Nitrous oxide production by Alcaligenes faecalis under transient and dynamic aerobic and anaerobic conditions

Abstract

Nitrous oxide can be a harmful by-product in nitrogen removal from wastewater. Since wastewater treatment systems operate under different aeration regimens, the influence of different oxygen concentrations and oxygen fluctuations on denitrification was studied. Continuous cultures of Alcaligenes faecalis TUD produced N 2 O under anaerobic as well as aerobic conditions. Below a dissolved oxygen concentration of 5% air saturation, the relatively highest N 2 O production was observed. Under these conditions, significant activities of nitrite reductase could be measured. After transition from aerobic to anaerobic conditions, there was insufficient nitrite reductase present to sustain growth and the culture began to wash out. After 20 h, nitrite reductase became detectable and the culture started to recover. Nitrous oxide reductase became measurable only after 27 h, suggesting sequential induction of the denitrification reductases, causing the transient accumulation of N 2 O. After transition from anaerobic conditions to aerobic conditions, nitrite reduction continued (at a lower rate) for several hours. N 2 O reduction appeared to stop immediately after the switch, indicating inhibition of nitrous oxide reductase, resulting in high N 2 O emissions (maximum, 1.4 mmol liter ؊1 h ؊1 ). The nitrite reductase was not inactivated by oxygen, but its synthesis was repressed. A half-life of 16 to 22 h for nitrite reductase under these conditions was calculated. In a dynamic aerobic-anaerobic culture of A. faecalis, a semisteady state in which most of the N 2 O production took place after the transition from anaerobic to aerobic conditions was obtained. The nitrite consumption rate in this culture was equal to that in an anaerobic culture (0.95 and 0.92 mmol liter ؊1 h ؊1 , respectively), but the production of N 2 O was higher in the dynamic culture (28 and 26% of nitrite consumption, respectively).

Metabolic specialization of denitrifiers in permeable sediments controls N2O emissions

“…When the sediment was kept anoxic and supplied continuously with replete nitrate, there was a net production of the denitrification pathway intermediates NO 2 − and N 2 O, with net production rates around 380% and 1.4%, respectively, of the N 2 production rate. Such accumulation of denitrification intermediates may have resulted from two factors; 1) poor coupling of individual denitrification steps within single organisms (Bergaust et al, 2008, Lilja and Johnson 2016, Otte et al 1996, Philippot et al 2001 or; 2) process partitioning within the denitrifying community, i.e. the presence of truncated forms of denitrification in different community members (Graf et al 2014, Kuypers et al 2018, Roco et al 2016, Shapleigh 2007.…”

The anaerobic oxidation of hydrazine: a novel reaction in microbial nitrogen metabolism

“…Alcaligenes faecalis TUD (LMD 89.147), an organism capable of denitri¢cation and heterotrophic nitri¢cation, was cultivated in an acetate-limited chemostat at 30³C and pH 8.0 with a dilution rate of 0.05 h 3I [13]. Saccharomyces cerevisiae T23D was grown aerobically in a glucose-limited chemostat with a dilution rate of 0.1 h 3I at 30³C and pH 5.0 [14].…”

Pathway of nitrous oxide consumption in isolated Pseudomonas stutzeri strains under anoxic and oxic conditions

“…In this, the oxygen (O2) concentration is considered the most important determinant next to pH and carbon availability (Richardson et al, 2009). Nitrous oxide is often described as the major end product during aerobic denitrification (Otte et al, 1996;Takaya et al, 2003;Morley et al, 2008). This can be attributed to the greater O2 sensitivity of NOS compared with other denitrification enzymes (Knowles, 1982).…”