title: Biodegradation of alkaline lignin byBacillus ligniniphilusL1.
abstract: BACKGROUND
  Lignin is the most abundant aromatic biopolymer in the biosphere and it comprises up to 30% of plant biomass. Although lignin is the most recalcitrant component of the plant cell wall, still there are microorganisms able to decompose it or degrade it. Fungi are recognized as the most widely used microbes for lignin degradation. However, bacteria have also been known to be able to utilize lignin as a carbon or energy source.Bacillus ligniniphilusL1 was selected in this study due to its capability to utilize alkaline lignin as a single carbon or energy source and its excellent ability to survive in extreme environments.
  
  
  RESULTS
  To investigate the aromatic metabolites of strain L1 decomposing alkaline lignin, GC-MS analysis was performed and fifteen single phenol ring aromatic compounds were identified. The dominant absorption peak included phenylacetic acid, 4-hydroxy-benzoicacid, and vanillic acid with the highest proportion of metabolites resulting in 42%. Comparison proteomic analysis was carried out for further study showed that approximately 1447 kinds of proteins were produced, 141 of which were at least twofold up-regulated with alkaline lignin as the single carbon source. The up-regulated proteins contents different categories in the biological functions of protein including lignin degradation, ABC transport system, environmental response factors, protein synthesis, assembly, etc.
  
  
  CONCLUSIONS
  GC-MS analysis showed that alkaline lignin degradation of strain L1 produced 15 kinds of aromatic compounds. Comparison proteomic data and metabolic analysis showed that to ensure the degradation of lignin and growth of strain L1, multiple aspects of cells metabolism including transporter, environmental response factors, and protein synthesis were enhanced. Based on genome and proteomic analysis, at least four kinds of lignin degradation pathway might be present in strain L1, including a Gentisate pathway, the benzoic acid pathway and the β-ketoadipate pathway. The study provides an important basis for lignin degradation by bacteria.
authors.affiliation: School of Environment and safty Engineering, Jiangsu University, Zhenjiang, Jiangsu China.|State Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou, Guangdong China.
authors.forename: Daochen
authors.initials: D
authors.lastname: Zhu
authors.affiliation: School of Environment and safty Engineering, Jiangsu University, Zhenjiang, Jiangsu China.
authors.forename: Peipei
authors.initials: P
authors.lastname: Zhang
authors.affiliation: School of Environment and safty Engineering, Jiangsu University, Zhenjiang, Jiangsu China.
authors.forename: Changxiao
authors.initials: C
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou, Guangdong China.
authors.forename: Weimin
authors.initials: W
authors.lastname: Zhang
authors.affiliation: School of Environment and safty Engineering, Jiangsu University, Zhenjiang, Jiangsu China.
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Sun
authors.affiliation: Biological Sciences Division and Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352 USA.
authors.forename: Wei-Jun
authors.initials: WJ
authors.lastname: Qian
authors.affiliation: Bioproducts, Sciences and Engineering Laboratory, Department of Biological Systems Engineering, Washington State University, Richland, WA 99354 USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Yang
keywords: Alkaline lignin; Bacillus ligniniphilus L1; GC–MS; Proteomics