Carbon monoxide conversion with Clostridium aceticum.

Area of Science:

• Microbial metabolism and biotechnology
• Bioreactor engineering for gas fermentation

Background:

• Acetogenic bacteria, like Clostridium aceticum, are crucial for syngas fermentation but exhibit variable carbon monoxide (CO) tolerance.
• High CO concentrations in syngas pose a challenge for the efficient utilization of these bacteria.

Purpose of the Study:

• To investigate the autotrophic potential and CO tolerance of Clostridium aceticum.
• To explore and enable efficient syngas fermentation using C. aceticum at high CO partial pressures.

Main Methods:

• Characterization of C. aceticum's growth and CO inhibition kinetics using a substrate inhibition model in batch cultures.
• Application of a continuously operated stirred-tank bioreactor with submerged membranes for cell retention.

Main Results:

• Clostridium aceticum demonstrated autotrophic ethanol production using CO as a substrate.
• The bacterium exhibits strong CO inhibition, with an optimal CO partial pressure of 5.4 mbar.
• Continuous fermentation in a membrane bioreactor achieved up to 70% CO conversion and space-time yields of 0.85 g·L⁻¹·hr⁻¹ acetate.

Conclusions:

• Despite CO sensitivity, C. aceticum can be utilized for syngas fermentation under optimized conditions.
• Membrane bioreactor technology is effective for retaining cells and enabling high CO conversion with CO-inhibited bacteria.