Characterization and flocculating properties of a novel bioflocculant produced by <Emphasis Type="Italic">Bacillus circulans</Emphasis>

We studied a novel bioflocculant, PX, that is produced from Bacillus Bacillus circulans X3, and has excellent flocculating activity with regard to its characterization and flocculating properties. The bioflocculant was purified from supernatant by ethanol precipitation, dialysis and gel permeation chromatography (GPC). The major component of PX was an acid polysaccharide including uronic (19.8%), pyruvic (6.5%) and acetic acids (0.7%). It consisted of galactose, mannose, xylitol, rhamnose and galacturonic acid in an approximate molar ration of 5:4.1:3:2:1.2. The molecular weight of PX was about 4.85 × 10⁴ Da as determined by GPC. The infrared spectrum of the bioflocculant indicated the presence of carboxyl, hydroxyl, amino and methoxyl groups. Studies of the flocculating properties revealed that it was stable at 60–100°C and pH 4–10. Moreover, it could flocculate a kaolin suspension over a wide range of pH and temperature in the presence of CaCl₂.