Effects of deep eutectic solvent on laccase activity and thermal stability

Eighteen deep eutectic solvent (DES) systems were systematically evaluated to optimize laccase biocatalysis. Five hydrogen bond acceptors (HBAs) significantly enhanced both enzyme activity and thermal stability. The choline dihydrogen phosphate (ChDHP)-glycerol DES yielded the highest activity increase (198 %). Moreover, a 50 % betaine-sorbitol (BS) solution retained 92 % activity after 1 h at 70 °C-55-fold higher than buffer-addressing a key thermal stability challenge. Fluorescence spectroscopy (FS) and molecular docking revealed that DES solutions stabilized laccase's native structure by forming hydrogen bonds with catalytic center histidine (His) and phenylalanine (Phe) residues. BS-laccase pretreatment increased glucose conversion by 30 % in distillers' grains (DG) and 54 % in poplar wood (PW). These findings establish DES as a sustainable, low-cost co-solvent that boosts enzymatic efficiency, offering molecular insights into HBA-enzyme interactions to guide biocatalytic system design for circular bioeconomy.