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Abstract A total of 50 Lactobacillus isolates including Lactobacillus casei (26%) , Lactobacillus paracasei (24%), Lactobacillus rhamnosus (20%), Lactobacillus fermentum (14%), Lactobacillus zeae (12%), Lactobacillus curvatus and Lactobacillus gasseri (2%) of each were recovered from 250 samples including 215 fecal samples from 3 days to1.5 years’ old healthy breast – feed infants and 35 breast milk samples from apparently healthy women. The identification of these isolates was based on cell, colony morphology, preliminary biochemical tests and MULDI TOF mass spectroscopy. The cell free supernatant cultures (CFSCs) of these isolates were screened for their evaluation of antimicrobial activities (estimated as inhibition zone diameters) by well diffusion method against four reference strains S. aureus, E. coli, S. typhi, and C. albicans. These activities were expressed as descending order S. aureus > S. typhi > E. coli > C.albicans. The effects of physical factors including incubation temperature (25oC, 37oC , 40oC ) and initial pH (5.5 , 6.4 , 6.8 and or 7.4) also the effect of nutritional factors; carbon source in media composition(glucose, fructose, starch) and nitrogen source (yeast ) on the antimicrobial content were evaluated by well diffusion method against reference strains. The highest production of antimicrobial content was recoded at incubation temperature 37oC, pH 6.4 and increased significantly up on enriched medium by glucose or fructose as Abstract a carbon source. On the other hand non-significant change was recoded up on yeast addition. The antimicrobial activities of CFSCs of the tested isolates grown at best condition was estimated against 20 clinical isolates of S.aureus and E. coli each which resulted in higher activity against S.aureus than E. coli. The antioxidant and immunomodulator activities of Lactobacillus isolates were also investigated. The total antioxidant capacity of the tested isolates was evaluated by phosphopmelybdenum method. The results revealed that the antioxidant activity of lactobacilli were varied among different species, the Lactobacillus rhamnosus, Lactobacillus fermentum and Lactobacillus zeae had greater antioxidant activity than Lactobacillus casei, Lactobacillus paracasei. The effect of oral administration of Lactobacillus paracasei on the mice was evaluated by flowcytometry analysis to estimation the immunomodulator activities. Data obtained showed that significant increase in the percentage of CD11c subpopulation and level of IFN-γ compared to the control group. Bacteriocins were partially purified from of CFSCs of Lactobacillus isolates by ammonium sulphate method and its antimicrobial activities were evaluated by well diffusion method. Electro photogram to 8 partially purified bacteriocin showed sharp single band at molecular weight of about 70 KDa. |