title: Characterization and identification of the xylanolytic enzymes from Aspergillus fumigatus Z5.
abstract: BACKGROUND
  Plant biomass, the most abundant natural material on earth, represents a vast source of food and energy in nature. As the main component of plant biomass, xylan is a complex polysaccharide comprising a linear β(1,4)-linked backbone of xylosyl residues substituted by acetyl, arabinosyl, glucuronysyl and 4-O-methylglucuronycyl residues.
  
  
  RESULTS
  Aspergillus fumigatus Z5 is an efficient plant biomass depolymerization fungus. In this study, its crude xylanolytic enzymes were characterized and identified by two-dimensional gel electrophoresis (2-DE). The optimal temperature for the crude xylanases was close to 60 °C, the highest xylanase activity was achieved at pH ranged from 3 to 6, and the crude xylanases also showed a very broad region of pH (3-11) stability. The maximal xylanase activity of 21.45 U · ml(-1) was observed in the fourth day of cultivation at 50 °C and 150 rpm with 2 % xylan as the sole carbon source. Zymogram analysis indicated that there were more than seven secreted proteins with xylanase activity. In the crude enzyme, two major endoxylanases, five cellulases and several associated enzymes were identified to be involved in the hydrolysis of polysaccharides. Of the total 13 xylanase genes in the Z5 genome, 11 were observed using q-PCR to be induced by xylan, one of which, An endo-1,4-β-xylanase with a low secretion level, was also expressed and characterized. The final hydrolysis products of xylan by crude enzyme mainly consisted of xylobiose.
  
  
  CONCLUSIONS
  This study provides a comprehensive understanding of the depolymerization of xylan by Z5 and will help to design enzymatic strategies for plant biomass utilization.
authors.affiliation: Jiangsu Key Lab and Engineering Center for Solid Organic Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China. 2011203046@njau.edu.cn.
authors.forename: Youzhi
authors.initials: Y
authors.lastname: Miao
authors.affiliation: Jiangsu Key Lab and Engineering Center for Solid Organic Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China. 844167318@qq.com.
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.affiliation: Viland Biotech Group, Qingdao, 266101, China. miaoyzaaa@hotmail.com.
authors.forename: Zhizhuang
authors.initials: Z
authors.lastname: Xiao
authors.affiliation: Jiangsu Key Lab and Engineering Center for Solid Organic Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China. soilplantmicrobe@gmail.com.
authors.forename: Qirong
authors.initials: Q
authors.lastname: Shen
authors.affiliation: Jiangsu Key Lab and Engineering Center for Solid Organic Waste Utilization, National Engineering Research Center for Organic-based Fertilizers, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China. rfzhang@njau.edu.cn.|Key Laboratory of Microbial Resources Collection and Preservation, Ministry of Agriculture, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, 100081, People's Republic of China. rfzhang@njau.edu.cn.
authors.forename: Ruifu
authors.initials: R
authors.lastname: Zhang
mesh_terms: D001232:Aspergillus fumigatus / Q000201:enzymology* / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D004795:Enzyme Stability; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D016681:Genome, Fungal; D006863:Hydrogen-Ion Concentration; D013696:Temperature; D014990:Xylans / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D014990:Xylans