Isolation and identification of Exopolysaccharide producing Cronobacter species from root nodules of leguminous plants

Exopolysaccharides have various applications due to their unique rheological properties as in food, pharmaceutical and other industries. Exopolysaccharides also have some medical applications as anti-cancer, anti-viral and immune-modulator. In present study, 72 bacterial strains were isolated from root nodules of eight different leguminous plants and screened for exopolysaccharide production. Out of 72 isolates, 15 bacterial isolates showing good growth and exopolysaccharide production in primary screening were secondarily screened. Two isolates of YC7 and YC10 showing maximum exopolysaccharide production of 3.6g/L and 3.0g/L per dry weight, and 890µg/ml of exopolysaccharide were estimated by phenol sulphuric acid assay. Both strains identified by 16s rRNA YC7 were Cronobacter dublinensis subsp. dublinensis DES187(T), and YC10 was Cronobacter muytjensii ATCC 51329(T). The synthetic carbon sources were replaced with agro-industrial waste products. Cane molasses gave maximum exopolysaccharide production (4.25 g/l and 710µg/ml) at 5%, and rice bran showed a negligible effect. The effect of UV mutagenesis was examined (4.35 g/l and 630µg/ml), and showed positive effect on exopolysaccharide production.