Spark of Life: Role of Electrotrophy in the Emergence of Life.

The emergence of life has been a subject of intensive research for decades. Different approaches and different environmental "cradles" have been studied, from space to the deep sea. Since the recent discovery of a natural electrical current through deep-sea hydrothermal vents, a new energy source is considered for the transition from inorganic to organic.

Screening for Hyperthermophilic Electrotrophs for the Microbial Electrosynthesis of Organic Compounds.

Microbial electrosynthesis has recently emerged as a promising technology for the sustainable production of organic acids, bioplastics, or biofuels from electricity and CO. However, the diversity of catalysts and metabolic pathways is limited to mainly mesophilic acetogens or methanogens. Here, eleven hyperthermophilic strains related to Archaeoglobales, Thermococcales, Aquificales, and methanogens were screened for microbial electrosynthesis.

characterization of electroactive biofilms inside porous electrodes with MR Imaging.

Identifying the limiting processes of electroactive biofilms is key to improve the performance of bioelectrochemical systems (BES). For modelling and developing BES, spatial information of transport phenomena and biofilm distribution are required and can be determined by Magnetic Resonance Imaging (MRI) , and even inside opaque porous electrodes. A custom bioelectrochemical cell was designed that allows MRI measurements with a spatial resolution of 50 μm inside a 500 μm thick porous carbon electrode.

Local Acidification Limits the Current Production and Biofilm Formation of MR-1 With Electrospun Anodes.

The anodic current production of MR-1 is typically lower compared to other electroactive bacteria. The main reason for the low current densities is the poor biofilm growth on most anode materials. We demonstrate that the high current production of MR-1 with electrospun anodes exhibits a similar threshold current density as dense spp biofilms.

From an extremophilic community to an electroautotrophic production strain: identifying a novel Knallgas bacterium as cathodic biofilm biocatalyst.

Coupling microbial electrosynthesis to renewable energy sources can provide a promising future technology for carbon dioxide conversion. However, this technology suffers from a limited number of suitable biocatalysts, resulting in a narrow product range. Here, we present the characterization of the first thermoacidophilic electroautotrophic community using chronoamperometric, metagenomic, and C-labeling analyses.

An air-breathing enzymatic cathode with extended lifetime by continuous laccase supply.

We present a novel concept of an air-breathing enzymatic biofuel cell cathode combined with continuous supply of unpurified laccase-containing supernatant of the white-rot fungus Trametes versicolor for extended lifetime. The air-breathing cathode design obviates the need for energy-intensive active aeration. In a corresponding long-term experiment at a constant current density of 50 µA cm, we demonstrated an increased lifetime of 33 days (cathode potential above 0.

Erratum to: Engineering of Microbial Electrodes.

In 30th page, Table 2, in the last row, the references 33 and 134 are inserted.

Effects of wastewater constituents and operational conditions on the composition and dynamics of anodic microbial communities in bioelectrochemical systems.

Over the last decade, there has been an ever-growing interest in bioelectrochemical systems (BES) as a sustainable technology enabling simultaneous wastewater treatment and biological production of, e.g. electricity, hydrogen, and further commodities.

Simultaneous use of a crossflow filtration membrane as microbial fuel cell anode - Permeate flow leads to 4-fold increased current densities.

A new concept for the combination of membrane bioreactors and microbial fuel cells is introduced, that aims at the production of electricity for reducing the overall energy consumption of wastewater treatment. In contrast to previous approaches, the anode is integrated as microfiltration membrane in sidestream crossflow configuration. Using a stainless steel filtration membrane with G.

Engineering of Microbial Electrodes.

This chapter provides an overview of the current state-of-the-art in the engineering of microbial electrodes for application in microbial electrosynthesis. First, important functional aspects and requirements of basic materials for microbial electrodes are introduced, including the meaningful benchmarking of electrode performance, a comparison of electrode materials, and methods to improve microbe-electrode interaction. Suitable current collectors and composite materials that combine different functionalities are also discussed.

The performance of microbial anodes in municipal wastewater: Pre-grown multispecies biofilm vs. natural inocula.

In this study, different inoculation strategies for continuously operated microbial anodes are analyzed and compared. After 20daysof operation with municipal wastewater anodes pre-incubated with a biofilm of the exoelectrogenic species Geobacter and Shewanella showed current densities of (65±8) μA/cm. This is comparable to the current densities of non-inoculated anodes and anodes inoculated with sewage sludge.

Selective natural induction of laccases in Pleurotus sajor-caju, suitable for application at a biofuel cell cathode at neutral pH.

Laccases are multicopper oxidoreductases with broad substrate specificity and are applied in biofuel cells at the cathode to improve its oxygen reduction performance. However, the production of laccases by e.g.

Unbalanced fermentation of glycerol in Escherichia coli via heterologous production of an electron transport chain and electrode interaction in microbial electrochemical cells.

Microbial electrochemical cells are an emerging technology for achieving unbalanced fermentations. However, organisms that can serve as potential biocatalysts for this application are limited by their narrow substrate spectrum. This study describes the reprogramming of Escherichia coli for the efficient use of anodes as electron acceptors.

Improving the performance of a biofuel cell cathode with laccase-containing culture supernatant from Pycnoporus sanguineus.

Laccases are multicopper oxidoreductases that can be used in biofuel cells to improve cathode performance by cathodic oxygen reduction. Here we present a laccase from the ligninolytic white-rot fungus Pycnoporus sanguineus that, in contrast to the Trametes versicolor laccase, can be produced in the absence of inducers in a standard culture medium. After 7days of cultivation the activity of this laccase in culture supernatant reached 2.

Using planktonic microorganisms to supply the unpurified multi-copper oxidases laccase and copper efflux oxidases at a biofuel cell cathode.

The feasibility to apply crude culture supernatants that contain the multicopper oxidases laccase or copper efflux oxidase (CueO) as oxygen reducing catalysts in a biofuel cell cathode is shown. As enzyme-secreting recombinant planktonic microorganisms, the yeast Yarrowia lipolytica and the bacterium Escherichia coli were investigated. The cultivation and operation conditions (choice of medium, pH) had distinct effects on the electro-catalytic performance.

Characterization of microbial current production as a function of microbe-electrode-interaction.

Microbe-electrode-interactions are keys for microbial fuel cell technology. Nevertheless, standard measurement routines to analyze the interplay of microbial physiology and material characteristics have not been introduced yet. In this study, graphite anodes with varying surface properties were evaluated using pure cultures of Shewanella oneidensis and Geobacter sulfurreducens, as well as defined and undefined mixed cultures.

Systematic screening of carbon-based anode materials for microbial fuel cells with Shewanella oneidensis MR-1.

We present a systematic screening of carbon-based anode materials for microbial fuel cells with Shewanella oneidensis MR-1. Under anoxic conditions nanoporous activated carbon cloth is a superior anode material in terms of current density normalized to the projected anode area and anode volume (24.0±0.

Overcoming bottlenecks of enzymatic biofuel cell cathodes: crude fungal culture supernatant can help to extend lifetime and reduce cost.

Enzymatic biofuel cells (BFCs) show great potential for the direct conversion of biochemically stored energy from renewable biomass resources into electricity. However, enzyme purification is time-consuming and expensive. Furthermore, the long-term use of enzymatic BFCs is hindered by enzyme degradation, which limits their lifetime to only a few weeks.

Cyclic electrodeposition of PtCu alloy: facile fabrication of highly porous platinum electrodes.

Cyclic electrodeposition of platinum and copper enables the fabrication of high surface area electrodes (roughness factors of >3000) by multiple alternation of alloy co-deposition and dealloying of copper from the just-fabricated alloy layers. The underlying processes, resulting electrode structures, and their applicability to potentially implantable glucose fuel cells are discussed.

High-porous platinum electrodes for functional electrical stimulation.

This paper reports on the preparation and characterization of highly porous platinum electrodes for functional electrical stimulation. Thin-film platinum electrodes were roughened by electrochemical deposition of platinum-copper alloys and subsequent removal of copper using cyclic voltammetry (CV). Prepared samples were characterized by electrochemical impedance spectroscopies (EIS), CVs and long-term pulse testing.

Strategies for the fabrication of porous platinum electrodes.

Porous platinum is of high technological importance due to its various applications in fuel cells, sensors, stimulation electrodes, mechanical actuators and catalysis in general. Based on a discussion of the general principles behind the reduction of platinum salts and corresponding deposition processes this article discusses techniques available for platinum electrode fabrication. The numerous, different strategies available to fabricate platinum electrodes are reviewed and discussed in the context of their tuning parameters, strengths and weaknesses.

Strategies to extend the lifetime of bioelectrochemical enzyme electrodes for biosensing and biofuel cell applications.

Enzymes are powerful catalysts for biosensor and biofuel cell electrodes due to their unique substrate specificity. This specificity is defined by the amino acid chain's complex three-dimensional structure based on non-covalent forces, being also responsible for the very limited enzyme lifetime of days to weeks. Many electrochemical applications, however, would benefit from lifetimes over months to years.

Carbon electrodes for direct electron transfer type laccase cathodes investigated by current density-cathode potential behavior.

Direct electron transfer from carbon electrodes to adsorbed laccase (EC 1.10.3.

Involvement and specificity of Shewanella oneidensis outer membrane cytochromes in the reduction of soluble and solid-phase terminal electron acceptors.

The formation of outer membrane (OM) cytochromes seems to be a key step in the evolution of dissimilatory iron-reducing bacteria. They are believed to be the endpoints of an extended respiratory chain to the surface of the cell that establishes the connection to insoluble electron acceptors such as iron or manganese oxides. The gammaproteobacterium Shewanella oneidensis MR-1 contains the genetic information for five putative OM cytochromes.