Synergistic antimicrobial activity of plasma-activated water and propylparaben: Mechanism and applications for fresh produce sanitation

Plasma-activated water (PAW) exhibits synergistic antimicrobial activity with propylparaben (PP), but the underlying mechanisms are not fully understood. Thus, the present study aimed to investigate the synergistic mechanism of the two antimicrobial agents and their application in decontaminating fresh produce. More than 6log reduction in Escherichia coli O157:H7 cells was achieved after PAW treatment combined with 4 mmol/L PP for 10 min, significantly higher than that of PAW (1.54-log reduction) or PP (2.18-log reduction) alone under the same conditions. PAW combined with PP caused remarkable morphological changes and increased intracellular reactive oxygen species levels in E. coli cells. Moreover, PAW combined with PP disrupted the bacterial membrane potential and integrity, suggesting that cell membrane could be the primary target of their antibacterial action. After washing treatment with PAW and 4 mmol/L PP for 30 min, the E. coli cells on spinach leaves decreased from 7.07 to 4.24 log10 CFU/g. The combination treatment caused no negative effects on the quality characteristics of spinach leaves, including color, chlorophyll, total phenolic content, and antioxidant activity. Thus, the simultaneous treatment of PAW and PP is an attractive approach to ensure microbial safety and improve the quality characteristics of fresh produce.

Automated summary

Plasma-activated water (PAW) shows synergistic antimicrobial activity with propylparaben (PP), achieving a significant reduction in Escherichia coli cells. The combination treatment causes morphological changes, increased reactive oxygen species levels, and disruption of bacterial membrane potential, indicating a potential primary target for their antibacterial action. The simultaneous treatment of PAW and PP on fresh produce ensures microbial safety without affecting quality characteristics.