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    Investigating effects of electron donor availability on cathodic microbial community structure and functional dynamics in electromethanogenesis

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    Name:
    AlaaRagab_Dissertation.pdf
    Size:
    14.02Mb
    Format:
    PDF
    Description:
    PhD Dissertation
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    Type
    Dissertation
    Authors
    Ragab, Alaa I. cc
    Advisors
    Saikaly, Pascal cc
    Committee members
    Vrouwenvelder, Johannes S. cc
    Arold, Stefan T. cc
    Katuri, Krishna
    Logan, Bruce
    Program
    Environmental Science and Engineering
    KAUST Department
    Biological and Environmental Science and Engineering (BESE) Division
    Date
    2019-10
    Embargo End Date
    2021-02-27
    Permanent link to this record
    http://hdl.handle.net/10754/661902
    
    Metadata
    Show full item record
    Access Restrictions
    At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation will become available to the public after the expiration of the embargo on 2021-02-27.
    Abstract
    Microbial electrochemical technologies (MET) exploit the bioelectrocatalytic activity of microorganisms, with a main focus on waste-to-resource recovery. Electromethanogenesis, a type of MET, describes the process of CO2 reduction specifically to methane, catalyzed by methanogens that utilize the cathode directly as an electron donor or through H2 evolving from the cathode surface. Applications are mainly in the direction of bioelectrochemical power-to-gas, as well as biogas upgrading and carbon capture and utilization. As the cathode and its associated microbial consortia are key to the process, larger scale applications require improvements especially in terms of optimal operational parameters, cathode materials and the dynamics of the effect of electron transfer within the cathodic biofilm. The focus of this dissertation is to improve the understanding of the dynamics and function of methaneproducing biofilms grown on cathodes in electromethanogenic reactors in the presence of two different electron donors: the cathode and the H2 evolving from the cathode surface. The spatial homogeneity of the microbial communities across the area of the cathode was demonstrated, which is relevant for large scale applications where reproducibility is required for predictable engineered systems. Metagenomic and metatranscriptomic methods were applied to elucidate the short-term changes in the actively transcribed methanogenesis and central carbon assimilation pathways in response to varying the availability of electrons by changing the set cathode potential in a novel Methanobacterium species enriched from electromethanogenic biocathodes. Although changes in functional performance were evident with varying potential, no significant differential expression was observed and genes from the methanogenesis and carbon assimilation pathways were highly expressed throughout. Indium tin oxide (ITO) as a potentially hydrogen evolution reaction (HER) – inert cathode material was evaluated using the mixotrophic Methanosarcina barkeri in an attempt to develop a simplified material-science driven approach to future electron transfer studies. It was found to be electrochemically unstable under the tested conditions, losing its conductivity over time. Overall, the findings from these studies provide new knowledge on the effects of electron donor availability on the functional performance and the biocathode community dynamics. The understandings derived from the study are relevant to methanogenic processes and should aid in system scaleup design.
    Citation
    Ragab, A. I. (2019). Investigating effects of electron donor availability on cathodic microbial community structure and functional dynamics in electromethanogenesis. KAUST Research Repository. https://doi.org/10.25781/KAUST-XF478
    DOI
    10.25781/KAUST-XF478
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-XF478
    Scopus Count
    Collections
    Biological and Environmental Science and Engineering (BESE) Division; Environmental Science and Engineering Program; PhD Dissertations

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