Influence of Acidic pH on Hydrogen and Acetate Production by an Electrosynthetic Microbiome

LaBelle, Edward V.; Marshall, C. W.; Gilbert, Jack A.; May, Harold D.

doi:10.1371/journal.pone.0109935

Cited by 130 publications

(118 citation statements)

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“…2). The unrecovered coulombs in the initial period appear to have accumulated in precursors such as formate and hydrogen; then some of the precursors might have been converted to acetate by electrosynthetic CO 2 conversion in the later phase [18]. The estimated acetate production rate was 561 mg/L/d, which is relatively higher than the previously reported autotrophic CO 2 reduction [19][20][21].…”

mentioning

confidence: 71%

Biologically activated graphite fiber electrode for autotrophic acetate production from CO₂in a bioelectrochemical system

Im¹,

Song²,

Jeon³

et al. 2016

Carbon letters

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Recently, microbial electrosynthesis (MESs) has been highlighted for the purpose of biological CO 2 reduction with simultaneous production of intermediates and value-added chemicals. The bioelectrochemical system (BES), which employs microorganisms and a bacterial community as a biocatalyst, has been developed to convert CO 2 , a greenhouse gas, into liquid biofuels, such as ethanol and butanol, as well as platform chemicals [1]. Several bacterial species, called cathodophilic microorganisms (e.g., Sporomusa ovata and Clostridium ljungdahlii) were reported to interact with a carbon electrode by accepting electrons supplied externally from a power supply [2][3][4]. Through this process, oxidized chemical molecules, such as CO 2 , can be converted to more reduced products, such as acetate and ethanol [4,5]. Since the first report of MESs with S. ovata [3,4], performance has been improved by efforts to optimize the reactor design, regulate the applied potential, and improve the bacterial enrichment method [6][7][8]. On the other hand, the interaction between microorganism and carbon materials is still unknown, which is the main factor limiting further improvement of the performance of the MES process. For example, insufficient information about microbecarbon interactions is delaying the advance of the process significantly when the input potential is <−410 mV vs standard hydrogen electrode (SHE), which is the theoretical minimum potential for hydrogen production [9].Carbon has been recognized as the best material for fuel cell applications owing to its good electrical conductivity, its potential for the impregnation of catalysts, and its cost effectiveness [10,11]. For the same reasons, a range of morphologies of carbon materials have been utilized as anode and cathode electrodes in BES in the form of carbon paper, cloth, graphite rod, and felt in BES systems [12]. The porous structure of carbon can also provide sufficient surface area for bacterial attachment, allowing the establishment of an electron transport system to the electrode, and good stability (i.e., resistant to oxidation and reduction). Modified carbon electrodes with chitosan and cyanuric chloride improved their electrosynthetic performance more than 6-fold compared to an untreated carbon electrode [12]. The excellent formation of biofilm on the carbon electrode, acting as a catalyst for MESs, can provide a novel application platform of carbon materials for useful chemical production and reduction of greenhouse gas with biotechnology.The electrochemical properties of microorganisms on the carbon electrode were investigated by cyclic voltammetry (CV), linear sweep voltammetry, and electrochemical impedance spectroscopy (EIS) to elucidate the electron transfer mechanisms between the bacteria and the electrode surface [13,14]. These analyses provided information on how electro-active bacteria interact with the carbon electrode, and the appropriate range of applied potentials in BES [6,8]. For the first demonstration of electromethanogenesis, methane was...

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mentioning

confidence: 71%

Biologically activated graphite fiber electrode for autotrophic acetate production from CO₂in a bioelectrochemical system

Im¹,

Song²,

Jeon³

et al. 2016

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“…Often, sulfate reducers such as Desulfovibrio sp. are also present in these enrichments (Marshall et al, 2013;LaBelle et al, 2014;Patil et al, 2015), suggesting that hydrogen produced by the sulfate reducers might have a role in these biofilms. However, the role of individual strains in mixed communities and the molecular mechanism of microbial electron uptake from the cathode is unclear in most cases.…”

Section: Efficient Interspecies Hydrogen Transfer In Mixed Electrosynmentioning

confidence: 91%

Enhanced microbial electrosynthesis by using defined co-cultures

2016

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Microbial uptake of free cathodic electrons presents a poorly understood aspect of microbial physiology. Uptake of cathodic electrons is particularly important in microbial electrosynthesis of sustainable fuel and chemical precursors using only CO 2 and electricity as carbon, electron and energy source. Typically, large overpotentials (200 to 400 mV) were reported to be required for cathodic electron uptake during electrosynthesis of, for example, methane and acetate, or low electrosynthesis rates were observed. To address these limitations and to explore conceptual alternatives, we studied defined co-cultures metabolizing cathodic electrons. The Fe(0)-corroding strain IS4 was used to catalyze the electron uptake reaction from the cathode forming molecular hydrogen as intermediate, and Methanococcus maripaludis and Acetobacterium woodii were used as model microorganisms for hydrogenotrophic synthesis of methane and acetate, respectively. The IS4-M. maripaludis co-cultures achieved electromethanogenesis rates of 0.1-0.14 μmol cm − 2 h − 1 at − 400 mV vs standard hydrogen electrode and 0.6-0.9 μmol cm − 2 h − 1 at − 500 mV. Co-cultures of strain IS4 and A. woodii formed acetate at rates of 0.21-0.23 μmol cm − 2 h − 1 at − 400 mV and 0.57-0.74 μmol cm − 2 h − 1 at − 500 mV. These data show that defined co-cultures coupling cathodic electron uptake with synthesis reactions via interspecies hydrogen transfer may lay the foundation for an engineering strategy for microbial electrosynthesis.

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“…Based on the highly expressed redox active proteins on the electrode (all of the proteins mentioned above are in the top 5% of total genes expressed on the electrode), and the consistent hydrogen production in the reactors [11][12][13] , extracellular enzymes and/or concentrated metals are likely functionalizing the electrode while hydrogen, ferredoxins, and/or cytochromes act as shuttles for different organisms in the biofilm. This would explain why microbes lacking an outer membrane can thrive on an electrode, and why previous studies ran electrohydrogenic biocathodes that could sustain hydrogen generation in the absence of a carbon source for over 1000 hours 2 .…”

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confidence: 99%

Metabolic Reconstruction and Modeling Microbial Electrosynthesis

Marshall¹,

Ross²,

Weisenhorn³

et al. 2016

Preprint

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Microbial electrosynthesis is a renewable energy and chemical production platform that relies on microbial cells to capture electrons from a cathode and fix carbon. Yet despite the promise of this technology, the metabolic capacity of the microbes that inhabit the electrode surface and catalyze electron transfer in these systems remains largely unknown. We assembled thirteen draft genomes from a microbial electrosynthesis system producing primarily acetate from carbon dioxide, and their transcriptional activity was mapped to genomes from cells on the electrode surface and in the supernatant. This allowed us to create a metabolic model of the predominant community members belonging to Acetobacterium, Sulfurospirillum, and Desulfovibrio. According to the model, the Acetobacterium was the primary carbon fixer, and a keystone member of the community. Transcripts of soluble hydrogenases and ferredoxins from Acetobacterium and hydrogenases, formate dehydrogenase, and cytochromes of Desulfovibrio were found in high abundance near the electrode surface. Cytochrome c oxidases of facultative members of the community were highly expressed in the supernatant despite completely sealed reactors and constant flushing with anaerobic gases. These molecular discoveries and metabolic modeling now serve as a foundation for future examination and development of electrosynthetic microbial communities.A microbial electrosynthesis system (MES) is a bioelectrochemical device that employs microbes to generate, or synthesize, valuable products from CO 2 and electrons from the cathode 1 . This technology has potential for the renewable generation of biofuels and commodity chemicals, therefore understanding which microbes and which metabolic pathways are involved on biocathodes is critical to improving the performance of MESs. Furthermore, this work has broader environmental implications including understanding ecological aspects of one carbon metabolism and extracellular electron transfer relevant to global biogeochemical cycling.Advances in microbial electrosynthesis and related biocathode-driven processes have primarily focused on the production of three compounds: hydrogen 2 , methane 3 , and acetate 4 . However, microbial electrosynthesis can be used to generate value-added multi-carbon compounds such as alcohols and various short-chain fatty acids 5 . To manipulate (and optimize) these systems it is valuable to understand the metabolic pathways and extracellular electron transfer (EET) enzymes or molecules involved in cathode oxidation, and we must determine how these cathodic electron transport components are coupled to energy conservation by the microbial cell. While an increasingly robust body of literature has been established relating to microbial communities metabolizing with an anodic electron acceptor 6-8 , much is still unclear about the diverse metabolic capabilities of microorganisms and communities growing on a cathode 9 . Recently, a multi-omics evaluation of a mixed-species, carbon

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Influence of Acidic pH on Hydrogen and Acetate Production by an Electrosynthetic Microbiome

Cited by 130 publications

References 46 publications

Biologically activated graphite fiber electrode for autotrophic acetate production from CO₂in a bioelectrochemical system

Biologically activated graphite fiber electrode for autotrophic acetate production from CO₂in a bioelectrochemical system

Enhanced microbial electrosynthesis by using defined co-cultures

Metabolic Reconstruction and Modeling Microbial Electrosynthesis

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Influence of Acidic pH on Hydrogen and Acetate Production by an Electrosynthetic Microbiome

Cited by 130 publications

References 46 publications

Biologically activated graphite fiber electrode for autotrophic acetate production from CO2in a bioelectrochemical system

Biologically activated graphite fiber electrode for autotrophic acetate production from CO2in a bioelectrochemical system

Enhanced microbial electrosynthesis by using defined co-cultures

Metabolic Reconstruction and Modeling Microbial Electrosynthesis

Contact Info

Product

Resources

About

Biologically activated graphite fiber electrode for autotrophic acetate production from CO₂in a bioelectrochemical system

Biologically activated graphite fiber electrode for autotrophic acetate production from CO₂in a bioelectrochemical system