Adaptation of anammox consortia in microbial fuel cell to low temperature: Microbial community and predictive functional profiling

The purpose of this study was to explore the tolerance mechanism of anammox consortia in microbial fuel cell (MFC) system at low temperature. Data showed that nearly 80 % total nitrogen removal was achieved after the temperature decreased from 30 °C to 15 °C. The nitrogen removal rate (NRR) of the system was decreased by 26.3 %, from 0.441 kgN·m−3·d−1 at 30 °C to 0.325 kgN·m−3·d−1 at 15 °C. Isotope experiment in 15NH4+-containing reactor found that much more 29N2 were produced than 30N2, confirming that anammox was the main 15NH4+ removal pathway and electrochemical oxidation participate in this process. High throughput sequencing analysis indicated the low temperature stimulated the enrichment of heterotrophic bacteria, such as Comamonadaceae and Rhodobacteraceae. While the relative abundance of Candidatus Brocadia, typical anammox bacteria, decreased significantly. Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis showed that the low temperature induced a more efficient expression in synthesis of unsaturated fatty acids (UFAs) and ABC membrane transports. This study indicates that anammox consortia are likely to maintain high nitrogen removal performance of MFC system by changing the proportion of membrane composition and EPS exportation.