Imaging and distribution of Cd(II) ions in electrotrophs and its response to current and electron transfer inhibitor in microbial electrolysis cells

Electrosynthesis of acetate from inorganic carbon (HCO3−) with simultaneous hydrogen production and Cd(II) removal in multifunctional microbial electrosynthesis systems (MES)

“…Therefore, the combined effect of EAB catalysis and circuital current were essential to establish high rates of Cd(II) removal and/or hydrogen production. Such effect has also been observed with mixed cultures or pure EAB for the removal of Cr(VI), Cd(II), Co(II) or Cu(II) [9][10]21] and in other systems for hydrogen evolution in the absence of metals [32]. The presence of Cd(II) ions substantially enhanced the production of hydrogen by strain X7, which was also reflected by almost one order of magnitude increase in the energy content, whereas only minor effects were observed with strain X3 and a slight inhibition was observed with X1 and X5 (Fig.…”

“…Duplicate two-chamber reactors comprising cylindrical chambers, 2.0 cm long, 3.0 cm in diameter and 14 mL each, as previously described [8,[10][11], were used in all experiments. The cathode electrodes were three-dimensional material of graphite felts (Sanye Co., Beijing) [20][21] whereas the anode electrodes were carbon rods.…”

“…The four EAB (X1, X3, X5 and X7), thriving at low nutrients under anaerobic conditions, were isolated from cathodes previously exposed to Cd(II) fed with bicarbonate as carbon source. They were harvested after 24 h incubation in an anaerobic and sterile medium (pH = 5.8) as previously described [10]. The cells were then concentrated and washed 3 times in sterile physiological saline solutions.…”

“…In addition to the sequestration and utilization of CO2 to control the greenhouse effect, another environmentally significant problem is the removal and/or recovery of heavy metals from wastewater, including Cd(II), a highly hazardous heavy metal often present in industrial organics-barren wastewaters from chemical manufacturing, mining, extractive metallurgy, nuclear, and other industries [6][7]. For this purpose, bioelectrochemical systems utilizing mixed or pure EAB cultures fed by bicarbonate have been shown to be effective methods for the reduction and recovery of Cd(II) [7][8][9][10][11]. Therefore, it can be envisaged that appropriately designed multifunctional MES using self-regenerative EAB should be able to convert inorganic carbon from CO2 sequestration to building block organics (e.g., acetate) while simultaneously reducing Cd(II) from wastewaters [12].…”

“…Pure cultures of four well characterized gram-negative EAB including Ochrobactrum sp X1, Pseudomonas sp X3, Pseudomonas delhiensis X5, and Ochrobactrum anthropi X7 were selected since they can efficiently remove Cd(II) with a variable degrees of intracellular distribution of different forms of cadmium [7,[9][10]. However, the simultaneous production of acetate from inorganic carbon and of hydrogen by these strains has not been shown.…”