Mode of action of leucocin K7 produced by Leuconostoc mesenteroides K7 against Listeria monocytogenes and its potential in milk preservation

Abstract

Objectives: To investigate the mode of action of leucocin K7 against Listeria monocytogenes and to assess its inhibitory effect on Lis. monocytogenes in refrigerated milk.

Results: A bacteriocin-producing strain, Leuconostoc mesenteroides K7, was isolated from a fermented pickle. The bacteriocin, leucocin K7, exhibited antagonistic activity against Lis. monocytogenes with an MIC of 28 µg/ml. It was sensitive to proteaseS and displayed good thermal stability and broad active pH range. Leucocin K7 had no effect on the efflux of ATP from Lis. monocytogenes but triggered the efflux of K(+) and the intracellular hydrolysis of ATP. It also dissipated the transmembrane electrical potential completely and transmembrane pH gradient partially. It 80 AU/ml inhibited the growth of Lis. monocytogenes by 2.3-3.9 log units in milk; when combined with glycine (5 mg/ml), it completely eliminated viable Lis. monocytogenes over 7 days

Conclusion: Leucocin K7 shows different mode of action from nisin and may have potential application in milk preservation.

Keywords: Bacteriocin; Leucocin K7; Leuconostoc mesenteroides; Listeria monocytogenes; Milk preservation; Mode of action.