title: Purification and characterization of two xylanases from alkalophilic and thermophilic Bacillus licheniformis 77-2.
abstract: The alkalophilic bacteria Bacillus licheniformis 77-2 produces significant quantities of thermostable cellulase-free xylanases. The crude xylanase was purified to apparent homogeneity by gel filtration (G-75) and ionic exchange chromatography (carboxymethyl sephadex, Q sepharose, and Mono Q), resulting in the isolation of two xylanases. The molecular masses of the enzymes were estimated to be 17 kDa (X-I) and 40 kDa (X-II), as determined by SDS-PAGE. The Km and V(max) values were 1.8 mg/mL and 7.05 U/mg protein (X-I), and 1.05 mg/mL and 9.1 U/mg protein (X-II). The xylanases demonstrated optimum activity at pH 7.0 and 8.0-10.0 for xylanase X-I and X-II, respectively, and, retained more than 75% of hydrolytic activity up to pH 11.0. The purified enzymes were most active at 70 and 75 degrees C for X-I and X-II, respectively, and, retained more than 90% of hydrolytic activity after 1 h of heating at 50 degrees C and 60 degrees C for X-I and X-II, respectively. The predominant products of xylan hydrolysates indicated that these enzymes were endoxylanases.
authors.affiliation: UNESP - State University of São Paulo, Biochemistry and Applied Microbiology Laboratory, Rua Cristóvão Colombo n 2265, 15054-000, São José do Rio Preto, SP, Brazil.
authors.forename: Valquiria B
authors.initials: VB
authors.lastname: Damiano
authors.forename: Richard
authors.initials: R
authors.lastname: Ward
authors.forename: Eleni
authors.initials: E
authors.lastname: Gomes
authors.forename: Heloiza Ferreira
authors.initials: HF
authors.lastname: Alves-Prado
authors.forename: Roberto
authors.initials: R
authors.lastname: Da Silva
mesh_terms: D001407:Bacillus / Q000145:classification* / Q000201:enzymology*; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D004789:Enzyme Activation; D004795:Enzyme Stability; D008970:Molecular Weight; D012680:Sensitivity and Specificity; D013045:Species Specificity; D013379:Substrate Specificity
chemical_list: D043364:Endo-1,4-beta Xylanases