Aerobic denitrifying characteristics of duckweed rhizosphere bacterium RWX31 was studied in this paper. Bacterium RWX31 exhibited efficient growth stability and nitrogen removal ability, with nitrate removal efficiency of 81.3% at an initial 140 mg l-1 NO3-N. Under aerobic conditions, the maximum nitrate-N removal rates were 30.9, 24.3 and 11.5 mg l-1 h-1, with nitrate, nitrite and ammonium as sole nitrogen source, respectively. The optimal conditions for aerobic denitriï¬cation were C : N ratio of 8, pH 7.2 and 27°C when nitrate served as the substrate, and shaking speed had no significant impact on nitrate removal efficiency within the range tested (dissolved oxygen concentration 3.5 to 7.3 mg l-1). Stationary test suggested that the association of duckweed and strain RWX31 performed better in nitrate-removal than by itself or in association with other bacteria species. According to the morphological observation and 16S rRNA gene analysis, strain RWX31 was preliminarily identiï¬ed as Pseudomonas sp. Strain RWX31 is the ï¬rst aerobic denitrifier isolated from duckweed Lemna minor rhizosphere with the potential to reduce nitrate leaching.
Key words: Aerobic denitrification, nitrogen removal, Pseudomonas, rhizobacteria
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