ABSTRACT
Four strains of aerobic denitrifying bacteria were isolated from biomembrane of the laboratory biofilter by selective medium. The denitrifying rates of these four strains were found more than 80% under aerobic condition for 40 hours. The denitrifying rate of A1 was highest, which was 99.05%. When measuring the course of nitrogen element changing, it is found that they accumulated nitrite expect the strain A1. The strain A1 was gram positive and spherical. It is identified as Pseudomonas putida based on its biochemical and morphological characters and phylogenetic analysis of 16S rDNA sequences(genbank accession NO.DQ836052.1). For the strain A1, the optimum beginning pH was 7.0 around, and the optimum tempera- ture was 30 ℃ around, The change of DO did not influence the effect of denitrification when it was more than 2.0 mg/L.