Ternary polyol-based deep eutectic solvents mediated by different pKa acids to facilitate enzymatic saccharification of peanut straw

Lignocellulosic biorefinery is severely limited by the inherent recalcitrance of lignin–carbohydrate complexes. Although polyol-based deep eutectic solvents (DESs) serve as green pretreatment media that suppress lignin recondensation by inhibiting benzyl carbocation generation, their practical enzymatic saccharification performance remains inferior to other DES categories. To overcome this critical drawback, the present work rationally constructed ternary polyol DESs mediated by acids with different pKa, and systematically evaluated their capacity to deconstruct peanut straw for enhanced sugar recovery. Under the ternary choline chloride–1,3-propanediol–oxalic acid DES treatment, a remarkable glucose yield of 92.53% was achieved after 72 h of enzymatic hydrolysis. Density functional theory (DFT) calculations further revealed the underlying molecular mechanisms: the multi-site hydrogen-bonding network formed by the ternary DES competitively breaks the inherent hydrogen bonds within lignin, effectively cleaving interunit lignin–carbohydrate linkages. Compared with binary DESs, the optimized ternary system achieves superior delignification and saccharification efficiencies simultaneously. This study not only provides an eco-efficient pretreatment route for agricultural waste, but also advances molecular-level understanding of DES–lignin intermolecular interactions. The gradient pKa acid co-modulation strategy proposed here can serve as a general framework for custom-designing task-specific DESs for diverse lignocellulose biorefinery applications.