Direct uptake of electrode electrons for autotrophic denitrification by Thiobacillus denitrificans

In this work, we reported that Thiobacillus denitrificans could utilize poised electrodes directly as sole electron donors for autotrophic denitrification in bioelectrochemical systems. A potential-dependent denitrification process was observed and catalyzed by the biofilms colonizing on the electrode surface, with a maximum nitrate removal rate of 21.12 ± 1.67 mmol NO3−− N L− 1 day− 1 m− 2 at a potential of − 500 mV. The intermediate products (nitrite and N2O) suggested that denitrification was the main electron transfer pathway, and dissimilatory nitrate reduction to ammonium was not present in this process. Cyclic voltammetry revealed the acclimation potentials played an important role in the electrochemical activity of the biofilms. Electron transport inhibitors suggested the participation of complex I, II, and III in the electron transfer during the denitrification.