HYPERTHERMOPHILIC HYDROGEN PRODUCTION BY GEOGLOBUS ACETIVORANS IN MICROBIAL ELECTROLYSIS CELLS

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2021-9-10

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Kaş, Aykut

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Utilization of hyperthermophilic microorganisms was suggested to improve reaction rates and insoluble pollutant degradation and minimize the risk of contamination in bioelectrochemical systems (BESs). So far only a small group of hyperthermophilic microorganisms were identified, which show the ability to donate electrons to solid electrodes in BESs and here we present a new culture that fits to this description. The iron reducing archaeal culture Geoglobus acetivorans, originally isolated from a hydrothermal structure, produced 1.53 ± 0.24 A/m2 peak current density in microbial electrolysis cells (MECs) operated at 80 °C. This current density value is 2.5 – 3 times higher than the previously reported electro-active behavior of closely related archaeal species of Ferroglobus placidus and Geoglobus ahangari with the exact reactor configuration. Maximum hydrogen production rate (QH2) was found as 0.57 ± 0.06 m3 H2/m3*d in the 5 mL Mini-MEC reactors fed with 10mM acetate. There was a visible biofilm formation on the anode and minimum 6 cycles of biohydrogen generation coupled with high current generation was observed. Upon longer operation of reactors, biofilm started to detach from the electrode surface and both hydrogen and current production were decreased. Cyclic voltammetry (CV) analysis produced a sigmoidal catalytic wave with a mid-point potential of −0.40 V (vs. Ag/AgCl). Direct electron transfer (DET) capability by G. acetivorans was shown with peak separation analysis, rapid current density recovery after media replacement and thick biofilm formation on the anode electrode. G. acetivorans was able to utilize complex organic waste in hyperthermophilic MECs, after initial biofilm formation with acetate.

Subject Keywords

Microbial electrolysis cell, Electrohydrogenesis, Hyperthermophiles, Iron-reducer archaea, Biohydrogen production, Geoglobus acetivorans

URI

https://hdl.handle.net/11511/94202

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

A. Kaş, “HYPERTHERMOPHILIC HYDROGEN PRODUCTION BY GEOGLOBUS ACETIVORANS IN MICROBIAL ELECTROLYSIS CELLS,” M.S. - Master of Science, Middle East Technical University, 2021.