A synergistic hydrothermal-deep eutectic solvents (DES) pretreatment for acquiring xylooligosaccharides and lignin nanoparticles from Eucommia ulmoides wood

To achieve an effective deconstruction for preparation of xylooligosaccharides (XOS) and lignin nanoparticles (LNPs) from Eucommia ulmoides, a synergistic pretreatment was successfully developed. Herein, the hemicelluloses were preferentially dissociated in acetic acid-catalyzed hydrothermal pretreatment (HTP) for preparation of XOS, and the hydrothermally-pretreated substrate was then subjected to deep eutectic solvents (DES) delignification for fabrication of LNPs. Results showed that the optimal yield (33.88% based on xylan) of XOS is obtained under the given HTP condition (170 °C, 0.5 h). NMR characterization showed that the linkages of lignin were mainly composed of β-O-4, β-β, β-5, etc. Besides, GPC analysis showed that the molecular weight of DES lignin fractions was lower (1130-1200 g/mol) than those of corresponding parent lignin fractions (8500-9620 g/mol). Further TEM characterization indicated that the optimal LNPs fraction has a narrow size distribution and the corresponding size is ranged from 60 to 110 nm. In short, the synergistic pretreatment could be used as a green and cost-effective approach for the development of bio-based chemicals and biomaterials from Eucommia ulmoides biomass.