Current Production by Bacterial Communities in Microbial Fuel Cells Enriched from Wastewater Sludge with Different Electron Donors

Electricity production by bacterial communities enriched from wastewater sludge with lactate, succinate, N-acetyl-d-glucosamine (NAG), acetate, formate, and uridine were monitored in dual-chamber microbial fuel cells (MFCs). Stable electricity production was observed after 300 h for communities enriched from lactate, acetate, and formate, while communities enriched with succinate, NAG, and uridine stabilized only after 700 h. The average peak current densities and maximum power densities generated from bacterial consortia were significantly higher than those generated from pure cultures of Shewanella oneidensis MR-1. Microbial assemblages were analyzed by DGGE, and planktonic and anode-attached bacterial communities varied as a function of electron donors: Firmicutes, β-Proteobacteria, and Bacteroidetes dominated the planktonic bacterial communities while anode-attached communities consisted mainly of δ-Proteobacteria, β-Proteobacteria, and Firmicutes. Similar bacterial populations were enriched in MFCs fed with lactate, NAG, and uridine and with succinate, acetate, and formate. Cross-feeding experiments with different fuels indicated that enriched microbial consortia were able to utilize a variety of fuel sources and displayed considerable stability, efficiency, and robustness of power generation in comparison to pure cultures. In addition, characterizations of cultivated Shewanella strains suggested that DGGE analysis likely missed active members of exoelectrogenic populations.