Structural Analysis of Alfa Grass (Stipa tenacissima L.) Lignin Obtained by Acetic Acid/Formic Acid Delignification

Abstract

Alfa grass lignin obtained by the acetic acid/formic acid/water CIMV pulping process was characterized by FTIR and (1)H, (13)C-(1)H 2D HSQC, and (31)P NMR spectroscopies. Lignin samples purified by further dissolution/precipitation or basic hydrolysis steps were also analyzed. The CIMV alfa lignin is a mixture of low molar mass compounds (M(n) = 1500 g/mol) of SGH type with β-O-4 ether bonds as the major interunit linkage. The crude lignin contains fatty acids and residual polysaccharides. It also contains large amounts of acetate and hydroxycinnamates, mostly in the γ-position of β-O-4 interunit linkages. Although partial acetylation induced by the process cannot be excluded, the absence of aromatic acetates and acetylated polysaccharides in crude lignin demonstrates the mildness of the process. By combining smooth alkaline hydrolysis and dissolution/precipitation steps to the CIMV pulping, it is possible to produce a purified lignin with a composition and a structure quite analogous to that of the native polymer in the plant.

A critique on the structural analysis of lignins and application of novel tandem mass spectrometric strategies to determine lignin sequencing

“…This study was chosen to exemplify the type of chemical manipulation that the lignin can be submitted to, prior of initiation of structural elucidation. [188] The authors treated the alfa grass lignin (VRL) obtained by the CIMV process, [147][148][149] by a complicated series of dissolution/precipitation and alkaline hydrolysis manipulations, which were accomplished as follows. The following is included to underscore the tedious process of converting VRL into an altered PML.…”

Effect of Biological Pretreatment with White-rot Fungus Trametes hirsuta C7784 on Lignin Structure in Carex meyeriana Kunth

“…2), the identified substructures are illustrated in Fig. 3, and the cross-signals were assigned as illustrated in Table 4 according to reported literature sources (Abdelkafi et al 2011;del Rio et al 2012;Villaverde et al 2009 Fig. 2.…”

Effect of structural changes of lignin during the autohydrolysis and organosolv pretreatment on Eucommia ulmoides Oliver for an effective enzymatic hydrolysis

“…However, the question that how the lignin changes during the different pretreatments still needs to be clarified. Multiple advanced techniques were utilized to investigate structural changes of lignin polymer from different kinds of pretreatments, such as acid treated lignin (Abdelkafi et al, 2011), organosolv lignin (Cetin and Özmen, 2002), and ionic liquid lignin (Wen et al, 2013a). Under these delignification conditions, lignin can be degraded or de-polymerized into small molecular fragments, which could be used as a potential and promising feedstock for developing bio-based chemicals and materials (Ragauskas et al, 2006.…”