Plantaricin LD1, a bacteriocin produced by Lactobacillus plantarum LD1, was characterized for biochemical and antimicrobial properties. Bacteriocin showed stability at high temperatures (100 A degrees C for 20 min and 121 A degrees C for 15 min under 15 psi pressure), in a pH range of 2.0-8.0 and also in the presence of organic solvents, surfactants and detergents. The crude preparation was not affected by catalase, amylase and lipase but activity was reduced in the presence of pepsin, trypsin and proteinase K showing proteinaceous nature of the compound. The molecular weight of bacteriocin was found to be similar to 6.5 kDa, and antimicrobial activity was confirmed by bioassay. It inhibited not only related strains but also other Gram-positive and Gram-negative bacteria such as Lactobacillus curvatus NRRL B-4562, Lactococcus lactis subsp. lactis NRRL B-1821, Enterococcus faecium NRRL B-2354, Enterobacter cloacae NRRL B-14298, Micrococcus luteus, Staphylococcus aureus, urogenic Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri and Vibrio sp. These properties of plantaricin LD1 suggest its applications not only in food safety but in therapeutics as well.