Enrichment of anodic biofilm inoculated with anaerobic or aerobic sludge in single chambered air-cathode microbial fuel cells

•Aerobic sludge-seeded MFC starts up faster and performs better than the anaerobic.•Bacterial diversity in aerobic activated sludge is superior to the anaerobic.•Long-term acclimation of sludge results in uniformity of microbial communities.•Anaeromusa, Geobacter, Zoogloea and Acinetobacter are dominant in enriched biofilm. Aerobic sludge after anaerobic pretreatment and anaerobic sludge were separately used as inoculum to start up air-cathode single-chamber MFCs. Aerobic sludge-inoculated MFCs arrived at 0.27V with a maximum power density of 5.79Wm−3, while anaerobic sludge-inoculated MFCs reached 0.21V with 3.66Wm−3. Microbial analysis with DGGE profiling and high-throughput sequencing indicated that aerobic sludge contained more diverse bacterial populations than anaerobic sludge. Nitrospira species dominated in aerobic sludge, while anaerobic sludge was dominated by Desulfurella and Acidithiobacillus species. Microbial community structure and composition in anodic biofilms enriched, respectively from aerobic and anaerobic sludges tended gradually to be similar. Potentially exoelectrogenic Geobacter and Anaeromusa species, biofilm-forming Zoogloea and Acinetobacter species were abundant in both anodic biofilms. This study indicated that aerobic sludge performed better for MFCs startup, and the enrichment of anodic microbial consortium with different inocula but same substrate resulted in uniformity of functional microbial communities.