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摘要
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Xylanases, key enzymes for hydrolyzing xylan, have diverse industrial applications. The biopro-cessing of agricultural byproducts to produce xylanase through fermentation approaches is gain-ing importance due to its significant potential to reduce enzyme production costs. In this work, the productivity of Streptomyces thermocarboxydus TKU045 xylanase was enhanced through liquid fermentation employing wheat bran as the sole carbon source. The maximum xylanase activity (25.314 ± 1.635 U/mL) was obtained using the following optima factors: 2% (w/v) wheat bran, 1.4% (w/v) KNO3, initial pH of 9.8, incubation temperature of 37.3 °C, and incubation time of 2.2 days. Xylanase (Xyn_TKU045), of 43 kDa molecular weight was isolated from the culture super-natant and was biochemically characterized. Analysis through liquid chromatography with tan-dem mass spectrometry revealed a maximum amino acid identity of 19% with an en-do-1,4-β-xylanase produced by Streptomyces lividans. Xyn_TKU045 exhibited optimal activity at pH 6 with remarkable stability within the pH range of 6.0 to 8.0. The enzyme demonstrated maximum efficiency at 60 °C and considerable stability at ≤70 °C. Mg2+, Mn2+, Ba2+, Ca2+, 2-mercaptoethanol, Tween 20, Tween 40, and Triton X-100 positively influenced Xyn_TKU045, while Zn2+, Fe2+, Fe3+, Cu2+, and sodium dodecyl sulfate exhibited adverse impact. The kinetic properties of Xyn_TKU045 were Km of 0.628 mg/mL, kcat of 75.075 s-1 and kcat/Km of 119.617 mL mg-1s-1. Finally, Xyn_TKU045 could effectively catalyze birchwood xylan into xylotriose and xylo-biose as the major products. |