This study focuses on the physicochemical characterization of lignin produced via enzymatic hydrolysis of hardwood chips. Enzymatically produced lignin (HL) was water-insoluble particles that contained carbohydrates that were chemically bound to lignin. The X-ray photoelectron spectroscopy (XPS), ¹H-NMR, ¹³C-NMR, ³¹P NMR and two-dimensional ¹H-¹³C HSQC, ¹H-¹³C HSQC-TOCSY, ¹H-¹³C HMBC NMR analyses confirmed that the HL samples with the lower internal ether linkages had fewer β-O-4 aryl ether and lignin-carbohydrate (LCC) bonds but more phenolic hydroxyl and carboxylate groups. Moreover, the samples with the lower sugar content were smaller and more porous. The chemical reactivity analysis of HL samples in various sulfo-functionalization reactions (sulfonation S, sulfomethylation SM, and sulfoethylation SE) revealed a direct correlation between the degree of substitution (DS) and phenolic guaiacyl (G) and the condensed hydroxyl group of HL. Also, the carbohydrate content and particle size of HL were inversely related to the degree of substitution of sulfo-functionalization of HL. The SM- and S- modified HL samples with adequate water solubility (9−10 g/L), charge density (≥1.9 mmol/g), and small particle size (5 μm) were shown to be effective stabilizers for clay suspensions via reducing the instability index (TSI∼10) and settling velocity (−4 %/h) of clay particles in the suspension. The results obtained in this study shed light on the significant role of residual carbohydrates and internal ether linkages of HL on the physicochemical properties and sulfo-functionalization of HL.

本研究的重点是通过硬木片的酶水解产生的木质素的物理化学特征。酶促产生的木质素 (HL) 是不溶于水的颗粒，其中含有化学结合到木质素的碳水化合物。X射线光电子能谱（XPS）、¹ H-NMR、¹³ C-NMR、³¹ P NMR和二维¹ H- ¹³ C HSQC、¹ H- ¹³ C HSQC-TOCSY、¹ H- ¹³C HMBC NMR 分析证实，具有较低内部醚键的 HL 样品具有较少的 β-O-4 芳基醚和木质素 - 碳水化合物 (LCC) 键，但具有更多的酚羟基和羧酸酯基团。此外，含糖量较低的样品更小，孔隙更多。HL 样品在各种磺基官能化反应（磺化 S、磺甲基化 SM 和磺乙基化 SE）中的化学反应性分析表明，取代度 (DS) 和酚类愈创木酰基 (G) 与 HL 的缩合羟基之间存在直接相关性。此外，HL 的碳水化合物含量和粒径与 HL 的磺基官能化的取代程度成反比。SM- 和 S- 改性的 HL 样品具有足够的水溶性 (9-10 g/L)、电荷密度 (≥1.9 mmol/g)、通过降低悬浮液中粘土颗粒的不稳定性指数 (TSI∼10) 和沉降速度 (-4 %/h)，小粒径 (5 μm) 被证明是粘土悬浮液的有效稳定剂。本研究中获得的结果阐明了 HL 的残留碳水化合物和内部醚键对 HL 的理化性质和磺基官能化的重要作用。