Extracellular Polysaccharide Production by a <i>Rhizobium </i>sp. from Root Nodules of <i>Dolichos biflorus</i>

601-606Extracellular polysaccharide (EPS) producing ability of the Rhizobium sp. isolated from the root nodules of the leguminous medicinal herb, Dolichos biflorus was examined. The bacteria produced high amount of extracellular polysaccharides in yeast extract mannitol medium. Growth and EPS production started simultaneously, and the production reached its maximum in the stationary phase of growth. Attempts were made to optimize the cultural requirements for growth and maximum EPS production . The bacteria produced maximum EPS when the medium was supplemented with mannitol (2 per cent), pyridoxal phosphate (2 μ g ml-1), FeSO4 (2 μ g ml-1), triton X-100 (0.05 per cent) and L- asparagine (0.3 per cent), in which the production was increased by 700 per cent over control. The EPS contained arabinose, xylose and rhamnose monomers. The possible role of the EPS production in the root nodule- Rhizobium symbiosis is discussed