Enhanced recovery of nitrous oxide from incineration leachate in a microbial electrolysis cell inoculated with a nosZ -deficient strain of Pseudomonas aeruginosa

High concentrations of nitrous oxide were recovered from partial nitrification treated leachate in a microbial electrolysis cell (MEC) inoculated with a nosZ -deficient strain of Pseudomonas aeruginosa. N 2 O conversion efficiencies > 90% were achieved when a potential of 0.8 V was applied to the MEC. The Δ nosZ strain was enriched in the 0.8 V MEC, but Achromobacter dominated the non-current control. Nitric oxide reductase genes were highly expressed by Δ nosZ cells growing in the 0.8 V MEC, consistent with enhanced nitrous oxide production rates. Concentrations of phenazine derivatives and transcripts from phenazine biosynthesis genes were also high in the 0.8 V MEC. Phenazine derivatives are known to act as electron shuttles, enhance biofilm formation, and help ward off competitors, thereby increasing the survivability of the Δ nosZ strain in the MEC. These results show that applied current stabilized growth of the Δ nosZ strain in the reactor and allowed it to sustainably generate high concentrations of nitrous oxide.