In an attempt to augment the profitability and sustainability of lignocellulosic biorefineries, lignin valorization has been deemed as an indispensable requirement. However, unsatisfactory solubility and recalcitrant condensed structures heavily limits the processability of lignin towards high value applications. Here, we exploited a high-solid ethylenediamine (EDA) pretreatment of corn stover and discovered a new aminolignin with an extraordinary aqueous solubility (greater than 86 wt% at pH = 2–8) and minimal condensed structures (M_w = 1200–1400 Da). We brought light to the unique amination reactions that took place in EDA pretreatments, such as α-amination, ammonolysis, and Schiff base reactions. These EDA induced amination introduced hydrophilic amine and amide groups into lignin substructures, which could be the main reason for the rapid room temperature solubilization of lignin, due to the great increase of lignin-water hydrogen bonds and polarity of lignin according to computational simulation. Furthermore, extremely high solid loadings (58 wt%) limited the mobility and accessibility of reactive lignin intermediates owing to pretreatment system keeping in the solid state, physically obstructing the lignin condensation. Chemically, α-amination of β-O-4 structures decreased the generation of condensed lignin as well. This solid-state EDA pretreatment is of great significance for improving the aqueous solubility of lignin and minimizing its condensation, and thus it holds promise for the development of lignin-first biomass fractionation.

为了提高木质纤维素生物精炼厂的盈利能力和可持续性，木质素增值已被视为必不可少的要求。然而，不令人满意的溶解度和顽固的缩合结构严重限制了木质素向高价值应用的可加工性。在这里，我们利用玉米秸秆的高固体乙二胺 (EDA) 预处理，发现了一种新的氨基木质素，它具有非凡的水溶性（在 pH = 2-8 时大于 86 wt%）和最小的缩合结构（M _w  = 1200-1400哒）。我们揭示了 EDA 预处理中发生的独特胺化反应，例如α-胺化、氨解和席夫碱反应。根据计算模拟，这些 EDA 诱导的胺化将亲水性胺和酰胺基团引入木质素亚结构，这可能是木质素在室温下快速溶解的主要原因，这是由于木质素 - 水氢键和木质素极性的大量增加。此外，由于预处理系统保持固态，物理上阻碍了木质素缩合，因此极高的固体负载（58wt%）限制了活性木质素中间体的流动性和可及性。化学上，β的α-胺化-O-4 结构也减少了凝聚木质素的产生。这种固态EDA预处理对于提高木质素的水溶性和减少其缩合具有重要意义，因此有望发展木质素优先的生物质分馏。