Lactic acid bacteria have received increased attention as a potential food preservative due to their strong antagonistic activity against many food-spoilage and pathogenic organisms. Three Pediococcus species, P acidilactici NCIM 2292, P pentosaceous. NCIM 2296 and P cervisiae NCIM 2171, were evaluated for bacteriocin production. Inhibitory substance were produced during the late growth phase and maximum production occurred at 37 degreesC after 36-48 h of incubation. Bacteriocins partially purified from these species by cold-acetone precipitation at 0 degreesC and cell adsorption desorption techniques have a broad inhibitory spectrum against microorganisms, including gram-negative bacteria such as Escherichia coli and Pseudomonas. Proteolytic enzymes inactivated these peptides, but amylase and lipase did not show any effect. The bacteriocins were stable over a wide pH range (3-8) and apparently most active at pH 4.0-5.0. They were heat-stable (1 h at similar to80 degreesC and autoclaving) at pH 5.0. No loss in activity was observed when stored under refrigeration (4-8degreesC). Tris-Tricine SDS-PAGE revealed the molecular masses of these peptides to be between 3.5 and 5.0 kDa.