Importance of the hydrogen route in up-scaling electrosynthesis for microbial CO<sub>2</sub>reduction

Blanchet, Elise; Duquenne, François; Rafrafi, Yan; Etcheverry, Luc; Erable, Benjamin; Bergel, Alain

doi:10.1039/c5ee03088a

Cited by 201 publications

(122 citation statements)

References 57 publications

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“…Low electron transfer rates from the cathode during microbially catalyzed electrosynthesis were generally considered to be limiting the feasibility of this process on a commercial scale (Blanchet et al, 2015). Moreover, overpotentials of 4200 mV had to be applied repeatedly to achieve significant electron transfer rates (Villano et al, 2010;Aulenta et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

Enhanced microbial electrosynthesis by using defined co-cultures

2016

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“…Summaries of rates of production and Coulombic efficiencies from the literature can be found in Patil et al (2015); Blanchet et al (2015); May et al (2016). The purpose of this review is to consider the evolving understanding of the possibilities in reactor design for each of these approaches.…”

Section: Introductionmentioning

confidence: 99%

How to Sustainably Feed a Microbe: Strategies for Biological Production of Carbon-Based Commodities with Renewable Electricity

Butler

Lovley

2016

Front. Microbiol.

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As interest and application of renewable energy grows, strategies are needed to align the asynchronous supply and demand. Microbial metabolisms are a potentially sustainable mechanism for transforming renewable electrical energy into biocommodities that are easily stored and transported. Acetogens and methanogens can reduce carbon dioxide to organic products including methane, acetic acid, and ethanol. The library of biocommodities is expanded when engineered metabolisms of acetogens are included. Typically, electrochemical systems are employed to integrate renewable energy sources with biological systems for production of carbon-based commodities. Within these systems, there are three prevailing mechanisms for delivering electrons to microorganisms for the conversion of carbon dioxide to reduce organic compounds: (1) electrons can be delivered to microorganisms via H2 produced separately in a electrolyzer, (2) H2 produced at a cathode can convey electrons to microorganisms supported on the cathode surface, and (3) a cathode can directly feed electrons to microorganisms. Each of these strategies has advantages and disadvantages that must be considered in designing full-scale processes. This review considers the evolving understanding of each of these approaches and the state of design for advancing these strategies toward viability.

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“…To overcome this drawback, halotolerant microbial anodes have been developed, which produce up to 80 A/m2 in electrolytes that contain 45 g/L NaCl, resulting in a conductivity of 10.4 S.m-1 [4,5]. Finally, a brief incursion into the mechanisms of CO2 reduction on a microbial cathode is proposed, showing the importance of the hydrogen route [6]. With the objective of scaling-up commercial electrosynthesis cells, the high current densities required to ensure economic efficiency would favour strong hydrogen evolution on the cathode and preclude biofilm formation on the electrode surface.…”

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confidence: 99%

How could chemical engineering help in deciphering electromicrobial mechanisms?

Bergel

2016

BIO Web of Conferences

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Electroactive microbial biofilms constitute a still-new research area of bioelectrochemistry, which proposes experimental systems that are original relative to those that have been studied for decades. In bioelectrochemistry, the interface is generally designed by the experimentalist, sometimes by using sophisticated surface modification protocols, in order to immobilize the biological component on the electrode surface in the best possible way. In contrast, in the case of electroactive biofilms, microorganisms do the work. The microbial cells produce slime that glues them to the electrode surface and forms complex biofilm/electrode interfaces, on which the experimentalist has very few action levers. In this context, chemical engineering methods can be very helpful to decipher the numerous interacting steps that control electron transfer and also to scale up the interfaces to actual applications.Electron transfer (ET) inside biofilms can occur through several direct and indirect pathways, which have been detailed elsewhere [1]. Electroactive biofilms can ensure fast electrochemical kinetics, close to reversible (Nernstian) ET. When biofilms display less efficient global kinetics, it is generally assumed that ET between the electrode and the redox biological compounds is not Nernstian. In contrast, it has recently been demonstrated that non-Nernstian global kinetics can be due to the presence of different ET pathways, each following a Nernstian type but around a different redox potential [2]. When this hypothesis is valid, the way to improve the biofilm electroactivity is no longer to try to enhance the ET rate between the electrode and the different redox compounds, but to drive the biofilm towards the production of the most efficient redox compounds. For example, growing an electroactive biofilm around ultra-microelectrodes has been shown to be an excellent way to improve the ET capability of the biofilm matrix, raising current density from 7 to 65 A/m2 on fully flat electrode surfaces [3].The nagging problem of scaling-up microbial electrochemical technologies is addressed in the second part of the presentation, starting with microbial fuel cells (MFC). Ideally, a microbial anode works at close-to-neutral pH, while an abiotic O2-reducing cathode should work at acidic pH. The pH a Corresponding

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Importance of the hydrogen route in up-scaling electrosynthesis for microbial CO₂reduction

Cited by 201 publications

References 57 publications

Enhanced microbial electrosynthesis by using defined co-cultures

Enhanced microbial electrosynthesis by using defined co-cultures

How to Sustainably Feed a Microbe: Strategies for Biological Production of Carbon-Based Commodities with Renewable Electricity

How could chemical engineering help in deciphering electromicrobial mechanisms?

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Importance of the hydrogen route in up-scaling electrosynthesis for microbial CO2reduction

Cited by 201 publications

References 57 publications

Enhanced microbial electrosynthesis by using defined co-cultures

Enhanced microbial electrosynthesis by using defined co-cultures

How to Sustainably Feed a Microbe: Strategies for Biological Production of Carbon-Based Commodities with Renewable Electricity

How could chemical engineering help in deciphering electromicrobial mechanisms?

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Importance of the hydrogen route in up-scaling electrosynthesis for microbial CO₂reduction