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Anaerobic Benzene Degradation in Albertan Sediments
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- Author / Creator
- Lee, Korris
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ABSTRACT
Benzene is a priority contaminant that is commonly coincident with fossil fuel entities, whether
natural or anthropogenic, and is characterized by high mobility and toxicity. In Alberta, Canada,
where oil and gas production comprises much of the provincial industrial output, benzene
contamination presents an omnipresent environmental risk to health and safety, necessitating
economical methods that can minimize such threats. In this study, bioremediation is
investigated as a benzene removal option for contaminated sites. Bioremediation can involve
the use of microorganisms to metabolize benzene, and typically requires either the potentiation
of available microbes (i.e. biostimulation) or the introduction of external microbes (i.e.
bioaugmentation) in situ. Remediators can benefit greatly in using indigenous cultures that have
been developed to maximize degradative capabilities and minimize time burden. This project,
therefore, is focused on the generation of anaerobic benzene degrading cultures (under
methanogenic, sulfate-reducing, iron-reducing, and nitrate-reducing conditions) derived from
indigenous Albertan sediments and analysis of their community properties and primary degrader
populations, while investigating different strategies to enhance their metabolic performance.
These include the implementation of iron-dissolution protocols with external chelators such as
acetohydroxamic acid and oxalic acid to expand ferric iron pools, and the addition of conductive
magnetite at nano and micrometer scales to enhance the conductivity of microbial morphologies
that can ease the transfer of electrons for metabolism. Lastly, an attempt was made to produce
the putative benzene carboxylase AbcDA in vitro and subvert the difficulties of culture creation
and maintenance entirely.
The research in this thesis demonstrated robust degradation of benzene in cultures sourced
from Albertan sediments in a multitude of redox conditions, including nitrate-reducing, ironreducing,
sulfate-reducing, and methanogenic contexts, with iron and nitrate-reducers exhibiting
the highest levels of benzene degradation (11-12 uM/d). Primary benzene degraders were
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identified in nitrate-reducing and iron-reducing cultures, namely Peptococcaceae and
Geobacter, respectively. Geobacter metallireducens was also identified at a species taxonomic
level in iron-reducing cultures. While the isolation of Geobacter from iron-reducing cultures was
unsuccessful, and putative benzene hydroxylases gmet 0231-0232 were not found within these
consortia, the potential of certain chelator combinations such as acetohydroxamic acid (aHA)
and oxalic acid in enhancing the benzene degrading performance of iron-reducing cultures was
demonstrated, although their specific functions within these cultures could not be elucidated. -
- Subjects / Keywords
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- Graduation date
- Fall 2022
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.