A novel extractive fermentation for the production of acetone-butanol by Clostridium acetobutylicum
Abstract
A novel process which integrates acetone-butanol fermentation with a simultaneous removal of toxic products by using polyvinylpyridine as an adsorbent was developed. The mathematical modeling and optimization of the integrated process were attempted. A productivity of 0.92 g/l/h and a final product concentration of 29.8 g/l were achieved in batch fermentation coupled with in situ batch adsorption. As compared to a controlled traditional batch acetonebutanol fermentation, the productivity and final product concentration were increased by 130% and 54%, respectively. In order to maximize the productivity and the overall product concentration, repeated fed-batch fermentations with continuous cyclic adsorptive separation were conducted. As compared to the controlled traditional batch acetone-butanol fermentation, the continuous extractive fed-batch fermentation showed increases in the final product concentration by 144% and in the fermentor productivity by 300% on average over a period of 240 hours of operation. The adsorbent polyvinylpyridine (PVP) was characterized in terms of equilibrium adsorption isotherm, adsorption dynamics, desorption dynamics and competitive adsorption. The Langmuir adsorption isotherm theory was applied and extended to describe the multicomponent adsorption process occurring in the fermentation broth and a multicomponent adsorption isotherm model was determined according to the experimental data. The kinetics of acetone-butanol fermentation was intensively studied in terms of the effects of environmental factors on cell growth kinetics, inhibition kinetics and product formation kinetics. It has been shown that the inhibition was the combined effect of butanol, acetate, butyrate and pH. The equation describing the combined inhibitory effect on the cell growth was statistically analyzed and mathematically expressed to have a parabolic type equation. The cell growth kinetics could be represented by the Monod equation modified with the inhibition function. A mathematical model representing the two distinct states of the culture, accounting for the combined inhibitory effect of the products and pH, and coupling the multicomponent adsorption isotherm, was developed and used to simulate acetone-butanol fermentation. The model showed a close fit to the experimental results of the adsorptive batch acetone-butanol fermentation.
Degree
Ph.D.
Subject Area
Chemical engineering|Microbiology
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