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

Abstract

Lignin is a complex biopolymer composed of aromatic alcohols known as monolignols. It is most commonly derived from wood, and is an integral part of the secondary cell walls of plants. As a biopolymer, lignin is unusual because of its heterogeneity and lack of a defined primary structure. The chemical structural analysis of the lignin polymer is mostly performed by destructive analysis methods. In these methods, the isolated lignin is depolymerized to produce small fragments that provide partial structural information of the original native structure. The large variation in size and molecular diversity of lignin makes its analysis one of the last frontiers for mass spectrometry. In this special feature article, Joseph Banoub and co‐workers critically describe the different mass spectrometry approaches that have been used to characterize lignin with a special emphasis on modern soft ionization methods. Pr. Banoub is principal research scientist at Fisheries and Oceans Canada and adjunct faculty member at the Memorial University of Newfoundland, St John's, NL, Canada. His present research interests include tandem mass spectrometry of biologically active molecules.

Comparative electrochemical study on monolignols and dimers relevant for the comprehension of the lignification process

“…chemical or enzymatic lignin degradation processes specifically targeting b-O-4 bonds (Fig. 6, Bugg et al, 2011;Banoub et al, 2015).…”

A comparative study of the electrospray ionization response of β‐O‐4′ lignin model compounds

“…The application of mass spectrometry in the analysis of lignin has recently gained popularity. Particularly, direct infusion electrospray ionization [1][2][3][4][5] and high-performance liquid chromatography mass spectrometry 6 have been used to study fragmentation patterns and mechanisms of various bond types in lignin model compounds and also to characterize lignin degradation products. Despite the growing use of electrospray ionization mass spectrometry in lignin analysis, the fundamental question of the relationship between ionization efficiency and analyte concentration has not been explored.…”

Top‐down lignomic matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry analysis of lignin oligomers extracted from date palm wood

“…9 As a consequence it appears that the only logical way to determine the natural structure of lignin is to isolate it from the vegetal matrix, without causing any structural change. 10,11 We have recently proposed a new paradigm for lignin structures, wherein the intact natural lignin oligomers present in the lignocellulosic biomass are not actually either one and/or a series of similar biomolecules, like an individual cellulose fiber; instead, they are composed of a series of different length linear related biosynthesized oligomers. 11 These oligomers may either be formed from homo-oligomer repeating units and/or be hetero-oligomers formed by mixed units, 11 although these compounds have never been completely described in their unprocessed natural form.…”

“…10,11 We have recently proposed a new paradigm for lignin structures, wherein the intact natural lignin oligomers present in the lignocellulosic biomass are not actually either one and/or a series of similar biomolecules, like an individual cellulose fiber; instead, they are composed of a series of different length linear related biosynthesized oligomers. 11 These oligomers may either be formed from homo-oligomer repeating units and/or be hetero-oligomers formed by mixed units, 11 although these compounds have never been completely described in their unprocessed natural form. In addition, it is proposed that the lignins present in the lignocellulosic biomass are attached by either ether and/or ester covalent links, in a crisscross manner, to both cellulose and hemicellulose fibers, thus forming a glycolignin network.…”

“…In addition, it is proposed that the lignins present in the lignocellulosic biomass are attached by either ether and/or ester covalent links, in a crisscross manner, to both cellulose and hemicellulose fibers, thus forming a glycolignin network. 11 As a result, shorter oligomers of lignin can be extremely useful in providing the blueprint on how the full lignin polymer is constructed.…”