Isolation and Characterization of Strains of Bifidobacteria with Probiotic Proprieties In vitro

In this study, twenty six (26) strains of bifidobacteria isolated from different origin were identified and characterized. The identification of isolates was based on phenotypic proprieties, the carbohydrates fermentation profiles and the Fructose-6-phosphoketolase test. Results showed that B. thermophilum was the predominant species (53.8%). The other strains were identified as B. bifidum (19.2%), B. longum (15.3%) and B. infantis (11.5%). Identified strains were then screened for their inhibitory effects against pathogenic bacteria by the agar diffusion method. 11 strains of bifidobacteria isolated produced antimicrobial compounds that were active against pathogenic bacteria especially Listeria monocytogenes strains. The inhibitory effects remain stable after a heat-treatment at 100°C for 5 min, but decreased after an enzymatic treatment with pronase-E and proteinase-K. Some antimicrobial producing strains tolerated hydrogen peroxide (100-200 μg ml ), oxbile salts 1 (0.3%) and the lysozyme (0.5 mg ml ) and could tolerate low pH values and survive to acidity shock (pH = 2). 1 The growth-inhibiting factors produced by bifidobacteria could be identified as bacteriocins-like and would be very beneficial for their application as food preservatives.