Anaerobic digestion under perfluorooctane sulfonate stress: Mechanistic insights into methane production inhibition, microbial responses, and functional adaptations.

Perfluorooctane sulfonate (PFOS) is a highly persistent and cytotoxic emerging pollutant that accumulates in sludge. Clarifying its effects on anaerobic digestion and its cytotoxicity on functional microbial metabolism is essential for evaluating the ecological risks it may pose during sludge disposal. This study investigated the effects of PFOS on methane production, microbial community responses and functional adaptations during anaerobic digestion. The results showed that environmentally relevant concentrations of PFOS had minimal effects on methane production. However, as PFOS accumulate at higher concentration, the cumulative methane production was decreased by 10% compared to the control. This reduction was primarily attributed to the inhibition of methanogens by PFOS, especially Methanosarcina, which was reduced by over 50% compared to the control. Cellular activity tests demonstrated that PFOS induced excessive reactive oxygen species and disrupted the cell membrane integrity. Further metabolic potential mining of biomarkers in F0 and F5 revealed that microorganisms enriched in functional genes associated with bacterial chemotaxis, quorum sensing and EPS metabolism were more likely to gain survival advantages under PFOS stress. This study reveals the cytotoxic mechanism of PFOS on microorganisms, deepens the understanding of microbial adaptations in anaerobic digester, and provides a theoretical basis for assessing the ecological risk of PFOS.