Thermostable β-xylosidase from Aspergillus fumigatus: Purification, characterization and potential application in lignocellulose bioethanol production

Thermostable β-xylosidase produced by Aspergillus fumigatus (A. fumigatus) XC6 can be efficiently extracted and purified via an aqueous two-phase system consisting of 20% (m/v) PEG 2000 and 25% (m/v) NaH₂PO₄ with a purification factor of approximately 16. Maximum activity of the purified β-xylosidase was observed at 75 °C and pH 4.5 using p-nitrophenyl-β-Dxylopyranoside (pNPXyl) as a substrate. The thermal stability of purified β-xylosidase is higher than that of compared fungal strains. Thermotolerant kluyveromyces marxianus was directly added to a fermentation system composed of 50 g L^‑1 rice straw and 10 g L^‑1 (NH₄)₂SO₄, but prehydrolysis with A. fumigatus XC6 pellets for 12 h yielded 11.2 g L^‑1 ethanol within 36 h, an amount 80% of the theoretical value. The results indicated that A. fumigatus XC6 β-xylosidase is a thermostable enzyme with high xylose production activity, and may have promising industrial application for cost-effective lignocellulosic bioethanol production.