Production of an extracellular polysaccharide bioflocculant by Klebsiella pneumoniae.

Klebsiella pneumoniae H12 produced a newly identified extracellular polysaccharide in an ethanol medium with a yield of 3.0 g/l. The molar composition of the polysaccharide was 56.04% galactose, 25.92% glucose, 10.92% galacturonic acid, 3.71% mannose, and 3.37% glucuronic acid. The addition of 0.5%-1.5% NaCl increased production. The polysaccharide flocculated with kaolin clay in suspension at the concentration of 1 ppm in a 300-ppm solution of CaCl2. Almost all bacterial species cells aggregated in the polysaccharide solution. The ability to flocculate with kaolin clay changed with the pH and with the concentrations of coexisting cation and anion species. The polysaccharide flocculant may participate in in vivo bacterial aggregation or adherence to host organisms.