Combination treatment of slightly acidic electrolyzed water with electron beam irradiation to mono- and mixed biofilms of Vibrio parahaemolyticus and Pseudomonas fluorescens

Effective antimicrobial measures are needed to control cross-contamination and rapid spoilage of food caused by Vibrio parahaemolyticus (V. parahaemolyticus) and Pseudomonas fluorescens (P. fluorescens). This study evaluated the combined effect of electron beam irradiation (EBI) combined with slightly acidic electrolytic water (SAEW) treatment on suspended bacteria and single and dual-species biofilms of V. parahaemolyticus and P. fluorescens. Colony counting results showed that EBI combined with SAEW treatment effectively removed biofilm cells. Confocal laser scanning microscopy and ATP leakage analysis showed that EBI combined with SAEW treatment damaged the membrane integrity of biofilm cells and caused ATP leakage. Field emission scanning electron microscopy (SEM) observations showed that EBI with or without SAEW significantly disrupted the threedimensional reticular structure of mono/co-cultured biofilm (extracellular polymeric substances) EPS, producing reticular perforation damage. Combined treatment with 60 mg/L SAEW and 0.5 kGy (kGy) EBI caused serious damage to the three-dimensional structure of the biofilms. The detection results of biofilm protein and DNA showed that EBI combined with SAEW could effectively destroy the extracellular polymeric matrix of biofilm, but the primary structure of the protein had no significant effect. These results suggest that SAEW(60 mg/L) combined with EBI(0.5 kGy) is effective in reducing microbial and biofilm attachment during the large yellow croaker storage processing.