3D porous Fe-based MOF composites promote methanogen immobilization, proliferation, and methanogenesis-related gene expression for methane enrichment

Traditional anaerobic digestion typically produces biogas containing only 50–70% CH 4 , resulting in substantial biogas upgrading requirements. Functionally isolating methanogenic cells in a standalone immobilized platform offers a potential strategy for methane enrichment. Herein, biologically adaptive Fe-based metal-organic framework (Fe-MOF) composites, namely perlite-supported Fe-MOF (PE@Fe-MOF) and polyurethane sponge-supported Fe-MOF (SP@Fe-MOF), were developed to immobilize Methanosarcina barkeri ( M. barkeri ) and enhance methanogenic performance. Quantitative results indicated that the Fe-MOF functional layer was a key factor driving microbial proliferation and methane enrichment. Compared with the free-cell blank (∼32%) and unmodified carriers (∼35–37%), both Fe-MOF-functionalized composites increased the CH 4 fraction to approximately 90%, accompanied by a significant increase in mcrA gene copy numbers ( p < 0.05). Moreover, SP@Fe-MOF exhibited superior cell colonization compared with PE@Fe-MOF, which facilitated the efficient immobilization of M. barkeri on the carrier. Transcriptomic analysis further revealed that SP@Fe-MOF enhanced methanogenesis by upregulating carbon metabolism and activating quorum-sensing-associated pathways related to biofilm stabilization. Ultimately, this rational three-dimensional carrier design demonstrates an upstream strategy for in-situ methane enrichment via cell-material interface interactions, providing a proof-of-concept for future biogas upgrading process development.