Biological valorization of methane and nitrogen gas-derived ammonia via methanotrophic bacteria for gut-beneficial nutrients

The in-situ upcycling of decentralized methane and nitrogen gas (N₂)-derived ammonia via methanotrophic bacteria is highly attractive. However, the toxic intermediate generated from ammonia oxidation significantly inhibits cell growth, thereby hindering efficient bioproduction. Herein, by integrating transcriptomic analysis, we develop rational metabolic engineering strategies and an optimized fed-batch fermentation to enhance ammonia utilization in a methanotrophic bacterium of Methylotuvimicrobium sanxanigenens. The modified M. sanxanigenens overexpressing hydroxylamine reductase efficiently co-assimilates methane and ammonia for cell protein synthesis, with an 18-fold increase in productivity. The resulting methanotrophic cell protein (MCP) not only exhibits an ideal essential amino acid profile but also contains bioactive nutrients, including polysaccharides and peptides. Oral administration of this nutritional MCP significantly ameliorates colitis symptoms in male mice by attenuating inflammatory progression and restoring the intestinal barrier. Moreover, MCP treatment maintains gut microbiota homeostasis and promotes the excretion of beneficial metabolites, thereby protecting the intestinal microenvironment. Hence, this study provides a promising biological approach for the local bio-valorization of decentralized CH₄ and air into functional feed additives. This biotechnology not only facilitates advancements in developing carbon-negative gas-to-value pathways but also drives green transformations in animal husbandry by reducing the use of antibiotics and vaccines.