Disinfection efficacy and mechanism of slightly acidic electrolyzed water on Staphylococcus aureus in pure culture

Slightly acidic electrolyzed water (SAEW), considered as a broad-spectrum and high-performance bactericide are increasingly applied in the food industry. However, its disinfection mechanism has not been completely elucidated. This study aims to examine the disinfection efficacy and mechanism of SAEW on Staphylococcus aureus, compared with that of sodium hypochlorite (NaClO) and hydrochloric acid (HCl). SAEW treatment significantly reduced S. aureus by 5.8 log CFU/mL in 1 min, while 3.26 and 2.73 log reductions were obtained with NaClO and HCl treatments, respectively. A series of biological changes including intracellular potassium leakage, TTC-dehydrogenase relative activity and bacterial ultrastructure destruction were studied following disinfection treatment of S. aureus. The results showed that SAEW decreased the relative activity of TTC-dehydrogenase by 65.84%. Comparing intracellular potassium leakage, the SAEW treatment caused a greater percent of protein leakage (108.34%) than the NaClO (18.75%) or HCl (0.84%) treatments. These results demonstrated the potent impact SAEW had on the permeability of cell membranes. In addition, the ranking of partly agglutinated cellular inclusion formation was HCl > SAEW > NaClO. It appeared that HCl, along with its low pH value, are responsible for most of the cytoplasmic disruptions. Overall, this study demonstrated that the disinfection mechanism of SAEW was disrupting the permeability of cell membrane and the cytoplasmic ultrastructures in S. aureus cells. (C) 2015 Elsevier Ltd. All rights reserved.