الفهرس 
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Abstract
Exopolysaccharides (EPSs) are high molecular weight polymers composed of saccharides subunits and are secreted by a microorganism into the surrounding environment. Microorganisms synthesize large spectrum multifunctional polysaccharides including intracellular polysaccharides, structural polysaccharides and extracellular polysaccharides (EPSs). Exopolysaccharides generally consist of monosaccharaides and some non carbohydrate substituents (such as protein, nucleic acids, lipids, acetate, pyruvate, succinate, and phosphate). Microbial EPS plays an important task in interaction between bacteria and their environment. Among all fungal and bacterial strains were isolated during this study, B. amyloliquefacien was the most frequent species recorded during this survey. In this connection, B. amyloliquefaciens showed potent isolate for exo-polysaccharide production. The results of this study highlight the fact that EPS production does not dependent only on the type of strain, but also on the medium composition and fermentation conditions. The use of mineral base-medium with added maltose and NaNO3 as carbon and nitrogen sources (M1) favored the production of EPS by B. amyloliquefaciens. In conclusion, depending on obtained results in this present study, the exopolysaccharides (EPSs) produced by B. amyloliquefacien was showed antibacterial activity against some gram-positive and negative bacteria in vitro. The promising results towards the utilization and modification of exopolysaccharides as future cheep sources for antibacterial properties.