The bacteriocin produced by L. casei isolated from infant stool sample was active against some food spoilage and pathogenic organisms including Gram-negative bacteria. The strongest activity was seen against S. aureus. The bacteriocin was sensitive to proteolytic enzyme (trypsin) and heat treatment (60°C for 20 min). The bacteriocin was active to various pH values from 3.0 to 7.0. The bacteriocin producer was found to harbor one plasmid of 4.5 Kb size. These results demonstrate the potential of L. casei strain as an alternative to food preservative in refrigerated foods.