Cloning, purification, and characterization of recombinant endo- β-1,4-D-xylanase of Bacillus sp. From soil termite abdomen

A novel endo-β-1,4-D-xylanase (xynBT) was identified from Bacillus sp. in soil termite abdomen and successfully cloned in Escherichia coli TOP10 and expressed in Escherichia coli BL21 (DE3) via pET-30a (+) as an expression vector. The full length gene consist of 801 bp ORF encoding a 267 amino acid polypeptide. The deduced amino acid sequence of xynBT displayed homology with glycoside hydrolase (GH) family 11 xylanase. Recombinant XynBT (r-XynBT), which was purified, showed an optimal pH and temperature of 5.5 and 40 °C, respectively. This enzyme was purified by the Immobilized Metal Affinity Chromatography (IMAC) method and has a molecular mass of 30 kDa, which was observed via sodium dodecyl polyacrylamide sodium electrophoresis (SDS-PAGE). Purified r-XynBT was the most stable at pH 5 for up to 120 min pre-incubation time and had a residual activity of 83%. Purified r-XynBT was also stable between 30 and 40 °C for 80 min of pre-incubation and had a residual activity of more than 50%. The presence of metal cations K⁺ and Na⁺ on r-XynBT increased its activity, while metal cations Mg²⁺, Cu²⁺, Zn²⁺, and Fe³⁺ were inhibitors.