-1 s-1) were determined in an unbuffered acidic solution, and they are approximately 35-45 times lower than a previously reported reaction rate between MC-LR and chlorine at pH 6. Peracetic acid reacted with M. aeruginosa cells as a function of PAA and cell concentrations, with 10 mg/L PAA resulting in 1-log reduction of total MC-LR within 15 min. Advanced oxidation by UV/PAA readily degraded MC-LR and MC-RR, outperforming UV/H2O2 at pH 7.7 by > 50% on an equimolar basis. Indirect photolysis at this pH is due to •OH and organic radicals, as determined by trials in the presence of excess tert-butanol to scavenge •OH. The process is less effective when the pH departs from neutral conditions (5.9 or 10.6) due to the decreased effects of both radicals. These findings suggest that PAA alone might be a viable option for cyanobacteria and microcystins control in preoxidation applications and that UV/PAA is an effective process for degrading MC-LR and MC-RR at neutral pH.
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Affiliation(s)
- Husein Almuhtaram
- Department of Civil and Mineral Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada.
| | - Ron Hofmann
- Department of Civil and Mineral Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada
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Chen J, Liu X, Pavlostathis SG. Long-term evaluation of the effect of peracetic acid on a mixed aerobic culture: Organic matter degradation, nitrification, and microbial community structure. WATER RESEARCH 2021; 190:116694. [PMID: 33316663 DOI: 10.1016/j.watres.2020.116694] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 11/03/2020] [Accepted: 11/27/2020] [Indexed: 06/12/2023]
Abstract
Peracetic acid (PAA) has been widely used as a disinfectant in many industries; its use in poultry processing is steadily increasing. However, information related to the potential inhibitory effect of PAA solutions (PAA and H2O2) on biological wastewater treatment processes used by the poultry processing industry is extremely limited. The work reported here assessed the long-term effect of PAA solution on aerobic degradation and nitrification in three bioreactors fed with poultry processing wastewater by quantifying the extent of COD removal and nitrification rates. Changes in culture viability, intracellular reactive oxygen species (ROS), and microbial community structure were also evaluated. COD removal and nitrification were not affected by H2O2 and PAA solutions added to the wastewater before feeding (indirect addition). However, both processes were significantly affected by high levels of H2O2 (i.e., 27 mg/L) and PAA solution (i.e., 60/8.4 mg/L PAA/H2O2) directly added to the reactors. Directly added PAA/H2O2 at 40/5.6 mg/L was the lowest dose resulting in nitrification inhibition. Fast recovery of COD removal and nitrification was observed when direct addition of H2O2 and PAA solution ended. Cell viability measurements revealed that the negative impact on nitrification was predominantly attributed to enzyme inhibition rather than to loss of cell viability. The impact on nitrification was not related to intracellular ROS levels. Microbiome analysis showed major shifts in community composition during the long-term addition of H2O2 and even more with PAA addition. No significant time-trend change in the relative abundance of ammonia-oxidizing bacteria or nitrite-oxidizing bacteria was observed, further supporting the conclusion that the negative impact on nitrification was attributed mainly to enzyme inhibition.
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Affiliation(s)
- Jinchen Chen
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, 30332-0512, USA
| | - Xiaoguang Liu
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, 30332-0512, USA
| | - Spyros G Pavlostathis
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, 30332-0512, USA.
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