The present invention relates to polymeric biosurfactants isolated from two bacterial strains of Microbacterium sp. strain BS-2 [MTCC 5822] and Brevibacillus sp. strain BS-207 [MTCC 5823]. The present invention relates to an acidic exopolysaccharide (EPS), termed Microsan, with chemical composition of glucose, mannose and glucuronic acid (?D-glucuronyl-(1-2)-D-mannosyl-(1-4)-D-glucose) produced by Microbacterium sp. strain BS-2 and a neutral EPS, termed Brevisan, of galactomannan with galactose and mannose residues in the ratio of 1 : 1 produced by Brevibacillus sp. strain BS-207. Both these polysaccharides exhibited surface-active and potential antibacterial, antioxidant, anti-inflammatory, and immunomodulatory activities.