الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
In the present work, prebiotic activity is expressed as the ratio between the growth intensity of the probiotic bacterium to that of the pathogenic Escherichia coli. This activity depends on the carbon source of the growth medium and the ability of the probiotic strain and the pathogenic one to utilize such source. This study focusing on exopolysaccharides produced by Lactobacillus delbrueckii bulgaricus, Lactobacillus helveticus and Lactobacillus casei and uses them as prebiotic for Lactobacillus re uteri, Lactobacillus rhamnosus, Lactobacillus acidophilus and Bifidobacterium bifidum. Optimization of culture conditions for maximum EPS production was studied. It was found that the best conditions were: the use of sucrose (20%) instead of glucose ofMRS medium, incubation at pH 7.0 and temp. 370 C for 72 hr. incubation under anaerobic conditions to give the highest EPS yield i.e., 13.99 g/I was recorded in case of L. helveticus when grown on the best conditions. It was found that L. delbrueckii bulgaricus exopolysaccharide has the highest prebiotic indices (1) varied from 79 to 101 On the other hand, L. helveticus and L. casei exopolysaccharides have the lowest prebiotic indices (I) varied from 14 to 24.