The coexisted nitrate and nitrite as a driving force for the aerobic denitrification of Peribacillus sp. EM-C3

A heterotrophic nitrifying and aerobic denitrifying strain was newly isolated from a biogas slurry sample and assigned to be Peribacillus sp. EM-C3 based on phylogenetic and morphological analyses. This strain was capable of removing approximately 95.96% of , 93.63% of , and 99.71% of without nitrite accumulation, with maximum conversion rates of 4.98, 2.73, and 3.17 mg/L/h, respectively. Nitrogen balance analysis showed that high total nitrogen loss (> 50%) was achieved by utilizing , , or as a nitrogen source. Importantly, the maximum and removal rates increased to 3.78 and 4.42 mg/L/h when both and were present in the system, as this promoted aerobic denitrification by the strain. The key activities of enzymes involved in nitrogen metabolism (ammonia monooxygenase, and nitrate and nitrite reductases) were 0.45, 0.15, and 0.01 U/mg protein, respectively. Taken together, these results show that the coexistence of nitrate and nitrite may promote aerobic denitrification by Peribacillus sp. EM-C3.