Production of Thermostable Bioflocculant from Bacillus subtilis and Optimization of Flocculation Conditions

Abstract

Bacteria strain H7, which produces flocculating substances, was isolated from the soil of
corn field at the College of Agriculture in Abu-Ghrib/Iraq, and identified as Bacillus subtilis
by its biochemical /physiological characteristics. The biochemical analysis of the partially
purified bioflocculant revealed that it was a proteoglycan composed of 93.2 % carbohydrate
and 6.1 % protein. The effects of bioflocculant dosage, temperature, pH, and different salts on
the flocculation activity were evaluated. The maximum flocculation activity was observed at
an optimum bioflocculant dosage of 0.2 mL /10 mL (49.6%). The bioflocculant had strong
thermal stability within the range of 30-80 °C, and the flocculating activity was over 50 %.
The bioflocculant had the highest flocculating activity at alkaline conditions pH 10 (71%), and
when many salts were used as cations, ZnSO4.7H2O, MnCl2, and CuSO4 enhanced
flocculation activity at 89%, 80%, and 73% respectively.