Charakterisierung mikrobieller Elektrosynthesewege

Als Alternative zur Photosynthese bietet die mikrobielle Elektrosynthese eine vielversprechende Technologie, welche eine direkte Konversion von CO$_{2}$ durch den Eintrag elektrischer Energie ermöglicht. Kathodische Elektronen dienen dabei elektroautotrophen Mikroorganismen als alleinige Energie- und Elektronenquelle. In der Literatur beschriebene Organismen sind jedoch fast ausschließlich von einen wasserstoffvermittelten Elektronentransport abhängig. Da sich bei der kathodischen Wasserstoffentstehung abiotische mit biotischen Effekten überlagern, ist eine Charakterisierung der mikroben-Elektroden-Interaktion in diesem Fall jedoch kaum möglich. In dieser Arbeit wurde daher gezielt nach elektroautotrophen Organismen gesucht, welche nicht in der Lage sind Wasserstoff zu verwerten. Durch die Charakterisierung von $\textit{Sulfolobus acidocaldarius}$ auf einer Kathode gelang erstmals der Nachweis eines elektroautotrophen Wachstums mit einem alternativen extrazellulären Elektronenaufnahme (EEA)-Mechanismus. Entscheidende Elemente darin scheinen Schwefeltransferasen einzunehmen. In einem zweiten Ansatz wurde für die Identifikation natürlicher EEAs eine kathodische Umweltanreicherungskultur charakterisiert. Ein vergleichbarer Mechanismus auf Basis von Schwefeltransferasen konnte ebenfalls im Hauptakteur der Kultur identifiziert werden. Dieser Stamm, welcher einen bisher unbekannten Vertreter der Chromatiaceae darstellt, besitzt eine Verwandtschaft zu " `$\textit{Ca}$. Tenderia electrophaga\u27\u27, einem elektrotrophen Bakterium aus einer marinen, kathodischen Anreicherung. Der Elektronentransport in diesem neuen Organismus scheint dabei neben Schwefeltransferasen auch über $\textit{c}$-Typ Cytochrome vermittelt zu werden. $\textit{C}$-Typ Cytochrome spielen in bioelektrochemischen Systemen eine entscheidende Rolle und wurden insbesondere in exoelektrogenen Stämmen an Anoden intensiv erforscht. Als zweites Ziel dieser Arbeit wurde daher eine Methode entwickelt um verbesserte, synthetische Elektronentransportketten zu identifizieren. Basierend auf der heterologen Expression von verschiedenen, homologen Genen für $\textit{c}$-Typ Cytochrome, konnte eine verbesserte Elektronentransferrate in $\textit{E. coli}$ erreicht werden. Diese setzt sich durch Gene aus den Modellorganismen $\textit{Shewanella oneidensis}$ und $\textit{Rhodopseudomonas palustris}$ zusammen. Insgesamt konnten in dieser Arbeit grundlegende Erkenntnisse zur Identifikation und Entwicklung neuer elektroautotropher Organismen gewonnen werden

Development of a production chain from vegetable biowaste to platform chemicals

Abstract Background A future bioeconomy relies on the development of technologies to convert waste into valuable compounds. We present here an attempt to design a biotechnological cascade for the conversion of vegetable waste into acetoin and electrical energy. Results A vegetable waste dark fermentation effluent containing mainly acetate, butyrate and propionate was oxidized in a bioelectrochemical system. The achieved average current at a constant anode potential of 0 mV against standard hydrogen electrode was 177.5 ± 52.5 µA/cm2. During this step, acetate and butyrate were removed from the effluent while propionate was the major remaining component of the total organic carbon content comprising on average 75.6%. The key players with regard to carbon oxidation and electrode reduction were revealed using amplicon sequencing and metatranscriptomic analysis. Using nanofiltration, it was possible to concentrate the propionate in the effluent. The effluent was revealed to be a suitable medium for biotechnological production strains. As a proof of principle, the propionate in the effluent of the bioelectrochemical system was converted into the platform chemical acetoin with a carbon recovery of 86%. Conclusions To the best of our knowledge this is the first report on a full biotechnological production chain leading from vegetable waste to the production of a single valuable platform chemical that integrates carbon elimination steps leading to the production of the valuable side product electrical energy

Electron transfer of extremophiles in bioelectrochemical systems

The interaction of bacteria and archaea with electrodes is a relatively new research field which spans from fundamental to applied research and influences interdisciplinary research in the fields of microbiology, biochemistry, biotechnology as well as process engineering. Although a substantial understanding of electron transfer processes between microbes and anodes and between microbes and cathodes has been achieved in mesophilic organisms, the mechanisms used by microbes under extremophilic conditions are still in the early stages of discovery. Here, we review our current knowledge on the biochemical solutions that evolved for the interaction of extremophilic organisms with electrodes. To this end, the available knowledge on pure cultures of extremophilic microorganisms has been compiled and the study has been extended with the help of bioinformatic analyses on the potential distribution of different electron transfer mechanisms in extremophilic microorganisms

Complete genome sequence of Kyrpidia sp. strain EA-1, a thermophilic knallgas bacterium, isolated from the Azores

Kyrpidia sp. strain EA-1 is a thermophilic hydrogen-oxidizing bacterium isolated from hydrothermal systems at São Miguel Island, Portugal. Here, we present the complete genome sequence of the strain assembled to a single circular chromosome. The genome spans 3,352,175 bp, with a GC content of 58.7%.Bundesministerium für Bildung und Forschung (BMBF

Development of a production chain from vegetable biowaste to platform chemicals

Abstract Background A future bioeconomy relies on the development of technologies to convert waste into valuable compounds. We present here an attempt to design a biotechnological cascade for the conversion of vegetable waste into acetoin and electrical energy. Results A vegetable waste dark fermentation effluent containing mainly acetate, butyrate and propionate was oxidized in a bioelectrochemical system. The achieved average current at a constant anode potential of 0 mV against standard hydrogen electrode was 177.5 ± 52.5 µA/cm2. During this step, acetate and butyrate were removed from the effluent while propionate was the major remaining component of the total organic carbon content comprising on average 75.6%. The key players with regard to carbon oxidation and electrode reduction were revealed using amplicon sequencing and metatranscriptomic analysis. Using nanofiltration, it was possible to concentrate the propionate in the effluent. The effluent was revealed to be a suitable medium for biotechnological production strains. As a proof of principle, the propionate in the effluent of the bioelectrochemical system was converted into the platform chemical acetoin with a carbon recovery of 86%. Conclusions To the best of our knowledge this is the first report on a full biotechnological production chain leading from vegetable waste to the production of a single valuable platform chemical that integrates carbon elimination steps leading to the production of the valuable side product electrical energy

MOESM1 of Development of a production chain from vegetable biowaste to platform chemicals

Additional file 1: Table S1. Primer sequences and amplicon size for the 16S Illumina MiSeq