Anaerobic Wastewater and Environmental Microbial Communities Readily Demethylate Methoxy Aromatic PPCPs

Pharmaceuticals and personal care products (PPCPs) can be metabolized by microbes during wastewater treatment, releasing not only the intact PPCPs but also their metabolites to the environment. There is an urgent need to understand PPCP transformation however the multitude of chemicals makes studying each microbial metabolism an arduous task. We propose that predicting microbial metabolism of PPCPs during wastewater treatment is best understood in the context of shared chemical structure. We recently described a methanogenic enrichment culture from anaerobic wastewater sludge that readily demethylates the common pharmaceutical naproxen (Aleve) to 6-O-desmethylnaproxen, with no loss of the metabolite observed. In this culture, methane was generated at stoichiometric amounts to naproxen demethylation, indicating that the methyl group removed from naproxen stimulates a complex microbial community. The natural methoxy aromatic compounds syringic and vanillic acids were also readily demethylated, and this shared metabolism prompted an examination of other methoxy aromatic xenobiotic compounds. In the present study we challenged the methanogenic wastewater culture with the methoxy aromatic UV filter oxybenzone and observed demethylation to benzophenone-1, which itself is an estrogenic contaminant. In addition, the pharmaceutical guaifenesin (Mucinex) was transformed to a novel demethlated metabolite whose environmental and health impacts are yet unknown. A second culture from sulfidic marine sediment was established to simulate anoxic environmental sediment receiving pharmaceutical contamination. Again, the natural and PPCP methoxy aromatic compounds were readily demethylated with accumulation of the metabolites. The demethylation of oxybenzone to the contaminant benzophenone by both cultures emphasizes the importance of methoxy aromatic demethylation in evaluating PPCP risk. This study provides experimental support to a systematic understanding of methoxy aromatic PPCP transformation, those investigated here and those not yet investigated. It suggests that methoxy aromatic PPCPs are transformed to demethylated metabolites during anaerobic wastewater treatment and the environment, and their metabolites may accumulate.