January 2025
·
15 Reads
Replacement of nitrate with ammonium at large scale cultivation of methanotrophs can improve the economic feasibility of these bacteria in methane-based biomanufacturing and methane removal. However, ammonia toxicity and N 2 O emission impede this option. The mechanism of ammonia oxidation in methanotrophs remains elusive, limiting the effort to detoxify ammonia via genetic engineering. Using an industrially promising methanotroph as a model, we identified a porin PorA that facilitated ammonium uptake. Inactivation of PorA remarkably relieved ammonia toxicity and reduced N 2 O production. Meanwhile, we demonstrated that haoA , cytL and hcp contributed to ammonia detoxification and cytL was involved in the conversion of NH 2 OH to N 2 O. A mutant strain with increased ammonium-utilizing ability and decreased N 2 O emission was constructed. High growth rate and cell biomass were achieved in fed-batch fermentation with this strain using ammonium. These results deepen our understanding of ammonia oxidation in methanotrophs and promote their applications in biomanufacturing and methane removal.