Selective Antimicrobial Activity of Slightly Acidic Electrolyzed Water: Differential Effects on Harmful and Beneficial Bacteria in Microbial Fermentation Systems

Microbial contamination in fermentation systems poses significant risks to safety and efficiency, as harmful microbes can proliferate while conventional disinfectants often indiscriminately harm beneficial lactic acid bacteria (LAB). This study investigated the selective antimicrobial activity of slightly acidic electrolyzed water (SAEW) against Salmonella enteritidis (S. enteritidis) and Lactobacillus plantarum (L. plantarum) using monoculture, co-culture and mechanistic analyses. Selectivity was dependent on available chlorine concentration (ACC): at 70 mg/L, S. enteritidis was completely eliminated, while > 40% of L. plantarum survived. In co-culture, 57.7% of L. plantarum remained viable and recovered, whereas S. enteritidis showed no regrowth. Mechanistic analysis revealed that S. enteritidis was more susceptible due to its thinner cell walls and weaker antioxidant defenses, in contrast to L. plantarum's thicker peptidoglycan layer and robust stress response, which provided partial resistance. To validate these findings in a practical fermentation context, SAEW was applied to Pennisetum sinese silage, where it suppressed undesirable microbes such as Enterobacter and Clostridium lachnoclostridium, enriched LAB populations and enhanced acidification. These results demonstrate SAEW as a residue-free agent for targeted pathogen control and microbial community modulation in fermentation environments.