Department of Chemistry, Louisiana State University, Baton Rouge, LA, 70803, USA.
National High Magnetic Field Laboratory, Tallahassee, FL, 32310, USA.
Nat Commun. 2019 Jan 21;10(1):347. doi: 10.1038/s41467-018-08252-0.
Lignin is a complex aromatic biopolymer that strengthens and waterproofs plant secondary cell walls, enabling mechanical stability in trees and long-distance water transport in xylem. Lignin removal is a key step in paper production and biomass conversion to biofuels, motivating efforts to re-engineer lignin biosynthesis. However, the physical nature of lignin's interactions with wall polysaccharides is not well understood. Here we show that lignin self-aggregates to form highly hydrophobic and dynamically unique nanodomains, with extensive surface contacts to xylan. Solid-state NMR spectroscopy of intact maize stems, supported by dynamic nuclear polarization, reveals that lignin has abundant electrostatic interactions with the polar motifs of xylan. Lignin preferentially binds xylans with 3-fold or distorted 2-fold helical screw conformations, indicative of xylans not closely associated with cellulose. These findings advance our knowledge of the molecular-level organization of lignocellulosic biomass, providing the structural foundation for optimization of post-harvest processing for biofuels and biomaterials.
木质素是一种复杂的芳香性生物聚合物，它增强并防水植物次生细胞壁，使树木具有机械稳定性，并在木质部中进行远距离水分运输。木质素的去除是纸张生产和生物量转化为生物燃料的关键步骤，这促使人们努力重新设计木质素的生物合成。然而，木质素与细胞壁多糖相互作用的物理性质还不是很清楚。在这里，我们表明木质素自组装形成高度疏水和动态独特的纳米域，并与木聚糖有广泛的表面接触。固态核磁共振光谱和动态核极化技术支持的完整玉米茎的研究表明，木质素与木聚糖的极性基序之间存在丰富的静电相互作用。木质素优先与具有 3 倍或扭曲 2 倍螺旋螺旋构象的木聚糖结合，这表明木聚糖与纤维素没有密切相关。这些发现增进了我们对木质纤维素生物质的分子水平组织的认识，为生物燃料和生物材料的收获后加工的优化提供了结构基础。
