Antimicrobial activity of autochthonous lactic acid bacteria isolated from Algerian traditional fermented milk “Raïb”

Abstract

Twenty samples of traditional fermented milk “Raib” were collected in eastern Algeria from individual household. They were evaluated for the presence of autochthonous bacteriocin-producing lactic acid
bacteria. From 13 of these samples 52 strains of lactic acid bacteria were isolated, and shown to exhibit inhibitory activity against the indicator strain Listeria monocytogenes. Five of these inhibitor-producing isolates were selected for further study on the basis of their relatively wide antimicrobial spectrum. The inhibitory spectra of activity of the selected strains were evaluated against a range of Gram-positive and Gram-negative test organisms. Listeria monocytogenes and Staphylococcus aureus were the most sensitive indicator tested. All the antimicrobial compounds produced by the selected lactic acid
bacteria were fully or partially inactivated by some of the proteolytic enzymes, but were unaffected by catalase which indicates their proteinaceous nature. The compounds were heat stable up to 120°C for
20 min, and were active from pH 3.0 to 10.0. Highest bacteriocin activity was recorded under acidic conditions and activity decreased with increasing alkalinity.