Mathematical Modeling of Acetone-Butanol-Ethanol Fermentation with Simultaneous Utilization of Glucose and Xylose by Recombinant Clostridium acetobutylicum

Studies on acetone-butanol-ethanol (ABE) fermentation of sugars from lignocellulosic biomass have been actively carried out in recent years, and recombinant strains have been developed to efficiently coutilize glucose and xylose, which are the dominant sugar types in most lignocellulosic biomass. However, there is a lack of mathematical models for describing and predicting the simultaneous utilization of glucose and xylose in ABE fermentation, particularly for the purpose of supporting optimization and control of the process. This study proposes a kinetic model for ABE fermentation with coutilization of glucose and xylose by recombinant Clostridium acetobutylicum. The model is developed based on unstructured models, that is, the Monod equation and the Luedeking-Piret model, and a modified concentration-dependent weighting factor is suggested to describe the simultaneous utilization of glucose and xylose based on the experimental analysis. A systematic identification approach is employed to obtain reliable estimates of model parameters for the cofermentation process, which involves highly nonlinear and correlated kinetics. The glucose- and xylose-associated parameter groups are sequentially estimated using single substrate- and cofermentation data, respectively, and in the combined model, a subset of the parameters is selected through an identifiability analysis for further refinement. The developed model is shown to accurately predict the dynamics of the cofermentation of glucose and xylose in ABE production at various glucose-to-xylose ratios, feeding rates, and feed concentrations.