Abstract: An aerobic denitrifying bacterium strain DN7 with excellent nitrate removal ability was isolated from the biocontact oxidation reactor treating bamboo process wastewater. The strain had a nitrate removal efficiency of 99.4% in 72 h. Cell microscopic observation demonstrated that the strain was a gramnegative bacillus with an average size of 0.5 μm×1.5 μm, and the colony was ivory. Based on its biochemical/morphological characteristics and its 16S rDNA sequence homologic analysis, this strain was identified as Defluvibacter lusatiensis. Its optimal carbon sources were small molecular organic compounds such as sodium citrate and glucose, and its nitrogen removal efficiency reached 99.0% when the medium C/N ratio was 9. The nitrogen removal efficiency could reach more than 96% when the nitrate concentration was below 138.48 mg·L^-1 and the nitrite concentration was lower than 1.0 mg·L^-1. The strain was not sensitive to DO, and the denitrification was favored under neutral or a bit alkaline condition. The DN7 also had good ability in degrading ammonim nitrogen, with the removal efficiency being 84.7% in 72 h.

Key words: aerobic denitrification, heterotrophic nitrification, isolation and identification.