Lignin Carbohydrate Complexes structure preserved throughout downstream processes for their valorization after recovery from industrial process water

Flow-through strategy to fractionate lignin from eucalyptus with formic acid/hydrochloric solution under mild conditions

Formic acid is an attractive solvent for the fractionation of lignocellulose for the production of biomaterials and chemicals, while the operation conducted in a batch manner is not conducive to mass transfer in separation process. In this research, eucalyptus was fractionated with formic acid/hydrochloric solution in a flow-through reactor at 95 °C, and the structural characteristics and the composition of fractionated lignin in different stages were investigated. Results showed that the fractionation efficiency was notably improved with a flow-through reactor, as evidenced by the low solid residue yield of 49.5% and the lignin removal rate of 79.4% as compared to the batch manner. During the fractionation process, the dissolution rate of lignin decreased gradually, and the obtained lignin samples showed low molecular weight (<3000), good uniformity (<2), and high thermal stability. The structure analysis showed that β-O-4, β-β, and β-5 linkages in lignin were degraded to varying degrees with increased time, and the degradation of G units was more severe than S ones.

Structural changes of lignin-carbohydrate complexes (LCCs) from Chinese quince fruits during the sequential fractionation of pectic and hemicellulosic polysaccharides

Chinese quince (Chaenomeles sinensis) fruits offer a potential source of pectin and hemicellulose. However, the existence of lignin-carbohydrate complexes (LCCs) can negatively impact the extraction of pectin and hemicellulose. In this work, LCCs were sequentially fractionated from Chinese quince during the removal of pectin and hemicellulose. The structures of LCCs were characterized by HPAEC, FT-IR, GPC, Py-GC/MS, TGA and 2D HSQC NMR. The results showed that the carbohydrate content and molecular weight of LCCs was found to be changed significantly after the removal of hemicellulose (KSH). The lignin in Björkman LCCs was found to be linked mainly to galactan and fructan, whereas the lignin LCC-AcOHs was found to be linked mainly to arabinan after the removal of KSH. The isolation of carbonate-soluble pectin (NSP) increased thermal stability of Björkman LCC fraction, however, the isolation of chelator-soluble pectin (CSP) increased the thermal stability of LCC-AcOHs. The S/G ratios of LCC-AcOHs increased and large amounts of S-type lignin released during sequential fractionation of pectin and hemicellulose. These results will be beneficial for understanding the mechanisms of pectin and hemicellulose isolation, thereby facilitating the potential application of Chinese quince as a valuable natural resource for food and other industries.

Synthesis of lignin-carbohydrate complex-based catalyst from Eragrostis tef straw and its catalytic performance in xylose dehydration to furfural

A new catalyst was successfully prepared by functionalization of the lignin-carbohydrate complex structure in the Eragrostis tef straw via simultaneous carbonization and sulfonation. The physical and chemical properties of the surface of the synthesized catalyst were checked by FTIR and XRD. The FTIR results indicate the prepared catalyst exhibited functional groups such as -SO₃H, -COOH, and -OH. The synthesis conditions like the temperature and time of carbonization and sulfonation showed significant effect the amount of the strong acid doped into the carbonized lignin-carbohydrate matrix. The newly prepared catalyst was checked for dehydration of xylose to furfural and revealed of course that it has the potential. The maximum yield of furfural 62.4% was achieved and the catalyst showed excellent reusability for 5 runs without significant loss of catalystic activity. The use of catalysts prepared from Eragrostis tef straw is a green strategy for converting xylose to furfural, as these catalysts are solving the problems associated with the use of mineral acid catalysts.