Characterization of a novel thermostable and xylose-tolerant GH 39 β-xylosidase from Dictyoglomus thermophilum

In this paper, a novel β-xylosidase, Xln-DT, from Dictyoglomus thermophilum DSM 3960 was cloned and expressed in E. coli BL21. The phylogenetic analysis showed that Xln-DT had a distant relationship with other β-xylosidases belonging to the GH 39 family. The enzymatic characterization displayed that Xln-DT had a high optimal temperature and a partially neutral pH, and the thermostability was improved by the ion Fe. Most importantly, there was no inhibition at 1 M xylose, and there was a 40% inhibition at 3 M xylose. Compared with the other β-xylosidases, Xln-DT possessed higher efficiency in xylobiose hydrolysis and had efficiency for biotransforming notoginsenoside R1 and ASI by removing the 1, 2 glycosidic bond linked to the C-6 and C-3 carbons. This study indicates that recombinant Xln-DT would be suitable for producing natural medicine, such as ginsenoside Rg1 and CA.