Fe3O4 nanoparticles promote methanogenesis in propionate acclimated system

Propionate accumulation is common in anaerobic digestion systems, while Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs) show potential in steering direct interspecies electron transfer (DIET) to facilitate methanogenesis from propionate. However, the effect of Fe 3 O 4 NPs in stable microbial communities remains unclear. This study demonstrated that 1.0 g/L Fe 3 O 4 NPs enhanced propionate degradation and methane production by 220 % and 55 % of the propionate-acclimated microbial consortia post-shock loading, as evidenced by batch-test. High propionate concentrations suppressed Geobacter , yet Fe 3 O 4 NPs enabled electron syntrophy between alternative DIET-participants ( Arcobacter , Syntrophobacter ) and methanogens ( Methanothrix , Methanobacterium ) serving as electron conduits. Network analysis further revealed that Fe 3 O 4 NPs activated interactions among potential electroactive microbes, highlighting the potentially ubiquitous presence of electron syntrophy. Even in propionate-stressed microbial communities, such mutualism may be rapidly activated by Fe 3 O 4 NPs, offering a practical solution for mitigating propionate accumulation and enhance digester performance.