Synergistic antimicrobial effect and mechanism of enterocin Gr17 and cinnamaldehyde against Escherichia coli and Candida albicans

Abstract

Abstract Bacteriocins and essential oils have potential synergistic antimicrobial effects to address food safety issues caused by spoilage microorganisms. Our previous study has illustrated the synergistic effects of Enterocin Gr17 (ENT) and cinnamaldehyde essential oil (CEO) against spoilage microorganisms, but the related synergistic mechanism is not clear. This study aimed to investigate the synergistic antimicrobial effect and mechanisms of ENT and CEO against Escherichia coli (E. coli) and Canidia Albicans (C. albicans). Time-killing assay revealed that ENT and CEO synergistically inhibited the growth of E. coli and C. albicans in a time-dependent manner, reducing viable counts by 6.99 and 4.86 lg CFU/mL, respectively. Alkaline phosphatase and zeta potential analysis illustrated that ENT with CEO synergistically disrupted the integrity of E. coli and C. albicans cell wall. The leakage of K+ and ATP, nucleic acid, protein and LDH release assays demonstrated that ENT and CEO synergistically damaged the permeability and integrity of membranes. ENT combined with CEO caused damage to the morphology and intracellular organization of E. coli, while C. albicans intracellular organization was more susceptible to change than morphology. At the metabolic level, ENT and CEO synergistically inhibited the respiratory metabolism of E. coli and C. albicans by inhibiting hexose monophosphate and tricarboxylic acid cycle pathways, respectively. Overall, ENT mainly disrupted cell wall integrity, facilitates the action of CEO on the cell membrane, synergistically destroyed cell membrane integrity, impacted energy metabolism, leading to cell death. This study provides a reference for in-depth understanding the synergistic antimicrobial mechanisms of natural antimicrobials.