Electrochemical Control of Cell Metabolism Improves Ethanol Production of Zymomonas mobilis in an Electro-Fermentation System

This study investigated ethanol fermentation by Zymomonas mobilis in an electro-fermentation system (EFS) for efficient alcohol production, which increased the ethanol titer by 12.8% compared to fermentation without electricity input. The underlying mechanism was revealed by exploring the correlation among intracellular redox parameters such as NAD(P)H/NAD(P)+ ratio, total antioxidant capacity, and cell membrane permeability. Transcriptome analysis further investigated that genes related to glucose uptake, ethanol, and succinic acid synthesis were upregulated in the cathode chamber, which promoted ethanol production. Two strategies to enhance EFS were proposed. First, the supplementation of electron shuttles (methylene blue, HNQ) can facilitate electron transport between electrodes and cells. Second, the manipulation of essential electricity-sensing genes (ZMO1211, ZMO1753) amplified the metabolic change. This study showed the possible use of electro-regulation for the efficient production of alcohol in Z. mobilis, which also provided insights into other microbial electrochemical processes in the future.