Evaluation of Antibacterial Activity of Milk Peptides Released during the Growth of Lactobacilli in Milk

The present study is carried out to evaluate the antibacterial peptides released during the growth of lactobacilli in milk. Among 8 isolates of lactobacilli and yoghurt cultures used for study, the yoghurt culture released the maximum quantity of peptides (90 ± 1.25 µg/ml). When tested for antibacterial activity only yoghurt culture filtrate showed the antibacterial potential. Further, yoghurt culture lysate was prepared, which was used to treat the milk to bring in proteolysis. The supernatant obtained after centrifugation of this treated milk was used to partially purify peptides by gel filtration using Sephadex G-50. One of the three fractions (F2) showed antibacterial activity against test organisms, E. coli, Salmonella sp. and Shigella dysentriae. The peptide fraction was incorporated into curd samples inoculated with different lactic cultures and spiked with E. coli to determine antibacterial activity. It was found that peptide showed a bacteriostatic effect on E. coli, and the viable count of it was almost reduced by two log cycles when compared with the control.