O&lt;sub&gt;2&lt;/sub&gt; versus N&lt;sub&gt;2&lt;/sub&gt;O respiration in a continuous microbial enrichment

Conthe Calvo, M.; Parchen, C.M.; Stouten, G.R.; Kleerebezem, R.; van Loosdrecht, Mark C.M.

doi:10.1007/s00253-018-9247-3

O₂ versus N₂O respiration in a continuous microbial enrichment

Title

O₂ versus N₂O respiration in a continuous microbial enrichment

Author

Conthe Calvo, M. (TU Delft BT/Environmental Biotechnology)
Parchen, C.M. (TU Delft Applied Sciences)
Stouten, G.R. (TU Delft BT/Environmental Biotechnology)
Kleerebezem, R. (TU Delft BT/Environmental Biotechnology)
van Loosdrecht, Mark C.M. (TU Delft BT/Environmental Biotechnology)

Faculty

Applied Sciences

Date

2018

Abstract

Despite its ecological importance, essential aspects of microbial N₂O reduction—such as the effect of O₂ availability on the N₂O sink capacity of a community—remain unclear. We studied N₂O vs. aerobic respiration in a chemostat culture to explore (i) the extent to which simultaneous respiration of N₂O and O₂ can occur, (ii) the mechanism governing the competition for N₂O and O₂, and (iii) how the N₂O-reducing capacity of a community is affected by dynamic oxic/anoxic shifts such as those that may occur during nitrogen removal in wastewater treatment systems. Despite its prolonged growth and enrichment with N₂O as the sole electron acceptor, the culture readily switched to aerobic respiration upon exposure to O₂. When supplied simultaneously, N₂O reduction to N₂ was only detected when the O₂ concentration was limiting the respiration rate. The biomass yields per electron accepted during growth on N₂O are in agreement with our current knowledge of electron transport chain biochemistry in model denitrifiers like Paracoccus denitrificans. The culture’s affinity constant (K_S) for O₂ was found to be two orders of magnitude lower than the value for N₂O, explaining the preferential use of O₂ over N₂O under most environmentally relevant conditions.