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Microbial Electrosynthesis: Feeding Microbes Electricity To Convert Carbon Dioxide and Water to Multicarbon Extracellular Organic Compounds

Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, USA.
mBio (Impact Factor: 6.88). 06/2010; 1(2). DOI: 10.1128/mBio.00103-10
Source: PubMed

ABSTRACT IMPORTANCE
Reducing carbon dioxide to multicarbon organic chemicals and fuels with electricity has been identified as an attractive strategy to convert solar energy that is harvested intermittently with photovoltaic technology and store it as covalent chemical bonds. The organic compounds produced can then be distributed via existing infrastructure. Nonbiological electrochemical reduction of carbon dioxide has proven problematic. The results presented here suggest that microbiological catalysts may be a robust alternative, and when coupled with photovoltaics, current-driven microbial carbon dioxide reduction represents a new form of photosynthesis that might convert solar energy to organic products more effectively than traditional biomass-based strategies.

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    • "Initially the term microbial electrosynthesis was used exclusively for the microbial reduction of carbon dioxide with the help of electricity (Nevin et al., 2010; Rabaey and Rozendal, 2010). But the research field was quickly widened by multiple studies that follow the same approach of optimizing microbial production by electrical enhancement from other substrates than CO 2 , often referred to as electro fermentation (Kim and Kim, 1988; Emde and Schink, 1990; Shin et al., 2002; Steinbusch et al., 2009; Rabaey and Rozendal, 2010; Choi et al., 2012). "
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    ABSTRACT: Microbial electrochemical techniques describe a variety of emerging technologies that use electrode-bacteria-interactions for biotechnology applications including the production of electricity, waste and wastewater treatment, bioremediation and production of valuable products. Central in each application is the ability of the microbial catalyst to interact with external electron acceptors and/or donors and its metabolic properties that enable the combination of electron transport and carbon metabolism. And here also lies the key challenge. A wide range of microbes has been discovered to be able to exchange electrons with solid surfaces or mediators but only a few have been studied in depth. Especially electron transfer mechanisms from cathodes towards the microbial organism are poorly understood but are essential for many applications such as microbial electrosynthesis. We analyse the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bio-production. Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bio-electrochemical systems. The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels. Key compounds such as electron carriers (e.g. cytochromes, ferredoxin, quinones, flavins) are identified and analysed regarding their possible role in electrode-microbe-interactions. This work summarizes our current knowledge on electron transport processes and uses a theoretical approach to predict the impact of different modes of transfer on the energy metabolism. As such it adds an important piece of fundamental understanding of microbial electron transport possibilities to the research community and will help to optimize and advance bio-electrochemical techniques.
    Frontiers in Microbiology 05/2015; 6. DOI:10.3389/fmicb.2015.00575 · 3.94 Impact Factor
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    • "Microbial bioelectrochemical systems (BESs) can use microorganisms as the catalyst to overcome high overpotential and low specificity of electrode reactions (Rabaey and Rozendal, 2010; Logan and Rabaey, 2012). Upon developing bioelectrocatalytic activity in biocathodes, the performance of reactors can be greatly optimized in terms of energy production (Xia et al., 2013), hydrogen evolution (Rozendal et al., 2008), CO 2 fixation to CH4 (Cheng et al., 2009) or acetate (Nevin et al., 2010; Zhang et al., 2013) in bioelectrosynthesis. Previously, we demonstrated that the conversion of glycerol to 1,3- propanediol (1,3-PDO), which is one of the oldest known biological processes (Saxena et al., 2009), can be stimulated by imposing a cathodic current to a mixed bacterial consortium fermenting glycerol (Zhou et al., 2013). "
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    ABSTRACT: In a microbial bioelectrochemical system (BES), organic substrate such as glycerol can be reductively converted to 1,3-propanediol (1,3-PDO) by a mixed population biofilm growing on the cathode. Here, we show that 1,3-PDO yields positively correlated to the electrons supplied, increasing from 0.27 ± 0.13 to 0.57 ± 0.09 mol PDO mol(-1) glycerol when the cathodic current switched from 1 A m(-2) to 10 A m(-2) . Electrochemical measurements with linear sweep voltammetry (LSV) demonstrated that the biofilm was bioelectrocatalytically active and that the cathodic current was greatly enhanced only in the presence of both biofilm and glycerol, with an onset potential of -0.46 V. This indicates that glycerol or its degradation products effectively served as cathodic electron acceptor. During long-term operation (> 150 days), however, the yield decreased gradually to 0.13 ± 0.02 mol PDO mol(-1) glycerol, and the current-product correlation disappeared. The onset potentials for cathodic current decreased to -0.58 V in the LSV tests at this stage, irrespective of the presence or absence of glycerol, with electrons from the cathode almost exclusively used for hydrogen evolution (accounted for 99.9% and 89.5% of the electrons transferred at glycerol and glycerol-free conditions respectively). Community analysis evidenced a decreasing relative abundance of Citrobacter in the biofilm, indicating a community succession leading to cathode independent processes relative to the glycerol. It is thus shown here that in processes where substrate conversion can occur independently of the electrode, electroactive microorganisms can be outcompeted and effectively disconnected from the substrate. © 2015 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.
    Microbial Biotechnology 04/2015; 8(3). DOI:10.1111/1751-7915.12240 · 3.21 Impact Factor
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    • "Pure cultures of Gram negative acetogens like Sporomusa silvacetica and Sporomusa sphaeroides and Gram positive acetogens like Clostridium ljungdahlii , Clostridium aceticum and the thermophile Moorella thermoacetica are all capable of reducing CO 2 to multicarbon compounds by MES (Nevin et al., 2011). Among all the tested acetogenic bacteria, Sporomusa ovata DSM-2662 was the most efficient electroautotroph with acetate production rates as high as 282 mM d −1 m −2 and with electricity conversion efficiency to acetate typically above 80% (Nevin et al., 2010; Gong et al., 2013; Nie et al., 2013; Zhang et al., 2013). The production of negligible amount of 2-oxobutyrate and formate in comparison to acetate by S. ovata was also reported (Nevin et al., 2010, 2011). "
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    ABSTRACT: Powering microbes with electrical energy to produce valuable chemicals such as biofuels has recently gained traction as a biosustainable strategy to reduce our dependence on oil. Microbial electrosynthesis (MES) is one of the bioelectrochemical approaches developed in the last decade that could have critical impact on the current methods of chemical synthesis. MES is a process in which electroautotrophic microbes use electrical current as electron source to reduce CO2 to multicarbon organics. Electricity necessary for MES can be harvested from renewable resources such as solar energy, wind turbine or wastewater treatment processes. The net outcome is that renewable energy is stored in the covalent bonds of organic compounds synthesized from greenhouse gas. This review will discuss the future of MES and the challenges that lie ahead for its development into a mature technology.
    Frontiers in Microbiology 03/2015; 6. DOI:10.3389/fmicb.2015.00201 · 3.94 Impact Factor
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