Biomass production of four Cynara cardunculus clones and lignin composition analysis

Four Cynara cardunculus clones, two from Portugal and two from Spain were studied for biomass production and their lignin was characterized. The clones differed in biomass partitioning: Spanish clones produced more capitula (54.5% vs. 43.9%), and Portuguese clones more stalks (37.2% vs. 25.6%). The heating values (HHV0) of the stalks were similar, ranging from 17.1 to 18.4 MJ/kg. Lignin was studied by analytical pyrolysis (Py-GC/MS(FID)), separately in depithed stalks (stalksDP) and pith. StalksDP had in average higher relative proportions of lignin derived compounds than pith (23.9% vs. 21.8%) with slightly different lignin monomeric composition: pith samples were richer in syringyl units as compared to stalksDP (64% vs. 53%), with S/G ratios of 2.1 and 1.3, respectively. The H:G:S composition was 7:40:53 in stalksDP and 7:29:64 in pith. The lignin content ranged from 18.8% to 25.5%, enabling a differentiation between clones and provenances. © 2015 Elsevier Ltd. All rights reserved.

Reactivity of syringyl and guaiacyl lignin units and delignification kinetics in the kraft pulping of eucalyptus globulus wood using Py-Gc-Ms/FID

Eucalyptus globulus sapwood and heartwood showed no differences in lignin content (23.0% vs. 23.7%) and composition: syringyl-lignin (17.9% vs. 18.0%) and guaiacyl-lignin (4.8% vs. 5.2%). Delignification kinetics of S- and G-units in heartwood and sapwood was investigated by Py-GC–MS/FID at 130, 150 and 170 °C and modeled as double first-order reactions. Reactivity differences between S and G-units were small during the main pulping phase and the higher reactivity of S over G units was better expressed in the later pulping stage. The residual lignin composition in pulps was different from wood or from samples in the initial delignification stages, with more G and H-units. S/G ratio ranged from 3 to 4.5 when pulp residual lignin was higher than 10%, decreasing rapidly to less than 1. The S/H was initially around 20 (until 15% residual lignin), decreasing to 4 when residual lignin was about 3%.

Prediction of Klason lignin and lignin thermal degradation products by Py-GC/MS in a collection of Lolium and Festuca grasses

A rapid method for the analysis of biomass feedstocks was established to identify the quality of the pyrolysis products likely to impact on bio-oil production. A total of 15 Lolium and Festuca grasses known to exhibit a range of Klason lignin contents were analysed by pyroprobe-GC/MS (Py-GC/MS) to determine the composition of the thermal degradation products of lignin. The identification of key marker compounds which are the derivatives of the three major lignin subunits (G, H, and S) allowed pyroprobe-GC/MS to be statistically correlated to the Klason lignin content of the biomass using the partial least-square method to produce a calibration model. Data from this multivariate modelling procedure was then applied to identify likely "key marker" ions representative of the lignin subunits from the mass spectral data. The combined total abundance of the identified key markers for the lignin subunits exhibited a linear relationship with the Klason lignin content. In addition the effect of alkali metal concentration on optimum pyrolysis characteristics was also examined. Washing of the grass samples removed approximately 70% of the metals and changed the characteristics of the thermal degradation process and products. Overall the data indicate that both the organic and inorganic specification of the biofuel impacts on the pyrolysis process and that pyroprobe-GC/MS is a suitable analytical technique to asses lignin composition. © 2007 Elsevier B.V. All rights reserved.

Comparison of mechanical properties of tension and opposite wood in Populus

In this paper we focused on the differences of mechanical properties of tension and normal wood of 1-year-old poplar trees, artificially tilted. Elastic and fracture properties have been measured and linked to the anatomy. Tension wood is well known because it prevents good surface finishing and leads to difficulties with sawing. We studied three main mechanical properties: young modulus, energy of cutting and longitudinal residual strain of maturation (with strain gauges) because of their importance in wood technology. Moreover, this work takes place in a larger project of study, the phenomena of axes re-orientation in trees (allowing by the production of reaction wood), where these data are required for biomechanical modelling. The results show that tension wood has a higher young modulus, needs a higher energy to be cut and exhibited a higher level of longitudinal residual strain of maturation than those of normal wood. The results suggest that these differences require deeper analysis of the wood than anatomy: measurement of microfibril orientation in the S2 layer and also the lignin composition in monomeric units.

n-Alkanes and phenols in bottom sediments and brown algae from the Blake-Bahama Abyssal Plain

Using gas chromatography technique we examined molecular composition of n-alkanes and lignin from bottom sediments of a core 385 cm long collected in the region of the Blake-Bahama Abyssal Plain. We determined C_org concentrations and lignin composition in soils, mangrove roots and leaves, in algae Sargassum and Ascophyllum, in corals and timber of a sunken ship; they were compared with data on lignin in bottom sediments. Mixed planktonogenic and terrigenous origin of organic matter in the core was proved with different proportions of terrigenous and planktonogenic components at different levels. Multiple changes in dominating sources of organic matter over a period required for accumulation of a four meter thick sedimentary sequence (about 4 m) are shown as obtained from changes in composition and contents of organic-chemical markers referring to classes of n-alkanes and phenols.

Chemical composition and enzymatic digestibility of sugarcane clones selected for varied lignin content

Abstract Background The recalcitrance of lignocellulosic materials is a major limitation for their conversion into fermentable sugars. Lignin depletion in new cultivars or transgenic plants has been identified as a way to diminish this recalcitrance. In this study, we assessed the success of a sugarcane breeding program in selecting sugarcane plants with low lignin content, and report the chemical composition and agronomic characteristics of eleven experimental hybrids and two reference samples. The enzymatic digestion of untreated and chemically delignified samples was evaluated to advance the performance of the sugarcane residue (bagasse) in cellulosic-ethanol production processes. Results The ranges for the percentages of glucan, hemicellulose, lignin, and extractive (based on oven-dry biomass) of the experimental hybrids and reference samples were 38% to 43%, 25% to 32%, 17% to 24%, and 1.6% to 7.5%, respectively. The samples with the smallest amounts of lignin did not produce the largest amounts of total polysaccharides. Instead, a variable increase in the mass of a number of components, including extractives, seemed to compensate for the reduction in lignin content. Hydroxycinnamic acids accounted for a significant part of the aromatic compounds in the samples, with p-coumaric acid predominating, whereas ferulic acid was present only in low amounts. Hydroxycinnamic acids with ester linkage to the hemicelluloses varied from 2.3% to 3.6%. The percentage of total hydroxycinnamic acids (including the fraction linked to lignin through ether linkages) varied from 5.0% to 9.2%, and correlated to some extent with the lignin content. These clones released up to 31% of glucose after 72 hours of digestion with commercial cellulases, whereas chemically delignified samples led to cellulose conversion values of more than 80%. However, plants with lower lignin content required less delignification to reach higher efficiencies of cellulose conversion during the enzymatic treatment. Conclusion Some of the experimental sugarcane hybrids did have the combined characteristics of high biomass and high sucrose production with low lignin content. Conversion of glucan to glucose by commercial cellulases was increased in the samples with low lignin content. Chemical delignification further increased the cellulose conversion to values of more than 80%. Thus, plants with lower lignin content required less delignification to reach higher efficiencies of cellulose conversion during the enzymatic treatment.

Lignin monomer composition is determined by the expression of a cytochrome P450-dependent monooxygenase in Arabidopsis

The phenylpropanoid pathway provides precursors for the biosynthesis of soluble secondary metabolites and lignin in plants. Ferulate-5-hydroxylase (F5H) catalyzes an irreversible hydroxylation step in this pathway that diverts ferulic acid away from guaiacyl lignin biosynthesis and toward sinapic acid and syringyl lignin. This fact led us to postulate that F5H was a potential regulatory step in the determination of lignin monomer composition. To test this hypothesis, we have used Arabidopsis to examine the impact of F5H overexpression. Arabidopsis is a useful model system in which to study lignification because in wild-type plants, guaiacyl and syringyl lignins are deposited in a tissue-specific fashion, while the F5H-deficient fah1 mutant accumulates only guaiacyl lignin. Here we show that ectopic overexpression of F5H in Arabidopsis abolishes tissue-specific lignin monomer accumulation. Surprisingly, overexpression of F5H under the control of the lignification-associated cinnamate-4-hydroxylase promoter, but not the commonly employed cauliflower mosaic virus 35S promoter, generates a lignin that is almost entirely comprised of syringylpropane units. These experiments demonstrate that modification of F5H expression may enable engineering of lignin monomer composition in agronomically important plant species.

Effect of the temperature on the composition of lignin pyrolysis products

The temperature dependence of the pyrolysis products of two types of lignin (Alcell lignin and Asian lignin) was investigated using pyrolysis-gas chromatography-mass spectrometry (PyGC-MS). About 50 compounds were identified and quantified for each type of lignin over a temperature range of 400-800C. The maximum yield of phenolic compounds was obtained at 600C for both lignins, which was 17.2% for Alcell lignin and 15.5% for Asian lignin. Most of the phenolic compounds had an individual yield of less than 1%; however, for Alcell lignin, 5-hydroxyvanillin was the highest yield at 4.29 wt%on dry ash-free lignin, and for Asian lignin, 2-methoxy-4-vinylphenol was the highest yield at 4.15 wt % on dry ash-free lignin.

Ferulates and lignin structural composition in cork

The structure of lignin and suberin, and ferulic acid (FA) content in cork from Quercus suber L. were studied. Extractive-free cork (Cork), suberin, desuberized cork (Cork(sap)), and milled-cork lignins (MCL) from Cork and Cork(sap) were isolated. Suberin composition was determined by GC-MS/FID, whereas the polymers structure in Cork, Corksap, and MCL was studied by Py-TMAH and 2D-HSQC-NMR. Suberin contained 94.4% of aliphatics and 3.2% of phenolics, with 90% of omega-hydroxyacids and alpha,omega-diacids. FA represented 2.7% of the suberin monomers, overwhelmingly esterified to the cork matrix. Py-TMAH revealed significant FA amounts in all samples, with about 3% and 6% in cork and cork lignins, respectively. Py-TMAH and 2D-HSQC-NMR demonstrated that cork lignin is a G-lignin (>96% G units), with a structure dominated by beta-O-4' alkyl-aryl ether linkages (80% and 77% of all linkages in MCL and MCLsap, respectively), followed by phenylcoumarans (18% and 20% in MCL and MCLsap, respectively), and smaller amounts of resinols (ca. 2%) and dibenzodioxocins (1%). HSQC also revealed that cork lignin is heavily acylated (ca. 50%) exclusively at the side-chain gamma-position. Ferulates possibly have an important function in the chemical assembly of cork cell walls with a cross-linking role between suberin, lignin and carbohydrates.

Topochemical distribution of lignin and hydroxycinnamic acids in sugar-cane cell walls and its correlation with the enzymatic hydrolysis of polysaccharides

Background: Lignin and hemicelluloses are the major components limiting enzyme infiltration into cell walls. Determination of the topochemical distribution of lignin and aromatics in sugar cane might provide important data on the recalcitrance of specific cells. We used cellular ultraviolet (UV) microspectrophotometry (UMSP) to topochemically detect lignin and hydroxycinnamic acids in individual fiber, vessel and parenchyma cell walls of untreated and chlorite-treated sugar cane. Internodes, presenting typical vascular bundles and sucrose-storing parenchyma cells, were divided into rind and pith fractions. Results: Vascular bundles were more abundant in the rind, whereas parenchyma cells predominated in the pith region. UV measurements of untreated fiber cell walls gave absorbance spectra typical of grass lignin, with a band at 278 nm and a pronounced shoulder at 315 nm, assigned to the presence of hydroxycinnamic acids linked to lignin and/or to arabino-methylglucurono-xylans. The cell walls of vessels had the highest level of lignification, followed by those of fibers and parenchyma. Pith parenchyma cell walls were characterized by very low absorbance values at 278 nm; however, a distinct peak at 315 nm indicated that pith parenchyma cells are not extensively lignified, but contain significant amounts of hydroxycinnamic acids. Cellular UV image profiles scanned with an absorbance intensity maximum of 278 nm identified the pattern of lignin distribution in the individual cell walls, with the highest concentration occurring in the middle lamella and cell corners. Chlorite treatment caused a rapid removal of hydroxycinnamic acids from parenchyma cell walls, whereas the thicker fiber cell walls were delignified only after a long treatment duration (4 hours). Untreated pith samples were promptly hydrolyzed by cellulases, reaching 63% of cellulose conversion after 72 hours of hydrolysis, whereas untreated rind samples achieved only 20% hydrolyzation. Conclusion: The low recalcitrance of pith cells correlated with the low UV-absorbance values seen in parenchyma cells. Chlorite treatment of pith cells did not enhance cellulose conversion. By contrast, application of the same treatment to rind cells led to significant removal of hydroxycinnamic acids and lignin, resulting in marked enhancement of cellulose conversion by cellulases.

Enzymatic Hydrolysis of Chemithermomechanically Pretreated Sugarcane Bagasse and Samples with Reduced Initial Lignin Content

Chemithermomechanical (CTM) processing was used to pretreat sugarcane bagasse with the aim of increasing cell wall accessibility to hydrolytic enzymes. Yields of the pretreated samples were in the range of 75-94%. Disk refining and alkaline-CTM and alkaline/sulfite-CTM pretreatments yielded pretreated materials with 21.7, 17.8, and 15.3% of lignin, respectively. Hemicellulose content was also decreased to some extent. Fibers of the pretreated materials presented some external fibrillation, fiber curling, increased swelling, and high water retention capacity. Cellulose conversion of the alkaline-CTM- and alkaline/sulfite-CTM-pretreated samples reached 50 and 85%, respectively, after 96 h of enzymatic hydrolysis. Two samples with low initial lignin content were also evaluated after the mildest alkaline-CTM pretreatment. One sample was a partially delignified mill-processed bagasse. The other was a sugarcane hybrid selected in a breeding program. Samples with lower initial lignin content were hydrolyzed considerably faster in the first 24 h of enzymatic digestion. For example, enzymatic hydrolysis of the sample with the lowest initial lignin content (14.2%) reached 64% cellulose conversion after only 24 h of hydrolysis when compared with the 30% observed for the mill-processed bagasse containing an initial lignin content of 24.4%. (C) 2011 American Institute of Chemical Engineers Biotechnol. Prog., 27: 395-401, 2011