Cloning and expression of a GH11 xylanase from Bacillus pumilus SSP-34 in Pichia pastoris GS115: Purification and characterization

GH11 xylanase from Bacillus pumilus is a monofunctional low molecular weight single polypeptide chain xylanase with biotechnological applications. The codon-optimized xynA gene was modified to replace the signaling factor with Pichia expression system. 876 bp gene was synthesized and expressed in methylotrophic yeast Pichia pastoris GS115. The recombinant protein was purified to apparent homogeneity by conventional protein purifications methods. The specific activity, kinetic parameters Km and Vmax, temperature optima, and pH optima of the recombinant protein were similar to the native protein. The kinetic properties of native and recombinant protein indicated structural similarities of the two. The temperature stability of the recombinant protein was higher than the native protein. The half-life (t1⁄2) at 55°C was 10.5 and 21 minutes for native and recombinant xylanase, respectively. The native GH11 xylanase had a molecular weight of 22 kDa and the recombinant protein had a higher molecular weight of 25 kDa, which could be due to glycosylation. This cloning and expression of the GH11 xylanase in P. pastoris opens the possibilities of 1) production of GH11 xylanases for industrial applications in an economical way 2) creating mutants for improved activity 3) creating mutants for improved thermal stability, and 4) desirable pH optima to meet the industrial requirements.