A two-phase model for ABE fermentation with a modified Clostridium acetobutylicum strain

Abstract

Acetone-Butanol-Ethanol (ABE) fermentation has regained interest due to the environmental problems generated by fossil fuels and the need to modify production chains including considerations of sustainability and circular economy. This work focuses on the modelling of ABE fermentation, with a Clostridium acetobutylicum mutated strain, to support the synthesis and improvement of butanol and acetone production process. To reach this objective, bioreactor fermentations with different glucose concentrations were developed. Results show that a two phases model (with a set of equations for the acidogenesis and another for the solventogenesis) generates satisfactory process predictions. In acidogenesis, the main effect on growth and acid production is due to the inhibition by acids, which can be quantified as a function of the total concentration of acids. While in the solventogenesis, inhibition must be quantified as a function of the total concentration of solvents. This model agrees with metabolic analysis that considers solvents generation being produced, simultaneously, from acids and sugars. For the studied system, acetone and butanol production is based on re-assimilated acids and pyruvate from glycolysis, with a distribution that changes with glucose availability.