Syngas fermentation and microbial electrosynthesis integration as a single process unit.

Area of Science:

• Biotechnology
• Electrochemistry
• Chemical Engineering

Background:

• Syngas fermentation is a key biotechnological process for converting carbon oxides into valuable chemicals.
• Microbial electrosynthesis offers a promising route to enhance bioconversion efficiency using electrochemical reducing power.
• Understanding the interplay between electrochemical potential and microbial activity is crucial for process optimization.

Purpose of the Study:

• To integrate syngas fermentation with microbial electrosynthesis as a single process unit.
• To investigate the impact of varying electrochemical potentials on acetic acid synthesis.
• To assess the effect of electrochemical reducing power on carbon monoxide (CO) inhibition during fermentation.

Main Methods:

• Syngas fermentation (15% CO, 15% H2, 20% N2, 50% CO2) was coupled with microbial electrosynthesis in open and closed-circuit modes.
• Electrochemical reducing power was applied ranging from -50 to -400 mV vs. Ag/AgCl (3.0 NaCl).
• Acetic acid production rates and CO consumption were monitored under different electrochemical conditions, including fed-batch operations.

Main Results:

• A benchmark potential of -150 mV vs. Ag/AgCl significantly enhanced acetic acid synthesis rates by 15-fold compared to open circuit conditions (0.263 mmol L-1h-1).
• No significant CO inhibition was observed, with approximately 60% of the supplied CO being consumed.
• Anodic potentials exceeding 2.0 V led to a substantial decrease in product formation.

Conclusions:

• The integration of microbial electrosynthesis with syngas fermentation is a viable strategy for enhancing acetic acid production.
• -150 mV is an optimal electrochemical potential for maximizing acetic acid yield and CO utilization.
• Fed-batch operations and managing anodic potential are critical for maintaining high efficiency in the integrated system.