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. 2016 Aug 3;11(8):e0158243.
doi: 10.1371/journal.pone.0158243. eCollection 2016.

Kinetic Study of Acetone-Butanol-Ethanol Fermentation in Continuous Culture

Edward A Buehler  1 , Ali Mesbah  1
Affiliations

Kinetic Study of Acetone-Butanol-Ethanol Fermentation in Continuous Culture

Edward A Buehler et al. PLoS One. .

Abstract

Acetone-butanol-ethanol (ABE) fermentation by clostridia has shown promise for industrial-scale production of biobutanol. However, the continuous ABE fermentation suffers from low product yield, titer, and productivity. Systems analysis of the continuous ABE fermentation will offer insights into its metabolic pathway as well as into optimal fermentation design and operation. For the ABE fermentation in continuous Clostridium acetobutylicum culture, this paper presents a kinetic model that includes the effects of key metabolic intermediates and enzymes as well as culture pH, product inhibition, and glucose inhibition. The kinetic model is used for elucidating the behavior of the ABE fermentation under the conditions that are most relevant to continuous cultures. To this end, dynamic sensitivity analysis is performed to systematically investigate the effects of culture conditions, reaction kinetics, and enzymes on the dynamics of the ABE production pathway. The analysis provides guidance for future metabolic engineering and fermentation optimization studies.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. The metabolic pathway of Clostridium acetobutylicum (adopted from [25]).
Fig 2
Fig 2. Comparison between model predictions and experimental time-course data (from [44]) for the key metabolites in continuous C. acetobutylicum culture.
Fig 3
Fig 3. Biomass concentration profiles during the two metabolic phases of fermentation.
The pH level 4.5 corresponds to the stationary biomass concentration during solventogenesis, while the pH level 6.0 corresponds to the exponential biomass growth during acidogenesis.
Fig 4
Fig 4. Butanol and butyrate concentration profiles for different inlet glucose concentration levels.
Due to the product inhibition effect, the concentration of butanol and butyrate asymptotically reaches a maximum level as the inlet glucose concentration increases.
Fig 5
Fig 5. Concentration profiles for ABE solvents and acids at acidogenic pH (6.0) and solventogenic pH (4.5).
At time 500 hr the culture pH is switched from 6.0 to 4.5 to demonstrate the shift from acidogenesis to solventogenesis.
Fig 6
Fig 6. The effect of dilution rate and culture pH on steady-state butanol productivity.
Fig 7
Fig 7. Steady-state butanol productivity as a function of dilution rate and culture pH.
Fig 8
Fig 8. Normalized dynamic sensitivity of acetone, butanol, and ethanol concentration to the enzyme production rates.
Fig 9
Fig 9. Normalized steady-state sensitivity of acetone, butanol, and ethanol concentration to different reaction kinetics along the metabolic pathway.
Fig 10
Fig 10. Normalized dynamic sensitivity of butanol concentration to the most sensitive reaction kinetics.
See this image and copyright information in PMC

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