title: Thermostable and alkalistable endoxylanase of the extremely thermophilic bacterium Geobacillus thermodenitrificans TSAA1: cloning, expression, characteristics and its applicability in generating xylooligosaccharides and fermentable sugars.
abstract: Xylanase encoding gene (1,224 bp) from Geobacillus thermodenitrificans was cloned in pET28a (+) vector and successfully expressed in Escherichia coli BL21 (DE3). The deduced amino acid sequence analysis revealed homology with that of glycosyl hydrolase (GH) 10 family with a high molecular mass (50 kDa). The purified recombinant xylanase is optimally active at pH 9.0 and 70 °C with T(1/2) of 10 min at 80 °C, and retains greater than 85 % activity after exposure to 70 °C for 180 min. The enzyme liberates xylose as well as xylooligosaccharides from birchwood xylan and agro-residues, and therefore, this is an endoxylanase. The xylan hydrolytic products (xylooligosaccharides, xylose, and xylobiose) find application as prebiotics and in the production of bioethanol. The xylanase being thermostable and alkalistable, it has released chromophores and phenolics from the residual lignin of pulps, suggesting its utility in mitigating chlorine requirement in pulp bleaching.
authors.affiliation: Department of Microbiology, University of Delhi South Campus, New Delhi 110021, India.
authors.forename: Digvijay
authors.initials: D
authors.lastname: Verma
authors.forename: Ashima
authors.initials: A
authors.lastname: Anand
authors.forename: T
authors.initials: T
authors.lastname: Satyanarayana
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D003001:Cloning, Molecular; D004187:Disaccharides / Q000737:chemistry; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000235:genetics; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D005285:Fermentation; D015870:Gene Expression; D056506:Geobacillus / Q000737:chemistry* / Q000201:enzymology / Q000235:genetics; D005965:Glucuronates / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D009844:Oligosaccharides / Q000737:chemistry*; D016366:Open Reading Frames; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D013696:Temperature; D014990:Xylans / Q000737:chemistry; D014994:Xylose / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D004187:Disaccharides; D005965:Glucuronates; D009844:Oligosaccharides; D011994:Recombinant Proteins; D014990:Xylans; C570991:xylooligosaccharide; D014994:Xylose; D043364:Endo-1,4-beta Xylanases; C004173:xylobiose