Abstract: ε-Poly-L-lysine (ε-PL), a poly cationic peptide with broad-spectrum antimicrobial activity, has been widely used as a natural preservative. In order to reveal the antimicrobial mechanism of ε-PL, its antibacterial properties against Escherichia coli were investigated. and the effects of ε-PL on the morphology, the growth curve, survival rate, cell-surface hydrophobicity, inner and outer membrane penetrating activity were studied. Results showed that ε-PL inhibited the growth of E. coli in a dose-dependent manner and the inhibition effect was positively correlated with ε-PL concentration, 100 μg/mL of ε-PL achieved significant antibacterial effect. In addition, ε-PL enhanced the hydrophobicity and permeability of E. coli membrane which led to the leakage of nucleic acid, protein and electrolyte and finally the cell death. The holes and micelles appeared on the cell membrane of E. coli and the cells became aggregative and adhesive after ε-PL treatment and was further confirmed by the dynamic light scattering. In conclusion, ε-PL may achieve the bacteriostatic effect by destroying the cell structure of E. coli and the antibacterial mechanism of ε-PL against E. coli is similar to the way described by the carpet model. These findings give insights for better application of ε-PL in the field of food preservation, and also have a reference value for the study of bacteriostatic mechanism of ε-PL against other bacteria.
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