title: Purification and characterization studies of a thermostable β-xylanase from Aspergillus awamori.
abstract: This study presents data on the production, purification, and properties of a thermostable β-xylanase produced by an Aspergillus awamori 2B.361 U2/1 submerged culture using wheat bran as carbon source. Fractionation of the culture filtrate by membrane ultrafiltration followed by Sephacryl S-200 and Q-Sepharose chromatography allowed for the isolation of a homogeneous xylanase (PXII-1), which was 32.87 kDa according to MS analysis. The enzyme-specific activity towards soluble oat spelt xylan, which was found to be 490 IU/mg under optimum reaction conditions (50°C and pH 5.0-5.5), was 17-fold higher than that measured in the culture supernatant. Xylan reaction products were identified as xylobiose, xylotriose, and xylotetraose. K (m) values (mg ml(-1)) for soluble oat spelt and birchwood xylan were 11.8 and 9.45, respectively. Although PXII-1 showed 85% activity retention upon incubation at 50 °C and pH 5.0 for 20 days, incubation at pH 7.0 resulted in 50% activity loss within 3 days. PXII-1 stability at pH 7.0 was improved in the presence of 20 mM cysteine, which allowed for 85% activity retention for 25 days. This study on the production in high yields of a remarkably thermostable xylanase is of significance due to the central role that this class of biocatalyst shares, along with cellulases, for the much needed enzymatic hydrolysis of biomass. Furthermore, stable xylanases are important for the manufacture of paper, animal feed, and xylooligosaccharides.
authors.affiliation: Laboratory of Enzyme Technology, Biochemistry Department, Chemistry Institute, Federal University of Rio de Janeiro, Av. Athos da Silveira Ramos 149, Bloco A, Ilha do Fundão, CEP 21941-909, Rio de Janeiro, RJ, Brazil.
authors.forename: Ricardo Sposina Sobral
authors.initials: RS
authors.lastname: Teixeira
authors.forename: Félix Gonçalves
authors.initials: FG
authors.lastname: Siqueira
authors.forename: Marcelo Valle de
authors.initials: MV
authors.lastname: Souza
authors.forename: Edivaldo Ximenes Ferreira
authors.initials: EX
authors.lastname: Filho
authors.forename: Elba Pinto da Silva
authors.initials: EP
authors.lastname: Bon
mesh_terms: D000818:Animals; D001230:Aspergillus / Q000201:enzymology*; D002850:Chromatography, Gel / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000379:methods; D003545:Cysteine / Q000378:metabolism; D004043:Dietary Fiber / Q000378:metabolism; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D020536:Enzyme Activators / Q000378:metabolism; D004795:Enzyme Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D008970:Molecular Weight; D013379:Substrate Specificity; D013997:Time Factors; D014462:Ultrafiltration / Q000379:methods; D014990:Xylans / Q000378:metabolism
chemical_list: D004043:Dietary Fiber; D020536:Enzyme Activators; D014990:Xylans; D043364:Endo-1,4-beta Xylanases; D003545:Cysteine