Extraction of light-colored lignin nanoparticles from Radiata pine using ternary deep eutectic solvents

Light-colored lignin nanoparticles (LNPs) have shown great potential in their conversion and high value-added applications. However, the direct extraction of light-colored LNPs from lignocellulosic materials remains a significant challenge in the field. In this study, we developed a very effective strategy for rapid extraction (1 h) of light-colored LNPs from radiata pine using a new ternary deep eutectic solvent (TDES) composed of benzyltrimethyl-ammonium chloride (BTMAC), formic acid (FA) and maleic acid (MA). The results indicated the obtained average particle size of LNPs ranged from 127 nm to 171 nm. The extraction process was optimized to achieve high yields (84.7 %), purity (94.1 %) and low polydispersity index (PDI = 1.96) while maintaining the light-colored LNPs (brightness ISO 24.15 %), which was 9.7, 10.5 and 2.5 folds higher than Kraft lignin, alkali lignin and lignosulfonate, respectively. Further evaluation revealed that the IC50 of the three LNPs samples were less than 60 μg·mL −1 , exhibiting significant antioxidant activity. In addition, the introduction of MA could protect the β-O-4 linkage from excessive cleavage and recondensation as well as avoid the deepening of LNPs color. This work not only presents an effective method for extracting light-colored LNPs but also highlights their advantageous properties, paving the way for sustainable product development utilizing lignocellulosic biomass.