Nativity of lignin carbohydrate bonds substantiated by biomimetic synthesis

Abstract

Direct evidence of lignin–carbohydrate linkages was found in lignin substrates isolated and synthetized mimicking their native state and overcoming any kind of harsh extraction and chemical pre-treatments.

Lignans in Knotwood of Norway Spruce: Localisation with Soft X-ray Microscopy and Scanning Transmission Electron Microscopy with Energy Dispersive X-ray Spectroscopy

“…Lignin was pelleted by centrifugation from the culture medium and washed with water. Lignin-bound proteins [ 52 ] were extracted with buffered 1 M NaCl, after which the carbohydrates bound to lignin [ 53 ] were diminished by a treatment with glycosyl hydrolases according to Warinowski et al (2016) [ 52 ]. After several washes with water, the lignin was lyophilised.…”

Thermal modification of wood—a review: chemical changes and hygroscopicity

“…The existence of these covalent bonds between the lignin and hemicelluloses places limitations on hemicellulose removal during autohydrolysis reactions [96]. Four different types of linkage between the hemicelluloses and lignin are proposed in the literature, namely: benzyl ethers, benzyl esters, c-esters and phenyl glycosidic [97,98]. Depending on the treatment temperature, esters will be hydrolysed…”

Possible mechanisms for the generation of phenyl glycoside‐type lignin–carbohydrate linkages in lignification with monolignol glucosides

“…We further investigated the anomeric signals observed in the spectra of cell wall fractions. In line with previous studies of various plant cell wall samples (Balakshin et al ., 2011; Yuan et al ., 2011; Wen et al ., 2012; Miyagawa et al ., 2013, 2014; Du et al ., 2014; You et al ., 2015; del Río et al ., 2016; Giummarella et al ., 2016, 2019b; Yang et al ., 2016; Yao et al ., 2016; Zhao et al ., 2017; Huang et al ., 2018; Yue et al ., 2018; Rencoret et al ., 2019; Zhang et al ., 2020), we observed a number of anomeric signals possibly arising from the PG‐type LC linkages in the suspected region ( δ C / δ H , 105–95/5.5–4.5) of the LCC‐AcOH spectra (Figure 7), whereas no clear signals were detected in this particular region of the pMWL spectra (Figure 5). Although many of the anomeric signals attributed to PG‐type LC linkages did not match precisely with the PG signals observed in the DHPs that incorporated monolignol glucosides, the LCC‐AcOH spectra of all the plant species tested displayed, albeit generally at low levels, conspicuous signals [ PG G/1′ at δ C / δ H : 100.5/4.85 (pine); 100.3/4.87 (eucalyptus); 100.4/4.87 (acacia); 100.3/4.85 (poplar); 100.2/4.85 (bamboo); Figure 7] that were well matched with the signals from guaiacyl PG‐type LC linkages in the spectra of CA/CN‐DHP and CN/BGL‐DHP incorporating coniferin ( PG G/1′ at δ C / δ H : 100.7–100.2/4.88–4.82; Figure 3).…”

“…The PG‐type LCCs, which contain glycoside linkages between the reducing ends of carbohydrates and the phenolic end groups of lignin polymers, have been implicated in lignocellulose preparations from various plant origins. These suggestions are primarily based on the observation that cell wall HSQC NMR spectra show characteristic correlation signals adjacent to the signals observed in reference spectra of various synthetic model compounds containing PG‐type LC linkages (Balakshin et al ., 2011; Yuan et al ., 2011; Wen et al ., 2012; Miyagawa et al ., 2013, 2014; Du et al ., 2014; You et al ., 2015; del Río et al ., 2016; Giummarella et al ., 2016, 2019b; Yang et al ., 2016; Yao et al ., 2016; Zhao et al ., 2017; Huang et al ., 2018; Yue et al ., 2018; Rencoret et al ., 2019; Zhang et al ., 2020). The putative PG‐type LC linkage signals reported in the literature do not always exhibit a precise match to synthetic model compound spectra, however (Miyagawa et al ., 2014).…”