In vitro mechanism of antibacterial activity of eucalyptus essential oil against specific spoilage organisms in aquatic products

The antibacterial activity and mechanism of plant essential oils against the specific spoilage organism of aquatic products in vitro were studied. All four selected essential oils performe antibacterial activities against five targeted bacterial strains (Escherichia coli, Shewanella putrefaciens, Pseudomonas aeruginosa, Vibrio parahaemolyticus, and Staphylococcus aureus), while eucalyptus essential oil (EEO) displayed the highest inhibitory effect in five strains. The minimum inhibitory concentrations (MIC) of EEO against five bacteria was in the range of 0.63–2.00 µl/ml. Scanning electron microscopy and transmission electron microscopy displayed noticeable damages of bacterial morphology and ultrastructure on two model bacteria. The increments of electric conductivity and the optical density at 260 nm and the decrease of intracellular ATP content, suggesting that the permeability of bacterial membrane increased while cell integrity and cell physiological function were damaged when treated with EEO at MIC. Therefore, the great potential of EEO in seafood preservation has been shown, which provides new insight for further researches. Novelty impact statement Essential oils extracted from natural plants are considered to be served as alternative sources of antibacterial components. In our study, eucalyptus essential oil (EEO) showed excellent antibacterial ability by affecting cell physiological function, which was possibly resulted from a loss of cell homeostasis. Therefore, it has a great potential in the utilization of EEO in seafood preservation.