title: Molecular and biochemical characterization of a new alkaline active multidomain xylanase from alkaline wastewater sludge.
abstract: A xylanase gene, xyn-b39, coding for a multidomain glycoside hydrolase (GH) family 10 protein was cloned from the genomic DNA of the alkaline wastewater sludge of a paper mill. Its deduced amino acid sequence of 1,481 residues included two carbohydrate-binding modules (CBM) of family CBM_4_9, one catalytic domain of GH 10, one family 9 CBM and three S-layer homology (SLH) domains. xyn-b39 was expressed heterologously in Escherichia coli, and the recombinant enzyme was purified and characterized. Xyn-b39 exhibited maximum activity at pH 7.0 and 60 °C, and remained highly active under alkaline conditions (more than 80 % activity at pH 9.0 and 40 % activity at pH 10.0). The enzyme was thermostable at 55 °C, retaining more than 90 % of the initial activity after 2 h pre-incubation. Xyn-b39 had wide substrate specificity and hydrolyzed soluble substrates (birchwood xylan, beechwood xylan, oat spelt xylan, wheat arabinoxylan) and insoluble substrates (oat spelt xylan and wheat arabinoxylan). Hydrolysis product analysis indicated that Xyn-b39 was an endo-type xylanase. The K (m) and V (max) values of Xyn-b39 for birchwood xylan were 1.01 mg/mL and 73.53 U/min/mg, respectively. At the charge of 10 U/g reed pulp for 1 h, Xyn-b39 significantly reduced the Kappa number (P < 0.05) with low consumption of chlorine dioxide alone.
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, People's Republic of China.
authors.forename: Yanyu
authors.initials: Y
authors.lastname: Zhao
authors.forename: Kun
authors.initials: K
authors.lastname: Meng
authors.forename: Huiying
authors.initials: H
authors.lastname: Luo
authors.forename: Huoqing
authors.initials: H
authors.lastname: Huang
authors.forename: Tiezheng
authors.initials: T
authors.lastname: Yuan
authors.forename: Peilong
authors.initials: P
authors.lastname: Yang
authors.forename: Bin
authors.initials: B
authors.lastname: Yao
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D004795:Enzyme Stability; D007700:Kinetics; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology; D013379:Substrate Specificity; D062065:Wastewater / Q000737:chemistry* / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D043364:Endo-1,4-beta Xylanases; D012722:Sewage; D062065:Wastewater