Anti-staphylococcal activity of bacteriocins of food isolates LD3 and LD4 in pasteurized milk.

Bacteriocins of LD3 and LD4 have been applied in milk for growth inhibition of . The enumeration of cells in nutrient broth and milk was found log 9.7 and 10.2 CFU/mL, respectively, whereas it was reduced with increasing concentration of bacteriocins suggesting loss of cell viability. The lethal concentration (LC) of enterocin LD3 and plantaricin LD4 against was 160 and 220 µg/mL, respectively. Bacteriocin-treated cells were stained red with propidium iodide (PI) indicating dead cells further confirms bactericidal nature. The enterocin LD3-treated cells showed higher infrared absorbance at 1451.82 cm corresponding to phospholipids suggesting membrane-acting nature of the bacteriocin. However, plantaricin LD4-treated cells did not show such alterations suggesting different mode of action. Both bacteriocins caused disruption and shrinkage of target cells, and leakage of intracellular contents as observed in transmission electron microscope (TEM). The present study suggests killing of in milk, therefore, enterocin LD3 and plantaricin LD4 may be applied in biopreservation of milk and related food products.