Electrochemically enhanced microbial CO conversion to volatile fatty acids using neutral red as an electron mediator

Area of Science:

• Industrial Biotechnology
• Microbial Metabolism
• Electrochemistry

Background:

• Biorefining C1 gas feedstock, like carbon monoxide (CO), into platform chemicals is industrially relevant but limited by low microbial conversion yields and growth rates.
• The Wood-Ljungdahl pathway, crucial for CO utilization, suffers from insufficient electron supply, hindering efficient conversion.
• Supplementing electron sources such as carbohydrates or hydrogen can enhance CO conversion, but alternative methods are sought.

Purpose of the Study:

• To investigate the use of electrode-based electron transfer in bioelectrochemical systems (BES) to overcome electron limitations in CO bioconversion.
• To enhance the production of volatile fatty acids (VFAs) from C1 gas feedstock.
• To compare the efficacy of a BES with neutral red (BES-NR) against controls for improved microbial CO utilization.

Main Methods:

• Utilized a bioelectrochemical system (BES) to supply electrons for microbial CO conversion.
• Compared a BES with neutral red (BES-NR) to a BES without neutral red and an open circuit control.
• Quantified coulombic efficiency, measuring the ratio of electrons recovered in VFAs to the total electrons supplied.

Main Results:

• The BES-NR demonstrated significantly higher coulombic efficiency compared to the control groups.
• Electrode-based electron transfer effectively compensated for the insufficient reducing equivalents in CO-utilizing microbes.
• The study confirmed the potential for increased volatile fatty acid production.

Conclusions:

• Carbon electrodes in BES provide a viable platform for regulating redox balance in microbial CO bioconversion.
• This approach offers a promising amendment to conventional C1 gas fermentation processes.
• Bioelectrochemical systems can enhance the efficiency and yield of converting CO into valuable chemicals.