Abstract:

Antimicrobial effect of ε-poly-L-lysine against Gram-negative Escherichia coli, Gram-positive Bacillus subtilis and Penicillum were studied by colormetry. Analysis on bacteria cell injury was conducted to investigate the detrimental effects of varying concentration of ε-poly-L-lysine and incubation time with ε-poly-L-lysine at its minimum inhibitory concentration on the morphology of bacteria. Results indicated that the MIC against the above two bacteria is less than 25 mg/L and less than 200 mg/L against Penicillium. ε-Poly-L-lysine shows analogical antimicrobial kinetics against different bacteria. The mechanism of action was further investigated by cell integrity and outer- and inner-membrane permeability assays and the profile of protein expression in bacteria. ε-Poly-L-lysine killed pathogenic bacteria by causing irreversible changes in both the inner and outer membranes.

Key words: ε-poly-L-lysine, antimicrobial mechanism, bacteria, bacterial cell