Document Type: Original Article
Department of Biotechnology and Genetic Engineering, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj-8100, Dhaka, Bangladesh
Department of Biotechnology and Genetic Engineering, Jahangirnagar University, Dhaka-1342, Bangladesh
Department of Biochemistry and Molecular Biology, Jahangirnagar University, Dhaka-1342, Bangladesh
Introduction: The increased need for a considerable β-glucosidase activity, especially in the enzymatic saccharification of cellulose for bioenergy, has strongly stimulated the identification of effective β-glucosidase producing microbes. This study was conducted to optimize culture conditions for β-glucosidase production from the identified new isolate of Bacillus subtilis (B1) and to find out ideal conditions for β-glucosidase activity.
Materials and Methods: For β-glucosidase production, the bacterium was cultivated in a basal medium. The culture condition was optimized at several pHs, different temperatures, varying cultivation periods, and various substrate concentrations. Finally, the activity of the β-glucosidase enzyme was investigated at different incubation periods, pH, temperatures, metal ions, and various percentages of methanol. The β-glucosidase activity was measured by the capability of the crude enzyme to convert p-nitrophenyl-β-D glucopyranoside (PNPG) into yellow product p-nitrophenol (PNP).
Results: Cellulolytic bacterial strain Bacillus subtilis (B1) showed high potentiality for β-glucosidase production at pH 7.0 after 24h incubation at 40°C. The highest level of enzyme production was achieved when 3% of CMC was provided in the culture medium. Optimum reaction conditions for β-glucosidase activity were shown to be 10 minutes, 60°C and at pH 7. Salts like magnesium sulfate (MgSO4), calcium chloride (CaCl2), and manganese sulfate (MnSO4) positively influenced the activity where NaCl and KCl had a negative effect. The presence of methanol (80%) appreciably enhanced the activity of the enzyme.
Conclusions: Complete saccharification of different industrial processes can be augmented by using this novel β-glucosidase produced by Bacillus subtilis strain isolated from the effluent of the biogas plant.