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Ammonium transformed into nitrous oxide via nitric oxide by Pseudomonas putida Y-9 under aerobic conditions without hydroxylamine as intermediate

Huang, Xuejiao, Xu, Yi, He, Tengxia, Jia, Hongjie, Feng, Mi, Xiang, Shudi, Wang, Shutong, Ni, Jiupai, Xie, Deti, Li, Zhenlun
Bioresource technology 2019 v.277 pp. 87-93
Pseudomonas putida, aerobic conditions, ammonia monooxygenase, ammonium, gene amplification, hydroxylamine, nitric oxide, nitrites, nitrous oxide, oxidation, total nitrogen
Previous studies have reported that hydroxylamine (NH2OH) is an inevitable intermediate of the ammonium (NH4+) oxidation pathway under aerobic conditions. In this study, Pseudomonas putida Y-9 was found to oxidize ammonium into N2O via NO without the accumulation of NH2OH and NO2− under aerobic conditions. NH2OH was nearly completely transformed into NO2− whether NH4+ was present in the medium, and NH4+ could accelerate the transformation of NH2OH to NO2− by promoting Y-9 growth. NH4+ was oxidized rapidly by Y-9 with or without the presence of NH2OH in the medium, and the decrease of total nitrogen reached 30.65 mg/L and 39.38 mg/L, respectively, which indicates that NH2OH inhibits the transformation efficiency of NH4+ to N2O. Gene amplification and enzyme assays demonstrated that ammonia monooxygenase doesn’t exist in Y-9. All results show that NH4+ can be transformed into N2O via NO by Y-9 under aerobic conditions without NH2OH as intermediate.