Nanomechanics of cellulose deformation reveal molecular defects that facilitate natural deconstruction

Published

April 29, 2019

Author(s)

Peter Ciesielski, Ryan Wagner, Vivek Bharadwaj, Jason Killgore, Ashutosh Mittal, Gregg Beckham, Stephen Decker, Michael Himmel, Michael Crowley

Abstract

Technologies surrounding utilization and processing of cellulosic materials have been important to human society for millennia. As with many materials, achieving a molecular-level understanding of the formation, characteristics, and functionality of defects within the material provides a basis for manipulating its properties and performance. We observed that mechanically induced defects in cellulose nanofibrils can serve as initiation sites for hydrolysis by processive cellulase enzymes. We hypothesize that this behavior results from breakages in surface glucan chains that result from the formation of kink-defects in response to bending stress. We further investigate the mechanical induction of kink defects by direct nanomanipulation with an atomic force microscope and demonstrate individual defects may be introduced into isolated nanofibrils. Finally, we use molecular dynamics and quantum mechanical simulations to provide a molecular-level understanding of mechanically-induced defect formation. These simulations provide additional evidence that kink defects may result in breakage of covalent bonds, and thereby increase the reactivity of cellulose fibrils to processive cellobiohydrolases. Collectively, our findings provide a refined understanding of the fundamental structure and behavior of cellulose nanofibrils and imply that cellulose processing paradigms could exploit systematic, nanomechanical introduction of defects to tune the materials properties and improve the reactivity of cellulose in conversion scenarios.

Citation

PNAS

Pub Type

Journals

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Keywords

Cellulose, Atomic Force Microscope, Moecular Dynamics, Biofuels, Nanomechanics

Citation

Ciesielski, P. , Wagner, R. , Bharadwaj, V. , Killgore, J. , Mittal, A. , Beckham, G. , Decker, S. , Himmel, M. and Crowley, M. (2019), Nanomechanics of cellulose deformation reveal molecular defects that facilitate natural deconstruction, PNAS, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=925633 (Accessed April 26, 2024)