A new biopolymer flocculant was produced by Enterobacter sp. BY-29. Flocculating activity increased in the presence of Al3+, Fe3+ or Fe2+. The flocculant had flocculating activity not only in inorganic suspensions of kaolin and active carbon but also in organic suspensions of cellulose and yeast. The flocculant was an acidic polysaccharide consisting of glucose, galactose, xylose and galacturonic acid, and its MW was about 2.5 x 10(6) Da.