Optimizing microbial electrolysis cell performance: strategies to mitigate electron mediator degradation on membranes

Area of Science:

• Microbial electrosynthesis
• Biotechnology
• Biochemical engineering

Background:

• Microbial electrosynthesis (MEC) utilizes microorganisms to convert electrical energy into chemical products.
• Succinic acid is a valuable platform chemical with diverse industrial applications.
• Neutral red (NR) acts as an electron mediator in some MEC systems.

Purpose of the Study:

• To investigate the role and stability of neutral red (NR) as an electron mediator in the electrosynthesis of succinic acid by Actinobacillus succinogenes.
• To understand the impact of NR integration and degradation on MEC efficiency.
• To explore strategies for maintaining NR stability and enhancing long-term electrosynthesis.

Main Methods:

• Electrochemical analysis of NR behavior within the MEC system.
• Monitoring succinic acid production during bacterial growth phases.
• Investigating NR incorporation into and degradation from the bacterial cell membrane.
• Evaluating the effect of external NR supplementation.
• Implementing ORP feedback-regulated MECs for NR conservation.

Main Results:

• Neutral red (NR) integrated into the cell membrane is essential for sustaining MEC efficiency.
• NR is susceptible to degradation, both intrinsically and induced by MEC operation.
• NR is readily incorporated into the cell membrane during the exponential growth phase.
• Supplemental NR addition did not significantly enhance succinic acid synthesis at any growth stage.
• Depleted membrane-associated NR was not sufficiently compensated by NR in the fermentation liquid.
• ORP feedback-regulated MECs effectively conserved membrane-associated NR, crucial for long-term electrosynthesis.

Conclusions:

• The presence of NR on the cell membrane is vital for MEC functionality in succinic acid production.
• External replenishment of NR is challenging due to its instability.
• Precise electro-potential regulation strategies can mitigate NR degradation and maintain system efficiency.