Insights into the Structural Changes and Potentials of Lignin from Bagasse during the Integrated Delignification Process

Making full use of the lignocellulose is of great significance to the current biorefinery enterprises. As a natural macromolecule polymer, lignin has a prominent potential as renewable feedstock to produce value-added products. In the present study, the integrated process combined hydrothermal pretreatment (HTP) and alkaline delignification was adopted to dissociate bagasse. The HTP process primarily promoted the conversion of hemicelluloses into xylo-oligosaccharides (XOS), and the subsequent delignification of substrates was achieved under low-alkaline dosage. Additionally, the lignin fractions originated from the integrated process were comprehensive and structurally elucidated via the NMR and GPC techniques. Furthermore, the effects of the bleaching processes (H2O2, ClO2, and O-3) on the structures of lignin were explored based on the DEL (double enzymatic lignin) isolated from bagasse. It was observed that ClO2 bleaching led to the obvious depolymerization of lignin and augment in p-hydroxyphenyl units, implying that ClO2 bleaching was more efficient in the delignification process. Moreover, Py-GC/MS was also applied to evaluate pyrolytic products of the lignins isolated during the integrated process. Significant amounts of vinyl phenolic compounds were produced from the bagasse lignins, which presented a favorable potential for the lignins in the production of vinyl phenolics.