Xun Zhang, Bingjun Liu, Sheng Xue, Xiangqin Jiang, Ruifeng Chen
Coal derived organic matter is structurally recalcitrant and poorly bioavailable, which limits microbial methane formation. This study investigated how magnetic field intensity regulates the microbial conversion of bituminous coal and methane production. Anaerobic cultures were established without a magnetic field (CK) and under low (LC, 10 mT), medium (MC, 20 mT), and higher (HC, 40 mT) magnetic field intensities. Methane production, Biolog EcoPlate profiling, FTIR spectroscopy, three dimensional excitation-emission matrix fluorescence spectroscopy, 16S rRNA gene sequencing, metatranscriptomics, and untargeted metabolomics were integrated to resolve the associated biological responses. The final methane yields in CK, LC, MC, and HC were 127.66, 253.89, 326.84, and 211.67 μmol g-1 coal, respectively. The MC treatment produced the highest methane yield and increased the day-7 average well color development to 0.71, which was 77.5% higher than CK. It also showed the greatest utilization of ester and acid substrates. Community analysis showed enrichment of Syntrophomonas, Clostridium_sensu_stricto_1, Bacillus and Methanosarcina under the MC condition. Metatranscriptomic analysis identified responses in methane metabolism, aromatic-ring metabolism, one-carbon metabolism, cofactor biosynthesis, and cofactor-related transcriptional functions. Untargeted metabolomics further showed that MC produced the largest overall shift in the metabolite feature profile, with 5,639 differential features relative to CK. Together, these results demonstrate an intensity-dependent magnetic response in coal biomethanation, with the medium magnetic field producing the strongest coordinated microbial and metabolic response. This study provides a system-level basis for evaluating magnetic stimulation as a non-contact and intensity-tunable strategy for enhancing the microbial conversion of recalcitrant coal-derived organic matter.