Understanding the Structural Changes of Lignin Macromolecules From Balsa Wood at Different Growth Stages

Abstract

Lignin is the most abundant aromatic biomacromolecule on the earth, which is an attractive raw material for producing bio-based chemicals, materials, and fuels. However, the complexity, heterogeneity, and variability of the lignin structure always hinders the value-added application of different sources of raw materials. In this study, double enzymatic lignin (DEL) was isolated from balsa grown for different lengths of time to understand the structural variations of lignin macromolecules during the growth of balsa for the first time. Confocal Raman microscopy and component analysis were used to monitor the lignin accumulation in balsa. Meanwhile, the structural characteristics and chemical reactivity of DELs were synthetically characterized by advanced 2D-HSQC and 31 P-NMR techniques. It was found that the balsa lignin is a typical hardwood lignin and it is overwhelmingly composed of CO bonds (i.e., β-O-4 linkages), whose content is elevated with increasing tree-age. Interestingly, carbon-carbon linkages (e.g., β-β and β-5) in these DELs isolated from 3-and 5-year-old balsa are gradually disappearing. Considering the increasing molecular weight of DELs with tree-age, it was concluded that lignin macromolecules in balsa wood were gradually polymerized within the growth period. Furthermore, abundant CO linkages with less CC linkages in the DELs from 3 and 5-year-old balsa wood suggested that these feedstocks are promising in current lignin-first biorefinery and will facilitate the conversion of aromatic chemicals from the lignin macromolecule. In short, a comprehensive understanding of native lignin during the growth of balsa wood will not only advance the understanding of biosynthetic pathways of lignin biopolymer, but also facilitate the deconstruction and value-added applications of this kind of feedstock.

Infrared photo-induced force microscopy unveils nanoscale features of Norway spruce fibre wall

“…The acquisition time was increased from 200 ms to 30 s to improve the signal-to-noise ratio. The information obtained from the point PiFM spectra mostly confirmed the observations from the hyPIR experiments: high lignin content and presence of condensed lignin structures in CCML and CML (Agarwal 2006;Burke et al 1974;Meier 1985;Whiting and Goring 1983;Zhang et al 2020) and axially oriented EFs in S 2 (Fig. 5).…”

“…The softwood lignin is of the guaiacyl type, formed mostly through oxidative polymerization of coniferyl alcohol (Jingjing 2011). The lignin content of wood is highest in CCML and CML (Zhang et al 2020). In these regions, the lignin is more condensed or cross-linked in comparison with the secondary wall lignin.…”

Recent advances in lignin-based carbon fibers (LCFs): precursors, fabrications, properties, and applications

“…Moreover, we found that native lignin samples from some fast-growing lignocellulosic biomasses were rich in β-O-4 aryl ether linkages, and these lignin fractions have a linear molecular structure. 24,25 For example, the native lignin from bamboo ( Phyllostachys pubescens ) parenchyma cells was rich in Syringyl (S-type) lignin units and β-O-4 linkages. 26 Furthermore, C-lignin, which is naturally abundant in the seed coats of some plant species, has been found to be essentially a homopolymer, synthesized almost entirely from caffeine in combination with growing polymer chains.…”

Overexpression of PtoMYB115 improves lignocellulose recalcitrance to enhance biomass digestibility and bioethanol yield by specifically regulating lignin biosynthesis in transgenic poplar

“…The NMR experiment was performed on a Bruker AVIII 400 MHz spectrometer as described [ 15 , 46 , 47 ]. The stem powders were incubated in acetate buffer (0.05 mM, 250 mL, pH = 4.8) with the loading of 6.0 mL Cel-lic ® CTec2 (100 filter paper activity mL −1 ).…”

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