High-level production of thermotolerant β-xylosidase of Aspergillus sp. BCC125 in Pichia pastoris: Characterization and its application in ethanol production

A gene coding for thermotolerant β-xylosidase from Aspergillus sp. BCC125 was characterized. The recombinant enzyme was expressed in methylotrophic yeast Pichia pastoris KM71 and especially high yield of secreted enzyme was obtained. β-xylosidase possessed high enzyme efficiency (Kcat/Km = 198.8 mM−1 s−1) toward pNP-β-D-xylopyranoside (pNPβX) with optimal temperature and pH for activity of 60 °C and pH 4.0–5.0, respectively. The identified β-xylosidase showed clear synergism with previously identified xylanase for hydrolysis of xylan in vitro as well as simultaneous saccharification and fermentation process (SSF) in vivo with Pichia stipitis.