Figure 1: Flocculating properties in aggregation of cells (left image) by a biopolymer polysaccharide produced during growth of strain Bacillus alvei NRC-14 at 30 oC under shaking condition; and IR-spectra (right image) of the biopolymer that showed chitosan-like structure (Abdel-Aziz et al. 2011)

Figure 2: Growth of strain Bacillus alvei NRC-14 under static conditions at room temperature (39±2 oC): A) formation of biofilm on MY broth medium; B) reversible-growth outside biofilm by the strain, as indicated at the surface of bottle, during 8 hrs; and C) synthesis of a highly viscous biopolymer during growth of the strain at refrigerator condition (4 oC)

Figure 3: Growth of strain NRC-14 (red color) and the biopolymer flocculant formation (blue color) when exposed to a cold-shock stress: cell growth after the exponential phase stops for few hours (acclimation period) and the growth rate decreased and re-enhance (A). After acclimation period (synthesis of CSPs), growth increased (B) and reached a maximum after 72 hrs

Figure 4: Growth of strain NRC-14 (red color) and the biopolymer flocculant formation (blue color) with sucrose (A) or powdered chitosan (B) as carbon sources

Figure 5: Enhancement in viscosity of the biopolymer flocculant produced by strain NRC-14 by increasing the incubation time

Figure 6: Efficacy of the purified biopolymer flocculant produced by the strain NRC-14 in aggregation and precipitation of kaolin particles after 10 min. Figures shown the precipitating action (right image) compare with the control (lift image)

Figure 7: Degradation of the purified biopolymer flocculant produced by strain NRC-14 by: (♦) β- 1,4- glucanase, (●) chitosanase, (▲) protease, or (■) a mixture of all. A reaction mixture containing 100 ml of the purified solution (10 %, v/v) was mixed with the enzymes for different periods at 37 oC. Concentrations of enzymes were 2.3, 8.6, and 3.0 U/ml for chitosanase, β -1,4- glucanase, and protease, respectively.

Figure 8: Effect of pH value on the viscosity (A) and flocculating activity (B) of the biopolymer flocculant produced by strain NRC-14

Figure 9: IR-spectra of the purified biopolymer flocculant produced by strain NRC-14: before (left image) and after (right image) heat treatment at 100 oC for 40 min.