What is it about?
Plant cell walls are composed of skeletal cellulose and a filling matrix of hemicelluloses and lignin. Cellulose has slender crystallite units referred to as microfibrils or elementary fibrils, and these crystallites form a dense network skeleton in the cell walls. In this study, we assessed the morphology and crystallinity of individually dispersed microfibrils isolated from the cell walls of wood, cotton, and ramie celluloses. It is well known that microfibrils in higher plants exhibit structural diversity, and these three plants, in particular, have distinct differences in the morphology and crystallinity of microfibrils. Our structural analyses combining atomic force microscopy (AFM), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), solid-state 13C NMR spectroscopy, and all-atom molecular dynamics (MD) simulations revealed the uniformity in the cross-sectional dimensions and crystallinity of the dispersed microfibrils, irrespective of the plant species. The majority of the microfibrils were dispersed as structural units with widths of approximately 2 to 3 nm, and their crystallite sizes and crystallinity degrees were approximately 2 nm and 20%, respectively. These structural profiles were in agreement with the simulation results; here, the model assumed that a single microfibril consisted of 18 cellulose molecules. These results from the direct dimensional assessments support a recent hypothesis in biophysics that a single biosynthesis system of cellulose, referred to as the terminal complex (TC), consisted of 18 synthases. Some of the dispersed microfibrils had bundled sizes of two or three microfibrils. We also demonstrated that this bundling was stabilized by the fusion of several crystallites.
Featured Image
Photo by FlyD on Unsplash
Why is it important?
It has been a common understanding that major three types of higher plant cellulose, or cotton-ramie, wood, and primary cell wall types, form thin microfibrils of cellulose Iβ crystallite with cross-sectional dimensions of approximately 5 to 6 nm, 3 to 4 nm, and 2 to 3 nm, respectively. In this study, wood and cotton-ramie-type microfibrils were found to be actually uniform in morphology, and their dimensions and crystallinity were equivalent to those of primary cell wall type. These structural profiles were explainable using the 18-chain model. The enlargement of crystallite dimensions was also observed in the process of maturation or drying of the cell walls, resulting in the structural diversity of these plant microfibrils.
Perspectives
By isolating and analyzing individual cellulose microfibrils in a state close to their native condition, we have demonstrated that their fundamental structure is essentially consistent—whether derived from ramies, cotton, or wood—regardless of whether the source is woody or non-woody. This finding suggests that cellulose biosynthesis operates through a conserved mechanism across diverse higher plant species, which we regard as a scientifically significant insight. Moreover, from the perspective of industrial application, this study shows that uniform and high-performance “cellulose nanofibers” can be obtained not only from wood but also from ramie, cotton, Erianthus, and even agricultural waste. This highlights the promising potential for expanding the range of biomass resources utilized in the development of sustainable materials.
Tsuguyuki Saito
Tokyo Daigaku
Read the Original
This page is a summary of: Uniform elementary fibrils in diverse plant cell walls, Proceedings of the National Academy of Sciences, April 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2426467122.
You can read the full text:
Contributors
The following have contributed to this page
