| Summary: | ε-Polylysine (ε-PL) was studied for the growth inhibition of <i>Shewanella putrefaciens</i> (<i>S. putrefaciens</i>). The minimal inhibitory concentration (MIC) of ε-PL against <i>S. putrefaciens</i> was measured by the broth dilution method, while the membrane permeability and metabolism of <i>S. putrefaciens</i> were assessed after ε-PL treatment. Additionally, growth curves, the content of alkaline phosphatase (AKP), the electrical conductivity (EC), the UV absorbance and scanning electron microscope (SEM) data were used to study cellular morphology. The impact of ε-PL on cell metabolism was also investigated by different methods, such as enzyme activity (peroxidase [POD], catalase [CAT], succinodehydrogenase [SDH] and malic dehydrogenase [MDH]) and cell metabolic activity. The results showed that the MIC of ε-PL against <i>S. putrefaciens</i> was 1.0 mg/mL. When <i>S. putrefaciens</i> was treated with ε-PL, the growth of the bacteria was inhibited and the AKP content, electrical conductivity and UV absorbance were increased, which demonstrated that ε-PL could damage the cell structure. The enzyme activities of POD, CAT, SDH, and MDH in the bacterial solution with ε-PL were decreased compared to those in the ordinary bacterial solution. As the concentration of ε-PL was increased, the enzyme activity decreased further. The respiratory activity of <i>S. putrefaciens</i> was also inhibited by ε-PL. The results suggest that ε-PL acts on the cell membrane of <i>S. putrefaciens</i>, thereby increasing membrane permeability and inhibiting enzyme activity in relation to respiratory metabolism and cell metabolism. This leads to inhibition of cell growth, and eventually cell death.
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