A highly efficient thermostable xylanase from Thermomyces dupontii J22: purification, properties and its application in xylan film modification.

Abstract

This study quantified the production, purification, enzymatic characteristics, and xylan film modification performance of extracellular xylanase (XynA) from Thermomyces dupontii J22. The thermostable xylanase activity attained 768.32 U/mL in the fermentation broth via submerged fermentation using corn cob as the substrate. XynA was purified to electrophoretic homogeneity by ammonium sulfate precipitation and DEAE-Cellulose chromatography, achieving a final specific activity of 59019.65 U/mg, a 26.18-fold purification, and a recovery yield of 40.52%. The molecular weight of XynA was approximately 24 kDa. XynA displayed an optimal pH of 7.5 and optimal temperature of 75 ℃, and was rapidly thermally activated at 55-60 ℃ while retaining high activity under alkaline conditions. The K _m values for beechwood and wheat xylan were 2.50 and 3.21 mg/mL, respectively, with corresponding V _max values of 138.90 and 111.30 µmol·min^- 1. XynA activity was enhanced by Na⁺, K⁺, Mg²⁺, Triton X-100, and β-mercaptoethanol. In xylan film modification, XynA treatment reduced tensile strength by only 16.88%, compared to a 56.25% reduction with NaOH treatment, while preserving a Young's modulus of 4.05 GPa. Atomic force microscopy and X-ray diffraction showed that XynA generated a uniform grid microstructure on film surfaces without severe structural damage. These results demonstrate that XynA is a highly efficient thermostable xylanase suitable for mild, eco-friendly functional modification of xylan-based biomaterials.