Structured modeling of a microbial system: III. Growth on mixed substrates

Area of Science:

• Biochemical Engineering
• Microbial Physiology
• Fermentation Technology

Background:

• Microbial growth and product formation often involve complex interactions with multiple carbon sources.
• Understanding substrate utilization and catabolite repression is crucial for optimizing fermentation processes.
• Existing models may not fully capture the dynamics of growth on mixed carbohydrate substrates.

Purpose of the Study:

• To extend a two-compartment model for describing microbial growth and product formation on mixed carbohydrate sources.
• To incorporate mechanisms of catabolite repression within an open-ended compartment model framework.
• To validate the model's predictive capabilities against experimental data for Streptococcus cremoris.

Main Methods:

• Development and extension of a two-compartment mathematical model.
• Simulation of batch triauxic, steady-state, and transient fermentation conditions.
• Experimental validation using the lactic acid bacterium Streptococcus cremoris grown on glucose, galactose, and lactose mixtures.

Main Results:

• The extended model successfully described microbial growth and product formation on mixed carbohydrate substrates.
• Simulations accurately predicted characteristic experimental observations, including substrate preference and carbohydrate adoption patterns.
• The model's ability to capture catabolite repression mechanisms was demonstrated.

Conclusions:

• The enhanced two-compartment model provides a robust framework for simulating microbial behavior on mixed carbon sources.
• This modeling approach accurately predicts substrate utilization dynamics and catabolite repression in Streptococcus cremoris.
• The findings have implications for optimizing industrial fermentation processes involving complex carbohydrate mixtures.