As the major component of the plant cell wall, cellulose is produced by all plant species at an
annual rate of over a hundred billion tonnes, making it the most abundant biopolymer on
Earth. The hierarchical assembly of cellulose glucan chains into crystalline fibrils, bundles
and higher-order networks endows cellulose with its high mechanical strength, but makes it
challenging to breakdown and produce cellulose-based nanomaterials and renewable
biofuels. In order to fully leverage the potential of cellulose as a sustainable resource, it is
important to study the supramolecular structure and hydrolysis of this biomaterial from the
nano- to the microscale.
In this thesis, we develop new chemical strategies for fluorescently labeling cellulose
and employ advanced imaging techniques to study its supramolecular structure at the singlefibril
level. The developed labeling method provides a simple and efficient route for
fluorescently tagging cellulose nanomaterials with commercially available dyes, yielding
high degrees of labeling without altering the native properties of the nanocelluloses. This
allowed the preparation of samples that were optimal for super-resolution fluorescence
microscopy (SRFM), which was used to provide for the first time, a direct visualization of
periodic disorder along the crystalline structure of individual cellulose fibrils. The
alternating disordered and crystalline structure observed in SFRM was corroborated with
time-lapsed acid hydrolysis experiments to propose a mechanism for the acid hydrolysis of
cellulose fibrils. To gain insight on the ultrastructural origin of these regions, we applied a
correlative super-resolution light and electron microscopy (SR-CLEM) workflow and
observed that the disordered regions were associated nanostructural defects present along
cellulose fibrils. Overall, the findings presented in this work provide significant
advancements in our understanding of the hierarchical structure and depolymerization of
cellulose, which will be useful for the development of new and efficient ways of breaking
down this polymer for the production of renewable nanomaterials and bio-based products
like biofuels and bioplastics. / Thesis / Doctor of Philosophy (PhD) / In this dissertation, we have studied in unprecedented detail the structure of cellulose – a
polymer that is found in every plant. As the main structural component of the plant cell wall,
cellulose endows trees with their strength and resilience while storing sunlight energy in its
chemical bonds. Since plant biomass represents eighty percent of all living matter on Earth,
cellulose is an abundant resource that can be used to produce sustainable and
environmentally benign nanomaterials and bioproducts, like biofuels and bioplastics. Our
ability to use cellulose as a renewable source of structural materials and energy is intimately
linked to our capacity to break apart its tight structural packing. Deconstructing cellulose
into various forms demands that we understand the multi-level organization of its structure
and the susceptible regions within it. To gain this information, in this thesis we develop new
labeling methods and apply state-of-the-art microscopy tools to directly visualize the
arrangement of cellulose fibrils at the nanoscale (comparable to 1/10,000 the width of a
human hair) and study their breakdown by acid treatment. The findings presented in this
work furthers our fundamental understanding of the natural structure of cellulose, which
has important implications on the development of industrial strategies to break down this
abundant and renewable biomaterial.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/27374 |
| Date | January 2022 |
| Creators | Babi, Mouhanad |
| Contributors | Moran-Mirabal, Jose, Chemistry and Chemical Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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