Sodium (Na~+) concentration effects on metabolic pathway and estimation of ATP use in dark fermentation hydrogen production through stoichiometric analysis

摘要

Batch experiments were conducted to investigate the effects of Na~+ concentration on hydrogen production with dark fermentation. The Na~+ concentration was varied from 0 to 8 g/L in the mixed culture using an anaerobic sludge treated by acid. The maximum hydrogen production was achieved with 1 g-Na~+/L, whereas the hydrogen production was decreased over 2 g-Na~+/L due to the inhibitory of Na~+. The mechanisms of Na~+ inhibition to the hydrogen production are studied using pure culture of Clos-tridium butyricum by calculating the energy balance. At a high sodium concentration, C. butyricum used a greater proportion of the ATP generated via fermentation for cell maintenance rather than for cell synthesis. Additionally, higher Na~+ concentrations shifted the fermentation process toward the acetate synthesis pathway instead of the butyrate pathway, and the value of Y_(x/atp) decreased. With high Na~+ concentrations, a greater ratio of hydrogen was produced via the oxidation of NADH. Excess hydrogen production decreased as the Na~+ concentration increased.