Physiological metabolism of electrochemically active bacteria directed by combined acetate and Cd(II) in single-chamber microbial electrolysis cells

Abstract

It is of great interest to explore physiological metabolism of electrochemically active bacteria (EAB) for combined organics and heavy metals in single-chamber microbial electrolysis cells (MECs). Four pure culture EAB varying degrees responded to the combined acetate (1.0–5.0 g/L) and Cd(II) (20–150 mg/L) at different initial concentrations in the single-chamber MECs, shown as significant relevance of Cd(II) removal (2.57–7.35 mg/L/h) and H2 production (0–0.0011 m3/m3/h) instead of acetate removal (73–130 mg/L/h), to these EAB species at initial Cd(II) below 120 mg/L and initial acetate below 3.0 g/L. A high initial acetate (5.0 g/L) compensated the Cd(II) inhibition and broadened the removal of Cd(II) to 150 mg/L. These EAB physiologically released variable amounts of extracellular polymeric substances with a compositional diversity in response to the changes of initial Cd(II) and circuital current whereas the activities of typical intracellular enzymes were more apparently altered by the initial Cd(II) than the circuital current. These results provide experimental validation of the presence, the metabolic plasticity and the physiological response of these EAB directed by the changes of initial Cd(II) and acetate concentrations in the single-chamber MECs, deepening our understanding of EAB physiological coping strategies in metallurgical microbial electro-ecological cycles.