Characteristics and metabolic pathway of Alcaligenes sp TB for simultaneous heterotrophic nitrification-aerobic denitrification

A novel heterotrophic nitrification-aerobic denitrification bacterium, Alcaligenes sp. TB (GenBank accession no. JQ044686), was isolated from a rotating drum biofilter for NO removal. Its characteristics and metabolic pathway for NO removal were comprehensively investigated. Experimental results showed that the nitrification and denitrification efficiency reached 99.42 and 96.44 %, respectively, after 44 h under the conditions of pH 7.2, 30 A degrees C, and 120 rpm. The tests with the addition of Pb2+ and Na2WO4 as the reductase inhibitor revealed that nitrite was the key intermediate to produce the nitrogen gas as the final product in the simultaneous heterotrophic nitrification and denitrification by strain TB. Based on the experimental results, the metabolic pathway of strain TB has been proposed that it carries out shortcut/complete simultaneous nitrification and denitrification with nitrite as an intermediate and nitrogen gas as a final product. The two potential metabolic pathways existing in strain TB can be described as NH4 (+) -> NH2OH -> NO2 (-) -> N2O -> N-2 and NH4 (+) -> NH2OH -> NO2 (-) -> NO3 (-) -> NO2 (-) -> N2O -> N-2. This work indicates that the strain TB may be a good candidate for the denitrification of the sewage.