Helicoidal pattern in secondary cell walls and possible role of xylans in their construction

Reis, Danièle; Vian, B.

doi:10.1016/j.crvi.2004.04.008

Cited by 73 publications

(67 citation statements)

References 19 publications

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“…This explanation of the observed biphasic behavior would be consistent with the general biomass composition, as the slowly hydrolyzed fraction of xylan could be embedded within lignin or linked to lignin via lignin-carbohydrate bonds [34]. This hypothesis is supported by ultrastructure studies of biomass [35,36]. Dammström further suggested the presence of a third kind of xylan, which is tightly bound to cellulose by hydrogen bonds [35].…”

Section: Model Prediction and Data Forsupporting

confidence: 59%

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Kinetic Modelling and Experimental Studies for the Effects of Fe2+ Ions on Xylan Hydrolysis with Dilute-Acid Pretreatment and Subsequent Enzymatic Hydrolysis

et al. 2018

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High-temperature (150-170 • C) pretreatment of lignocellulosic biomass with mineral acids is well established for xylan breakdown. Fe 2+ is known to be a cocatalyst of this process although kinetics of its action remains unknown. The present work addresses the effect of ferrous ion concentration on sugar yield and degradation product formation from corn stover for the entire two-step treatment, including the subsequent enzymatic cellulose hydrolysis. The feedstock was impregnated with 0.5% acid and 0.75 mM iron cocatalyst, which was found to be optimal in preliminary experiments. The detailed kinetic data of acid pretreatment, with and without iron, was satisfactorily modelled with a four-step linear sequence of first-order irreversible reactions accounting for the formation of xylooligomers, xylose and furfural as intermediates to provide the values of Arrhenius activation energy. Based on this kinetic modelling, Fe 2+ turned out to accelerate all four reactions, with a significant alteration of the last two steps, that is, xylose degradation. Consistent with this model, the greatest xylan conversion occurred at the highest severity tested under 170 • C/30 min with 0.75 mM Fe 2+ , with a total of 8% xylan remaining in the pretreated solids, whereas the operational conditions leading to the highest xylose monomer yield, 63%, were milder, 150 • C with 0.75 mM Fe 2+ for 20 min. Furthermore, the subsequent enzymatic hydrolysis with the prior addition of 0.75 mM of iron(II) increased the glucose production to 56.3% from 46.3% in the control (iron-free acid). The detailed analysis indicated that conducting the process at lower temperatures yet long residence times benefits the yield of sugars. The above kinetic modelling results of Fe 2+ accelerating all four reactions are in line with our previous mechanistic research showing that the pretreatment likely targets multiple chemistries in plant cell wall polymer networks, including those represented by the C-O-C and C-H bonds in cellulose, resulting in enhanced sugar solubilization and digestibility.

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Section: Model Prediction and Data Forsupporting

confidence: 59%

“…This hypothesis is supported by ultrastructure studies of biomass [35,36]. Dammström further suggested the presence of a third kind of xylan, which is tightly bound to cellulose by hydrogen bonds [35].…”

Section: Model Prediction and Data Forsupporting

confidence: 54%

Kinetic Modelling and Experimental Studies for the Effects of Fe2+ Ions on Xylan Hydrolysis with Dilute-Acid Pretreatment and Subsequent Enzymatic Hydrolysis

et al. 2018

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“…Xylans have been associated with changes in microfibril orientation, both in polylamellate cell walls that have many alternating layers and in more conventional secondary walls, where microfibril orientation changes among the typical three layers (Reis and Vian, 2004). To extend this result to conifer tracheids, we combined immunolocalization of xylans and mannans with polarized light microscopy to show relationships with cellulose orientation.…”

Section: Xylans Are Associated With Reorientation Of Cellulose Microfmentioning

confidence: 99%

“…Xylans may function as twisting agents, acting at the boundary between cell wall layers where microfibril angle is changing (Reis and Vian, 2004). Xylans have been specifically localized to the transition zone between the S1 and S2 layers and may act as helper molecules controlling the orientation, aggregation, and alignment of microfibrils (Reis and Vian, 2004).…”

mentioning

confidence: 99%

Localization of Cell Wall Polysaccharides in Normal and Compression Wood of Radiata Pine: Relationships with Lignification and Microfibril Orientation

Donaldson

Knox²

2011

Plant Physiology

123

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The distribution of noncellulosic polysaccharides in cell walls of tracheids and xylem parenchyma cells in normal and compression wood of Pinus radiata, was examined to determine the relationships with lignification and cellulose microfibril orientation. Using fluorescence microscopy combined with immunocytochemistry, monoclonal antibodies were used to detect xyloglucan (LM15), b(1,4)-galactan (LM5), heteroxylan (LM10 and LM11), and galactoglucomannan (LM21 and LM22). Lignin and crystalline cellulose were localized on the same sections used for immunocytochemistry by autofluorescence and polarized light microscopy, respectively. Changes in the distribution of noncellulosic polysaccharides between normal and compression wood were associated with changes in lignin distribution. Increased lignification of compression wood secondary walls was associated with novel deposition of b(1,4)-galactan and with reduced amounts of xylan and mannan in the outer S2 (S2L) region of tracheids. Xylan and mannan were detected in all lignified xylem cell types (tracheids, ray tracheids, and thickwalled ray parenchyma) but were not detected in unlignified cell types (thin-walled ray parenchyma and resin canal parenchyma). Mannan was absent from the highly lignified compound middle lamella, but xylan occurred throughout the cell walls of tracheids. Using colocalization measurements, we confirmed that polysaccharides containing galactose, mannose, and xylose have consistent correlations with lignification. Low or unsubstituted xylans were localized in cell wall layers characterized by transverse cellulose microfibril orientation in both normal and compression wood tracheids. Our results support the theory that the assembly of wood cell walls, including lignification and microfibril orientation, may be mediated by changes in the amount and distribution of noncellulosic polysaccharides.

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“…The role of xylan in the secondary wall is not clear. However, it has been suggested that xylans coat the cellulose microfibrils (Awano et al, 2002) and may influence the helicoidal orientation of the microfibrils (Reis and Vian, 2004). Biochemical analyses showed that several species, such as wheat (Triticum aestivum; Porchia et al, 2002), pea (Pisum sativum; Waldron and Brett, 1983;Baydoun et al, 1989), poplar (Populus spp), and sycamore (Acer pseudoplatanus; Dalessandro and Northcote, 1981), harbor xylosyltransferase activities thought to be responsible for xylan formation.…”

Section: Introductionmentioning

confidence: 99%

TheArabidopsis irregular xylem8Mutant Is Deficient in Glucuronoxylan and Homogalacturonan, Which Are Essential for Secondary Cell Wall Integrity

Persson¹,

et al. 2007

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The secondary cell wall in higher plants consists mainly of cellulose, lignin, and xylan and is the major component of biomass in many species. The Arabidopsis thaliana irregular xylem8 (irx8) mutant is dwarfed and has a significant reduction in secondary cell wall thickness. IRX8 belongs to a subgroup of glycosyltransferase family 8 called the GAUT1-related gene family, whose members include GAUT1, a homogalacturonan galacturonosyltransferase, and GAUT12 (IRX8). Here, we use comparative cell wall analyses to show that the irx8 mutant contains significantly reduced levels of xylan and homogalacturonan. Immunohistochemical analyses confirmed that the level of xylan was significantly reduced in the mutant. Structural fingerprinting of the cell wall polymers further revealed that irx8 is deficient in glucuronoxylan. To explore the biological function of IRX8, we crossed irx8 with irx1 (affecting cellulose synthase 8). The homozygous irx1 irx8 exhibited severely dwarfed phenotypes, suggesting that IRX8 is essential for cell wall integrity during cellulose deficiency. Taken together, the data presented show that IRX8 affects the level of glucuronoxylan and homogalacturonan in higher plants and that IRX8 provides an important link between the xylan polymer and the secondary cell wall matrix and directly affects secondary cell wall integrity.

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Helicoidal pattern in secondary cell walls and possible role of xylans in their construction

Cited by 73 publications

References 19 publications

Kinetic Modelling and Experimental Studies for the Effects of Fe2+ Ions on Xylan Hydrolysis with Dilute-Acid Pretreatment and Subsequent Enzymatic Hydrolysis

Kinetic Modelling and Experimental Studies for the Effects of Fe2+ Ions on Xylan Hydrolysis with Dilute-Acid Pretreatment and Subsequent Enzymatic Hydrolysis

Localization of Cell Wall Polysaccharides in Normal and Compression Wood of Radiata Pine: Relationships with Lignification and Microfibril Orientation

TheArabidopsis irregular xylem8Mutant Is Deficient in Glucuronoxylan and Homogalacturonan, Which Are Essential for Secondary Cell Wall Integrity

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