Bioupcycling Methane\nand CO<sub>2</sub> for Succinate\nProduction by an Engineered Type I Methanotrophic Bacterium

Methane, a byproduct of agricultural activities, has\nshown potential\nas a nonedible substrate for biomanufacturing. The production of succinate\nby a methanotrophic bacterium utilizing methane presents an innovative\nroute for the sustainable synthesis of chemicals. In this study, Methylotuvimicrobium buryatense 5GB1S was genetically\nmodified through the reconstruction of an artificial serine cycle\nto enable the bioconversion of both methane and CO<sub>2</sub> into\nsuccinate. The <sup>13</sup>C labeling analysis confirmed the CO<sub>2</sub> fixing in M. buryatense 5GB1S,\nleading to a 46% improvement in carbon conversion efficiency and a\n107% increase in succinate production compared to the wild-type strain.\nThe transcriptome data on carbon metabolisms was assessed to guide\nfuture optimizations for strengthening the overall carbon flux from\nmethane to succinate. Finally, the maximum succinate titer of 299.36\nmg/L was achieved under oxygen-limited conditions in 3 L bioreactors,\nwhich resulted in the volumetric productivity of 199.60 mg/L/day,\nrepresenting a 23-fold enhancement compared to the wild-type strain.\nThis study offers a new strategy for upcycling greenhouse gases into\nsuccinate in a sustainable manner through methanotrophic-based biomanufacturing.