Magnetite nanoparticles facilitate methane production from ethanol via acting as electron acceptors

Abstract

Potential for interspecies hydrogen transfer within paddy soil enrichments obtained via addition of magnetite nanoparticles and ethanol (named as PEM) was investigated. To do this, PEM derived from rice field of Hangzhou (named as PEM-HZ) was employed, because it offered the best methane production performance. Methane production and Fe (III) reduction proceeded in parallel in the presence of magnetite. Inhibition experiments with 2-bromoethane sulfonate (BES) or phosphate showed that interspecies hydrogen transfer and Fe (III) reduction also occurred in methane production from ethanol. 16S rRNA-based Illumina sequencing results showed that Dechloromonas, Thauera, Desulfovibrio and Clostridium were the dominant putative Fe (III) -reducers, and that hydrogenotrophic Methanobacterium accounted for about 88% of the total archaeal community. These results indicated that magnetite nanoparticles that acted as electron acceptor could facilitate rapid oxidation of ethanol by members of the Fe (III) -reducers in PEM-HZ and establishment of the syntrophic relationship of Fe (III) -reducers with Methanobacterium via interspecies hydrogen transfer. Our results could offer a model to understand the microbial interaction with magnetite from a novel angle during methanogenesis.

Magnetite nanoparticles enable a rapid conversion of volatile fatty acids to methane

“…28 It is noteworthy that the considerable enrichment of Thauera (60%) in the SEM was observed compared with the SEC (12.9%), indicating its important role in the conversion of propionate to methane. Thauera was also identied during the syntrophic oxidation of acetate and ethanol in paddy soil, 13,21 and has been described for its ability to reduce Fe(III) oxides using acetate and ethanol as electric donors under anaerobic conditions. 13,21,29 Thus, a high proportion of Thauera species identied in the SEM suggested that it was most closely related to reduction of Fe(III) in magnetite.…”

“…Thauera was also identied during the syntrophic oxidation of acetate and ethanol in paddy soil, 13,21 and has been described for its ability to reduce Fe(III) oxides using acetate and ethanol as electric donors under anaerobic conditions. 13,21,29 Thus, a high proportion of Thauera species identied in the SEM suggested that it was most closely related to reduction of Fe(III) in magnetite. Additionally, 16S rRNA-based Illumina sequencing of the archaeal community in the SEM revealed that Methanobacterium (11%) was the major dominant species, which utilizes H 2 and CO 2 to produce methane.…”

Conductive particles enable syntrophic acetate oxidation between Geobacter and Methanosarcina from coastal sediments

“…Many of these environments are rich in (semi)conductive minerals like magnetite (34,35), pyrite (36,37) or black carbon resulting from incomplete burning of plant biomass (38)(39)(40). Electrically conductive iron-oxide minerals and carbon chars (magnetite, granular activated carbon, biochar) were previously shown to stimulate direct interspecies electron transfer (DIET), a recently described form of interspecies electron transfer (12,(41)(42)(43)(44)(45)(46)(47)(48)(49), whereas strict H 2 -based interactions were shown to remain unaffected by the addition of conductive materials (44). DIET is a syntrophic association where electrons are transferred via conductive and/or redox active cell surface structures between an electron-donating species (electrogen) and an electron-accepting species (electrotroph) (47)(48)(49).…”

Temperature Controls Crystalline Iron Oxide Utilization by Microbial Communities in Methanic Ferruginous Marine Sediment Incubations

“…Since sediment incubations are less defined than pure culture studies, other potential mechanisms could have been operative in addition to or instead of mDIET. Magnetite could have served as electron acceptor ( Yang et al, 2015 ), or as part of an iron redox cycle, could have been important in the production of H 2 from acetate to support hydrogenotrophic methanogenesis ( Jiang et al, 2013 ); however, iron reduction was not observed in our incubations concurrently while methanogenesis was on-going (Figure 1 ). More research is required to elucidate the exact mechanism for enhanced methanogenesis in the presence of crystalline iron oxides.…”

“…In addition, Orenia might have been involved in iron reduction together with Pelobacter spp., who are capable of fermentative and dissimilatory Fe(III) reduction ( Lovley et al, 1995 ). Syntrophic interactions that occur between microbes and iron minerals during methanogenic fermentation of organic matter mediate the electron transfer during these interactions ( Kato et al, 2012 ; Yang et al, 2015 ). Although an isolated species within the genus, Orenia metallireducens strain Z6, can reduce both poorly crystalline and crystalline iron oxides ( Dong et al, 2016 ), the reduction of amended magnetite and hematite was not detectable based on a lack of increasing Fe 2+ concentrations at 30°C.…”