Characterization of a GH11 Xylanase from Endophytic Chaetomium globosum DX-THS3 with Excellent pH Stability and its Role in Enhancing Lignocellulose Degradation.

Xylanase is the core enzyme responsible for degrading xylan, a major component of lignocellulose, and holds significant application value in fields such as food, feed, and biorefining. In this study, a xylanase gene, Xyn108, was identified from the genome of the lignocellulose-degrading endophytic fungus Chaetomium globosum DX-THS3 and successfully expressed in Pichia pastoris. The xylanase Xyn108 belongs to glycoside hydrolase family 11 (GH11), with a molecular weight of approximately 38 kDa. The enzyme exhibited optimal activity at pH 6.0 and 40 °C, and demonstrated good stability within pH 3.0–9.0 and at temperatures below 50 °C (retaining > 50% residual activity after 180 min incubation). Xyn108 displayed high enzymatic activity towards beechwood xylan and possessed hydrolytic capacity toward microcrystalline cellulose. Crucially, Xyn108 exhibited significant synergistic effects with the commercial cellulase Cellic CTec2 in hydrolyzing pretreated rice straw. The highest synergistic degrees, reaching 1.34 and 1.24 for NaOH-pretreated and H₂SO₄-pretreated straw, respectively, were achieved at a xylanase/cellulase activity ratio of 1:3. The enzyme’s excellent pH adaptability, low-temperature activity, and remarkable synergistic effects highlight its significant application potential in industrial sectors such as feed processing, paper manufacturing, and biofuel production.