BACILLUS THURINGIENSIS FERMENTATION OF WASTEWATER AND WASTEWATER SLUDGE – PRESENCE AND CHARACTERIZATION OF CHITINASES

Abstract

This study investigated the presence of chitinases in Bacillus thuringiensis ssp kurstaki HD‐1(Bt) fermented broths of wastewater sludge (non‐hydrolyzed and hydrolyzed); starch industry wastewater and soyameal. Chitinase activity was absent in soyameal and present in others. Chitinase demonstrated peaks at pH 4.0 and temperatures 40 and 50°C with higher activity between pH 4–5 and 10–11. The chitinase band on SDS‐PAGE was found to be between 36 and 45 kDa for non‐hydrolyzed (NH) and hydrolyzed sludge (TH) and starch industry wastewater. The chitinase profile during fermentation showed peaks at 15 and 30 h for non‐hydrolyzed and hydrolyzed sludge and 15 and 24 h for starch industry wastewater. Chitinase retained 96–99 % activity after two weeks incubation at room temperature and pH 4. Bioassays with supplementation of Bt chitinases showed 1.2 fold increase in entomotoxicity of wastewater sludge and a small increase in starch industry wastewater. This study sheds light on production of Bt chitinases in alternative media which will have a long term effect on entomotoxicity of these formulations.