Codon-optimized expression and characterization of a pH stable fungal xylanase in Pichia pastoris

Novel xylanase (EC 3.2.1.8) is in great demand due to its industrial significance. In this study, we have developed and characterized a novel xylanase-producing yeast strain. This mature xylanase gene xyn11A consists of 870 base pairs and belongs to GH11 family. The gene sequence was optimized and synthesized, and was then cloned into yeast vector pGAPZA under the control of the constitutive GAP promoter. SDSPAGE analysis indicates that Xyn11A is extracellularly expressed as a glycosylated protein in P. pastoris. Xyn11A is optimally active at 70 ◦C and pH 7.4. This xylanase retained more than 90% of its activity after incubation at 50 ◦C and 60 ◦C for up to 1 h. Xyn11A is also stable over a wide range of pH (2.0–11.0). Most metal ions tested such as copper (Cu2+) and lead (Pb2+) have little inhibitory effects on Xyn11A. It is also resistant to pepsin and proteinase K digestion, retaining 80% and 90% of its activity after digestion at 37 ◦C for 1 h, respectively. Those superior properties make Xyn11A a robust xylanase with great potential for industrial use. To the best of our knowledge, this is the first report of xylanase from the fungus Corynascus thermophilus.