Mechanistic insights into the attenuation of antibiotic resistance genes in thermophilic anaerobic co-digestion of food waste: A comprehensive metagenomic and absolute quantification study

Food waste (FW) is a significant source of antibiotic resistance genes (ARGs) and anaerobic digestion is an effective strategy to limit the spread of antimicrobial resistance. In this study, ARGs diversity and abundance, along with their relationship to the microbial community were investigated by metagenomic and qPCR during thermophilic anaerobic co-digestion of FW, kitchen waste (KW) and garden waste (GW). Results indicate that R_FK (FW + KW) and R_FG (FW + GW) effectively reduced 9 and 13 representative ARG subtypes (removal rates exceeding 1 log unit), and completely eliminated 16 and 30 ARG subtypes, respectively, outperforming R_F (FW). The Redundancy analysis indicated positive correlations between ARG removal rates and methane content, and negative correlations with volatile short-chain fatty acids and ammonia nitrogen. Procrustes and network centrality analyses suggested that removing resistant bacteria like Firmicutes and Bacteroidota in R_FK and R_FG contributed to efficient ARG removal. Co-digestion enhanced ARG elimination by improving reactor performance and altering bacterial communities.