Molecular Characterization of a New Alkaline-Tolerant Xylanase from Humicola insolens Y1

Abstract EN

An endo-1,4-β-xylanase-encoding gene, xyn11B, was cloned from the thermophilic fungus Humicola insolens Y1.

The gene encodes a multimodular xylanase that consists of a typical hydrophobic signal sequence, a catalytic domain of glycoside hydrolase (GH) family 11, a glycine-rich linker, and a family 1 carbohydrate binding module (CBM1).

Deduced Xyn11B shares the highest identity of 74% with a putative xylanase from Podospora anserina S mat+.

Recombinant Xyn11B was successfully expressed in Pichia pastoris and purified to electrophoretic homogeneity.

Xyn11B had a high specific activity of 382.0 U mg−1 towards beechwood xylan and showed optimal activity at pH 6.0 and 50°C.

Distinct from most reported acidic fungal xylanases, Xyn11B was alkaline-tolerant, retaining 30.7% of the maximal activity at pH 9.0.

The Km and Vmax values for beechwood xylan were 2.2 mg mL−1 and 462.8 μmol min−1 mg−1, respectively.

The enzyme exhibited a wider substrate specificity and produced a mixture of xylooligosaccharides.

All these favorable enzymatic properties make Xyn11B attractive for potential applications in various industries.