Regulation of the dark fermentation products by electro-fermentation in reactors without membrane

This study evaluated the enhancement in hydrogen production from cheese whey by applying electro-fermentation in membrane-less reactors and comparing it with conventional dark fermentation. The electro-fermentation reactors used stainless-steel electrodes, and the set potentials evaluated on the working electrodes (E-W) were -0.5, -0.2, +0.1, and +0.4 V (vs. NHE). The electro-fermentation increased the hydrogen production with all E-W values, with the best performance at E-W = -0.5 V (4.0 +/- 0.7 L H-2/L-d and 2.5 +/- 0.3 mol H-2/mol glucose). The electro-fermentation stimulated the H-2 production by ethanol-type fermentation compared to conventional dark fermentation. The negative potentials decreased biomass generation but increased hydrogen production and medium-chain fatty acids, while the positive potentials enhanced ethanol production attributed to Enterococcus sp. Clostridium butyricum, Clostridium tertium, and Enterococcus sp. were present at all conditions tested but with different relative abundances. Implementing the E-W allows for regulating the fermentation towards specific value-added products.