Differences between Lignin in Unprocessed Wood, Milled Wood, Mutant Wood, and Extracted Lignin Detected by ¹³C Solid-State NMR

Abstract

Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy was applied to intact and isolated loblolly pine wood samples to identify potential structural changes induced by tree age, milling, lignin extraction, or naturally occurring mutations. Special attention was paid to ketone and aldehyde as well as nonpolar alkyl groups, which could be observed at low concentrations (<2 in 1000 C) using improved spinning-sideband suppression with gated decoupling. Carbonyl structures were present in intact wood, and there are more keto groups than aldehydes. Their concentrations increased from juvenile to mature wood and with milling time, whereas extraction did not alter the C=O fraction. Significant amounts of aldehyde and dihydroconiferyl alcohol residues were present in coniferyl aldehyde dehydrogenase-deficient wood, confirming solution-state NMR spectra of the corresponding lignin. These results demonstrate the utility of solid-state NMR as an assay for changes in the lignin structure of genetically modified plants.

Chemical, structural and energy properties of hydrochars from microwave-assisted hydrothermal carbonization of glucose

“…The peaks between 170 and 200 ppm are due to the presence of carboxylic acid, aldehydes or ketones moieties [36]. The spectrum also shows carbohydrate resonances (specifically CH 2 OH groups around 62 ppm, CHOH groups around 72 ppm, and anomeric O-C-O carbons around 90 ppm) in the O-alkyl region between 60 and 100 ppm [37,38]. These functional groups have already been indicated by the FT-IR result.…”

Abundant and Stable Char Residues in Soils: Implications for Soil Fertility and Carbon Sequestration

“…The spectra of carbons not bonded to hydrogen (thin lines in Figure 1) show that most of the aromatic carbons are not protonated and resonate near 130 ppm, which is characteristic of fused aromatic rings as found in char, 20 while nonprotonated carbons of substituted . 25,29 The signals of all types of alkyl carbons, between 97 and 7 ppm, are quite negligible (∼9% of the total spectral area, see Table 1). This indicates that carbon not derived from char represents only a small fraction of the organic carbon in these horizons, and it is consistent with the low H:C ratios (ca.…”

Experimental techniques for characterising water in wood covering the range from dry to fully water-saturated

“…For generating representative samples of larger wood volumes, several studies have used milled wood Himmel and Mai 2015;Xie et al 2010;Zaihan et al 2009Zaihan et al , 2011, but it could be speculated if this gives a representative material or might produce unwanted side effects, for example a change in sample chemistry. Milling is not as intense a method for subdividing wood as ball milling which has been shown to change the material chemistry (Mao et al 2006) and internal chemical bonding (Schwanninger et al 2004). Nonetheless, different particle size fractions generated from milling might not have identical chemical composition if some anatomical fractions (e.g.…”