Highly alkali-stable and cellulase-free xylanases from Fusarium sp. 21: Heterologous expression, purification and biochemical comparison

Xylanases play an important role in the food, biobleaching and biofuel industries. Here, three new xylanases of the glycosyl hydrolase 11 (GH11) family, named Xyn11A, Xyn11B, and Xyn11C, from the fungus Fusarium sp. 21, were heterologously expressed in E. coli and characterized. These three xylanases displayed a strong specificity towards beechwood and corncob xylan, with no activity for other substrates such as CMC (carboxymethylcellulose), locust bean gum and pNPX (p-nitrophenyl-ß-D-xylopyranoside). Xyn11A showed much a higher activity against corncob xylan, while Xyn11B and Xyn11C presented higher activities against beechwood xylan. Beechwood xylan hydrolysates produced by these three xylanases contained xylobiose (DP2), xylotriose (DP3) and xylooligosaccharides (XOS). As Xyn11A, Xyn11B and Xyn11C, have good pH stability and high substrate specificity, these might be widely utilized in pulp and paper biobleaching industries, wine and fruit juice clarification processes and xylooligosaccharide production.