Electron transport bifurcation in bioanode with the metabolic shift to nitrate reduction

Electron transport bifurcation in bioanode determines the performance of microbial electrochemical technologies with the presence of an alternative electron acceptor. Here, the bioanode responses including electron transfer efficiency, microbial community, and microbial structure are investigated with the metabolic shift from current production to denitrification. Electrochemical measurements including cyclic voltammetry and electrochemical impedance spectra are performed to identify the change of electron transfer pathways in bioanode. Electron transfer efficiency for electrode reduction decreases ∼17 % with nitrate reduction. Biofilm resistance and charge transfer resistance increase from 23.3 Ω and 22.5 Ω to 36.6 Ω and 61.4 Ω with the metabolic shift, respectively. These results are mainly due to the loss of exoelectrogens inhabited in bioanode. Confocal imaging results indicate the elevated proportion of inactive cells in bioanode as the denitrification. Our results propose a possible mechanism for electron transfer bifurcation in bioanode with the metabolic shift from electrode reduction to soluble electron acceptor reduction.