An Efficient CO₂-Upcycling Platform Based on Engineered Halomonas TD with Enhanced Acetate-Utilizing Capacity via...

Area of Science:

• Synthetic Biology and Metabolic Engineering
• Biotechnology and Bioprocessing
• Environmental Biotechnology

Background:

• Global CO2 emissions necessitate innovative carbon capture and utilization (CCU) strategies.
• Existing biohybrid CO2 conversion methods often suffer from low saline tolerance and carbon conversion rates (CCR).
• Halomonas TD, a salt-resistant bacterium, presents a potential chassis for robust CO2 bioconversion.

Purpose of the Study:

• To engineer a salt-tolerant microbial platform for efficient biohybrid conversion of CO2-derived electrolytes (CDE).
• To enhance carbon conversion rate (CCR) and produce a diverse range of value-added bioproducts.
• To assess the technological and economic feasibility of the developed platform for carbon footprint reduction.

Main Methods:

• Adaptive evolution of Halomonas TD to create the TD80 strain with enhanced acetate utilization via aceE gene mutation.
• Metabolic engineering of TD80 to introduce various biosynthesis pathways for poly-3-hydroxybutyrate (PHB), ectoine, and other bioproducts.
• Development of a non-canonical pathway to recycle malonyl-CoA for increased PHB content and co-production strategies.

Main Results:

• Engineered TD80 strains achieved high yields of PHB (29.6 g L-1) and ectoine (26.0 g L-1).
• Recycling malonyl-CoA increased PHB content from 60 wt% to 80 wt% in fed-batch studies.
• Co-production of ectoine and PHB boosted CDE-to-product CCR to 53.7 mol%, with TD80 engineered for formate utilization.

Conclusions:

• The engineered Halomonas TD80 platform demonstrates efficient and versatile biohybrid CO2 upcycling.
• The developed microbial strains exhibit high saline CDE tolerance and improved carbon conversion rates.
• Technology and economy assessment confirms the platform's efficiency and economic viability for carbon footprint reduction.