title: Integrated intracellular metabolic profiling and pathway analysis approaches reveal complex metabolic regulation by Clostridium acetobutylicum.
abstract: BACKGROUND
  Clostridium acetobutylicum is one of the most important butanol producing strains. However, environmental stress in the fermentation process usually leads to a lower yield, seriously hampering its industrialization. In order to systematically investigate the key intracellular metabolites that influence the strain growth and butanol production, and find out the critical regulation nodes, an integrated analysis approach has been carried out in this study.
  
  
  RESULTS
  Based on the gas chromatography-mass spectrometry technology, the partial least square discriminant analysis and the pathway analysis, 40 metabolic pathways linked with 43 key metabolic nodes were identified. In-depth analysis showed that lots of amino acids metabolism promoted cell growth but exerted slight influence on butanol production, while sugar metabolism was favorable for cell growth but unfavorable for butanol synthesis. Besides, both lysine and succinic acid metabolism generated a complex effect on the whole metabolic network. Dicarboxylate metabolism exerted an indispensable role on cell growth and butanol production. Subsequently, rational feeding strategies were proposed to verify these conclusions and facilitate the butanol biosynthesis. Feeding amino acids, especially glycine and serine, could obviously improve cell growth while yeast extract, citric acid and ethylene glycol could significantly enhance both growth and butanol production.
  
  
  CONCLUSIONS
  The feeding experiment confirmed that metabolic profiling combined with pathway analysis provided an accurate, reasonable and practical approach to explore the cellular metabolic activity and supplied a basis for improving butanol production. These strategies can also be extended for the production of other important bio-chemical compounds.
authors.affiliation: Key Laboratory of System Bioengineering (Tianjin University), Ministry of Education, Tianjin, 300072, People's Republic of China. liuhuan@tju.edu.cn.|SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, People's Republic of China. liuhuan@tju.edu.cn.
authors.forename: Huanhuan
authors.initials: H
authors.lastname: Liu
authors.affiliation: TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, 300457, People's Republic of China. huangdi@nankai.edu.cn.|Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, 300071, People's Republic of China. huangdi@nankai.edu.cn.|Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, 300457, People's Republic of China. huangdi@nankai.edu.cn.
authors.forename: Di
authors.initials: D
authors.lastname: Huang
authors.affiliation: Key Laboratory of System Bioengineering (Tianjin University), Ministry of Education, Tianjin, 300072, People's Republic of China. jpwen@tju.edu.cn.|SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, People's Republic of China. jpwen@tju.edu.cn.
authors.forename: Jianping
authors.initials: J
authors.lastname: Wen
mesh_terms: D020001:1-Butanol / Q000378:metabolism; D046969:Clostridium acetobutylicum / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D005285:Fermentation; D042541:Intracellular Space / Q000378:metabolism*; D016018:Least-Squares Analysis; D053858:Metabolic Networks and Pathways; D055442:Metabolome; D055432:Metabolomics / Q000379:methods*
chemical_list: D020001:1-Butanol