Iron reducing sludge as a source of electroactive bacteria: assessing iron reduction in biofilm bacteria, planktonic cells and isolates from a microbial fuel cell

In this study, bacteria from a microbial fuel cell (MFC) and isolates were evaluated on their Fe³⁺ reduction capability at different concentrations of iron using acetate as the sole source of carbon. The results demonstrated that the planktonic cells can reach an iron reduction up to 60% at 27 mmol Fe³⁺. Azospira oryzae (µ 0.89 ± 0.27 d⁻¹) and Cupriavidus metallidurans CH34 (µ 2.34 ± 0.81 d⁻¹) presented 55 and 62% of Fe³⁺ reduction, respectively, at 16 mmol l⁻¹. Enterobacter bugandensis (µ 0.4 ± 0.01 d⁻¹) 40% Fe³⁺ at 27 mmol l⁻¹, Citrobacter freundii ATCC 8090 (µ 0.23 ± 0.05 d⁻¹) and Citrobacter murliniae CDC2970-59 (µ 0.34 ± 0.02 d⁻¹) reduced Fe³⁺ in ~ 50%, at 55 mmol l⁻¹. This is the first report on these bacteria on a percentage of iron reduction. These results may be useful for anode design to contribute to a higher energy generation in MFCs.