Production and Rheological Properties of Bioflocculant Produced by Bacillus sp. DP-152

The culture conditions for Bacillus sp. DP-152 in the flask were investigated for the production of polysaccharide locculant, DP-152. The optimum pH and temperature for the locculant production were 8.0 and <TEX>$30^{circ}C$</TEX>, respectively. The avorable substrates for flocculant production were soluble tarch and ammonium nitrate. The medium composition was optimized as follows: 30 g soluble starch, 0.75 g <TEX>$NH_4NO_3,; 2.0g; K_2;HPO_4,; 0.1; g KH_2PO_4,; 0.2g; MgSO_4.; 7H_2O,; and; 0.2g; MnSO_4~5H_2O$<TEX> in 11 of distilled water. Under this optimized condition, flocculating activity has been improved 4-fold compared with that of the basal medium. In the culture flask, the highest flocculating activity was obtained after 70 h of cultivation and the amount of bioflocculant DP-152 yielded was 12.4 g/<TEX>$ell$</TEX>. The solution of bioflocculant DP-152 showed non-Newtonian characteristics. Bioflocculant DP-152 exhibited apparently higher viscosity at all concentrations compared to that of zooglan (from Zoogloea ramigera), and it was stable over a wide range of temperatures and pHs.