Denitrification characteristics and pathways of a facultative anaerobic denitrifying strain, Pseudomonas denitrificans G1

Abstract

Excessive nitrate in aquaculture systems has attracted wide attention. To isolate novel aerobic denitrifying strain and characterize its nitrogen removal processes, a facultative anaerobic denitrification bacterium, identified as Pseudomonas denitrificans G1, was isolated from marine sediments. Strain G1 could grow and remove 90-98% of nitrate and 97-99% of nitrite under an aerobic or anaerobic condition in 24 h, with the total nitrogen removal rate of 33-38% (87-100 mg/L). The highest denitrification rate could reach 15.1 mg/(L·h). The suitable condition for the denitrification of G1 is C/N ratio 5-22, dissolved oxygen 0-4.68 mg/L, salinity 0-30 g NaCl/L, pH 7-9.5. Under the aerobic condition, G1 grew fast; however, the mass spectrographic analysis showed that the gas product was N₂O. Under the anaerobic conditions, G1 grow relatively slowly, but could also achieve effective denitrification and the final product was N₂. In denitrification of aquaculture wastewater, strain G1 can remove 60.57% of nitrate and 36.36% of total nitrogen; meanwhile, there was a slight accumulation of ammonia nitrogen. P. denitrificans strain G1 has potential in denitrification processes for the treatment of aquaculture wastewater. However, the regulation of reaction conditions and gas products needs to be further studied.

Keywords: Aerobic denitrification; Anaerobic denitrification; Denitrification mechanism; Nitrogen removal; Pseudomonas denitrificans.