Elementary mode analysis reveals that Clostridium acetobutylicum modulates its metabolic strategy under external stress

Kumar, Manish; Saini, Supreet; Gayen, Kalyan

doi:10.1039/c4mb00126e

Cited by 21 publications

(11 citation statements)

References 52 publications

(81 reference statements)

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“…Our findings support the previously suggested hypothesis (Clarke et al 1988;Millat et al 2013b) that, at least in continuous culture, a small solventogenic subpopulation is present under acidogenic conditions. Furthermore, a recently published elementary mode analysis reported that 'stressed' batch cultures of C. acetobutylicum simultaneuously exhibit acidogenic and solventogenic characteristics (Kumar et al 2014), which could result from the superposition of those coexisting acid-and solvent-forming subpopulations.…”

Section: Discussionmentioning

confidence: 99%

Coenzyme A-transferase-independent butyrate re-assimilation in Clostridium acetobutylicum—evidence from a mathematical model

Millat

Voigt

Janssen

et al. 2014

Appl Microbiol Biotechnol

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(2014) Coenzyme A-transferaseindependent butyrate re-assimilation in Clostridium acetobutylicum -evidence from a mathematical model. Applied Microbiology and Biotechnology, 98 (21 A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk Coenzyme A-transferase-independent butyrate re-assimilation in Clostridium acetobutylicum -Evidence from a mathematical model Abstract: The hetero-dimeric CoA-transferase CtfA/B is believed to be crucial for the metabolic transition from acidogenesis to solventogenesis in Clostridium acetobutylicum as part of the industrial-relevant acetone-butanol-ethanol (ABE) fermentation. Here, the enzyme is assumed to mediate re-assimilation of acetate and butyrate during a pH-induced metabolic shift and to faciliate the first step of acetone formation from acetoacetyl-CoA. However, recent investigations using phosphate-limited continuous cultures have questioned this common dogma.To adress the emerging experimental discrepancies, we investigated the mutant strain Cac-ctfA398s::CT using chemostat cultures. As a consequence of this mutation, the cells are unable to express functional ctfA and are thus lacking CoA-transferase activity. A mathematical model of the pH-induced metabolic shift, which was recently developed for the wild type, is used to analyse the observed behaviour of the mutant strain with a focus on re-assimilation activities for the two produced acids.Our theoretical analysis reveals that the ctfA mutant still re-assimilates butyrate, but not acetate. Based upon this finding, we conclude that C. acetobutylicum possesses a CoA-tranferase-independent butyrate uptake mechanism that is activated by decreasing pH levels. Furthermore, we observe that butanol formation is not inhibited under our experimental conditions, as suggested by previous batch culture experiments. In concordance with recent batch experiments, acetone formation is abolished in chemostat cultures using the ctfa mutant.

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Section: Discussionmentioning

confidence: 99%

Coenzyme A-transferase-independent butyrate re-assimilation in Clostridium acetobutylicum—evidence from a mathematical model

Millat

Voigt

Janssen

et al. 2014

Appl Microbiol Biotechnol

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“…Despite the versatility of C. acetobutylicum in producing acids, H 2 and ABE, very little is known about the dynamic regulation of metabolic networks, stoichiometry and directionality of metabolic fluxes in this bacterium [ 26 ]. It is believed that the efficiency of substrate conversion to final product solely depends on the direction of carbon intermediates and electron flow in the fermentation pathway [ 27 , 28 ].…”

Section: Resultsmentioning

confidence: 99%

Quantitative proteomic analysis of the influence of lignin on biofuel production by Clostridium acetobutylicum ATCC 824

Raut

Couto

Pham

et al. 2016

Biotechnol Biofuels

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BackgroundClostridium acetobutylicum has been a focus of research because of its ability to produce high-value compounds that can be used as biofuels. Lignocellulose is a promising feedstock, but the lignin–cellulose–hemicellulose biomass complex requires chemical pre-treatment to yield fermentable saccharides, including cellulose-derived cellobiose, prior to bioproduction of acetone–butanol–ethanol (ABE) and hydrogen. Fermentation capability is limited by lignin and thus process optimization requires knowledge of lignin inhibition. The effects of lignin on cellular metabolism were evaluated for C. acetobutylicum grown on medium containing either cellobiose only or cellobiose plus lignin. Microscopy, gas chromatography and 8-plex iTRAQ-based quantitative proteomic technologies were applied to interrogate the effect of lignin on cellular morphology, fermentation and the proteome.ResultsOur results demonstrate that C. acetobutylicum has reduced performance for solvent production when lignin is present in the medium. Medium supplemented with 1 g L−1 of lignin led to delay and decreased solvents production (ethanol; 0.47 g L−1 for cellobiose and 0.27 g L−1 for cellobiose plus lignin and butanol; 0.13 g L−1 for cellobiose and 0.04 g L−1 for cellobiose plus lignin) at 20 and 48 h, respectively, resulting in the accumulation of acetic acid and butyric acid. Of 583 identified proteins (FDR < 1 %), 328 proteins were quantified with at least two unique peptides. Up- or down-regulation of protein expression was determined by comparison of exponential and stationary phases of cellobiose in the presence and absence of lignin. Of relevance, glycolysis and fermentative pathways were mostly down-regulated, during exponential and stationary growth phases in presence of lignin. Moreover, proteins involved in DNA repair, transcription/translation and GTP/ATP-dependent activities were also significantly affected and these changes were associated with altered cell morphology.ConclusionsThis is the first comprehensive analysis of the cellular responses of C. acetobutylicum to lignin at metabolic and physiological levels. These data will enable targeted metabolic engineering strategies to optimize biofuel production from biomass by overcoming limitations imposed by the presence of lignin.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0523-0) contains supplementary material, which is available to authorized users.

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“…In aerobic metabolism, respiration is the major source of ATP production, whereas in anaerobic metabolism such as ABE fermentation of C. acetobutylicum, glycolysis and acidogenesis are the major source for ATP biosynthesis (Kumar et al, 2014). The effect of reduced intracellular ATP level on glycolysis and cell growth under anaerobic condition was analyzed.…”

Section: Reducing Cell Energy State Accelerated Glucose Utilization Amentioning

confidence: 99%

Enforcing ATP hydrolysis enhanced glycolysis and promoted solvent production under anaerobic conditions

Dai¹,

Zhu²,

Dong³

et al. 2020

Preprint

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Background The intracellular ATP level, an indicator of cellular energy state, plays a critical role in regulating the intracellular metabolic activities. The classical ATP paradox that the glycolytic rate negatively correlates with the intracellular ATP level was well studied. Reducing intracellular ATP level could stimulate the glycolytic rate, thereby enhancing products accumulation in aerobic conditions. However, there are limited studies about the effect of reducing cellular ATP level on anaerobic glycolysis and products formation.Results Taking anaerobic ABE (acetone-butanol-ethanol) fermentation by Clostridium acetobutylicum as a model, we reduced the intracellular ATP level by introducing an independent ATP hydrolysis module of F 1 -ATPase. We found that the low intracellular ATP level in C. acetobutylicum compared to that in aerobic microbes, was further reduced and the glucose uptake was remarkably enhanced, achieving a 78.8% increase of volumetric glucose utilization rate. The total solvent production was improved with increase in productivity (46.5%), titer (9.9%) and yield (14.5%) compared to control, with an early onset of solventogenesis and a shortened fermentation period. Consistently, genome-scale metabolic modeling revealed the elevated metabolic fluxes through glycolysis, TCA cycle, and pyruvate metabolism in F 1 -ATPase overexpression strain.Conclusions Decreasing the cellular energy level could further enhance the glycolytic rate at anaerobic condition and lead to significantly improvement on solvents synthesis. Our findings provide a novel strategy for improving ABE fermentation performance, which is beneficial for industrial Weizmann process. Engineering intracellular ATP level can thus be considered as a promising tool to enhance the efficiency of other anaerobic fermentation processes.

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Elementary mode analysis reveals that Clostridium acetobutylicum modulates its metabolic strategy under external stress

Cited by 21 publications

References 52 publications

Coenzyme A-transferase-independent butyrate re-assimilation in Clostridium acetobutylicum—evidence from a mathematical model

Coenzyme A-transferase-independent butyrate re-assimilation in Clostridium acetobutylicum—evidence from a mathematical model

Quantitative proteomic analysis of the influence of lignin on biofuel production by Clostridium acetobutylicum ATCC 824

Enforcing ATP hydrolysis enhanced glycolysis and promoted solvent production under anaerobic conditions

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