Electro-fermentation (EF) merges traditional industrial fermentation with electrochemistry. An imposed electrical field influences the fermentation environment and microbial metabolism in either a reductive or oxidative manner. The benefit of this approach is to produce target biochemicals with improved selectivity, increase carbon efficiency, limit the use of additives for redox balance or pH control, enhance microbial growth, or in some cases enhance product recovery. We discuss the principles of electrically driven fermentations and how EF can be used to steer both pure culture and microbiota-based fermentations. An overview is given on which advantages EF may bring to both existing and innovative industrial fermentation processes, and which doors might be opened in waste biomass utilization towards added-value biorefineries.

Trends

Traditional industrial fermentations show several limiting constraints.

Electro-fermentation drives metabolism with the direct integration of an electrochemical cell.

Electro-fermentation offers a hybrid metabolism in which electrons are exchanged with solid electrodes as alternative oxidizing/reducing equivalents.

Electro-fermentation can (i) stabilize/optimize fermentation metabolisms by controlling imbalances due to substrate purity, redox/pH conditions, byproduct accumulation, etc.; (ii) establish oxidative or reductive conditions to drive carbon chain breakdown or elongation; (iii) increase ATP synthesis and improve microbial biomass yield; and (iv) extract target products by selective membranes.

Catalytic activity of electro-active microorganisms, metabolic pathways, electrode materials, reactor technology, and product recovery: a multidisciplinary research approach is needed.