Quorum sensing inhibitory effect of hexanal on Autoinducer‐2 (AI‐2) and corresponding impacts on biofilm formation and enzyme activity in Erwinia carotovora and Pseudomonas fluorescens isolated from vegetables.

Hexanal is an essential oil component which has quorum sensing (QS) inhibitor effect on vegetable spoilage bacteria such as Erwinia carotovora (E. carotovora) and Pseudomonas fluorescens (P. fluorescens). However, the QS inhibitory (QSI) effect of hexanal on Autoinducer‐2 (AI‐2), biofilm formation, and enzyme activity is not well understood. Our results showed that the contents of AI‐2 produced by E. carotovora were higher than P. fluorescens, and the 4,5‐Dihydroxy‐2,3‐pentanedione (DPD) concentrations were significantly (p <.05) inhibited by hexanal. Adding DPD exogenously could form more biofilm when inhibited by 1/2 of minimum inhibitory concentration (MIC) of hexanal, which showed that QSI effect of hexanal on biofilm was due to its inhibition on AI‐2. There was no significant increase in enzyme activity, which suggested that enzyme inhibition by hexanal may not due to AI‐2. Understanding the relationship between QSI effect of hexanal on AI‐2, biofilm formation, and enzyme activity can improve to suppress decomposition of vegetables after harvest. Practical applications: Hexanal is an EO component which has shown good QSI effect on biofilm formation and exoenzyme activities of P. fluorescens and E. carotovora. However, the reason for the QSI effect of hexanal was still unclear. In this study, hexanal as a QS inhibitor on these two vegetable spoilage bacteria was studied from the perspective of AI‐2 signal molecule. Understanding the QS inhibition of hexanal on AI‐2 signal molecule of spoilage bacteria and its relationship with biofilm formation and enzyme activity was necessary for the application of more EO components as QS inhibitor to suppress corruption of vegetables after harvest. [ABSTRACT FROM AUTHOR]