Dynamic Thermodynamic Simulation of ADM1 Validates the Hydrogen Inhibition Approach and Suggests an Unfeasible Butyrate Degradation Pathway

In this work, a dynamic calculation of the thermodynamics of the considered reactions in ADM1 highlighted the role of hydrogen on VFA degradation. In ADM1, a hydrogen inhibition factor based on its concentration is used to represent the same effect. Our comparison of a thermodynamic-based against the simpler concentration-based inhibition factor during dynamic simulations validates the ADM1 approach. Our results also show the need to correct the VFAs Gibbs energies with temperature if a thermodynamic-based inhibition is to be used. The thermodynamics of butyrate degradation under both experimental and simulated conditions suggest the unfeasibility of the reaction and the need for a revision of the current pathway biochemistry.