Enhancement of methane fermentation in the presence of Ni2+ chelators

The enhancement of methane fermentation in the presence of Ni2+ chelators, citric acid (CA), nitrilotriacetic acid (NTA), and ethylene diamine tetraacetic acid (EDAT) respectively, was investigated in this study. The results showed that the addition of chelating agents promoted methane fermentation of acetate. At a sodium acetate concentration of 7 g/L, temperature of 35 °C, and Ni2+ concentration of 20 μM, methane production was enhanced 34.1%, 49.2%, and 38.6%, by the addition of 10 μM CA, NTA and EDTA, respectively. The formation of soluble complexes between chelating agents and Ni2+ favored the dissolution of Ni2+ from their sulfides, and the bioavailability of Ni2+ was dramatically increased. By the addition of 10 μM NTA, the concentration of dissolved Ni2+ was greatly increased from 58 to 1020 μg/L. Accompanying with that, the concentrations of F430 and coenzyme M of the biomass increased 37% and by four-fold, respectively.