Exploring the lactate-acetate-driven dark fermentation: Hydrogen output, metabolite profiles, and microbial dynamics

Lactate is key to favor different metabolic routes for improving hydrogen production and maximizing the substrate use during dark fermentation. This study investigates the impact of initial lactate-acetate concentrations on batch dark fermentation for hydrogen and metabolites production. Experiments showed that an initial 25% lactate-acetate (2:1 mol ratio) addition significantly enhances hydrogen production and increases yields of butyrate and caproate, with Clostridium playing a key role. In contrast, initial 40% lactate-acetate reduced hydrogen yields and metabolite concentrations, likely due to a decrease in Clostridium and increase in Lactococcus abundances. Initial acetate improved hydrogen production and final metabolite concentrations, particularly valerate, while reducing Enterococcus abundance, which negatively impacts. Pearson correlation revealed that acetate has a stronger effect on butyrate production compared to lactate, with Enterobacter and Klebsiella as key microbial contributors. This study highlights the potential of the lactate-acetate-driven dark fermentation process, improving the hydrogen production through balanced contributions.