Effect of redox potential on biohydrogen production during dark fermentation of food wastes in bioreactor

In recent years, hydrogen production from food waste has attracted interest as a sustainable method for waste valorisation. Many studies were conducted on intensification parameters of fermentation, but very few focus on redox potential influence (ORP). This investigation addressed this challenge by performing discontinuous dark fermentations in bioreactor using synthetic food waste as substrate at different initial ORPs. Reducing the initial ORP of the culture broth to −322 ± 8 mV enhanced biohydrogen yield and productivity, achieving 98 ± 5 mL H 2 g −1 COD initial and 85 ± 3 mL H 2 h −1 L −1 reactor , corresponding to an increase of 57 % and 30 % respectively. Lowering initial ORPs promoted hydrogen-producing metabolic pathways and a higher relative abundance of C. butyricum . This study also demonstrates that controlling the redox potential during fermentation above the ORP range of the 2H + /H 2 redox pair negatively impacts hydrogen production and promotes the growth of undesirable microorganisms. • Initial redox potential regulation improves H 2 productivity from food wastes. • Lowering initial ORP at – 322 mV enhances H 2 production from food wastes by 57 %. • Hydrogen-producing bacteria are promoted by reduced initial ORP. • Lactate and propionate accumulation are limited at low initial ORP. • Distinct HPB develop when controlling the ORP at levels above the optimal range.