Variations in the denitrifying microbial community and functional genes during mesophilic and thermophilic anaerobic digestion of cattle manure.

In this study, the anaerobic digestion (AD) of cattle manure was conducted at two temperatures (mesophilic: 35 °C; thermophilic: 55 °C) to analyze the dynamics of the denitrifying functional microbial community and functional genes. The cumulative N2O production under thermophilic conditions was 130.3% higher than that under mesophilic conditions. Thermophilic AD decreased the abundance of nosZ, which was more functional than other denitrifying genes. Firmicutes, Proteobacteria, and Bacteroidetes were the main phyla, and they were also related to denitrification during AD. Redundancy analysis indicated that pH, temperature, and NH4+-N mainly affected the functional bacterial community. Temperature altered the co-occurrence patterns of the bacterial community and the keystone genera in AD. Desulfovibrio in mesophilic AD and Thiobacillus in thermophilic AD were closely related to nitrogen transformation among the keystone genera. The variations in the abundances of members of the denitrifying microbial community and functional genes during AD suggest that thermophilic AD may have caused greater nitrogen losses.