Abstract: The antibacterial activity and the underlying mechanism of vapor-phase linalool against Escherichia coli were investigated in this study. The antibacterial effect of linalool was determined and compared with that of 10 other isolate aroma compounds by vapor phase fumigation. Results showed that linalool, carvacrol, and thymol had significant antibacterial activity, with minimal inhibitory concentrations of 200, 100 and 150 μL/L, and minimum bactericidal concentrations of 200, 150 and 200 μL/L, respectively. The surface hydrophobicity of E. coli, as determined using the fluorescence probe 8-anilino-1-naphthalene sulfonate, increased after linalool treatment, indicating that the cell wall of E. coli was damaged to some extent. Transmission electron microscope (TEM) and scanning electron microscope (SEM) analysis showed that the ultrastructure of E. coli was altered after treatment with linalool vapor. Bacterial cells were shrunk and the structural integrity of both the cell wall and membrane was damaged, leading to the leakage of intracellular contents (mainly ions, nucleic acid and soluble proteins) and uneven cytoplasmic distribution. Fluorescence spectra showed that the fluorescent amino acid residues were exposed on the surface of proteins after linalool treatment. Fatty acid analysis showed that the percentages of C13:0 and C17:1 in the cell wall were increased, while the percentage of C18:0 was decreased. These results demonstrated that linalool vapor exerted antibacterial activity by disrupting the cell membrane structure and changing the fatty acid composition.

Key words: linalool, Escherichia coli, vapor-phase antibacterial activity, antibacterial mechanism