Metagenomics insights into humification improvement and antimicrobial resistance reduction during hyperthermophilic...

Compared to conventional thermophilic composting, hyperthermophilic composting elevates fermentation temperature and electric field composting facilitates oxygen transfer, with both strategies promoting humification and reshaping the microbial community structure. This study coupled hyperthermophilic composting with electric field composting (HEC) to further enhance livestock manure humification while suppressing antimicrobial resistance. A composting strategy consisting of 12-day hyperthermophilic pretreatment and 28-day electric field composting was implemented. Integrating analyses of the humification process, metagenomics, metabolic pathways, and key microbiota linked to humification and antimicrobial resistance, this study indicated that HEC strategy triggered an initial hyperthermophilic surge and sustained thermophilic, with potential enhancement of aerobic metabolic activity under the applied electric field, thereby driving microbial succession from Proteobacteria to Firmicutes and Actinobacteria. The favorable conditions and microbiota shift enhanced metabolic activity, accelerated transformation of organic substrates, and increased aromatic precursor accumulation, resulting in a 2.5-fold increase in humic acid carbon compared with conventional thermophilic composting. Meanwhile, HEC reduced antibiotic resistance genes (ARGs) abundance and diversity by suppressing resistance-associated microbiota, particularly Proteobacteria and Bacteroidetes, which predominantly harbor antibiotic efflux genes (e.g., adeF). The attenuation of ARGs abundance and diversity reached 66.1% and 74.2%, respectively, compared with 43.3% and 48.8% in conventional thermophilic composting after 40d fermentation, and meanwhile, dominant humus-forming microbiota were relatively less associated with ARGs. This study elucidated the mechanisms underlying enhanced humification and ARG mitigation during the HEC process, thereby offering an effective strategy for resource recovery from livestock manure.