Bactericidal action of slightly acidic electrolyzed water against Escherichia coli and Staphylococcus aureus via multiple cell targets

Isolation and Identification of Postharvest Rot Pathogens in Citrus × tangelo and Their Potential Inhibition with Acidic Electrolyzed Water

This study focused on the identification of rot-causing fungi in Citrus × tangelo (tangelo) with a particular emphasis on investigating the inhibitory effects of acidic electrolyzed water on the identified pathogens. The dominant strains responsible for postharvest decay were isolated from infected tangelo fruits and characterized through morphological observation, molecular identification, and pathogenicity detection. Two strains were isolated from postharvest diseased tangelo fruits, cultured and morphologically characterized, and had their gene fragments amplified using primers ITS1 and ITS4. The results revealed the rDNA-ITS sequence of two dominant pathogens were 100% homologous with those of Penicillium citrinum and Aspergillus sydowii. These isolated fungi were confirmed to induce tangelo disease, and subsequent re-isolation validated their consistency with the inoculum. Antifungal tests demonstrated that acidic electrolyzed water (AEW) exhibited a potent inhibitory effect on P. citrinum and A. sydowii, with EC50 values of 85.4 μg/mL and 60.12 μg/mL, respectively. The inhibition zones of 150 μg/mL AEW to 2 kinds of pathogenic fungi were over 75 mm in diameter. Furthermore, treatment with AEW resulted in morphological changes such as bending and shrinking of the fungal hyphae surface. In addition, extracellular pH, conductivity, and absorbance at 260 nm of the fungi hypha significantly increased post-treatment with AEW. Pathogenic morphology and IST sequencing analysis confirmed P. citrinum and A. sydowii as the primary pathogenic fungi, with their growth effectively inhibited by AEW.

Slightly acidic electrolyzed water significantly restrains the accumulation of the microalgae Pseudokirchneriella subcapitata in hydroponic systems

AIMS

This study explored the effects of slightly acidic electrolyzed water (SAEW) on algae to exploit technologies that effectively suppress algal growth in hydroponic systems and improve crop yield.

METHODS AND RESULTS

The effects of SAEW on algal growth and the response mechanisms of algae to SAEW were investigated. Moreover, we studied whether the application of SAEW adversely affected tomato seedling growth. The results showed that SAEW significantly inhibited algal growth and destroyed the integrity of the algal cells. In addition, the intracellular oxidation-reduction system of algae was greatly influenced by SAEW. The H2O2, O2-, malondialdehyde (MDA), and reactive oxygen species (ROS) fluorescence signals were significantly induced by SAEW, and superoxide dismutase (SOD), peroxidase (POD), and glutathione reductase (GR) activities were greatly enhanced by a low SAEW concentration but significantly inhibited by SAEW with a high available chlorine concentration, which may contribute to heavy oxidative stress on algal growth and cell structure break down, eventually causing the death of algae and cell number decrease. We also found that regardless of the concentration of SAEW (from 10 to 40 mg L-1), there was no significant change in the germination index, length, or fresh weight of the hydroponic tomato seedlings.

CONCLUSIONS

Our findings demonstrate that SAEW can be used in hydroponic systems to restrain algae with no negative impact on tomato plants.

Bactericidal Efficacy and Mechanisms of Non-Electrolytic Slightly Acidic Hypochlorous Water on Pseudomonas fragi and Pseudomonas fluorescens

Chilled pork is frequently contaminated with Pseudomonas fragi and Pseudomonas fluorescens. In this study, the bactericidal efficacy and mechanisms of non-electrolytic slightly acidic hypochlorous water (NE-SAHW) against two strains of these two species were evaluated. The results showed that the antibacterial efficacy of NE-SAHW was positively correlated with the concentration level of NE-SAHW and negatively correlated with the initial populations of the strains. The strains of small populations were completely inhibited when provided with each level of NE-SAHW. The killed cells of P. fragi were 0.94, 1.39, 4.02, and 5.60 log10 CFU/mL, respectively, and of P. fluorescens they were 1.21, 1.52, 4.14, and 5.74 log10 CFU/mL, respectively, when the initial populations of the strains were at high levels (about 7 log10 CFU/mL). Both strains were completely killed within 12 s with the available chlorine concentration (ACC) of 50 mg/L of NE-SAHW. Morphological changes in both cells were observed by using a Scanning Electron Microscope (SEM) and it was discovered that the cell membranes were damaged, which led to the leakage of the intracellular substances, including K+, nucleic acid, and protein. In terms of the Fourier Transform Infrared Spectroscopy (FTIR) results, NE-SAHW destroyed the structures of membrane proteins and cell structure proteins, and influenced the composition of polysaccharides. The bacteria were definitely dead after treatment by NE-SAHW compared to the control according to the results of flow cytometry. These results demonstrated the potential bactericidal property of NE-SAHW when applied to the meat and other food sterilization industries.

Sublethally injured microorganisms in food processing and preservation: Quantification, formation, detection, resuscitation and adaption

Sublethally injured state has been recognized as a survival strategy for microorganisms suffering from stressful environments. Injured cells fail to grow on selective media but can normally grow on nonselective media. Numerous microorganism species can form sublethal injury in various food matrices during processing and preservation with different techniques. Injury rate was commonly used to evaluate sublethal injury, but mathematical models for the quantification and interpretation of sublethally injured microbial cells still require further study. Injured cells can repair themselves and regain viability on selective media under favorable conditions when stress is removed. Conventional culture methods might underestimate microbial counts or present a false negative result due to the presence of injured cells. Although the structural and functional components may be affected, the injured cells pose a great threat to food safety. This work comprehensively reviewed the quantification, formation, detection, resuscitation and adaption of sublethally injured microbial cells. Food processing techniques, microbial species, strains and food matrix all significantly affect the formation of sublethally injured cells. Culture-based methods, molecular biological methods, fluorescent staining and infrared spectroscopy have been developed to detect the injured cells. Cell membrane is often repaired first during resuscitation of injured cells, meanwhile, temperature, pH, media and additives remarkably influence the resuscitation. The adaption of injured cells negatively affects the microbial inactivation during food processing.

Applications of water activated by ozone, electrolysis, or gas plasma for microbial decontamination of raw and processed meat

A raw or processed meat product can be a breeding ground for spoilage bacteria (Enterobacteriaceae, Lactobacillus spp., Pseudomonas spp., etc.). Failure of decontamination results in food quality loss and foodborne illnesses caused by pathogens such as Salmonella, Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes. Often, meat processors decontaminate the carcass using cheap chemicals or artificial antimicrobial agents not listed on the ingredient list, which is discouraged by health-conscious consumers. Foods with clean labels became more popular during the COVID-19 pandemic, which led consumers to choose healthier ingredients. Novel methods of controlling or improving meat safety are constantly being discovered. This review focuses on novel means of electrochemically activate water that is being investigated as a sanitizing agent for carcasses and processing area decontamination during production or at the end. Water can be activated by using non-thermal techniques such as ozonation, electrolysis, and cold plasma technologies. Recent studies showed that these activated liquids are powerful tools for reducing microbial activity in raw and processed meat. For instance, plasma-activated water can be used to enhance microbiological safety and avoid the negative effects of direct gaseous plasma on the organoleptic aspects of food products. In addition, electrolyzed water technology offers hurdle enhancement by combining with non-thermal strategies that have great potential. Ozonation is another way of activating water which provides a very convenient way to control microbiological safety and finds several recent applications as aqueous ozone for meat decontamination. These solutions are highly reactive and convenient for non-conventional applications in the meat industry related to food safety because of their antimicrobial or antiviral impact. The present review highlights the efficacy of activated-water decontamination of raw and processed meat via non-thermal solutions.

Bactericidal Effect and Associated Properties of Non-Electrolytic Hypochlorite Water on Foodborne Pathogenic Bacteria

This study investigated the broad-spectrum bactericidal activity of non-electrolytic hypochlorite water (NEHW) and detected its hydroxyl radical content compared with that of slightly acidic electrolytic water (SAEW). Based on the results of UV scanning and storage stability, higher hypochlorite content and stronger oxidation were found to be responsible for the stronger bactericidal effect of NEHW. NEHW can achieve 99% bacterial disinfection effect by treating with 10 mg/L available chlorine concentration for more than 5 minutes. At the same time, the storage stability of NEHW was higher than that of SAEW. After 20 days of storage under sealed and dark conditions, the pH value only increased by 7.9%, and the effective chlorine concentration remained nearly 80%. The results showed that NEHW had higher germicidal efficacy and storage stability than SAEW.

The positive contribution of ultrasound technology in muscle food key processing and its mechanism-a review

Traditional processing methods can no longer meet the demands of consumers for high-quality muscle food. As a green and non-thermal processing technology, ultrasound has the advantage of improving processing efficiency and reducing processing costs. Of these, the positive effect of power ultrasound in the processing of muscle foods is noticeable. Based on the action mechanism of ultrasound, the factors affecting the action of ultrasound are analyzed. On this basis, the effect of ultrasound technology on muscle food quality and its action mechanism and application status in processing operations (freezing-thawing, tenderization, marination, sterilization, drying, and extraction) is discussed. The transient and steady-state effects, mechanical effects, thermal effects, and chemical effects can have an impact on processing operations through complex correlations, such as improving the efficiency of mass and heat transfer. Ultrasound technology has been proven to be valuable in muscle food processing, but inappropriate ultrasound treatment can also have adverse effects on muscle foods. In the future, kinetic models are expected to be an effective tool for investigating the application effects of ultrasound in food processing. Additionally, the combination with other processing technologies can facilitate their intensive application on an industrial level to overcome the disadvantages of using ultrasound technology alone.

Antibacterial Effect of Eugenol on Shigella flexneri and Its Mechanism

Shigella flexneri (Sh. flexneri), which can be found in food and the environment, is a widespread food-borne pathogen that causes human diarrhea termed “shigellosis”. In this study, eugenol, a natural active substance, was investigated for its antibacterial activity against Sh. flexneri. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of eugenol against Sh. flexneri ATCC 12022 was 0.5 and 0.8 mg/mL. The growth curves and inhibitory effect in LB broth, PBS, vegetable juice, and minced pork showed that eugenol had a good activity against Sh. flexneri. Research findings indicated the superoxide dismutase activity of Sh. flexneri was inhibited after eugenol treatment, resulting in concentrations of intracellular reactive oxygen species and an increase in malondialdehyde. The flow cytometry analysis and field emission scanning electron microscopy results revealed obvious damage to cell membrane integrity and changes in the morphology of Sh. flexneri. In addition, the intracellular ATP concentration leaked from 0.5 μM to below 0.05 μM and the membrane potential showed a concentration-dependent depolarization after eugenol treatment. In summary, eugenol exerted strong antibacterial activity and has the potential to control Sh. flexneri in the food industry.

Variation of Soil Microbial Community and Sterilization to Fusarium oxysporum f. sp. niveum Play Roles in Slightly Acidic Electrolyzed Water-Alleviated Watermelon Continuous Cropping Obstacle

It is critical to exploit technologies for alleviating watermelon continuous cropping obstacle which frequently occurs and results in the limiting production and economic losses of watermelon. This study aimed to explore the effects of slightly acidic electrolyzed water (SAEW) on watermelon continuous cropping obstacles. The results showed that SAEW significantly improved the growth of watermelon seedlings cultivated in continuous cropping soil and caused a mass of changes to the diversity of the soil microbial community. Compared with Con, SAEW decreased the diversity index of bacteria by 2%, 0.48%, and 3.16%, while it increased the diversity index of fungus by 5.68%, 10.78%, and 7.54% in Shannon, Chao1, and ACE index, respectively. Besides, the enrichment level of Fusarium oxysporum f. sp. niveum (FON) was remarkably downregulated by 50.2% at 14 days of SAEW treatment, which could decrease the incidence of Fusarium wilt disease. The wet and dry weights of FON mycelia in the fluid medium were depressed more than 93%, and the number of FON colonies in continuous cropping soil was reduced by 83.56% with SAEW treatment. Additionally, a strong correlation between watermelon, FON, and SAEW was presented by correlation analysis. Furthermore, the content of endogenous reactive oxygen species (ROS) was over quadruply increased by SAEW, which may contribute to the sterilizing effect of SAEW on FON. Taken together, our findings demonstrated that exogenous SAEW could alter the soil microbial diversity and decrease the accumulation of FON, which improved the growth of watermelon seedlings and finally alleviated continuous cropping obstacles of watermelon.

Optimization and Effect of Water Hardness for the Production of Slightly Acidic Electrolyzed Water on Sanitization Efficacy

Slightly acidic electrolyzed water (SAEW) has been recently proposed as a novel promising sanitizer and cleaner in the agricultural and food industries. However, several factors, including water hardness, were considered to strongly affect the physical properties and sanitization efficacy of SAEW. To study the effect of water hardness on the SAEW production, we evaluated the production properties and sanitization effect of SAEW, which was generated from water sources in 16 representatively geographical locations of South Korea. The results showed that the hardness of water sources from Kangwon-do, Jeollanam-do, and Daegu was 22-41 ppm; that from Busan, Gyeongnam-do, Gwangju Bukgu was 80-443 ppm, and that from seven other locations was 41-79 ppm. SAEW is produced from water hardness less than 50 ppm and greater than 80 ppm was beyond the accepted pH range (5.0-6.5). Notably, high-hardness water (>80 ppm) containing 5% HCl could be used to produce SAEW with accepted pH. The SAEW generated from low-hardness water with additions of 2% HCl and 2 M NaCl at 7 A showed accepted pH and higher germicidal effect. Furthermore, SAEW with the available chlorine concentration of 27-41 mg/L for 1 min was sufficient to completely inactivate non-spore-forming foodborne pathogens. Sanitization efficacy was not markedly affected by storage conditions for SAEW at 40 ppm. Our results demonstrated that the degree of water hardness is an important factor in the production of SAEW, which would provide a foundation for commercial application of SAEW.

Efficacy of Slightly Acidic Electrolyzed Water for Inactivation of Cronobacter sakazakii and Biofilm Cells

ABSTRACT

The disinfection efficacy and mechanism of activity of slightly acidic electrolyzed water (SAEW) were investigated against Cronobacter sakazakii. Treatment with three concentrations of SAEW decreased C. sakazakii by 23 to 55% after 2 min. Propidium iodide uptake and scanning electron micrographs indicated that SAEW treatment damaged cell integrity and changed membrane permeability resulting in leakage of nucleic acids (109.7%), intercellular proteins (692.3%), and potassium ions (53.6%). The ability to form biofilms was also reduced. SAEW treatment reduced the activity of superoxide dismutase and catalase from 100.73 and 114.18 U/mg protein to 50.03 and 50.13 U/mg protein, respectively. Expression of C. sakazakii response regulator genes (katG, rpoS, phoP, glpK, dacC, and CSK29544_RS05515) was reduced, which blocked repair of osmotic stress-induced damage and inhibited biofilm formation. These findings provide insight into the effects of SAEW on bacterial genotype and phenotype.

HIGHLIGHTS

Electrolyzed Water and Its Pharmacological Activities: A Mini-Review

Electrolyzed water (EW) is a new type of cleaning and disinfecting agent obtained by means of electrolysis with a dilute sodium chloride solution. It has low cost and harm to the human body and is also friendly to the environment. The anode produces acidic electrolyzed water (AEW), which is mainly used to inhibit bacterial growth and disinfect. The cathode provides basic electrolyzed water (BEW), which is implemented to promote human health. EW is a powerful multifunctional antibacterial agent with a wide range of applications in the medicine, agriculture, and food industry. Studies in vitro and in vivo show that it has an inhibitory effect on pathogenic bacteria and viruses. Therefore, EW is used to prevent chronic diseases, while it has been found to be effective against various kinds of infectious viruses. Animal experiments and clinical trials clearly showed that it accelerates wound healing, and has positive effects in oral health care, anti-obesity, lowering blood sugar, anti-cancer and anti-infectious viral diseases. This review article summarizes the application of EW in treating bacteria and viruses, the prevention of chronic diseases, and health promotion.

Synergistic interaction of tap water-based neutral electrolyzed water combined with UVA irradiation to enhance microbial inactivation on stainless steel

As an emerging electrolyzed water (EW) technology, tap water-based neutral electrolyzed water (TNEW) is an attractive alternative to other types of conventional EW for sterilization of food contact surfaces. In this study, we sought to identify strategies for improving TNEW inactivation efficiencies of major foodborne pathogenic bacteria. We investigated the synergistic antimicrobial effect of TNEW and ultraviolet-A light (UVA) combination treatment against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on stainless steel. The data confirmed that simultaneous TNEW and UVA treatment for 60 min reduced E. coli O157:H7, S. Typhimurium, and L. monocytogenes population by 2.15, 1.55, and 2.65 log CFU/cm², respectively. The synergistic cell count reductions in E. coli O157:H7, S. Typhimurium, and L. monocytogenes in the combination treatment group were 1.17, 0.59, and 1.62 log units, respectively. Additionally, the mechanisms of the synergistic bactericidal effects of TNEW and UVA were identified through several approaches. Mechanistic investigations suggested that the synergistic effect was associated with intracellular reactive oxygen species generation, bacterial cell membrane damage, and inactivation of dehydrogenase. These findings demonstrate that treatment with TNEW and UVA light can enhance the microbiological safety of food contact surfaces during food processing.

The Bactericidal Efficacy and the Mechanism of Action of Slightly Acidic Electrolyzed Water on Listeria monocytogenes' Survival

In the present work, the bactericidal efficacy and mechanism of slightly acidic electrolyzed water (SAEW) on L. monocytogenes were evaluated. The results showed that the strains of L. monocytogenes were killed completely within 30 s by SAEW whose available chlorine concentration (ACC) was higher than 12 mg/L, and it was confirmed that ACC is the main factor affecting the disinfection efficacy of SAEW. Moreover, our results demonstrated that SAEW could destroy the cell membrane of L. monocytogenes, which was observed by SEM and FT-IR, thus resulting in the leakage of intracellular substances including electrolyte, protein and nucleic acid, and DNA damage. On the other hand, the results found that SAEW could disrupt the intracellular ROS balance of L. monocytogenes by inhibiting the antioxidant enzyme activity, thus promoting the death of L. monocytogenes. In conclusion, the bactericidal mechanism of SAEW on L. monocytogenes was explained from two aspects including the damage of the cell membrane and the breaking of ROS balance.

Contribution of ultrasound and slightly acid electrolytic water combination on inactivating Rhizopus stolonifer in sweet potato

Effects of ultrasound (US, 300, 400, and 500 W) and slightly acidic electrolyzed water (SAEW, 10, 30, and 50 mg/L) combination on inactivating Rhizopus stolonifer in sweet potato tuberous roots (TRs) were investigated. US at 300, 400, and 500 W simultaneous SAEW with available chlorine concentration of 50 mg/L at 40 and 55 °C for 10 min significantly inhibited colony diameters (from 90.00 to 6.00-71.62 mm) and spores germination (p < 0.05). US + SAEW treatment could destroy cell membrane integrity and lead to the leakage of nucleic acids and proteins (p < 0.05). Scanning and transmission electron microscopy results showed that US + SAEW treatment could damage ultrastructure of R. stolonifer, resulted in severe cell-wall pitting, completely disrupted into debris, apparent separation of plasma wall, massive vacuoles space, and indistinct intracellular organelles. US500 + SAEW50 treatment at 40 and 55 °C increased cell membrane permeability, and decreased mitochondrial membrane potential of R. stolonifer. In addition, US500 + SAEW50 at 40 °C and US300 + SAEW50 at 55 °C controlled R. stolonifer growth in sweet potato TRs during 20 days of storage, suggesting effective inhibition on the infection of R. stolonifer. Therefore, US + SAEW treatment could be a new efficient alternative method for storing and preserving sweet potato TRs.

Electrolyzed Oxidizing Water and Its Applications as Sanitation and Cleaning Agent

Electrolyzed oxidizing water (EOW) is one of the promising novel antimicrobial agents that have recently been proposed as the alternative to conventional decontamination methods such as heat and chemical sanitizers. Acidic EOW with pH ranging from 2 to 5 is regarded most applicable in the antimicrobial treatment of vegetables and meats. Neutral and alkaline electrolyzed water have also been explored in few studies for their applications in the food industry. Neutral electrolyzed water is proposed to solve the problems related to the storage and corrosion effect of acidic EOW. Recently, the research focus has been shifted toward the application of slightly acidic EOW as more effective with some supplemental physical and chemical treatment methods such as ultrasound and UV radiations. The different applications of electrolyzed water range from drinking water and wastewater to food, utensil, and hard surfaces. The recent studies also conclude that electrolyzed water is more effective in suspensions as compared with the food surfaces where longer retention times are required. The commercialization of EOW instruments is not adopted frequently in many countries due to the potential corrosion problems associated with acidic electrolyzed water. This review article summarizes the EOW types and possible mechanism of action as well as highlights the most recent research studies in the field of antimicrobial applications and cleaning. Electrolyzed water can replace conventional chemical decontamination methods in the industry and household. However, more research is needed to know its actual mechanism of antimicrobial action along with the primary concerns related to EOW in the processing of different food products.

Comparison of Inactivation Effect of Slightly Acidic Electrolyzed Water and Sodium Hypochlorite on Bacillus cereus Spores

Bacillus cereus spores are concerns for food spoilage and foodborne disease in food industry due to their high resistance to heat and various disinfectants. The aim of this study was to investigate the inactivation of B. cereus spores by slightly acidic electrolyzed water (SAEW) in comparison to sodium hypochlorite (NaClO) with same available chlorine content (ACC). In this study, the efficacy of SAEW with different concentrations of ACC (40, 60, 80, 100, and 120 mg/L) on the inactivation of B. cereus spores, and the effect of SAEW combined with mild heat treatment (60°C), was examined in pure culture suspensions. Heat resistance and pyridine-2,6-dicarboxylic acid (DPA) release of the spores were also determined. The results showed that the sporicidal effect of the SAEW was significantly higher compared with the NaClO with the same concentration of ACC. Furthermore, the inactivation efficacy was largely dependent on ACC and treatment time. Moreover, the sporicidal activity of the SAEW was significantly improved when combined with a mild heat treatment (60°C). The majority of the DPA was released from spores, and the spores exhibited less resistance to heat after SAEW treatment for 30 min. These findings indicate that SAEW could effectively inactivate B. cereus spores, making it a promising and environmentally friendly decontamination technology for application in the food industry.

Nonthermal Plasma Induces the Viable-but-Nonculturable State in Staphylococcus aureus via Metabolic Suppression and the Oxidative Stress Response

As a novel nonthermal technology, nonthermal plasma (NTP) has attracted a lot of attention. However, it could induce microorganisms into a viable but nonculturable (VBNC) state, posing a potential risk to food safety and public health. In this study, the molecular mechanisms of VBNC Staphylococcus aureus induced by NTP were investigated. With the use of a propidium monoazide quantitative PCR (PMA-qPCR) technique combined with a plate count method, we confirmed that 8.1 to 24.3 kJ NTP induced S. aureus into a VBNC state at a level of 7.4 to 7.6 log10 CFU/ml. The transcriptomic analysis was conducted and revealed that most energy-dependent physiological activities (e.g., metabolism) were arrested in VBNC S. aureus, while the oxidative stress response-related genes (katA, dps, msrB, msrA, and trxA) were significantly upregulated. In addition, this study showed that the ATP depletion by carbonyl cyanide m-chlorophenyl hydrazone (CCCP) pretreatment could accelerate the formation of VBNC S. aureus The NTP-generated oxidative stress triggers the staphylococcal oxidative stress response, which consumes part of cellular energy (e.g., ATP). The energy allocation is therefore changed, and the energy assigned for other energy-dependent physiological activities (cell growth and division, etc.) is reduced, subsequently forcing S. aureus into a VBNC state. Therefore, the alterations of energy allocation should be some of the major contributors to the induction of VBNC S. aureus with NTP exposure. This study provides valuable knowledge for controlling the formation of VBNC S. aureus during NTP treatment.IMPORTANCE In recent years, nonthermal plasma (NTP) technology has received a lot of attention as a promising alternative to thermal pasteurization in the food industry. However, little is known about the microbial stress response toward NTP, which could be a potential risk to food safety and impede the development of NTP. A viable but nonculturable (VBNC) state is one of the most common survival strategies employed by microorganisms against external stress. This study investigated the mechanisms of the formation of VBNC Staphylococcus aureus by NTP in a more comprehensive and systematic aspect than had been done before. Our work confirmed that the NTP-generated oxidative stress induced changes in energy allocation as a driving force for the formation of VBNC S. aureus This study could provide better knowledge for controlling the occurrence of VBNC S. aureus induced by NTP, which could lead to more rational design and ensure the development of safe foods.

Effect of platinum electrode materials and electrolysis processes on the preparation of acidic electrolyzed oxidizing water and slightly acidic electrolyzed water

Electrolyzed oxidizing water (EOW) can be divided into acidic electrolyzed oxidizing water (AEOW) and slightly acidic electrolyzed water (SAEW). AEOW has the characteristics of low pH (pH < 2.7) and high oxidation-reduction potential (ORP > 1100 mV). SAEW is slightly acidic (pH = 5-6) and has an ORP of 700-900 mV. AEOW and SAEW both have a certain amount of active chlorine content (ACC), so they have the characteristics of broad spectrum, rapidity and high efficiency of sterilization. At present, there is little systematic research on AEOW and SAEW preparation. However, it is very important to study the preparation process, including electrode material and electrolytic process. First, the effects of Pt electrodes with different thermal decomposition temperatures on AEOW's pH, ORP and ACC values were investigated in detail. Next, for the SAEW preparation, the process is based on the preparation of AEOW by ion-exchange membrane electrolysis, reasonably mixing the electrolyzed cathode and anode solution. The effects of technological conditions such as electrolysis time, current density and electrolyte concentration have been systematically studied, and it is expected to get SAEW with a pH value slightly less than 7, a higher ORP value and a certain amount of ACC.

Effect of Electrolyzed Water on the Disinfection of Bacillus cereus Biofilms: The Mechanism of Enhanced Resistance of Sessile Cells in the Biofilm Matrix

This study examined the disinfection efficacy and mechanism of electrolyzed water (EW) on Bacillus cereus biofilms. B. cereus strains, ATCC 14579 and Korean Collection for Type Cultures (KCTC) 13153 biofilms, were formed on stainless steel (SS) and plastic slide (PS) coupons. Mature biofilms were treated with slightly acidic EW (SAEW), acidic EW (AEW), and basic EW (BEW). SAEW (available chlorine concentration, 25 ± 1.31 mg L^-1; pH 5.71 ± 0.16; and oxidation reduction potential, 818 to 855 mV) reduced ATCC 14579 biofilms on plastic slides to below the detection limit within 30 s. However, biofilms on SS coupons showed a higher resistance to the SAEW treatment. When the disinfection activities of three types of EW on biofilms were compared, AEW showed a higher bactericidal activity, followed by SAEW and BEW. In contrast, BEW showed a significantly ( P < 0.05) higher biofilm dispersal activity than AEW and SAEW. SAEW disinfection of the B. cereus biofilms was due to the disruption of the B. cereus plasma membrane. The higher resistance of biofilms formed on the SS coupon might be due to the higher number of attached cells and extracellular polymeric substances formation that reacts with the active chlorine ions, such as hypochlorous acid and hypochlorite ion of SAEW, which decreased the disinfection efficacy of SAEW. This study showed that the EW treatment effectively disinfected B. cereus biofilms, providing insight into the potential use of EW in the food processing industry to control the biofilm formation of B. cereus.