Abstract
Bifidobacterium bifidum was isolated from the stool of newly born infant using the morphological and biological tests of the Berge’s Manual,1986.The B. bifidum antimicrobial substances were extracted and purified by Gel-filtration. Results showed that two peptides were found for the bifidin . The inhibition zone of the first peptide for Staphylococcus aureus was 13 mm , whereas the second peptide was 8 mm. The activity of the inhibited substances of the above local strain was increased during the incubation period . The total numbers of B. bifidum were 78 x 106 c.f.u / ml after incubation for 24 hr and decreased to 11 x 106 c.f.u / ml for 48 hr . The inhibition zone was 12 mm after incubation for 24 hr and increased to 15 mm after incubation for 48 hr.Results also showed that heat treatment at 60 , 80 and 100 C° at 30 minutes were not affected and the inhibition zone had been stable. The inhibition zones at these temperatures was 14, 13, 12 mm, respectively . The most effective PH values was 6 PH and the inhibition zone was 15 mm. Staph. aureus was the most sensitive species, whereas E. coli was the most resistant to bifidin and the zone of inhibition, were 15 , 9 mm, respectively . The zones of inhibition for B. subtilis , Proteus vulgaris , Brevibacterium sp. , Klepsella aerogenes , Salmonella typhi were 13 , 12 , 11 , 10 and 10 mm, respectively .In conclusion, due to the bacteriocin and in view of health benefits , the B. bifidum could be used for elongating the shelf life of some fermanted dairy products .
