A coculture-coproduction system designed for enhanced carbon conservation through inter-strain CO₂ recycling

Area of Science:

• Biotechnology
• Metabolic Engineering
• Synthetic Biology

Background:

• Carbon loss as CO2 is a major challenge in biofuel production from biomass.
• Existing methods to improve carbon conservation require additional reduced co-substrates.
• Lignocellulosic biomass contains a heterogeneous mixture of sugars, offering potential for strategic utilization.

Purpose of the Study:

• To develop a novel coculture system for enhanced carbon conservation during biofuel production.
• To demonstrate a proof-of-concept utilizing the natural heterogeneity of lignocellulosic sugars.
• To circumvent the need for additional reduced co-substrates by balancing CO2-emitting and CO2-fixing pathways.

Main Methods:

• Development of a coculture-coproduction system using two catabolically orthogonal Escherichia coli strains.
• One strain (G2E) converts glucose to ethanol, while the other (X2S) converts xylose to succinate.
• Utilized 13C-labeling studies to track carbon flow and CO2 exchange between strains.

Main Results:

• The G2E + X2S coculture recycled 24% of evolved CO2, achieving a 77% carbon conservation efficiency.
• This efficiency is significantly higher than the 64% achieved when converting all sugars solely to ethanol.
• Discovered latent pyruvate exchange between strains and significant carbon rearrangement within the X2S strain.

Conclusions:

• Exploiting lignocellulosic sugar heterogeneity in coculture systems can significantly improve carbon conservation in biofuel production.
• The developed coculture system effectively balances CO2-emitting and CO2-fixing pathways.
• This approach offers a promising strategy to mitigate carbon loss in advanced biofuel manufacturing.