MACROSCALE TO NANOSCALE BIOMECHANICAL INVESTIGATION OF XYLAN’S ROLE IN THE GRASS CELL WALL
Open Access
- Author:
- Breunig, Lee Daniel
- Graduate Program:
- Plant Biology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 14, 2017
- Committee Members:
- Daniel J. Cosgrove, Dissertation Advisor/Co-Advisor
Daniel J Cosgrove, Committee Chair/Co-Chair
Ying Gu, Committee Member
Charles T Anderson, Committee Member
Squire J Booker, Outside Member - Keywords:
- xylan
GAX
Glucuronoarabinoxylan
Plant cell wall
Poaceae
Primary Cell Wall
Mechanics
Creep
Stress Strain
Nanoindentation
Nano-mechanical Mapping
AFM
Diferulic Acid
Computational Modeling
Grass
Xylanase
BsXynC
GH30
EC 3.2.1.136
EC 3.2.1.8 - Abstract:
- The cell walls of grasses are a major source of food for humans, feed for livestock, and the feedstock for ethanol fuel production. The dominant hemicellulose in grasses is glucuronoarabinoxylan (GAX). While the chemical composition of the grass primary cell wall is known, the mechanical structure of how these part forms an expandable rigid foam is not known. Light microscopy techniques lack the resolution or sensitivity or both to determine the nano-scale structure of the cell wall. This work used mechanical assays developed for material science and mechanical engineering combined with biochemistry based enzymatic degradation of specific wall polymers to demonstrate that GAX forms a primary load bearing mechanical network in grass cell walls at the macro-scale and nano-scale by resisting the motion of elementary cellulose micro fibrils (CMF). These techniques were also used to demonstrate that mixed linkage glucan (MLG) forms a retarded viscous network at the macro-scale. Computational modeling data, which was replicated with in vitro binding of model compounds highlights the limitations and likely artifacts caused by the widely-used methods of GAX extraction, casting skepticism on the in muro conclusions drawn from in vitro experiments. New techniques for GAX extraction are proposed, but the first attempt extracted MLG from the GAX and cellulose residue. These experiments were used to test the accuracy of the current model of the grass primary cell wall.