NanoFe₃O₄ accelerates methanogenic straw degradation by improving energy metabolism

The impacts of nanoFe₃O₄ on the composition of degradation products, microbial community, and microbial metabolic functions during rice straw anaerobic degradation were investigated. Under nanoFe₃O₄ addition, CH₄ production and straw degradation increased by 81% and 10.4%, respectively, in paddy soil enrichment. Coupling product chemistry and microbial community during straw degradation found that nanoFe₃O₄ effectively promoted the hydrolysis-acidification-methanogenesis of straw, which made lignin-, lipid-, protein-, tannin-like and VFAs products rapidly increase and then quickly decrease. Moreover, the relative abundance of Clostridiaceae and Methanosarcina corresponded with increased hydrolysis and acetoclastic methanogenesis with nanoFe₃O₄ addition. Cellular processes, environmental information processing and metabolism, especially energy metabolism, were enhanced functions of the microbial community during straw degradation with nanoFe₃O₄. The nanoFe₃O₄ addition may improve the electron transfer efficiency, stimulate energy release, reduce Gibbs free energy of the half reaction of organic carbon oxidation (ΔG_cox⁰) and promote energy metabolism to accelerate straw degradation and CH₄ generation.