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=198.8mM(-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.