Removal of ammonium and nitrate by the hypothermia bacterium Pseudomonas putida Y-9 mainly through assimilation

The removal of ammonium and nitrate by bacterium via assimilation could prevent the nitrogen loss. In this study, the removal efficiency and conversion characteristics of ammonium and nitrate by a cold-tolerant bacterium, Pseudomonas putida Y-9, were explored. Strain Y-9 efficiently removed ammonium and nitrate (less than 100 mg L-1) with removal rates of greater than 99.36% and 82.00%, respectively. The ammonium removal efficiency still reached 87.24% when the ammonium concentration was up to 500 mg L-1, and strain Y-9 preferentially used ammonium over nitrate. Furthermore, less than 0.12% of the nitrogen was converted to nitrite, and 78.03% and 55.30% of the nitrogen were transformed into biological nitrogen when strain Y-9 was cultivated in ammonium and nitrate media, respectively. Nitrate reductase and nitrite reductase activity were detected in strain Y-9, while ammonia monooxygenase activity was undetectable. Allylthiourea showed no effect on ammonium removal but sodium azide strongly inhibited nitrate removal by strain Y-9. Altogether, the results revealed that strain Y-9 could remove large amounts of ammonium and nitrate, mainly through assimilation, and results in nearly no harmful nitrite accumulation. (C) 2021 Published by Elsevier B.V.

Automated summary

The bacterium Pseudomonas putida Y-9 efficiently removes ammonium and nitrate through assimilation, with almost no harmful nitrite accumulation.