The antihistamine diphenhydramine is demethylated by anaerobic wastewater microorganisms. (July 2018)

• Record Type: Journal Article
• Authors: Wolfson, Sarah J.; Porter, Abigail W.; Villani, Thomas S.; Simon, James E.; Young, Lily Y.
• Is Part Of: Chemosphere. Volume 202(2018)
• Page Start: 460
• Page End: 466
• Publication Date: 2018-07
• Subjects: Pharmaceutical -- Transformation -- Anaerobic microbiology -- Diphenhydramine -- Methanogenesis -- Wastewater treatment; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2018.03.093
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: While emerging pharmaceutical contaminants are monitored in wastewater treatment and the environment, there is little information concerning their microbial metabolites. The transformation of diphenhydramine by microorganisms in anaerobic digester sludge was investigated using anaerobic cultures amended with 1 mM diphenhydramine as the sole carbon source. Complete transformation of the parent compound to a persistent metabolite occurred within 191 days. Using GC/MS analysis, the metabolite was identified as N-desmethyl diphenhydramine. Loss of the parent compound diphenhydramine followed a first order rate constant of 0.013 day −1 . There was no observed decrease in metabolite concentration even after a further 12 months of incubation, suggesting that the metabolite resists further degradation during wastewater treatment. Bacterial community diversity in the diphenhydramine transforming assay cultures showed enrichment in Comamonadaceae, Symbiobacteriaceae, Anaerolineaceae, and Prevotellaceae relative to unamended background controls. An anaerobic toxicity assay demonstrated that diphenhydramine has an inhibitory effect on both fermentative bacteria and methanogenic archaea in the wastewater community. In contrast, the metabolite N-desmethyl diphenhydramine partially suppressed methanogens but did not impact the fermenting community. To our knowledge, this is the first report of diphenhydramine metabolism by a bacterial community. The limited transformation of diphenhydramine by wastewater microorganisms indicates that N-desmethyl diphenhydramine will enter the environment along with unmetabolized diphenhydramine. Graphical abstract: Image 1 Highlights: The antihistamine diphenhydramine was demethylated by anaerobic wastewater microbes. The metabolite N-desmethyl diphenhydramine accumulates stoichiometrically. Diphenhydramine can inhibit fermentative bacteria and methanogenic archaea. N-desmethyl diphenhydramine inhibited methanogens but did not affect fermenters. N-desmethyl diphenhydramine, once released, has unknown effects in the environment.