Structural elucidation of Eucalyptus lignin and its dynamic changes in the cell walls during an integrated process of ionic liquids and successive alkali treatments

Abstract

An integrated process based on ionic liquids ([Bmim]Cl and [Bmim]OAc) pretreatment and successive alkali post-treatments (0.5, 2.0, and 4.0% NaOH at 90°C for 2h) was performed to isolate lignins from Eucalyptus. The structural features and spatial distribution of lignin in the Eucalyptus cell wall were investigated thoroughly. Results revealed that the ionic liquids pretreatment promoted the isolation of alkaline lignin from the pretreated samples without obvious structural changes. Additionally, the integrated process resulted in syringyl-rich lignin macromolecules with more β-O-4' linkages and less phenolic hydroxyl groups. Confocal Raman microscopy analysis showed that the dissolution behavior of lignin was varied in the morphologically distinct regions during the successive alkali treatments, and lignin dissolved was mainly stemmed from the secondary wall regions. These results provided some useful information for understanding the mechanisms of delignification during the integrated process and enhancing the potential utilizations of lignin in future biorefineries.

Transcriptional regulation of microalgae for concurrent lipid overproduction and secretion

“…1L) in overexpressing cells than WT. Consistent with the previous reports, these results demonstrated that NobZIP1 overexpression redirected energy and carbon precursors toward lipogenesis from protein and carbohydrate synthesis ( 6 , 17 , 21 ). Thereafter, we sought to gain further insight into structural changes of overexpressing cells, and hence, we examined the cell morphology and subcellular changes by transmission electron microscopy (TEM), which revealed significant ultrastructural changes in overexpressing strains (Fig.…”

Understanding the Distribution and Structural Feature of Eucalyptus Lignin Isolated by γ-Valerolactone/Water/Acid System

“…The weight-average ( M w ) and number-average ( M n ) molecular weights of lignin were determined by gel permeation chromatography (GPC) with an ultraviolet (UV) detector at 280 nm on a PL-gel 10 μm mixed-B 7.5 mm i.d. column . The acetylation of lignin was performed to improve the lignin solubility in tetrahydrofuran for GPC analysis, and the detailed process is given in the Supporting Information .…”

Torrefaction at 200 °C of Pubescens Pretreated with AlCl3 Aqueous Solution at Room Temperature

“… 15 − 18 The characteristic absorbance of lignin occurred at 1635, 1605, 1513, 1462, 1426, 1029, and 834 cm –1 , 16 , 19 where the weak band at 1635 cm –1 was assigned to the conjugated C=O stretching of the aromatic ring. 17 , 18 The absorbance bands at 1605 and 1513 cm –1 were assigned to C–C and C=C stretching of the aromatic ring of lignin, while the band at 1029 cm –1 was due to the C–O stretching of O-CH 3 and C-OH. 20 The bands at 1740 cm –1 (belonging to C=O stretching in xylan or C=O stretching vibration of carbonyl, carboxyl, and acetyl groups in hemicellulose), 1246 cm –1 (belonging to C=O stretching vibration in xyloglucan), and 1056 cm –1 (belonging to C–O stretching vibrations or C-OH bending in hemicellulose) were assigned to the characteristic absorbance of hemicellulose.…”

“… 20 The bands at 1740 cm –1 (belonging to C=O stretching in xylan or C=O stretching vibration of carbonyl, carboxyl, and acetyl groups in hemicellulose), 1246 cm –1 (belonging to C=O stretching vibration in xyloglucan), and 1056 cm –1 (belonging to C–O stretching vibrations or C-OH bending in hemicellulose) were assigned to the characteristic absorbance of hemicellulose. 17 , 21 The bands at 1378, 1165, 1117, and 896 cm –1 were assigned to the characteristic absorbance of cellulose, whereas those at 1165, 1117, and 896 cm –1 were assigned to C–O–C asymmetric stretching at the β-(1-4)-glycosidic linkage, stretching of the glucose ring in plane, and glucose ring stretching. 15 , 20 …”