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Process Engineering of the Acetone-Ethanol-Butanol (ABE) Fermentation in a Linear and Feedback Loop Cascade of Continuous Stirred Tank Reactors: Experiments, Modeling and Optimization

Department of Bioprocess Engineering, Beuth University of Applied Sciences Berlin, Seestraße 64, 13347 Berlin, Germany
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Author to whom correspondence should be addressed.
Academic Editor: Martin Olazar
Fuels 2021, 2(2), 108-129; https://doi.org/10.3390/fuels2020007
Received: 24 January 2021 / Revised: 13 February 2021 / Accepted: 20 February 2021 / Published: 1 April 2021
(This article belongs to the Special Issue Biomass Conversion to Biofuels)
The production of butanol, acetone and ethanol by Clostridium acetobutylicum is a biphasic fermentation process. In the first phase the carbohydrate substrate is metabolized to acetic and butyric acid, in the following second phase the product spectrum is shifted towards the economically interesting solvents. Here we present a cascade of six continuous stirred tank reactors (CCSTR), which allows performing the time dependent metabolic phases of an acetone-butanol-ethanol (ABE) batch fermentation in a spatial domain. Experimental data of steady states under four operating conditions—with variations of the pH in the first bioreactor between 4.3 and 5.6 as well as the total dilution rate between 0.042 h−1 and 0.092 h−1—were used to optimize and validate a corresponding mathematical model. Beyond a residence time distribution representation and substrate, biomass and product kinetics this model also includes the differentiation of cells between the metabolic states. Model simulations predict a final product concentration of 8.2 g butanol L−1 and a productivity of 0.75 g butanol L−1 h−1 in the CCSTR operated at pHbr1 of 4.3 and D = 0.092 h−1, while 31% of the cells are differentiated to the solventogenic state. Aiming at an enrichment of solvent-producing cells, a feedback loop was introduced into the cascade, sending cells from a later state of the process (bioreactor 4) back to an early stage of the process (bioreactor 2). In agreement with the experimental observations, the model accurately predicted an increase in butanol formation rate in bioreactor stages 2 and 3, resulting in an overall butanol productivity of 0.76 g L−1 h−1 for the feedback loop cascade. The here presented CCSTR and the validated model will serve to investigate further ABE fermentation strategies for a controlled metabolic switch. View Full-Text
Keywords: biofuel; biobutanol; ABE-fermentation; clostridium; continuous reactor; process model; multi stage process biofuel; biobutanol; ABE-fermentation; clostridium; continuous reactor; process model; multi stage process
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MDPI and ACS Style

Karstens, K.; Trippel, S.; Götz, P. Process Engineering of the Acetone-Ethanol-Butanol (ABE) Fermentation in a Linear and Feedback Loop Cascade of Continuous Stirred Tank Reactors: Experiments, Modeling and Optimization. Fuels 2021, 2, 108-129. https://doi.org/10.3390/fuels2020007

AMA Style

Karstens K, Trippel S, Götz P. Process Engineering of the Acetone-Ethanol-Butanol (ABE) Fermentation in a Linear and Feedback Loop Cascade of Continuous Stirred Tank Reactors: Experiments, Modeling and Optimization. Fuels. 2021; 2(2):108-129. https://doi.org/10.3390/fuels2020007

Chicago/Turabian Style

Karstens, Katja, Sergej Trippel, and Peter Götz. 2021. "Process Engineering of the Acetone-Ethanol-Butanol (ABE) Fermentation in a Linear and Feedback Loop Cascade of Continuous Stirred Tank Reactors: Experiments, Modeling and Optimization" Fuels 2, no. 2: 108-129. https://doi.org/10.3390/fuels2020007

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