Molecular and Catalytic Characterization of Acidophilic Xylanase Bacillus Subtilis K40b

Bacillus subtilis K40b was isolated from rice rhizospheres and its potential for production of xylanase was evaluated using biochemical methods. The gene for xylanase in B. subtilis K40b was amplified, sequenced and assigned to the NCBI Genebank. The gene size was estimated to be 563 bp encoding 413 amino acids. Comparison of the xylanase gene with reference sequences showed that the xylanase of B. subtilis k40b belongs to the glycosyl hydrolyase family 11 (GH11) and was closely related to Bacillus xylanase. Response surface methodology using a central composite design was applied to determine the optimum temperature and pH of the xylanase B. subtilis K40b catalytic activity. Testing was carried out at temperatures of 25 to 75 °C and pH values of 4.5 to 8.5. ANOVA was used to derive a quadratic model equation for prediction of enzyme activity. Results showed that the optimal conditions for xylanase activity were 6.5 pH and 50°C. Alkaline pH and temperatures >70°C and <50°C resulted in a noticeable decrease in xylanase activity.