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.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/661902 |
| Date | 10 1900 |
| Creators | Ragab, Alaa I. |
| Contributors | Saikaly, Pascal, Biological and Environmental Sciences and Engineering (BESE) Division, Vrouwenvelder, Johannes S., Arold, Stefan T., Katuri, Krishna, Logan, Bruce |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2021-02-27, 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. |
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