Demonstrated role of sulfate-reducing bacterial consortia in anaerobic paracetamol biodegradation

The escalating global production and usage of paracetamol (C₈H₉NO₂), a widely administered analgesic and antipyretic pharmaceutical, has led to its ubiquitous presence in environmental matrices, including surface waters, municipal wastewater, and even potable water sources. Owing to its persistence and bioaccumulative potential, paracetamol poses a significant ecotoxicological threat, particularly through trophic transfer in aquatic ecosystems. Conventional wastewater treatment methods often fall short in completely eliminating such micropollutants. In this context, bioremediation offers a promising, sustainable, and cost-effective alternative for pharmaceutical remediation. This study investigates the anaerobic degradation potential of two sulfate-reducing bacterial consortia, designated Consortium I and Consortium II, isolated from Okhla landfill leachate and enriched with distinct Postgate media formulations. Paracetamol was introduced at varying concentrations (50-500 mg/L), with and without supplementation of an auxiliary carbon source, sodium lactate. Metagenomic profiling via 16S rRNA sequencing revealed that Consortium I was primarily composed of Clostridium (40.1%) and Acidipropionibacterium (31.2%), whereas Consortium II exhibited a dominant presence of Clostridium (80.3%) and Bacillus (7.99%). Consortium II exhibited superior degradation kinetics, achieving complete removal of 500 mg/L paracetamol in 48 h under lactate-free conditions. Conversely, the presence of sodium lactate significantly attenuated degradation efficiency, suggesting substrate competition and metabolic preference. Gas chromatography-mass spectrometry (GC-MS) identified 4-aminophenol and hydroquinone as transient intermediates, supporting a proposed anaerobic degradation pathway for paracetamol. These findings underscore the potential of native sulfate reducing bacterial consortia in the bioremediation of contaminants and provide mechanistic insight into anaerobic paracetamol degradation, offering a viable strategy for enhanced treatment efficacy of contaminated waste streams.