Atmospheric nitrous oxide (N2O), known for its much higher greenhouse gas potential than CO2, plays a crucial role in climate change [1]. N2O emissions from wastewater treatment plants (WWTPs), resulting from biological processes within these facilities, are emerging as a relevant concern [2]. This study aims to investigate the use of immobilised N2O-respiring microorganisms [3] as a potential method to mitigate N2O emissions from WWTPs.
Pure cultures of several N2O-respiring microorganisms (isolates belonging to the genera Pseudomonas, Comamonas or Alcaligenes as well as Wolinella succinogenes) were successfully immobilised in Ca2+-alginate beads (2 or 4 %, w/v, alginate). Cell proliferation and colonies formation were observed under appropriate anaerobic N2O respiration conditions with 10 or 100 % N2O in the culture headspace. At high cell densities, gas bubbles, presumably consisting of N2 gas, appeared and occasionally even disrupted the integrity of the alginate beads. Microrespirometry was used to investigate the N2O consumption rates of alginate-immobilised cells as a function of the number of alginate beads.
This study demonstrates the potential of alginate-immobilised bacteria as a method for reducing N2O emissions in wastewater treatment plants, which holds promise for climate change mitigation strategies.
References
1 Griffis, T.J., Chen, Z., Baker, J.M., Wood, J.D., Millet, D.B., Lee, X., Venterea, R.T. and Turner, P.A. (2017) Nitrous oxide emissions are enhanced in a warmer and wetter world. Proc. Natl. Acad. Sci. USA 114, 12081-12085.
2 Kampschreur, M.J., Temmink, H., Kleerebezem, R., Jetten, M.S.M. and van Loosdrecht, M.C.M. (2009) Nitrous oxide emission during wastewater treatment. Water Res. 43, 4093-4103.
3 Hein, S. and Simon, J. (2019) Bacterial nitrous oxide respiration: electron transport chains and copper transfer reactions. Adv. Microb. Physiol. 75, 137-175.