title: Purification and characterization of thermostable xylanase and beta-xylosidase by the thermophilic bacterium Bacillus thermantarcticus.
abstract: Bacillus thermantarcticus, a thermophilic bacterium isolated from Antarctic geothermal soil near the crater of Mount Melbourne, produced extracellular xylanase (1,4-beta-D-xylan xylanohydrolase; E.C. 3.2.1.8) and beta-xylosidase (1,4-beta-D-xylan xylohydrolase; E.C. 3.2.1.37). Each extracellular enzyme was separated by gel filtration with Sephacryl S-200 and further purified to homogeneity (119-fold for xylanase and 160-fold for beta-xylosidase). The optimum temperatures were 80 degrees C for xylanase at pH 5.6 and 70 degrees C for beta-xylosidase at pH 6.0. The isoelectric points and molecular masses were 4.8 and 45 kDa for xylanase and 4.2 and 150 kDa for beta-xylosidase, respectively. Xylanase was stable at 60 degrees C for 24 h, whereas it showed a half life at 70 degrees C of 24 h and at 80 degrees C for 50 min. beta-xylosidase activity did not decrease after 1 h at 60 degrees C. Km of xylanase for xylan was 1.6 mg/ml, Km of beta-xylosidase for p-nitrophenyl-beta-D-xylopyranoside was 0.5 mM and for o-nitrophenyl-beta-D-xylopyranoside was 1.28 mM. The action of two enzymes on xylan gave only xylose.
authors.affiliation: Istituto di Chimica Biomolecolare, CNR, Via Campi Flegrei, 34, 80078 Pozzuoli, Napoli, Italy.
authors.forename: Licia
authors.initials: L
authors.lastname: Lama
authors.forename: Valeria
authors.initials: V
authors.lastname: Calandrelli
authors.forename: Agata
authors.initials: A
authors.lastname: Gambacorta
authors.forename: Barbara
authors.initials: B
authors.lastname: Nicolaus
mesh_terms: D001411:Geobacillus stearothermophilus / Q000201:enzymology* / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D008970:Molecular Weight; D014990:Xylans / Q000378:metabolism; D014995:Xylosidases / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D014990:Xylans; D006026:Glycoside Hydrolases; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase