Biochemical Characterization of a GH11 Xylanase from Xylanase-Producing Trichoderma citrinoviride

Xylan, a prevalent component of lignocellulose, ranks as the second most abundant carbohydrate in nature. Endo-1,4-xylanase, pivotal for its ability to cleave β-1,4-glycosidic linkages within xylan, is crucial for various applications in the food/feed processing, biofuel production, and paper/pulp industries. Although Trichoderma citrinoviride is renowned for its robust xylan-degrading capacity, the biochemical properties of xylanases derived from T. citrinoviride remain largely uncharacterized. Therefore, this study was conducted to explore the biochemical characteristics of a glycoside hydrolase family 11 xylanase derived from T. citrinoviride (TciGH11). This newly identified enzyme efficiently hydrolyzed beechwood xylan into xylooligosaccharides, exhibiting optimal activity at pH 4.5 and 50 °C, with a specific activity of 1801.5 U mg^-1 against beechwood xylan. Kinetic analysis revealed a Michaelis constant (K_m), turnover number (k_cat), and catalytic efficiency (k_cat/K_m) of 3.82 mg ml^-1, 977.8 s^-1, and 256.0 ml mg^-1 s^-1, respectively. Structural modeling analysis demonstrated that the non-conserved residues in TciGH11, specifically Glu162 and Ser165, affected the substrate binding properties, potentially resulting in different enzymatic activity compared to that of other xylanases from the Tricoderma genus. Overall, these results could be instrumental in advancing the utilization of lignocellulosic biomass, thereby supporting sustainable bioprocessing of lignocellulosic biomass.