Partial purification and characterization of two bacteriocin-like inhibitory substances produced by bifidobacteria

Bifidobacterium spp. RBL 68 and RBL 85 isolated from newborn faeces were found to produce two bacteriocin-like inhibitory substances (BLIS) with inhibitory activities against a wide range of Grampositive and Gram-negative bacteria. The production of these BLIS began in late exponential phase of growth and reached a maximum activity during and after the stationary phase. An activity level of 33 and 15 AU/ml at the end of the exponential phase that is (12 h) and maximum activity (65 and 35 AU/ml) at the beginning of the stationary phase that is (24 and 36 h) were recorded in MRS broth at 37°C for RBL 68 and RBL 85, respectively. The two BLIS, produced by RBL 68 and RBL 85, were partially purified by a three-step purification protocol resulting in a specific activity of 2.66 x 10 and 7.68 x 10 AU/mg and purification fold of 122.8 and 95, respectively. Complete inactivation of the two BLIS activities were observed after treatment with proteolytic enzymes, including chymotrypsin, pronase E and proteinase K. These proteinaceous compounds were active against food-borne diseases and food spoilage pathogens such as Listeria monocytogenes, which make them potentially useful as antimicrobial agents in foods.