ena-STUDY-HELMHOLTZ CENTRE FOR ENVIRONMENTAL RESEARCH - UFZ.-19-05-2016-11:50:00:597-60
Inhibitory effect of coumarin on syntrophic fatty acid oxidizing and methanogenic cultures and biogas reactor microbiomes
Coumarins are widely found in plants as natural constituents having antimicrobial activity. When considering plants rich in coumarins for biogas production, adverse effects on microorganisms driving the anaerobic digestion process are expected. Furthermore, coumarin derivatives like warfarin, which is used as anti-coagulating medicine, are found in wastewater affecting its treatment. Coumarin as the structure common to all coumarins inhibits the anaerobic digestion process. However, 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 L 1 to pure cultures of the methanogens Methanosarcina barkeri and Methanospirillum hungatei leading to up to 25% less methane production. Acetate production of syntrophic propionate and butyrate degrading cultures of Syntrophobacter fumaroxidans and Syntrophomonas wolfei were inhibited by 72% at a coumarin concentration of 1 g L 1. Coumarin also inhibited acetogenesis and acetoclastic methanogenesis by a complex biogas microbiome. When a coumarin-adapted microbiome was used, acetogenesis and methanogenesis remained unaffected. According to amplicon sequencing of bacterial 16S rRNA genes and mcrA genes, the microbial communities of both microbiomes were similar though Methanoculleus was more and Methanobacterium was less abundant in the coumarin-adapted microbiome compared to the non-adapted microbiome. However, our results show that well-dosed feeding with coumarin-rich feedstocks to full-scale biogas reactors will allow adaption to coumarins by structural and functional community reorganization and coumarin degradation.
Coumarins are widely found in plants as natural constituents having antimicrobial activity. When considering plants rich in coumarins for biogas production, adverse effects on microorganisms driving the anaerobic digestion process are expected. Furthermore, coumarin derivatives like warfarin, which is used as anti-coagulating medicine, are found in wastewater affecting its treatment. Coumarin as the structure common to all coumarins inhibits the anaerobic digestion process. However, 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 L 1 to pure cultures of the methanogens Methanosarcina barkeri and Methanospirillum hungatei leading to up to 25% less methane production. Acetate production of syntrophic propionate and butyrate degrading cultures of Syntrophobacter fumaroxidans and Syntrophomonas wolfei were inhibited by 72% at a coumarin concentration of 1 g L 1. Coumarin also inhibited acetogenesis and acetoclastic methanogenesis by a complex biogas microbiome. When a coumarin-adapted microbiome was used, acetogenesis and methanogenesis remained unaffected. According to amplicon sequencing of bacterial 16S rRNA genes and mcrA genes, the microbial communities of both microbiomes were similar though Methanoculleus was more and Methanobacterium was less abundant in the coumarin-adapted microbiome compared to the non-adapted microbiome. However, our results show that well-dosed feeding with coumarin-rich feedstocks to full-scale biogas reactors will allow adaption to coumarins by structural and functional community reorganization and coumarin degradation.