Effect of Slightly Acidic Electrolyzed Water for InactivatingEscherichia coliO157:H7 andStaphylococcus aureusAnalyzed by Transmission Electron Microscopy

Abstract

The use of different available chlorine concentrations (ACCs) of slightly acidic electrolyzed water (SAEW; 0.5 to 30 mg/liter), different treatment times, and different temperatures for inactivating Escherichia coli O157:H7 and Staphylococcus aureus was evaluated. The morphology of both pathogens also was analyzed with transmission electron microscopy. A 3-min treatment with SAEW (pH 6.0 to 6.5) at ACCs of 2 mg/liter for E. coli O157:H7 and 8 mg/liter for S. aureus resulted in 100% inactivation of two cultures (7.92- to 8.75-log reduction) at 25°C. The bactericidal activity of SAEW was independent of the treatment time and temperature at a higher ACC (P > 0.05). E. coli O157:H7 was much more sensitive than S. aureus to SAEW. The morphological damage to E. coli O157:H7 cells by SAEW was significantly greater than that to S. aureus cells. At an ACC as high as 30 mg/liter, E. coli O157:H7 cells were damaged, but S. aureus cells retained their structure and no cell wall damage or shrinkage was observed. SAEW with a near neutral pH may be a promising disinfectant for inactivation of foodborne pathogens.

Effect of Anolyte on Background Microflora, Salmonella, and Listeria monocytogenes on Catfish Fillets

“…In their study using electrolyzed oxidizing water (pH 2.5, ORP of 1,150 mV, residual chlorine of 60 mg/liter), Liao et al (14) also reported a disruption of E. coli cellular membrane and attributed this damage to the high ORP. Nan et al (22) used slightly acidic electrolyzed water (electrolysis of a mixture of NaCl and HC1, resulting in water with a pH of 6.2 to 6.3, an ORP of 849 to 857 mV, and an RCL of 10 to 30 mg/liter) to treat E. coli and documented similar disruption of the cellular membrane, as observed for Salmonella in this study.…”

“…2B), when compared with the Salmonella cells treated with anolyte. Previous reports showed that another gram positive bacterium, S. aureus, was not as sensitive as E. coli when treated with NaCl (7) or slightly acidic (6.2 to 6.3) EW (22). However, in this study the morphological effects of the anolyte-treated L. monocytogenes exhibited some disruption of the outer cellular membrane (Fig.…”

“…Liao et al (14) treated E. coli 0157:H7 with EW (pH 2.5, free chlorine level of 50 ppm, and an ORP of 1,150 mV) and found that 95% of the cells were inactivated, and transmission electron microscopy showed disruption of the cell wall. Nan et al (22) treated both E. coli 0157:H7 and S. aureus with near neutral electrolyzed water (pH 6.0 to 6.5); transmission electron microscopy also showed cell wall disruption. With the outer cell wall disrupted, the bacterium is no longer able to divide.…”

Efficacy of Slightly Acidic Electrolyzed Water for Reduction of Foodborne Pathogens and Natural Microflora on Shell Eggs

“…Each bacterium was hydrated according to manufacturer's directions and cultured in tryptic soy broth supplemented with 0.6% (w/v) yeast extract (TSBYE, CVCC, Beijing, China) at 37℃ for 24 h. Cells of each culture were separately centrifuged at 3,000×g for 10 min at 4℃ (3K15, Sigma, Germany) and the supernatants were discarded. The cell pellets were washed twice with 0.1% peptone water and then re-suspended in 10 mL of the same solution (Nan et al, 2010 solution was diluted in sterile deionized water to obtain the same ACCs with SAEW. Sodium hypochlorite (NaClO) solution was prepared by diluting 8% NaClO solution using deionized water to obtain the final different concentrations, and deionized water was used as control for this experiment.…”

Application of slightly acidic electrolyzed water and ultrasound for microbial decontamination of kashk

“…The antimicrobial effect of SAEW has been proved and its application is widely accepted as an environmentally friendly sanitization method (5,6). SAEW is generated based on electrolysis of a dilute hydrochloric acid (HCl) and/or NaCl solution in an electrolytic chamber without a membrane (7).…”