Purification, characterization and bactericidal mechanism of a broad spectrum bacteriocin with antimicrobial activity against multidrug-resistant strains produced by Lactobacillus coryniformis XN8

The multidrug-resistant strains of food spoilage bacteria and foodborne pathogenic bacteria in food are badly in need of being controlled by effective bio-preservatives. In this study, the XN8 strain was isolated from Jiangshui and identified as Lactobacillus coryniformis according to 16S rRNA gene sequence. One of the bacteriocins produced by XN8 was purified by ammonium sulfate precipitation and a series of chromatographic column, and designated as lactocin XN8-A (LXA). The molecular mass of LXA was 3100.0242 Da by MALDI-TOF MS. The LXA showed good heat, pH and storage stabilities. However, it was sensitive to proteases. The LXA was found to have a broad antimicrobial spectrum on both Gram-positive and Gram-negative bacteria including multidrug-resistant strains and Listeria monocytogenes. Its minimum inhibitory concentration (MIC) for both Escherichia coli and Staphylococcus aureus was 6.85 mu g/mL. The LXA had a bactericidal mode without cell lysis by the growth curve and time-kill assay. The results of electron microscope showed that the LXA destroyed membrane permeability and induced pore formation of target cells. Furthermore, the LXA induced cell cycle arrest at both G1 and G2/M phase by cell cycle analysis. This research suggests that the LXA has promising potential as bio-preservative in food industry. (C) 2016 Elsevier Ltd. All rights reserved.