Inhibitory effect of coumarin on syntrophic fatty acid-oxidizing and methanogenic cultures and biogas reactor microbiomes

Denny Popp*, Caroline M. Plugge, Sabine Kleinsteuber, Hauke Harms, Heike Sträuber

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

13 Citations (Scopus)

Abstract

Coumarins are widely found in plants as natural constituents having antimicrobial activity. When considering plants that are rich in coumarins for biogas production, adverse effects on microorganisms driving the anaerobic digestion process are expected. Furthermore, coumarin derivatives, like warfarin, which are used as anticoagulating medicines, are found in wastewater, affecting its treatment. Coumarin, the structure common to all coumarins, inhibits the anaerobic digestion process. However, the details of this inhibition are still elusive. Here, we studied the impact of coumarin on acetogenesis and methanogenesis. First, coumarin was applied at four concentrations between 0.25 and 1 g · liter-1 to pure cultures of the methanogens Methanosarcina barkeri and Methanospirillum hungatei, which resulted in up to 25% less methane production. Acetate production of syntrophic propionate- and butyrate-degrading cultures of Syntrophobacter fumaroxidans and Syntrophomonas wolfei was inhibited by 72% at a coumarin concentration of 1 g · liter-1. Coumarin also inhibited acetogenesis and acetoclastic methanogenesis in a complex biogas reactor microbiome. When a coumarin-adapted microbiome was used, acetogenesis and methanogenesis were not inhibited. According to amplicon sequencing of bacterial 16S rRNA genes and mcrA genes, the communities of the two microbiomes were similar, although Methanoculleus was more abundant and Methanobacterium less abundant in the coumarin-adapted than in the nonadapted microbiome. Our results suggest that well-dosed feeding with coumarin-rich feedstocks to full-scale biogas reactors while keeping the coumarin concentrations below 0.5 g · liter-1 will allow adaptation to coumarins by structural and functional community reorganization and coumarin degradation.

Original languageEnglish
Article numbere00438-17
Number of pages14
JournalApplied and Environmental Microbiology
Volume83
Issue number13
DOIs
Publication statusPublished - 2017

Keywords

  • 16S rRNA genes
  • Amplicon sequencing
  • Anaerobic digestion
  • McrA genes
  • Plant secondary metabolites

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