Efficient nitrogen removal via simultaneous ammonium assimilation and heterotrophic denitrification of Paracoccus denitrificans R-1

Abstract

Summary: Although diverse microorganisms can remove ammonium and nitrate simultaneously, their metabolic mechanisms are not well understood. Paracoccus denitrificans R-1 showed the maximal NH4+ removal rate 9.94 mg L−1·h−1 and 2.91 mg L−1·h−1 under aerobic and anaerobic conditions, respectively. Analysis of the nitrogen balance calculation and isotope tracing experiment indicated that NH4+ was consumed through assimilation. The maximal NO3− removal rate of strain R-1 was 18.05 and 19.76 mg L−1·h−1 under aerobic and anaerobic conditions, respectively. The stoichiometric consumption ratio of acetate to nitrate was 0.902 and NO3− was reduced to N2 for strain R-1 through 15NO3− isotopic tracing experiment, which indicated a respiratory process coupled with the oxidation of electron donors. Genomic analysis showed that strain R-1 contained genes for ammonium assimilation and denitrification, which effectively promoted each other. These findings provide insights into microbial nitrogen transformation and facilitate the simultaneous removal of NH4+ and NO3− in a single reactor.

Keywords

• aquatic biology
• aquatic science
• Biogeochemistry
• microbial metabolism
• microbiology