Syngas fermentation and microbial electrosynthesis integration as a single process unit

Abstract

Industrially relevant syngas (15 % CO, 15% H2, 20% N2 in 50% CO2) fermentation and microbial electrosynthesis were integrated as a single process unit in open and closed-circuit modes. This study examined the impact of electrochemical reducing power from –50 to –400 mV on the acetic acid synthesis and CO inhibition on fermentation. –150 mV vs. Ag/AgCl (3.0 NaCl) was identified as the lowest benchmark potential for improved acetic acid synthesis rate (0.263 mmol L−1h−1), which is 15-fold higher than the open circuit mode’s rate. No significant inhibition by CO in the fermentation was observed, while 60% of the gas was consumed. Anodic potential above 2.0 V substantially lowered the product formation. Superseding the fermentation medium with fresh inoculum through a fed-batch operation helped lower the anodic potential.