Potent eradication of mixed-species biofilms using photodynamic inactivation coupled with slightly alkaline electrolyzed water

Abstract

This study pioneered a novel anti-biofilm technology of photodynamic inactivation (PDI) coupled with slightly alkaline electrolyzed water (SAlEW) as solvent to dissolve photosensitizer, and its potency was verified through monitoring the biomass, cell viability, cell regrowth capacity and spatial structures of the mixed-species biofilms of Vibrio parahaemolyticus and Shewanella putrefaciens. The action mechanism was clarified by measuring the reactive oxygen species (ROS), physicochemical properties of photosensitizer sodium copper chlorophyll (SCC). Results showed that SAlEW greatly improved the permeability and stability of SCC, as well as its ROS production, which potently destroyed the key chemical composition of extracellular polymeric substances (EPS) and hence negatively altered the spatial structures of the biofilms. Moreover, PDI coupled with SAlEW significantly decreased the biomass of 72.4%, viable cells of 3.51 Log CFU/mL and cell viability of 85.7% in the mixed-species biofilms with 150 μM SCC and 4.56 J/cm2 radiation, and notably, it efficiently eradicated the mixed-species biofilms on the surfaces of fish scales or stainless steel, supported by that the cell viability was reduced by 86% and 70%, respectively. Therefore, PDI coupled with SAlEW is a promising strategy to control biofilms contamination in the food industry.