title: Production of beta-xylosidase activity by Trichoderma harzianum strains.
abstract: Nine Trichoderma harzianum strains were screened for beta-xylosidase activity when grown in solid-state cultures on media containing wheat bran as the carbon source. All strains produced beta-xylosidase activity, the most active being in extracts of cultures of T. harzianum strain 4. A beta-xylosidase was purified by ammonium sulfate precipitation, ultrafiltration, gel filtration, and ion exchange chromatography from solid-state cultures of T. harzianum strain C. Enzyme preparations yielded a single band when stained for protein following eletrophoresis. The molecular weight value, calculated following SDS-PAGE, was determined to be 60 kDa. beta-Xylosidase was most active at pH 4.0-4.5 and 70 degrees C. This enzyme had a Km value of 0.053 mM. The phenol-sulfuric acid method detected the presence of a small amount of carbohydrate in the purified enzyme preparation. beta-Xylosidase was active against some p-nitrophenylglycosides. The enzyme was inactive against xylan and PNPG. beta-xylosidase activity was inhibited by xylose and SDS. Iodoacetamide, dithiothreitol, gluconolactone, glucose, and mercuric chloride failed to inactivate this enzyme's activity. A synergistic effect was observed when beta-xylosidase from T. harzianum strain C and beta-xylanase from Aspergillus fumigatus were incubated with pretreated arabinoxylan.
authors.affiliation: Laboratório de Enzimologia, Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, CEP 70910-900, Brasil.
authors.forename: F
authors.initials: F
authors.lastname: de A Ximenes
authors.forename: F Q
authors.initials: FQ
authors.lastname: de Paula Silveira
authors.forename: E X
authors.initials: EX
authors.lastname: Filho
mesh_terms: D008970:Molecular Weight; D013045:Species Specificity; D014242:Trichoderma / Q000201:enzymology*; D014995:Xylosidases / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase