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

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