Thermodynamic Evaluation of Dual Substrate Growth

Area of Science:

• Microbial physiology and biotechnology
• Biochemical engineering
• Synthetic biology

Background:

• Electrochemical reduction of carbon dioxide (CO2) yields C1-C2 compounds.
• These compounds can supplement primary substrates like glucose for microbial growth.
• Mechanisms of dual-substrate utilization impacting growth rate and yield are not well understood.

Purpose of the Study:

• To develop a thermodynamic framework for predicting microbial growth dynamics on dual substrates.
• To elucidate the optimal strategies for consuming glucose and C1-C2 compounds.
• To understand the competitive advantages of generalist microbes in dual-substrate environments.

Main Methods:

• Developed a generalized, species-agnostic thermodynamic framework.
• Partitioned anabolic and catabolic fluxes for glucose/secondary substrate combinations.
• Predicted maximum growth rate and yield as a function of substrate ratio.

Main Results:

• Optimal strategy involves using secondary substrates as electron donors, conserving glucose for assimilation.
• Biomass yield is maintained until glucose becomes limiting for anabolism.
• Lowering glucose fraction and assimilating auxiliary carbon reduces yield; growth rate follows similar trends.
• Dual substrate growth allows generalists to outcompete specialists in resource-limited conditions.

Conclusions:

• Theoretical framework accurately predicts dual-substrate growth dynamics.
• Dual substrate utilization provides a competitive edge for generalist microbes.
• Findings align with experimental observations in natural and engineered environments.