title: Direct cloning, expression of a thermostable xylanase gene from the metagenomic DNA of cow dung compost and enzymatic production of xylooligosaccharides from corncob.
abstract: OBJECTIVE
  To acquire a thermostable xylanase, that is suitable for xylooligosaccharide production from pretreated corncobs, the metagenomic method was used to obtain the gene from an uncultured environmental microorganism.
  
  
  RESULTS
  A thermostable xylanase-encoding gene (xyn10CD18) was cloned directly from the metagenomic DNA of cow dung compost. When xyn10CD18 was expressed in Bacillus megaterium MS941, extracellular xylansae activity at 106 IU/ml was achieved. The purified recombinant Xyn10CD18 was optimally active at pH 7 and 75 °C as measured over 10 min. It retained over 55% of its initial activity at 70 °C and pH 7 after 24 h. Its action on birchwood xylan for 18 h liberated xylooligosaccharides with 2°-4° of polymerization, with xylobiose and xylotetraose as the main products. When pretreated corncobs were hydrolyzed by Xyn10CD18 for 18 h, the xylooligosaccharides (DP 2-4) products increased to 80% and the xylose was just increased by 3%.
  
  
  CONCLUSIONS
  Xyn10CD18 is a thermostable endoxylanase and is a promising candidate for biomass conversion and xylooligosaccharide production.
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology, Education Ministry of China, No. 29, 13 Main Street, Tianjin Economic and Technological Development Zone, Tianjin, 300457, China.
authors.forename: Ming-zhe
authors.initials: MZ
authors.lastname: Sun
authors.forename: Hong-chen
authors.initials: HC
authors.lastname: Zheng
authors.forename: Ling-cai
authors.initials: LC
authors.lastname: Meng
authors.forename: Jun-she
authors.initials: JS
authors.lastname: Sun
authors.forename: Hui
authors.initials: H
authors.lastname: Song
authors.forename: Yun-juan
authors.initials: YJ
authors.lastname: Bao
authors.forename: Hai-sheng
authors.initials: HS
authors.lastname: Pei
authors.forename: Zheng
authors.initials: Z
authors.lastname: Yan
authors.forename: Xiu-qing
authors.initials: XQ
authors.lastname: Zhang
authors.forename: Jing-sheng
authors.initials: JS
authors.lastname: Zhang
authors.forename: Yi-han
authors.initials: YH
authors.lastname: Liu
authors.forename: Fu-ping
authors.initials: FP
authors.lastname: Lu
mesh_terms: D000818:Animals; D002417:Cattle; D003001:Cloning, Molecular / Q000379:methods*; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004795:Enzyme Stability; D005965:Glucuronates / Q000096:biosynthesis*; D054892:Metagenome; D009844:Oligosaccharides / Q000096:biosynthesis*; D012988:Soil Microbiology; D013696:Temperature; D003313:Zea mays / Q000737:chemistry
chemical_list: D005965:Glucuronates; D009844:Oligosaccharides; C570991:xylooligosaccharide; D043364:Endo-1,4-beta Xylanases