Thiamphenicol decouples acidogenesis from methanogenesis and redirects carbon flux toward volatile fatty acids in sludge anaerobic digestion

Abstract

Antibiotic residues in waste activated sludge (WAS) may disrupt anaerobic carbon conversion, yet how phenicol antibiotics redistribute carbon between acidogenesis and methanogenesis remains unclear. At 10 mg/g TSS, methane production decreased by 63.2% while VFAs reached 131-fold the control. This functional decoupling was underpinned by microbial fates: hydrolytic-acidogenic bacteria were largely retained or enriched, whereas methanogenic archaea and syntrophic bacteria were severely depleted. Concurrently, bacteria–archaea ecological networks underwent reorganization, with positive correlations partially rebounding at moderate TAP exposure. The network collapsed at high TAP, with substantial loss of connector taxa mediating inter-module metabolite exchange. Metagenomic evidence further revealed a functional asymmetry: genes involved in substrate transport and amino acid metabolism were maintained or showed increased relative abundance, while methanogenic genes and AI-2-associated communication genes exhibited decreased relative abundance. PLS-PM revealed that TAP was positively associated with the acidogenic bacterial community (β = 0.960) but negatively with methanogenic potential (β = -0.998). Accordingly, the methane share dropped from 98.7% to 18.1%, while VFAs increased to 81.9% of the COD-equivalent product pool. This work advances the understanding of antibiotic-driven functional imbalance and carbon flux redirection in sludge anaerobic digestion, providing a mechanistic basis for managing antibiotic-laden sludge prior to energy recovery.