Naproxen Transformation by a Wastewater Consortium

The microbial transformation of pharmaceutical compounds often results in recalcitrant metabolites, and understanding the behavior of the responsible microbial communities is integral to this transformation. Pharmaceutical compounds are potential carbon substrates for microbes. In this work, the community ecology and biochemistry of naproxen demethylation was investigated in an anaerobic wastewater community. Enrichment cultures were established with anaerobic wastewater sludge inoculum and provided naproxen as the sole carbon source. Primary enrichment cultures transformed 1mM naproxen to 6-O-desmethylnaproxen (DMN) in 22 days. Continual enrichment, naproxen addition, and culture transfer resulted in consistent transformation of naproxen with no loss of DMN observed. Methane was also generated at 0.83mmol per 1mM naproxen transformed. In addition to naproxen, the consortium readily demethylated syringic acid and vanillic acid. DNA analysis revealed a community of acetogenic bacteria and syntrophic acetate oxidizing archaea. Combined with the chemical data, this suggests the enriched consortium performs aromatic O-demethylation by a tight syntrophy between acetogenic bacteria and syntrophic acetate oxidizers. The proposed model of carbon transfer through the anaerobic wastewater food web elucidates community level metabolism of aromatic O-methyl contaminants.