Department of Forest Biomaterials and Technology/Wood Science, Swedish University of Agricultural Sciences (SLU), 756 51, Uppsala, Sweden.
Division of Molecular Biophysics and Integrated Bioimaging, Department of Cellular and Tissue Imaging, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Mail Stop Donner, Berkeley, CA, 94720, USA.
Sci Rep. 2023 Feb 9;13(1):2350. doi: 10.1038/s41598-023-29113-x.
Lignocellulose biomass has a tremendous potential as renewable biomaterials for fostering the "bio-based society" and circular bioeconomy paradigm. It requires efficient use and breakdown of fiber cell walls containing mainly cellulose, hemicellulose and lignin biopolymers. Despite their great importance, there is an extensive debate on the true structure of fiber walls and knowledge on the macromolecular nano-organization is limited and remains elusive in 3D. We employed dual-axis electron tomography that allows visualization of previously unseen 3D macromolecular organization/biopolymeric nano-architecture of the secondary S2 layer of Norway spruce fiber wall. Unprecedented 3D nano-structural details with novel insights into cellulose microfibrils (~ 2 nm diameter), macrofibrils, nano-pore network and cell wall chemistry (volume %) across the S2 were explored and quantified including simulation of structure related permeability. Matrix polymer association with cellulose varied between microfibrils and macrofibrils with lignin directly associated with MFs. Simulated bio-nano-mechanical properties revealed stress distribution within the S2 and showed similar properties between the idealized 3D model and the native S2 (actual tomogram). Present work has great potential for significant advancements in lignocellulose research on nano-scale understanding of cell wall assembly/disassembly processes leading to more efficient industrial processes of functionalization, valorization and target modification technologies.
木质纤维素生物质具有巨大的潜力，可以作为可再生生物材料，促进“基于生物的社会”和循环生物经济范式。它需要有效地利用和分解主要含有纤维素、半纤维素和木质素生物聚合物的纤维细胞壁。尽管它们非常重要，但关于纤维壁的真实结构存在广泛的争论，对大分子纳米组织的了解有限，在 3D 中仍然难以捉摸。我们采用双轴电子断层扫描技术，能够可视化以前看不见的挪威云杉纤维壁二级 S2 层的 3D 大分子组织/生物聚合物纳米结构。探索和量化了 S2 中纤维素微纤维（~2nm 直径）、大纤维、纳米孔网络和细胞壁化学（体积%）的前所未有的 3D 纳米结构细节，并获得了新的认识，包括与结构相关渗透性的模拟。与纤维素结合的基质聚合物在微纤维和大纤维之间存在差异，木质素直接与 MF 结合。模拟的生物纳米力学性能显示了 S2 内的应力分布，并显示了理想的 3D 模型和天然 S2（实际断层扫描）之间的相似特性。本工作在木质纤维素研究方面具有很大的潜力，可以在纳米尺度上深入了解细胞壁组装/拆卸过程，从而为功能化、增值和目标修饰技术的更有效的工业过程提供支持。
