Determination of Sugarcane Bagasse Lignin S/G/H Ratio by Pyrolysis GC/MS

Abstract

In this work, analytical pyrolysis (Py-GC-MS) was employed to identify lignin markers derived from H, S, and G phenylpropanoid units in sugarcane bagasse. Temperatures of 450 and 500 • C allowed the detection of key products that were informative on the bagasse lignin composition. The method was validated by comparing the S/G ratio as determined by the nitrobenzene oxidation (NBO) standard method for five sugarcane varieties. The S/G ratio as determined by Py-GC-MS, taking into consideration all known lignin markers in the analysis, resulted in a correlation coefficient of 0.85 with a linear regression coefficient of 0.74. When a group of selected markers (M2) was used, the correlation coefficient between methods was improved to 0.95 and the linear regression coefficient was adjusted to 0.92. M2 markers consisted of five syringyl markers (syringol, 4-methylsyringol, 4-ethylsyringol, 4-vinylsyringol, and trans-4-propenylsyringol) and four guaiacyl markers (guaiacol, 4-vinylguaiacol, 4-methylguaiacol, and vanillin). Importantly, Py-GC-MS allowed for the study of lignin composition in sugarcane bagasse without the need to remove the extractives, minimizing the work with sample preparations.

Lignification in Sugarcane: Biochemical Characterization, Gene Discovery, and Expression Analysis in Two Genotypes Contrasting for Lignin Content

“…The values for lignin content presented in our study are significantly lower than those previously reported for sugarcane bagasse (Lopes et al, 2011;Masarin et al, 2011;Rezende et al, 2011). Sugarcane bagasse is the residue produced after Suc extraction and is composed of 39% cellulose, 25% hemicelluloses, and 23% lignin, among other minor components (Carroll and Somerville, 2009).…”

“…Here, only the internode, the region between two adjacent nodes, was used for lignin determination, while the highly lignified and fibrous nodes were discarded. Therefore, the high lignin values previously reported for sugarcane bagasse (Lopes et al, 2011;Masarin et al, 2011;Rezende et al, 2011) reflect the lignin content of a mixture of internodes and nodes and, therefore, cannot be directly compared with the values obtained here.…”

Recent innovations in analytical methods for the qualitative and quantitative assessment of lignin

“…Thermochemical evaluations of lignin monomers have become increasing prevalent [4,5,13,59,[61][62][63][64][65][66]68,70,126,157,159,183,240,242,293,295,[298][299][300][301]303,305,306,308]. When heated, lignin linkages are cleaved, permitting the identification of individual monomeric moieties.…”

“…S/G lignin ratios have proven to be important parameters for gauging the recalcitrance of lignin, although no clear trend has been established as to whether or not a high S content results in increased monomeric sugar release following an enzymatic hydrolysis. The traditional methods for measuring lignin monomer composition include NMR, pyGCMS, pyMBMS, and various wet chemical methods such as nitrobenzene oxidation (NBO) and thioacidolysis [4,5,13,56,58,59,[61][62][63][64][65][66]68,70,126,135,157,159,183,240,242,[291][292][293][294][295][296][297][298][299][300][301][302][303][304][305][306][307]. Common pyrolysis and mass spectral fragments are listed in Table 8, and illustrated in Fig.…”

Cell Walls: Structure and Biogenesis

“…Lignin is usually described by the relative abundance and ratio of the H-, G-, and S-units (Campbell & Sederoff 1996). With some notable exceptions lignins from gymnosperms are composed of G-units only (with minor amounts of H-units), whereas grass lignins, including that from sugarcane (He & Terashima 1991;Lopes et al 2011), comprise mostly S-and G-units, with H-units much less abundant. Lignins in many crops may be acylated with different organic acids (Ralph et al 2004), but the biochemistry and functions of lignin acylation have not been elucidated.…”