[Isolation and identification of aerobic denitrifying bacterium Defluvibacter lusatiensis strain DN7 and its...

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 microm x 1.5 microm, 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 x L(-1) and the nitrite concentration was lower than 1.0 mg x 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.