Abstract
BackgroundClostridium 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. ResultsBased 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.ConclusionsThe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0436-4) contains supplementary material, which is available to authorized users.
Highlights
Clostridium acetobutylicum is one of the most important butanol producing strains
We focused on the intracellular metabolic profiling and the pathway analysis of C. acetobutylicum to explore the effect of key metabolites on the strain growth and butanol synthesis systematically
Fermentation profiles for cell growth and butanol production As shown in Fig. 1, the typical acidogensis period stretched from the lag to the mid-log phase (0–32 h), and the solventogensis spanned from the mid-log phase to stationary, and to the decline phase (32–76 h)
Summary
Clostridium acetobutylicum is one of the most important butanol producing strains. 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. As a species of strictly anaerobic bacteria, Clostridia catabolizes a variety of sugars for cellular events, accompanying with the production of toxic metabolites, such as acetic acid, butyric acid, ethanol, butanol and acetone, which seriously inhibit cell growth and butanol production due to the acidified intracellular environment and the insufficient ATP production capacity [6], and even lead to the “acid crash” [7]. It is critical to maintain high activity of the strain and improve the fermentation performance for butanol production
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