水热协同低共熔溶剂预处理促进木质纤维拆解与利用OA

Taking poplar(PL)as the research object,the twin-screw extrusion(E),hydrothermal(P),deep eutectic solvent(DES)pretreatment,and multi-step synergistic pretreatment(E-DES/P-DES/P-E-DES)were conducted,respectively.The DES system was composed of choline chloride/p-toluenesulfonic acid/1,4-butanediol.The effects of different pretreatment systems on the fractionation of PL,the changes in the physicochemical structure characteristics of pretreated substrates/lignin,the enzymatic hydrolysis performance of cellulose,and the antioxidant performance of recycled lignin were investigated by scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),and nuclear magnetic resonance(NMR).The results showed that the multi-step synergistic pretreatment significantly promoted the efficient fractionation and utilization of PL.The removal of hemicellulose and lignin of PL-P-E-DES residues reached 88.54％and 83.46％,as well as the yields of glucose and xylose(99.69％and 78.66％),and the yield of xylooligosaccharides(45.71％),respectively.The SEM images showed that the PL-P-E-DES residues presented obvious curling and pore structures that was much severe than others.The XRD analysis indicated that the natural type Ⅰ crystalline of cellulose remained in all systems,and the crystallinity(CrI)of PL-P-E-DES residues reached 70.38％.The FT-IR results showed that the signals of hemicellulose and lignin of PL-P-E-DES residues were significantly weakened.The gel permeation chromatography(GPC)results showed that the weight-average molecular weight(Mw)of PL-DES lignin(PL-DES-L)was 1 587.The NMR results showed that the condensation signals of the syringyl(S)and the guaiacyl(G)units in lignin increased,while the content of phenolic hydroxyl groups increased simultaneously.The total phenolic hydroxyl content of the lignin recovered after PL-P-E-DES reached 2.81 mnmol/g.The lowest IC50 value of PL-E-DES-L against DPPH radicals was only 56.16 mg/L,slightly higher than the positive control vitamin C(Vc,35.36 mg/L).Therefore,the multi-step synergistic pretreatment not only improved the fractionation efficiency of PL but also promoted the conversion and application of cellulose,hemicellulose,and lignin to monosaccharides,oligosaccharides,and antioxidant products,respectively.