Optimizing butyrate production from methanol and CO₂ in microbial electrosynthesis

Area of Science:

• Biotechnology and Bioengineering
• Renewable Energy Conversion
• Chemical Synthesis

Background:

• Microbial electrosynthesis (MES) converts CO2 into chemicals using renewable electricity.
• Chain elongation upgrades acetate to butyrate using soluble electron donors.
• Methanol is a sustainable alternative electron donor to ethanol for MES.

Purpose of the Study:

• To determine optimal operating conditions for maximizing butyrate production in methanol-assisted MES.
• To evaluate the efficiency of methanol as an electron donor for butyrate production via chain elongation.

Main Methods:

• Batch bottle experiments to identify optimal temperature, pressure, and methanol/CO2 ratio.
• Fed-batch operation of a MES cell under optimized conditions.
• Analysis of butyrate production rates, titers, and selectivity.

Main Results:

• Optimal conditions for butyrate production were 35°C, 1 atm, and a 3:1 methanol/CO2 ratio.
• MES cell achieved an average butyrate production rate of 107.4 g m-2 d-1 with 75.2% selectivity.
• Temperature was critical; lower temperatures (23°C) favored acetate production.

Conclusions:

• Comprehensive optimization of operational parameters for methanol-assisted chain elongation in MES was achieved.
• Demonstrated an effective strategy for high-yield butyrate production from CO2 and methanol using MES.
• Highlights the pivotal role of temperature in controlling product selectivity in MES.