title: Cloning, expression, and characterization of a novel alkali-tolerant xylanase from alkaliphilic Bacillus sp. SN5.
abstract: A xylanase gene (xyn11A) was cloned from the genomic library of alkalophilic Bacillus sp. SN5. It encoded a polypeptide of 366 amino acids, consisting of a family 11 glycoside hydrolase, a short linker region, and a family 36 carbohydrate-binding module (CBM). The intact xylanase Xyn11A and the CBM-linker-truncated Xyn11A-LC were expressed in Escherichia coli BL21 (DE3). Both purified recombinant proteins exhibited the highest activity at 55 °C. The optimal pH for Xyn11A activity was 7.5, whereas Xyn11A-LC showed a broad pH profile (>80% activity at pH 5.5-8.5) with optimal activity at pH 5.5 and 7.5-8.0. They had high alkali tolerance, retaining over 80% residual activity after preincubation at pH 8.5-11.0 at 37 °C for 1 H. Xyn11A-LC showed better thermal stability, lower affinity, and lower catalytic activity to insoluble xylan than Xyn11A, whereas its specific activity for soluble beechwood xylan (4,511.9 U/mg) was greater than that of Xyn11A (3,136.4 U/mg). These results implied that the CBM of Xyn11A could change the enzymatic properties and play a role in degrading insoluble xylan. Xyn11A-LC is a family 11 alkali-tolerant cellulase-free xylanase with high specific activity, which qualifies it as a potential candidate for industrial applications, especially in the paper industry.
authors: National Engineering Lab for Industrial Enzymes, Institute of Microbiology, Chinese Academy of Sciences, Beijing, People's Republic of China; National Engineering Lab for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, People's Republic of China; College of Life Science, Shanxi Normal University, Linfen, People's Republic of China.
authors: Wenqin
authors: W
authors: Bai
authors: Yanfen
authors: Y
authors: Xue
authors: Cheng
authors: C
authors: Zhou
authors: Yanhe
authors: Y
authors: Ma
mesh_terms: D000468:Alkalies / Q000737:chemistry*; D001407:Bacillus / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular / Q000379:methods*; D004789:Enzyme Activation; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D015202:Protein Engineering / Q000379:methods; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D014995:Xylosidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D000468:Alkalies; D011994:Recombinant Proteins; D014995:Xylosidases
keywords: alkali tolerance; carbohydrate-binding module; catalytic domain; xylanase