A Study on the Antibacterial Activity of Lactic Acid Bacteria Isolated from Traditional Iranian Milk Samples

198 Lactic acid bacteria (LAB) were isolated from Iranian milk samples. Almost all isolatedLAB showed inhibitory activity towards E. coli and S. aureus as Gram negative and Grampositive indicators, respectively. No role was observed for hydrogen peroxide in the activity ofall isolated strains while organic acids proved a prominent role in all detected inhibitoryactivities. Within isolated LAB, four strains represented the inhibitory activity against S. aureusbased on the production of bacteriocin-like inhibitory substances (BLIS). Inactivation of theactivity by proteolytic enzymes demonstrated the proteinaceous nature of the antimicrobialcompounds. The selected producers were identified as L. lactis, E. faecium 1, E. hirae and E.faecium 2 based on biochemical tests according to Bergy's manual of systematic bacteriology.L. lactis had the highest Minimum Inhibitory Concentration (320 IU/ml) and showedbacteriostatic mode of activity towards the indicator bacteria.