A xylose-tolerant β-xylosidase from Paecilomyces thermophila: Characterization and its co-action with the endogenous xylanase

An extracellular β-xylosidase from the thermophilic fungus Paecilomyces thermophila J18 was purified 31.9-fold to homogeneity with a recovery yield of 2.27% from the cell-free culture supernatant. It appeared as a single protein band on SDS–PAGE with a molecular mass of approx 53.5 kDa. The molecula...

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Bibliographic Details
Published in:Bioresource technology 2008-09, Vol.99 (13), p.5402-5410
Main Authors: Yan, Q.J., Wang, L., Jiang, Z.Q., Yang, S.Q., Zhu, H.F., Li, L.T.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Characterization
Electrophoresis, Polyacrylamide Gel
Endo-1,4-beta Xylanases - metabolism
Enzyme Stability
Fundamental and applied biological sciences. Psychology
Hydrogen-Ion Concentration
Kinetics
Molecular Weight
Paecilomyces
Paecilomyces - enzymology
Paecilomyces - growth & development
Paecilomyces thermophila
Substrate Specificity
Synergistic action
Triticum
Xylose - metabolism
Xylose-tolerant
Xylosidases - isolation & purification
Xylosidases - metabolism
β-Xylosidase
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Summary:An extracellular β-xylosidase from the thermophilic fungus Paecilomyces thermophila J18 was purified 31.9-fold to homogeneity with a recovery yield of 2.27% from the cell-free culture supernatant. It appeared as a single protein band on SDS–PAGE with a molecular mass of approx 53.5 kDa. The molecular mass of β-xylosidase was 51.8 kDa determined by Superdex 75 gel filtration. The enzyme was a glycoprotein with a carbohydrate content of 61.5%. It exhibited an optimal activity at 55 °C and pH 6.5, respectively. The enzyme was stable in the range of pH 6.0–9.0 and at 55 °C. The purified enzyme hydrolyzed xylobiose and higher xylooligosaccharides but was inactive against xylan substrates. It released xylose from xylooligosaccharides with a degree of polymerization ranging between 2 and 5. The rate of xylose released from xylooligosaccharides by the purified enzyme increased with increasing chain length. It had a K m of 4.3 mM for p-nitrophenol-β- d-xylopyranoside and was competitively inhibited by xylose with a K i value of 139 mM. Release of reducing sugars from xylans by a purified xylanase produced by the same organism increased markedly in the presence of β-xylosidase. During 24-hour hydrolysis, the amounts of reducing sugar released in the presence of added β-xylosidase were about 1.5–1.73 times that of the reaction employing the xylanase alone. This is the first report on the purification and characterization of a β-xylosidase from Paecilomyces thermophila.
ISSN:0960-8524
1873-2976
DOI:10.1016/j.biortech.2007.11.033