Characterization of a nitrous oxide-reducing bacterial consortium

Abstract

Nitrous oxide (N2O) is a greenhouse gas with a global warming potential 310 times higher than that of carbon dioxide. In this study, an N2O-reducing consortium was obtained by enrichment culture using advanced treatment sludge as the inoculum. The dominant bacteria in the consortium were Sulfurovum (17.95%), Geobacter (14.63%), Rectinema (11.45%), and Chlorobium (8.24%). The consortium displayed optimal N2O reducing activity when acetate was supplied as the carbon source at a carbon/nitrogen ratio (mol·mol-1) of 6.3. The N2O reduction rate increased with increasing N2O concentration at less than 3,000 ppm. Kinetic analysis revealed that the maximum N2O reduction rate of the consortium was 163.9 µg-N·g-VSS-1·h-1. Genes present in the consortium included nosZ (reduction of nitrous oxide to N2), narG (reduction of nitrate to nitrite), nirK (reduction of nitrite to nitric oxide), and norB (reduction of nitric oxide to nitrous oxide). These results indicate that the N2O-reducing consortium is a promising bioresource that can be used in denitrification and N2O mitigation. © 2019, The Korean Society for Microbiology and Biotechnology