Methanogen

About: Methanogen is a research topic. Over the lifetime, 1146 publications have been published within this topic receiving 48254 citations.

Suppression of methanogenesis in paddy soil increases dimethylarsenate accumulation and the incidence of straighthead disease in rice

Abstract: Some soil microbes can methylate arsenic (As) and produce dimethylarsenate (DMA) as a main product. Excessive accumulation of DMA by rice plants can cause the straighthead disease, a physiological disorder leading to substantial yield losses. DMA can also be demethylated in soil, but the mechanism and the microbes involved are not well understood. We investigated the dynamics of methylated As species, including monomethylarsenate (MMA), DMA and dimethyl-monothioarsenate (DMMTA), in three paddy soils that produced the straighthead disease. The soils were incubated under flooded conditions with or without the addition of 2-bromoethanesulfonate (BES), a specific inhibitor of methanogenesis. DMA and DMMTA concentrations in porewater increased initially as soil redox potential decreased, and then decreased rapidly coinciding with the production of methane. BES addition largely suppressed methanogenesis and the disappearance of DMA and DMMTA, but not of MMA. BES addition suppressed the transcript levels of archaeal 16S rRNA and, particularly, mcrA gene encoding methyl-coenzyme reductase subunit A. Among the core genera of archaea, the absolute abundances of Methanomassiliicoccus and Methanosarcina were decreased significantly by BES in the three soils. In a pot experiment with two soils, BES addition significantly increased DMA accumulation in rice husks and the incidence of the straighthead disease in rice. The results suggest that DMA and DMMTA demethylation in paddy soil is coupled to methanogenesis with Methanomassiliicoccus and Methanosarcina likely playing an important role.

Understanding gaseous reduction in swine manure resulting from nanoparticle treatments under anaerobic storage conditions

Abstract: Manure is an impending source of carbon (C), sulfur (S) and water (H2O). Consequently, microbial populations utilize these constituents to produce methane (CH4), carbon dioxide (CO2), greenhouse gases (GHGs), and hydrogen sulfide (H2S). Application of nanoparticles (NPs) to stored manure is an emerging GHG mitigation technique. In this study, two NPs: nano zinc oxide (nZnO) and nano silver (nAg) were tested in swine manure stored under anaerobic conditions to determine their effectiveness in mitigating gaseous emissions and total gas production. The biological sources of gas production, i.e., microbial populations were characterized via Quantitative Polymerase Chain Reaction (qPCR) analysis. Additionally, pH, redox, and VFAs were determined using standard methods. Each treatment of the experiment was replicated three times and NPs were applied at a dose of 3 g/L of manure. Also, headspace gas from all treatment replicates were analyzed for CH4 and CO2 gas concentrations using an SRI-8610 Gas Chromatograph and H2S concentrations were measured using a Jerome 631X meter. Nanoparticles tested in this study reduced the cumulative gas volume by 16%–79% compared to the control. Among the NPs tested, only nZnO consistently reduced GHG concentrations by 37%–97%. Reductions in H2S concentrations ranged from 87% to 97%. Gaseous reductions were likely due to decreases in the activity and numbers of specific gas producing methanogenic archaea and sulfate reducing bacterial (SRB) species.

Thermophilic methanogenic consortium for conversion of cellulosic biomass to bioenergy

Abstract: A system for the efficient conversion of plant biomass to methane is provided, where the conversion includes use of a thermophilic methanogenic consortium containing a cellulolytic thermophile, an acetate-oxidizing thermophile and a thermophilic methanogen, the combination of which hydrolyzes hexoses and pentoses, oxidizes acetate and provides a hydrogen sink, to convert plant biomass to the theoretical limit of bioenergy.

Hydrogenotrophic methanogenesis dominates at high pH

Abstract: One potential design for a geological disposal facility (GDF) for intermediate level radioactive waste (ILW) involves the use of a cement base grout which will establish a highly alkaline environment for extended time periods [1]. Methane generation by colonising microbes could impact the long-term performance of the facility by influencing gas pressures and potentially leading to the migration of 14C to the biosphere [1]. Sediments acquired from a wide-range of anthropogenic alkaline sites in the UK were used to develop acetoclastic and hydrogenotrophic methanogen enrichment cultures over a broad range of pH values (7.0–12.0). The generation of methane from hydrogen and acetate was assessed to determine the dominant methanogenic pathways. Archaeal community analysis via Illumina MiSeq was employed to describe the populations involved and the acetoclastic inhibitor methyl fluoride was utilised to confirm the lack of acetate-dependent methane generation under alkaline conditions. High pH (pH>9.0) microcosms employing alkaline sediments were dominated by hydrogen-consuming methanogens of the orders Methanobacteriales and Methanomicrobiales, with no acetate consumption detected under these conditions. In contrast, neutral pH microcosms employing control sediments were dominated by acetoclastic methanogens of the order Methanosarcinales and demonstrated high acetate consumption rates. The rate of acetate consumption and proportion of acetoclastic methanogens decreased in a linear fashion as the pH within cultures was increased, however hydrogen consumption rates remained stable up to pH 11.0. The data shown suggests hydrogenotrophic methanogenesis is the dominant methanogenic pathway at high pH which could have important consequences on gas pressures within a GDF.