title: Characteristics of thermostable endoxylanase and β-xylosidase of the extremely thermophilic bacterium Geobacillus thermodenitrificans TSAA1 and its applicability in generating xylooligosaccharides and xylose from agro-residues.
abstract: An extremely thermophilic bacterial isolate that produces a high titer of thermostable endoxylanase and β-xylosidase extracellularly in an inducible manner was identified as Geobacillus thermodenitrificans TSAA1. The distinctive features of this strain are alkalitolerance and halotolerance. The endoxylanase is active over a broad range of pH (5.0-10.0) and temperatures (30-100 °C) with optima at pH 7.5 and 70 °C, while β-xylosidase is optimally active at pH 7.0 and 60 °C. The T 1/2 values of the endoxylanase and β-xylosidase are 30 min at 80 °C, and 180 min at 70 °C, respectively. The endoxylanase activity is stimulated by dithiothreitol, but inhibited strongly by EDAC and Woodward's reagent K. N-BS and DEPC strongly inhibited β-xylosidase. MALDI-ToF (MS/MS) analysis of tryptic digest of β-xylosidase revealed similarity with that of G. thermodenitrificans NG 80-2, and suggested that this belongs to the GH 52 glycosyl hydrolase super family. The action of endoxylanase on birch wood xylan and agro-residues such as wheat bran and wheat straw liberated xylooligosaccharides similar to endoxylanases of the family 10 glycoside hydrolases, while the enzyme preparation having both endoxylanase and β-xylosidase liberated xylose as main hydrolysis product.
authors.affiliation: Department of Microbiology, University of Delhi South Campus, New Delhi 110021, India. anand.ashima@yahoo.in
authors.forename: Ashima
authors.initials: A
authors.lastname: Anand
authors.forename: Vikash
authors.initials: V
authors.lastname: Kumar
authors.forename: T
authors.initials: T
authors.lastname: Satyanarayana
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D004043:Dietary Fiber; D004229:Dithiothreitol / Q000494:pharmacology; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D004795:Enzyme Stability; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000494:pharmacology; D056506:Geobacillus / Q000201:enzymology*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007555:Isoxazoles / Q000494:pharmacology; D007700:Kinetics; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism; D014994:Xylose / Q000737:chemistry / Q000378:metabolism*; D014995:Xylosidases / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004043:Dietary Fiber; D007555:Isoxazoles; D009844:Oligosaccharides; C009686:N-ethyl-5-phenylisoxazolium-3'-sulfonate; D014994:Xylose; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase; D043364:Endo-1,4-beta Xylanases; D005022:Ethyldimethylaminopropyl Carbodiimide; D004229:Dithiothreitol