Effect of humic acids on the activity of pure and mixed methanogenic cultures

Khadem, Ahmad F.; Azman, Samet; Plugge, Caroline M.; Zeeman, G.; Lier, J.B. van; Stams, Alfons Johannes Maria

doi:10.1016/j.biombioe.2017.02.012

Cited by 46 publications

(14 citation statements)

References 27 publications

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“…Moreover, methanogenesis by M. hungatei from H 2 -CO 2 was more strongly inhibited than methanogenesis from formate. Different responses of methanogens to other inhibitors, like humic acids or ammonia, were also observed in previous studies (13,14). Humic acids were found to inhibit methanogenesis by Methanobacterium formicicum, Methanobrevibacter arboriphilicus, and Methanosarcina barkeri in pure-culture experiments, in contrast to Methanospirillum hungatei and Methanosaeta concilii, which were not inhibited (13).…”

Section: Discussionsupporting

confidence: 65%

“…Different responses of methanogens to other inhibitors, like humic acids or ammonia, were also observed in previous studies (13,14). Humic acids were found to inhibit methanogenesis by Methanobacterium formicicum, Methanobrevibacter arboriphilicus, and Methanosarcina barkeri in pure-culture experiments, in contrast to Methanospirillum hungatei and Methanosaeta concilii, which were not inhibited (13). Additionally, a higher ammonia tolerance of Methanoculleus bourgensis than Methanobacterium congolense was observed previously (14).…”

Section: Discussionsupporting

confidence: 65%

“…The effect of coumarin on methanogenesis was studied in batch tests using a microbiome grown in the absence of coumarin (from a coumarin-free reactor) and a coumarin-adapted microbiome (from a reactor exposed to coumarin), both producing biogas. The effects of coumarin on the acetoclastic methanogenesis were studied by adding 13 C-methylgroup-labeled acetate as the substrate. This enabled differentiation between acetoclastic methanogenesis and acetate conversion via syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis.…”

Section: Figmentioning

confidence: 99%

“…As the percentage of 13 C-labeled CO 2 was generally lower than 2%, it was inferred that acetate was almost exclusively converted to methane via acetoclastic methanogenesis. Up to 60% of the produced methane was 13 C labeled (Fig. 4).…”

Section: Figmentioning

confidence: 99%

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Inhibitory Effect of Coumarin on Syntrophic Fatty Acid-Oxidizing and Methanogenic Cultures and Biogas Reactor Microbiomes

Popp

Plugge

Kleinsteuber

et al. 2017

Appl Environ Microbiol

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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 Ϫ1 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 Ϫ1 . 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 Ϫ1 will allow adaptation to coumarins by structural and functional community reorganization and coumarin degradation. IMPORTANCECoumarins from natural and anthropogenic sources have an inhibitory impact on the anaerobic digestion process. Here, we studied in detail the adverse effects of the model compound coumarin on acetogenesis and methanogenesis, which are two important steps of the anaerobic digestion process. Coumarin concentrations lower than 0.5 g · liter Ϫ1 had only a minor impact. Even though similar inhibitory effects can be assumed for coumarin derivatives, little effects on the anaerobic treatment of wastewater are expected where concentrations of coumarin derivatives are lower than 0.5 g · liter Ϫ1 . However, when full-scale reactors are fed with coumarin-rich feedstocks, the biogas processes might be inhibited. Hence, these feedstocks should be utilized in a well-dosed manner or after adaptation of the microbial community.KEYWORDS 16S rRNA genes, amplicon sequencing, anaerobic digestion, plant secondary metabolites, mcrA genes

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Section: Discussionsupporting

confidence: 65%

Section: Discussionsupporting

confidence: 65%

Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

See 2 more Smart Citations

Inhibitory Effect of Coumarin on Syntrophic Fatty Acid-Oxidizing and Methanogenic Cultures and Biogas Reactor Microbiomes

Popp

Plugge

Kleinsteuber

et al. 2017

Appl Environ Microbiol

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“…All the inoculums were dominated by the acetoclastic methanogen Methanosaeta (relative abundance between 57 to 66%). Similar to the present study, previous works by Khadem et al (2017) and Ghasimi et al (2016) have observed that Methanosaeta can withstand HA concentrations up to 3 g L -1 . The study by Khadem et al (2017) have suggested that Methanosaeta has better resistance to HA inhibition when compared to other methanogens, because of the cell wall structure of Methanosaeta.…”

Section: Methanogenesissupporting

confidence: 80%

Anaerobic treatment of solid manure residues

Yap¹

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Spent bedding, which is a mix of bedding stubble, faeces, urine, spilt water and animal feed, is a major by-product of livestock farming in Australia and the United States. In Australia, such residues are stockpiled for passive composting prior to land spreading to harness the nutrient value. Key concerns are uncontrolled greenhouse gas emissions, odour, losses of nutrients, and the potential for ground and surface water contamination. A sustainable management alternative is anaerobic digestion (AD), whereby organic matter in the spent bedding is converted into useable methane energy and nutrients are mobilized for subsequent recovery. However, AD technology is not currently available in Australia at a sufficiently low cost and low level of complexity for on-farm adoption. In addition, the AD characteristics of solid manure residues are not well understood, posing significant uncertainty for AD design and optimization. In response, this thesis examines a leachbed AD approach, which is particularly suitable for high solids wastes such as spend bedding, and can be cost-effective and simple to construct and operate.A pilot scale (200 L) leachbed system was constructed and operated. Spent bedding was collected from Australian piggeries and wetted with water leachate in the enclosed leachbed via two distinct operating modes: trickling and flood-and-drain. The water leachate was heated in both configurations, aimed at a 37 o C operating temperature. Results showed comparable methane recovery for both the trickling and flood-and-drain modes at 50% of the biochemical methane potential (B0 = 195 -218 L CH4 kg VSfed -1 ) in both cases. This indicated that AD performance was insensitive to the mode of leachate flow. However, the flood-and-drain leachbed did mobilise more particulates into the leachate than the trickling leachbed, which could cause a materials-handling problem with pumping of leachate onfarm. Inoculation with solid digestate from a previous leachbed (inoculum-to-substrate ratio of 0.22 on a VS basis) hastened the AD start-up, but methane recovery remained at 50 % of the Bo. Post-digestion testing indicated that methane recovery was limited by insufficient indigenous inoculum and/or by chemical inhibition.To clarify the effects of operating conditions on AD performance at high solids content, a series of batch tests were performed at smaller laboratory scale. These tested the viability of indigenous inoculum in spent bedding (from the manure component), together with the effects of operating temperature and solids concentration. Results showed that spent bedding actually did have sufficient indigenous inoculum to recover the full Bo of the spent bedding. However, to operate at higher solid loading (≥ 10 % TS content) and higher II temperatures (55 ºC), methanogenic activity could be boosted by inoculation with leachate and/or solid digestate from a former leachbed batch. The use of leachate as an inoculum would preserve leachbed volume for fresh waste and easier handling.Chemical analysis of digestat...

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