Changes in wheat straw cell walls during ozone pretreatment

Holzforschung ◽  
2020 ◽  
Vol 74 (12) ◽  
pp. 1157-1167
Author(s):  
Elena M. Ben’ko ◽  
Dmitriy G. Chukhchin ◽  
Valeriy V. Lunin
Keyword(s):  
Cell Wall ◽  
Wheat Straw ◽  
Plant Biomass ◽  
Lignin Content ◽  
Cellulose Microfibrils ◽  
Primary Cell Wall ◽  
Residual Lignin ◽  
Intercellular Substance ◽  
Lignin Removal ◽  
Wall Stiffness

AbstractTreatment of plant biomass with ozone is a promising delignification method. It was shown that lignin removal from the cell wall during ozonation was limited by topochemical reactions and toke place in the secondary rather in the primary cell wall. The separation of cellulose microfibrils, the loss of cell wall stiffness and complete removal of intercellular substance during the delignification process were visualized by SEM. The dependence of the average diameter of the cellulose microfibril aggregates in the cell wall of ozonized straw on ozone consumption was studied. Lignin removal caused an increase of size of cellulose microfibrils aggregates. It was demonstrated that there was an optimal degree of delignification, at which cellulose became more accessible to enzymes in the subsequent bioconversion processes. The data on the ozone consumption, residual lignin content, and sugars yield in the enzymatic hydrolysis of ozonized wheat straw were obtained. It was also found that the optimum delignification degree for sugars yield was ≈10% of residual lignin content and optimum ozone consumption was 2 mol·О3/mol C9PPU (phenylpropane structural unit) of lignin in raw straw.

Kinetics Research of Wheat Straw Atmospheric Pressure Pulping with Microwave Radiation

2012 ◽  
Vol 610-613 ◽  
pp. 1726-1730
Author(s):  
Hong Zhu ◽  
Hong Xu Qiao
Keyword(s):  
Activation Energy ◽  
Wheat Straw ◽  
Microwave Radiation ◽  
Atmospheric Pressure ◽  
Lignin Content ◽  
Removal Rate ◽  
Black Liquor ◽  
Alkali Concentration ◽  
Paper Pulp ◽  
Lignin Removal

The lignin removal of pulping process is left in black liquor, and with relation to the paper pulp lignin. The higher the black liquor lignin content is, the bigger the lignin of paper pulp is removed. This paper analyzes the delignification mechanism of wheat straw atmospheric pressure pulping with microwave radiation. The relations of black liquor lignin content and alkali concentration to pulping time are described in detail. The results show that delignification process is divided into two stages: quick stage and residual stage. The lignin removal rate in the first stage is much higher than the second stage, that is, lignin has been removed more sufficiently after quick stage. In first stage, reaction order of delignification is 1.0, and 0.7 with respect to OH-, the activation energy is 38.62 kJ • mol-1. The latter delignification also belongs to the first-order reaction and 4.4 with respect to OH-, the activation energy is 75.56 kJ • mol-1. Apparently, residual stage needs to consume large amounts of energy to removal lignin.

scholarly journals Overexpression of the rice BAHD acyltransferase AT10 increases xylan-bound p-coumarate and reduces lignin in Sorghum bicolor

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Yang Tian ◽  
Chien-Yuan Lin ◽  
Joon-Hyun Park ◽  
Chuan-Yin Wu ◽  
Ramu Kakumanu ◽  
...  
Keyword(s):  
Cell Wall ◽  
Sorghum Bicolor ◽  
Cell Walls ◽  
Lignin Content ◽  
Complex Structure ◽  
Enzymatic Saccharification ◽  
Cellulose Microfibrils ◽  
Biomass Composition ◽  
Bioenergy Crops ◽  
Transgenic Lines

Abstract Background The development of bioenergy crops with reduced recalcitrance to enzymatic degradation represents an important challenge to enable the sustainable production of advanced biofuels and bioproducts. Biomass recalcitrance is partly attributed to the complex structure of plant cell walls inside which cellulose microfibrils are protected by a network of hemicellulosic xylan chains that crosslink with each other or with lignin via ferulate (FA) bridges. Overexpression of the rice acyltransferase OsAT10 is an effective bioengineering strategy to lower the amount of FA involved in the formation of cell wall crosslinks and thereby reduce cell wall recalcitrance. The annual crop sorghum represents an attractive feedstock for bioenergy purposes considering its high biomass yields and low input requirements. Although we previously validated the OsAT10 engineering approach in the perennial bioenergy crop switchgrass, the effect of OsAT10 expression on biomass composition and digestibility in sorghum remains to be explored. Results We obtained eight independent sorghum (Sorghum bicolor (L.) Moench) transgenic lines with a single copy of a construct designed for OsAT10 expression. Consistent with the proposed role of OsAT10 in acylating arabinosyl residues on xylan with p-coumarate (pCA), a higher amount of p-coumaroyl-arabinose was released from the cell walls of these lines upon hydrolysis with trifluoroacetic acid. However, no major changes were observed regarding the total amount of pCA or FA esters released from cell walls upon mild alkaline hydrolysis. Certain diferulate (diFA) isomers identified in alkaline hydrolysates were increased in some transgenic lines. The amount of the main cell wall monosaccharides glucose, xylose, and arabinose was unaffected. The transgenic lines showed reduced lignin content and their biomass released higher yields of sugars after ionic liquid pretreatment followed by enzymatic saccharification. Conclusions Expression of OsAT10 in sorghum leads to an increase of xylan-bound pCA without reducing the overall content of cell wall FA esters. Nevertheless, the amount of total cell wall pCA remains unchanged indicating that most pCA is ester-linked to lignin. Unlike other engineered plants overexpressing OsAT10 or a phylogenetically related acyltransferase with similar putative function, the improvements of biomass saccharification efficiency in sorghum OsAT10 lines are likely the result of lignin reductions rather than reductions of cell wall-bound FA. These results also suggest a relationship between xylan-bound pCA and lignification in cell walls.

scholarly journals Xyloglucan Is Not Essential for the Formation and Integrity of the Cellulose Network in the Primary Cell Wall Regenerated from Arabidopsis Protoplasts

Plants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 629 ◽  
Author(s):  
Hiroaki Kuki ◽  
Ryusuke Yokoyama ◽  
Takeshi Kuroha ◽  
Kazuhiko Nishitani
Keyword(s):  
Cell Wall ◽  
Cellulose Microfibril ◽  
Mechanical Stability ◽  
Molecular Model ◽  
Primary Cell ◽  
Cellulose Microfibrils ◽  
Primary Cell Wall ◽  
Imaging Analysis ◽  
Cellulose Deposition ◽  
Initial Assembly

The notion that xyloglucans (XG) play a pivotal role in tethering cellulose microfibrils in the primary cell wall of plants can be traced back to the first molecular model of the cell wall proposed in 1973, which was reinforced in the 1990s by the identification of Xyloglucan Endotransglucosylase/Hydrolase (XTH) enzymes that cleave and reconnect xyloglucan crosslinks in the cell wall. However, this tethered network model has been seriously challenged since 2008 by the identification of the Arabidopsis thaliana xyloglucan-deficient mutant (xxt1 xxt2), which exhibits functional cell walls. Thus, the molecular mechanism underlying the physical integration of cellulose microfibrils into the cell wall remains controversial. To resolve this dilemma, we investigated the cell wall regeneration process using mesophyll protoplasts derived from xxt1 xxt2 mutant leaves. Imaging analysis revealed only a slight difference in the structure of cellulose microfibril network between xxt1 xxt2 and wild-type (WT) protoplasts. Additionally, exogenous xyloglucan application did not alter the cellulose deposition patterns or mechanical stability of xxt1 xxt2 mutant protoplasts. These results indicate that xyloglucan is not essential for the initial assembly of the cellulose network, and the cellulose network formed in the absence of xyloglucan provides sufficient tensile strength to the primary cell wall regenerated from protoplasts.

Interspecific comparison of elutable cell wall extensin precursors by transmission electron microscopy

1986 ◽  
Vol 44 ◽  
pp. 284-285
Author(s):  
J. W. Heckman ◽  
M. J. Kielszewski ◽  
D. T. A. Lamport ◽  
E. P. Muldoon ◽  
B. T. Terhune ◽  
...  
Keyword(s):  
Cell Wall ◽  
Higher Plants ◽  
Gel Filtration ◽  
Cellulose Microfibrils ◽  
Primary Cell Wall ◽  
Wall Model ◽  
Intact Cells ◽  
Transmission Electron ◽  
Macromolecular Network ◽  
Covalently Linked

In addition to cellulose microfibrils, the primary cell wall of many higher plants contains extensin, a class of hydroxyproline-rich glycoprotein (HRGP). Despite its predominately hydrophilic amino acid composition, most cell wall HRGP remains insoluble even after complete deglycosylation with anhydrous HF, suggesting a covalently linked macromolecular network. This led to the development of the "warp-weft" cell wall model, based on an extensin network ("weft") penetrated by cellulose microfibrils (the "warp")(FIG. 1). Extensin precursors elute rapidly from intact cells and cell wall preparations of tomato, carrot, and cucumber, with mild salt solutions. Tomato precursors, at least, are block copolymers of a few repeating sequences. Gel filtration data and immuno-crossreactivity suggest that tomato P2 and cucumber callus precursor are similar. TEM confirms the rod-like structure and the lengths of these molecules.

Direct visualization of cross-links in the primary plant cell wall

1990 ◽  
Vol 96 (2) ◽  
pp. 323-334 ◽  
Author(s):  
M. C. MCCANN ◽  
B. WELLS ◽  
K. ROBERTS
Keyword(s):  
Cell Wall ◽  
Plant Cell Wall ◽  
Three Dimensional ◽  
Preliminary Evidence ◽  
Cellulose Microfibrils ◽  
Primary Cell Wall ◽  
Positive Role ◽  
Extraction Step ◽  
Cross Links ◽  
Wall Construction

We have investigated the structure of the onion primary cell wall at high resolution, using shadowed replicas of rapidly frozen deep-etched specimens. We have sequentially extracted polymers from the wall and have visualized both these and the remaining structures at each extraction step. By viewing the structures in as near their native state as possible, an accurate three-dimensional picture of wall construction has been assembled, facilitated by viewing stereo pairs of micrographs. Our observations show that the physical links between cellulose microfibrils that we observe in the intact wall are generally shorter (20–40 nm) than the isolated molecules we extract (30->700nm), suggesting that lateral interactions must occur between linking polymers and cellulose in muro. These cross-links are hemicellulosic and we believe them to be xyloglucans: their removal allows increased lateral association of microfibrils. Na2CO3-extractable pectic fractions form a separate coextensive network, the removal of which does not affect basic cellulose/ hemicellulose architecture. Preliminary evidence for a lamellate model of wall construction has been obtained. In addition, we propose a positive role for hemicellulose in maintaining the ordered spacing of cellulose micronbrils, perhaps regulating wall porosity and strength. The basic wall parameters that we derive impose constraints on possible cell wall models.

Arrangement of cellulose microfibrils in the wheat straw cell wall

2008 ◽  
Vol 72 (1) ◽  
pp. 122-127 ◽  
Author(s):  
Hui Yu ◽  
Ruigang Liu ◽  
Dawa Shen ◽  
Zhonghua Wu ◽  
Yong Huang
Keyword(s):  
Cell Wall ◽  
Wheat Straw ◽  
Cellulose Microfibrils

scholarly journals Identifying transcription factors that reduce wood recalcitrance and improve enzymatic degradation of xylem cell wall in Populus

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Chiaki Hori ◽  
Naoki Takata ◽  
Pui Ying Lam ◽  
Yuki Tobimatsu ◽  
Soichiro Nagano ◽  
...  
Keyword(s):  
Cell Wall ◽  
Populus Tremuloides ◽  
Cell Walls ◽  
Enzymatic Degradation ◽  
Plant Biomass ◽  
Lignin Content ◽  
Enzymatic Saccharification ◽  
Wall Structure ◽  
Xylem Cell

AbstractDeveloping an efficient deconstruction step of woody biomass for biorefinery has been drawing considerable attention since its xylem cell walls display highly recalcitrance nature. Here, we explored transcriptional factors (TFs) that reduce wood recalcitrance and improve saccharification efficiency in Populus species. First, 33 TF genes up-regulated during poplar wood formation were selected as potential regulators of xylem cell wall structure. The transgenic hybrid aspens (Populus tremula × Populus tremuloides) overexpressing each selected TF gene were screened for in vitro enzymatic saccharification. Of these, four transgenic seedlings overexpressing previously uncharacterized TF genes increased total glucan hydrolysis on average compared to control. The best performing lines overexpressing Pt × tERF123 and Pt × tZHD14 were further grown to form mature xylem in the greenhouse. Notably, the xylem cell walls exhibited significantly increased total xylan hydrolysis as well as initial hydrolysis rates of glucan. The increased saccharification of Pt × tERF123-overexpressing lines could reflect the improved balance of cell wall components, i.e., high cellulose and low xylan and lignin content, which could be caused by upregulation of cellulose synthase genes upon the expression of Pt × tERF123. Overall, we successfully identified Pt × tERF123 and Pt × tZHD14 as effective targets for reducing cell wall recalcitrance and improving the enzymatic degradation of woody plant biomass.

scholarly journals Assessment of Primary Cell Wall Nanomechanical Properties in Internal Cells of Non-Fixed Maize Roots

Plants ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 172 ◽  
Author(s):  
Liudmila Kozlova ◽  
Anna Petrova ◽  
Boris Ananchenko ◽  
Tatyana Gorshkova
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Plant Growth ◽  
Cell Walls ◽  
Maize Root ◽  
Primary Cell ◽  
Primary Cell Wall ◽  
Tissue Cell ◽  
Nanomechanical Properties ◽  
Wall Stiffness

The mechanical properties of cell walls play a vital role in plant development. Atomic-force microscopy (AFM) is widely used for characterization of these properties. However, only surface or isolated plant cells have been used for such investigations, at least as non-embedded samples. Theories that claim a restrictive role of a particular tissue in plant growth cannot be confirmed without direct measurement of the mechanical properties of internal tissue cell walls. Here we report an approach of assessing the nanomechanical properties of primary cell walls in the inner tissues of growing plant organs. The procedure does not include fixation, resin-embedding or drying of plant material. Vibratome-derived longitudinal and transverse sections of maize root were investigated by AFM in a liquid cell to track the changes of cell wall stiffness and elasticity accompanying elongation growth. Apparent Young’s modulus values and stiffness of stele periclinal cell walls in the elongation zone of maize root were lower than in the meristem, i.e., cell walls became more elastic and less resistant to an applied force during their elongation. The trend was confirmed using either a sharp or spherical probe. The availability of such a method may promote our understanding of individual tissue roles in the plant growth processes.

Kinetics Analysis of Wheat Straw Pulping Process

2013 ◽  
Vol 860-863 ◽  
pp. 1012-1016 ◽  
Author(s):  
Ming Xian Cui ◽  
Wei Song ◽  
Zong Yu Liu
Keyword(s):  
Activation Energy ◽  
Wheat Straw ◽  
Lignin Content ◽  
Removal Rate ◽  
Black Liquor ◽  
Alkali Concentration ◽  
Slow Stage ◽  
First Order ◽  
Lignin Removal ◽  
Two Stages

This paper analyzes the delignification mechanism of wheat straw pulping process. The lignin removal of pulping process is left in black liquor. The higher the black liquor lignin content is, the bigger the lignin of paper pulp is removed. The relations of black liquor lignin content and alkali concentration to pulping time are described in detail. The results show that delignification process is divided into two stages: quick and slow stage. The lignin removal rate in the first stage is much higher than the second, that is, lignin has been removed more sufficiently after quick stage. In first stage, reaction order of delignification is 1.0, and 0.7 with respect to OH-, the activation energy is 38.62 kJ • mol-1. The latter delignification also belongs to the first-order reaction and 4.4 with respect to OH-, the activation energy is 75.56 kJ • mol-1. Apparently, slow stage needs to consume large amounts of energy to removal lignin.

scholarly journals Early response to GA3-treatment in the pedicel of table grape genotypes with different susceptibility to berry drop reveals responses elicited in cell wall yield and modification of lignin content

2019 ◽  
Author(s):  
Marco Meneses ◽  
Miguel García-Rojas ◽  
Claudia Muñoz-Espinoza ◽  
Tomás Carrasco-Valenzuela ◽  
Bruno Defilippi ◽  
...  
Keyword(s):  
Cell Wall ◽  
Lignin Content ◽  
Lignin Biosynthesis ◽  
Table Grape ◽  
Primary Cell ◽  
Postharvest Quality ◽  
Primary Cell Wall ◽  
Thompson Seedless ◽  
Strong Response ◽  
Berry Size

Abstract Background Gibberellins (GA3) are the most sprayed growth regulator for table grape production worldwide, increasing berry size of seedless varieties through pericarp cell expansion. However, these treatments also exacerbate berry drop, which has a detrimental effect on the postharvest quality of commercialized clusters. Several studies have suggested that pedicel stiffening caused by GA3 would have a role in this disorder. Nevertheless, transcriptional and phenotypic information regarding pedicel responses to GA3 is minimal.Results Characterization of responses to GA3 treatments using the lines L23 and Thompson Seedless showed that the former was up to six times more susceptible to berry drop than the latter. GA3 also increased the diameter and dry matter percentage of the pedicel on both genotypes. Induction of lignin biosynthesis-related genes by GA3 has been reported, so the quantity of this polymer was measured. The acetyl bromide method detected a decreased concentration of lignin seven days after GA3 treatment, due to a higher cell wall yield of the isolated fractions of GA3 -treated pedicel samples which caused a dilution effect. Thus, an initial enrichment of primary cell wall components in response to GA3 was suggested, particularly in the L23 background. A transcriptomic profiling was performed to identify which genes were associated with these phenotypic changes. This analysis identified 1,281 and 1,787 genes differentially upregulated by GA3 in L23 and cv. Thompson Seedless, respectively. Concomitantly, 1,202 and 1,317 downregulated genes were detected in L23 and cv. Thompson Seedless (FDR≤0.05). Gene ontology analysis of upregulated genes showed enrichment in pathways including phenylpropanoids, cell wall metabolism, xylem development, photosynthesis and the cell cycle at seven days post GA3 application. Twelve genes were characterized by qPCR and striking differences were observed between genotypes, mainly in genes related to cell wall synthesis.Conclusions High levels of berry drop are related to an early strong response of primary cell wall synthesis in the pedicel promoted by GA3 treatment. Genetic backgrounds can produce similar phenotypic responses to GA3 , although there is considerable variation in the regulation of genes in terms of which are expressed, and the extent of transcript levels achieved within the same time frame.

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