Intracellular accumulation of hydrophobic 1,3-PDN inhibits methanogenesis in rumen methanogens

Methane (CH4) from ruminants is a major source of agricultural greenhouse gas and represents a loss of dietary energy. 3-Nitrooxypropanol (3-NOP) is a known methanogenesis inhibitor, but its hydrophilic nature may limit the cellular accessibility to methanogens. Here, we systematically evaluated 1,3-propanediol dinitrate (1,3-PDN), a more hydrophobic derivative of 3-NOP, for its antimethanogenic potential and underlying mode of action using ruminal fermentation, pure-culture assays, multi-omics analyses, and molecular docking. Intracellular accumulation assays indicated greater cellular accumulation of 1,3-PDN than 3-NOP in rumen-derived methanogen Methanobrevibacter olleyae. Ruminal fermentation assays showed that 1,3-PDN reduced CH4 production by ~55%, and altered hydrogen (H2) metabolism, leading to 11-fold increase in H2 accumulation. Metatranscriptomic profiling revealed that 1,3-PDN significantly altered the active archaeal community, with a notable reduction in Methanobrevibacter_A and suppression of hydrogenotrophic methanogenesis. Molecular docking suggested that 1,3-PDN may bind to the conserved active site of methyl-coenzyme M reductase (MCR), potentially contributing to MCR-associated inhibition. Proteomic analysis further indicated that 1,3-PDN supplementation downregulated key MCR subunits and simultaneously affected other redox-sensitive methanogenesis-related processes, including tetrahydromethanopterin S-methyltransferase subunits and proteins involved in the biosynthesis of cofactors F430 and cobalamin. Nitrogen-equivalent assay suggested partial contribution of nitrite to the methanogenesis inhibition and oxidative effects induced by 1,3-PDN. Together, these findings identify 1,3-PDN as an effective inhibitor of ruminal methanogenesis with enhanced cellular enrichment, providing mechanistic insights for the rational development of new CH4 inhibitors.