Lignin is widely recognized as a key factor influencing the recalcitrance of lignocellulosic biomass, yet the specifics of this relationship remain complex and not fully understood due to the complex interplay between lignin content variation and cell wall structure. Bamboo, which exhibits greater recalcitrance compared to wood in biorefinery processing, was chosen as the focus of investigation in this study. Three variants of with high, middle and low lignin contents were systematically analyzed and compared, in terms of molecular structure of lignin, hemicelluloses and cellulose, cell wall polymer spatial orientation, lignin-carbohydrate complex (LCC) linkages, cell wall geometrical size, as well as deconstruction efficiency, including delignification, alkaline extraction, and cellulose enzymatic hydrolysis efficiency. Findings reveal that an increase in lignin content generally lowers bamboo's deconstruction efficiency, but the mechanisms are more nuanced than previously thought. While lignin content variations do not significantly affect the molecular structure of xylan, cellulose and the chemical linkage type of LCC linkages, they do impact cellulose crystallinity, xylan orientation and notably, the thickness of fiber cell wall in the free fiber stands of bamboo. These findings highlight that lignin's role extends beyond mere physical protection of the cell wall, but also induces subtle variations in polymer structure and cell wall morphologies, which collectively influence the deconstruction efficiency of bamboo cell walls.

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木质素在木质纤维素生物质中的复杂作用：竹子的案例研究

木质素被广泛认为是影响木质纤维素生物质顽抗性的关键因素，但由于木质素含量变化和细胞壁结构之间复杂的相互作用，这种关系的细节仍然复杂且尚未完全了解。与木材相比，竹子在生物精炼加工中表现出更大的顽抗性，因此被选为本研究的研究重点。对高、中、低木质素含量的三种变体，从木质素、半纤维素和纤维素的分子结构、细胞壁聚合物空间取向、木质素-碳水化合物复合物（LCC）键合、细胞壁几何尺寸等方面进行了系统分析和比较，以及解构效率，包括脱木质素、碱提取和纤维素酶水解效率。研究结果表明，木质素含量的增加通常会降低竹子的解构效率，但其机制比之前想象的更加微妙。虽然木质素含量变化不会显着影响木聚糖、纤维素的分子结构和LCC键的化学键类型，但它们确实影响纤维素结晶度、木聚糖取向，尤其是竹子自由纤维中纤维细胞壁的厚度。这些发现强调，木质素的作用不仅仅是细胞壁的物理保护，而且还引起聚合物结构和细胞壁形态的微妙变化，这些变化共同影响竹细胞壁的解构效率。