title: Site-directed mutagenesis and thermostability of xylanase XYNB from Aspergillus niger 400264.
abstract: Xylanase is one of the most important hemicellulases in industry. However, its low thermostability limits its applications. In this study, one thermostable xylanase-producing strain 400264 was obtained from screening 11 Aspergillus niger strains (producing thermotolerant xylanase), and the optimum temperature of crude xylanase extracted from it was 55°C. Original activity of the crude xylanase is 64% at 60°C and 55% at 85°C with an incubation time of 30 min, respectively. After the expression of recombinant xylanase gene (xynA/xynB), the XYNB (xylanase B) showed higher thermostability than XYNA (xylanase A). Recombinant enzyme XYNB retained 94% of its activity for 10 min at 85°C, while XYNA with no activity left. Site-directed mutagenesis was performed to replace Ala33 of XYNB by Ser33 resulting 19% decrease in enzyme activity after incubating at 85°C for 30 min. It suggested that the Ala33 residue may have a certain effect on the thermophilic adaptation of xylanase.
authors.affiliation: Microbiology and Metabolic Engineering Key Laboratory of Sichuan Province, College of Life Science, Sichuan University, Sichuan, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Xie
authors.forename: Lingling
authors.initials: L
authors.lastname: Song
authors.forename: XinRan
authors.initials: X
authors.lastname: Li
authors.forename: XiuLi
authors.initials: X
authors.lastname: Yi
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Dairong
authors.initials: D
authors.lastname: Qiao
authors.forename: Yi
authors.initials: Y
authors.lastname: Cao
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004795:Enzyme Stability; D006358:Hot Temperature; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D050505:Mutant Proteins; D011994:Recombinant Proteins; D043364:Endo-1,4-beta Xylanases