Optimizing anaerobic digestion for antibiotic degradation and antimicrobial resistance mitigation

Anaerobic digestion (AD) is widely applied to treat antibiotic pharmaceutical wastewater for antimicrobial resistance mitigation and synchronous bio-energy recovery. However, process efficiency and risk control depend critically on operational strategies. Here, we systematically evaluated the roles of feedstock composition and digestive temperature in optimizing lincomycin-containing AD. Glucose-rich mesophilic digestion achieved superior lincomycin degradation and methane recovery compared to thermophilic and protein-rich systems. Transformation product analysis suggested that glucose-rich feedstock might facilitate the furan ring-opening step during lincomycin degradation, possibly owing to structural and metabolic similarities between glucose and lincomycin. The enrichment of lincomycin-degrading Clostridium and Methanobacterium in response to glucose-rich mesophilic condition, together with their potential syntrophic interaction, further supported the accelerated lincomycin degradation and methanation. Metagenome-assembled genome analysis revealed that protein-rich and thermophilic operation intensified the proliferation of host consortia harboring gene clusters with antibiotic resistance gene-mobile genetic element (ARG-MGE) co-occurrence, and induced putative horizontal transfer of ARG, resulting in the increased ARG abundance. ARG proliferation in thermophilic systems was associated with enrichment of lincomycin-resistant consortia (JAAYZQ01 sp034428935 and Tenuifilum sp018056955) after antibiotic exposure, which preferentially enriched under higher-temperature conditions. In contrast, glucose-rich digesters exhibited a reduced potential for horizontal gene transfer mediated by MGEs and natural conjugation. Overall, feedstock composition exerted a greater influence on antimicrobial resistance dissemination compared to temperature. Collectively, our findings provide an operational framework for sustainable treatment and valorization of antibiotic-containing wastewater.