Modeling a propionate-oxidizing syntrophic coculture using thermodynamic principles.

Area of Science:

• Microbial Ecology
• Biochemical Engineering
• Thermodynamics

Background:

• Cocultures of Syntrophobacter fumaroxidans and Methanospirillum hungatei are crucial in anaerobic digestion.
• Accurate biokinetic modeling is essential for understanding and optimizing these processes.
• Existing models often struggle with thermodynamic consistency and parameter repeatability.

Purpose of the Study:

• To compare four biokinetic models for a S. fumaroxidans and M. hungatei coculture.
• To evaluate the impact of different growth yield and hydrogen inhibition functions.
• To identify models that adhere to thermodynamic principles and provide repeatable parameters.

Main Methods:

• Developed and compared four biokinetic models differing in growth yield (dynamic/constant) and hydrogen inhibition (noncompetitive/thermodynamic).
• Trained models using batch experimental data and analyzed fitted parameters.
• Validated model predictive power using chemostat experimental data.
• Assessed thermodynamic consistency by calculating Gibbs free energy changes.

Main Results:

• All four models accurately fitted the training data.
• ADM1-like models yielded parameters inconsistent with literature and violated the second law of thermodynamics on test data.
• Models with thermodynamic-based inhibition and dynamic growth yields produced consistent, repeatable parameters aligned with literature and thermodynamic laws.

Conclusions:

• Implementing thermodynamic-based functions in biokinetic models enhances predictive accuracy and reliability.
• Dynamic computation of growth yields is crucial for robust model parameterization.
• Thermodynamic constraints are vital for developing scientifically sound biokinetic models of microbial ecosystems.