Wood Lignin Research Articles

Syringyl ratio and its relation to the erythro ratio of β-O-4-structure in leaf cell walls

In case of wood cell walls, there is a very clear relationship between the aromatic structure of lignin and the stereo configuration of β-O-4-structures; the syringyl ratio (S ratio, syringyl/(syringyl + guaiacyl)) obtained by the nitrobenzene oxidation method is linearly correlated to the erythro ratio (E ratio) of β-O-4 structure (erythro/(erythro + threo)) obtained by the ozonation method. In this study, 21 leaf samples and 9 stem samples were analyzed to examine whether such relationships can be found in the lignin of leaf and stem cell wall samples. Although some correlation between the S and E ratios was found in leaf and stem cell wall samples, the correlation was not as clear as in the case of woods (correlation coefficient, R2= 0.988 for 21woods and R2= 0.653 for all the leaf, stem and wood samples). In addition, the E ratios of some leaf samples were lower than 0.5, which is the lowest limit of the E-ratio for wood lignin. It was demonstrated that wood, stem and leaf samples are roughly distinguished by the yield of ozonation and nitrobenzene oxidation products from the sample (not from lignin), but not by the apparent lignin content obtained by the Klason method. The presence of syringyl nuclei in the leaves of Ginkgo, which is classified as gymnosperm, was confirmed by nitrobenzene oxidation.

Фактор неидеальности в энтропийно-мультифрактальном анализе самоорганизованных структур растительных полимеров (лигнинов)

An attempt has been made to introduce the generalized non-ideality factor of systems g (GNF) into information entropy equations that describe self-organized structures of essentially nonequilibrium systems with the use of studying the topological properties of high molecular weight compounds in solutions using wood lignins as an example. The factor g as a relative thermodynamic characteristic connects the ideal and real models of systems in which two competitive (opposite in sign and action) processes can be distinguished: order (−) ↔ chaos (+); attraction (−) ↔ repulsion (+); compression (−) ↔ extension (+); clustering (−) ↔ decay (+), etc.g = 1 + 〈– βord + αnord〉 = 1 + 〈– pi (β) + pi (α)〉, где – βord ≡ 1/nΣinβi и αnopd ≡ 1/nΣniαi are relative average characteristics (pi – probabilities) of oppositely occurring processes. The factor g varies in the interval 0≤ g ≥1 and depends on which of the competitive processes prevails. For αnord = 0 g → 0, for βord = 0 g→2, for g = 1 the behavior of the elements of the system will be ideal. The factor g is introduced into any classical equations suitable for studying ideal systems with the aim of using them to describe real systems (for example, the equations of Henry, Raoult, Van’t Hoff, general gas, etc.). Strictly mathematically, the factor g is defined through the values M – measure, e – size (scale), and d – dimension as a ratio of logarithms of measures of real (М*) and ideal (М0) states of the object: gth = lnМ*/lnМ0 = d/D, where M* and M0 can be the number of elements in the structure of the fractal real (for example, cluster) or mathematical object (for example, Sierpinski triangle) Nd and the number of elements in the structure of the object in the perfect condition, having the property of multi-scale and self-similarity, ND, where d and D are the fractal and Euclidean dimensions. As a thermodynamic characteristic gth is defined by the ratio of thermodynamic functions, functionals, for example, ΔGi*/ΔGi, where ΔGi* = –RTlnаi is real and, ΔGi = –RTlnNi is ideal state; the number of moles of n* − real state of matter to n − ideal state of matter; relative entropies of the system ΔSreal/ΔSid (ΔSid − Boltzmann entropy). New expressions of the information and thermodynamic entropies with a fractional (0:1) moment of order and with the entropic gS and gth non-ideality factors are obtained for the analysis of self-organized quasi-equilibrium structures in the Renyi formalism SgSM–Rn(p) = R/(1 – gS)lnΣNipgSi; SgthM–Rn = R/(gth)ln(ΣNi=1pigth – 1); in the Tsallis formalism SgSM–TS (p) = R(1 – ΣiN(e)pigS)/(gS – 1); SgthM–TS (p) = R(1 – ΣiN(e)pi1–gth)/gth with an application for studying the topological properties of high-molecular compounds by hydrodynamic methods, as well as the thermodynamics of polymer solutions.For citation: Makarevich N.A. Non-Ideality Factor in Multifractal and Entropy-Based Analysis of Self-Organized Structures of Plant Polymers (Lignins). Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 2, pp. 194–212. DOI: 10.37482/0536-1036-2021-2-194-212

Upgrade the torrefaction process of bamboo based on autohydrolysis pretreatment

Torrefaction is a routine and effective method for recovering energy from biomass. In this study, autohydrolysis pretreatment was proposed to upgrade the torrefaction process of moso bamboo, and their relationship was evaluated. Results showed that about 80.24 % of bamboo hemicellulose were dissolved during autohydrolysis pretreatment. Compared with main chain, arabinan side chain of hemicellulose was much easier to be degraded, and more uniform hemicellulose could be obtained at 160 °C. The O/C values of autohydrolysis solid residues and the mass yield of torrefied bamboo decreased gradually with the enhancement of reaction severity (autohydrolysis and/or torrefaction), while the HHV values increased. The higher torrefaction temperature or autohydrolysis pretreatment severity was, the better thermostability of torrefied bamboo could be observed. 2D-HSQC of milled wood lignin revealed that autohydrolysis pretreatment can effectively accelerate the degradation of β-O-4 linkage in lignin and increase G-type lignin content during torrefaction process. Compared with direct torrefaction, prehydrolysis can greatly facilitate the torrefaction process and enhance the quality of final products.

Kelarutan Lignin Kayu Cepat Tumbuh dalam Ekstraksi Alkali

The dissolution of wood lignin in the alkali solution were analyzed for two fast growing species, sengon (Paraserianthes falcataria) dan leda (Eucalyptus deglupta). Wood samples were extracted in 1% sodium hydroxide solution in cold and hot temperatures for 24 and 1 h, respectively. Extractable substances content, permanganate consumption (expressed as assumed lignin content) were analyzed from the filtrates, lignin content and diastereomeric of β-O-4 structure were analyzed from the wood residue after alkali extraction. The extracted substances from both of wood in hot alkali was higher than in cold alkali solution, although the time of cold alkali extraction was much longer that hot alkali extraction. Assumed lignin content in the extract was quite high in both samples which were 34.4-42.9% and 35.5-39.8% including 2,15-2,29% dan 1,04-1,32% of lignin for cold and hot alkali extraction, respectively. The changes in stereo isomeric form, erythro and threo, of β-O-4 structure of lignin in wood residue indicated that partial depolimerization of lignin was takec place during alkali treatment.

Strong, Hydrostable, and Degradable Straws Based on Cellulose-Lignin Reinforced Composites.

The huge consumption of single-use plastic straws has brought a long-lasting environmental problem. Paper straws, the current replacement for plastic straws, suffer from drawbacks, such as a high cost of the water-proof wax layer and poor water stability due to the easy delamination of the wax layer. It is therefore crucial to find a high-performing alternative to mitigate the environmental problems brought by plastic straws. In this paper, all natural, degradable, cellulose-lignin reinforced composite straws, inspired by the reinforcement principle of cellulose and lignin in natural wood are developed. The cellulose-lignin reinforced composite straw is fabricated by rolling up a wet film made of homogeneously mixed cellulose microfibers, cellulose nanofibers, and lignin powders, which is then baked in oven at 150 °C. When baked, lignin melts and infiltrates the micro-nanocellulose network, acting as a polyphenolic binder to improve the mechanical strength and hydrophobicity performance of the resulting straw. The obtained straws demonstrate several advantageous properties over paper straws, including 1) excellent mechanical performance, 2) high hydrostability, and 3) low cost. Moreover, the natural degradability of the cellulose-lignin reinforced composite straws makes them promising candidates to replace plastic straws and suggests possible substitutes for other petroleum-based plastics.

Changes of Meranti, Padauk, and Merbau Wood Lignin during the ThermoWood Process.

Thermal modification is an environmentally friendly process in which technological properties of wood are modified using thermal energy without adding chemicals, the result of which is a value-added product. Wood samples of three tropical wood species (meranti, padauk, and merbau) were thermally treated according to the ThermoWood process at various temperatures (160, 180, 210 °C) and changes in isolated lignin were evaluated by nitrobenzene oxidation (NBO), Fourier-transform infrared spectroscopy (FTIR), and size exclusion chromatography (SEC). New data on the lignins of the investigated wood species were obtained, e.g., syringyl to guaiacyl ratio values (S/G) were 1.21, 1.70, and 3.09, and molecular weights were approx. 8600, 4300, and 8300 g·mol−1 for meranti, padauk, and merbau, respectively. Higher temperatures cause a decrease of methoxyls and an increase in C=O groups. Simultaneous degradation and condensation reactions in lignin occur during thermal treatment, the latter prevailing at higher temperatures.

Molecular structure of poplar lignin obtained by p-Toluene sulfonic acid (p-TsOH) and formic acid delignification

Poplar wood sawdust was chemically modified and separated into fractions using a mixture of p-toluene sulfonic acid (p-TsOH) and formic acid under different conditions. The optimum conditions of poplar lignin separation were determined by single-factor experiment. The mixed acid lignin (MAL) and the solid residues were subjected to comprehensive structural characterization by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), X-ray diffraction (XRD), and scanning electron microscope (SEM). At the mass ratio of 5:1 of p-TsOH and formic acid, temperature of 80 °C, acid concentration of 75%, and reaction time of 20 min, more than 80% of lignin was removed, and almost all of the cellulose was retained in the solid residue. The results indicated that the p-TsOH/formic acid achieved rapid and nearly-complete dissolution of wood lignin below the water boiling temperature by enhancing the cleavage of interunitary bonds in lignin (β-O-4′ bond) and the 4-hydroxy-3-methoxy cinnamic acid structure in the lignin.

Delignified Wood from Understanding the Hierarchically Aligned Cellulosic Structures to Creating Novel Functional Materials: A Review

AbstractUtilization of hierarchically aligned natural cellulosic structures has become a leading natural template scaffold for a diverse range of functional applications. This natural scaffold derived from wood by partial or full removal of lignin without altering or disturbing the hierarchically aligned cellulosic structure is known as delignified wood (DW). Over the past five years, various types of functional materials for diverse applications have been fabricated using DW. This review aims to highlight the significance of DW in functional material development by discussing the delignification impacts on the wood cell wall properties and review the different strategies used in functional materials fabrication. The first part of this review discusses the fundamental aspects of wood cell wall structure in relation to wood chemistry and lignin biosynthesis. The second part focuses on the different delignification methods used in partial and full lignin removal from wood cell walls and the fundamental properties (i.e., physical, mechanical, and chemical) of DW. The third part of this review discusses the strategies and the detailed current literature regarding the development of diverse functional materials based on DW. A greater understanding of DW provides the potential for further development of DW‐based functional materials for a diverse range of future applications.

Chemical characterization of Wood and Bark biomass of the invasive species of Tree-of-heaven (Ailanthus altissima (Mill.) Swingle), focusing on its chemical composition horizontal variability assessment

ABSTRACT Aim of this study is to evaluate the potential of a rational utilization of wood and bark of the invasive species of tree-of-heaven (Ailanthus altissima (Mill.) Swingle), through their thorough chemical characterization. Extractives, celluloses, hemicelluloses, lignin, and ash contents of wood and bark material of different tree sections were examined, using wet chemical analyses/extractions. The horizontal variability of the chemical composition of the stems from pith to cambium was investigated, as well as the differences between early- and late-wood, different annual rings, sapwood and heartwood, and differences between wood and bark. The material’s equilibrium moisture content, density, pH, colour, and calorific value were also determined. Bark material presented higher extractives, slightly higher lignin, much higher ash, and slightly lower holocellulose content than wood. As the tree-age increases, the wood and bark present lower lignin, but a linear increase of holocellulose and extractives. The heartwood demonstrated more extractives, lignin and ash, and less holocellulose than sapwood. Very low ash contents and high calorific values constitute features highly crucial for its utilization in solid biofuel production. The optimum harvesting time for the highest possible utilization of extractives and holocellulose is after the 21st year, while for lignin after the 5th year.

SUGARCANE BAGASSE LIGNIN OBTAINED BY DIFFERENT EXTRACTION METHODS

Sugarcane bagasse (SB) is a by-product of ethanol production obtained in large quantities worldwide, including Brazil. Lignin is one of SB components, and its extraction is of great interest due to its vast potential for use. In this study, sugarcane bagasse was subjected to two methods of lignin extraction to obtain: Klason lignin (LKL) and milled wood lignin (MWL). The syringil/guaiacyl ratio of the lignin obtained from sugarcane bagasse was 1.67. Thermogravimetric analysis showed that LKL is more resistant to thermal degradation than MWL. According to the FTIR spectra, LKL yields a more oxidized lignin, presenting greater changes in its structure than MWL. Thus, this study provides information on the changes caused by different extractions and strengthens future studies on the transformation of lignin into products of high added value.

Biomass Energy Potential for Domestic Combustion in Myanmar: Characterization of Biomass Fuel Pellets

Biomass is the largest contributing energy source in Myanmar due to low cost and environmental consequences. Myanmar annually produces 5.77 million ton of rice husk on 26.21 million ton of paddy rice production and 114,975 cubic ton of wood left in the forest on annually 365,000 ton of wood logs. Myanmar still needs more energy consumption to develop the agricultural economy and biomass energy in the future of the country although electricity supply is expected to increase to 55 percent in 2021-2022 FY. In this work, the chemical composition and energy composition of rice husk and assorted wood were determined. And then, the physicomechanical properties of rice husk pellets without doing size reduction but assorted wood pellets with size reduction were analyzed and compared these results with ISO 17225-6 and ISO 17225-2 standards. The assorted wood lignin content was higher than of rice husk. The ash content of rice husk was higher than that of assorted wood due to large amount of ash forming compounds such as silicon dioxide and potassium oxide in rice husk. The bulk density, net calorific value, and mechanical durability of assorted wood pellets were higher than that of rice husk pellets due to the larger amount of lignin in assorted wood. The physicomechanical properties of produced pellets were complied with ISO standards.

High-Throughput MicroRNA and mRNA Sequencing Reveals that MicroRNAs may be Involved in Peroxidase-Mediated Cold Tolerance in Potato

Low-temperature is one of the most severe abiotic stresses affecting the potato production as the cultivated potato (Solanum tuberosum) is frost sensitive. MicroRNAs have been identified in response to low-temperature stress in plants. Here, via high throughput sequencing, we described the profiling of low-temperature stress response to miRNA and mRNA in potato. Two small RNA and six mRNA libraries were constructed and sequenced. Exactly 294 known and 211 novel microRNAs were identified, 24 microRNAs had the higher expression quantity in Treatment group (EG) than in Control group (CG), and 80 microRNAs had the lower expression in EG than CG. A total of 3298 differentially expressed genes (DEGs) were detected, with 1629 up-regulated and 1669 down-regulated. The metabolism pathway of phenylpropanoid biosynthesis (ko00940) is the common KEGG pathway in differentially expressed miRNA and mRNA. In this pathway, StuPOD13654 and StuPOD32147 are peroxidase which mainly catalyzes the coniferyl and sinapyl alcohol to form guaiac wood lignin monomer and syringyl lignin monomer, which are controlled by stu-novel-miR28211 and stu-novel-miR43095. These indicated that microRNAs may play essential roles in the low-temperature tolerance of potato.

Solar-assisted fabrication of large-scale, patternable transparent wood.

Transparent wood is considered a promising structural and light management material for energy-efficient engineering applications. However, the solution-based delignification process that is used to fabricate transparent wood generally consumes large amounts of chemicals and energy. Here, we report a method to produce optically transparent wood by modifying the wood's lignin structure using a solar-assisted chemical brushing approach. This method preserves most of the lignin to act as a binder, providing a robust wood scaffold for polymer infiltration while greatly reducing the chemical and energy consumption as well as processing time. The obtained transparent wood (~1 mm in thickness) demonstrates a high transmittance (>90%), high haze (>60%), and excellent light-guiding effect over visible wavelength. Furthermore, we can achieve diverse patterns directly on wood surfaces using this approach, which endows transparent wood with excellent patternability. Combining its efficient, patternable, and scalable production, this transparent wood is a promising candidate for applications in energy-efficient buildings.

Wood-Derived Hydrogels as a Platform for Drug-Release Systems.

Wood (cellulose and lignin)-based hydrogels were successfully produced as platforms for drug-release systems. Viscoelastic and cross-linking behaviors of precursor solutions were tuned to produce highly porous hydrogel architectures via freeze-drying. Pore sizes in the range of 100–160 μm were obtained. Varying lignin molecular structure played a key role in tailoring swelling and mechanical performance of these gels with organosolv-type lignin showing optimum properties due to its propensity for intermolecular cross-linking, achieving a compressive modulus around 11 kPa. Paracetamol was selected as a standard drug for release tests and its release rate was improved with the presence of lignin (50% more compared to pure cellulose hydrogels). This was attributed to a reduction in molecular interactions between paracetamol and cellulose. These results highlight the potential for the valorization of lignin as a platform for drug-release systems.

In Situ Lignin Modification toward Photonic Wood

Lignin serves as a binder that forms strong matrices of the cell walls of wood. However, it has many photolabile chromophore groups that create a monotonic brownish color and make wood susceptible to photodegradation. Herein, a new strategy is reported for modifying lignin using an in situ, rapid, and scalable process that involves the photocatalytic oxidation of native lignin in wood by H2 O2 and UV light. The reaction selectively eliminates lignin's chromophores while leaving the aromatic skeleton intact, thus modulating the optical properties of wood. The resulting "photonic wood" retains ≈80% of its original lignin content, which continues to serve as a strong binder and water-proofing agent. As a result, photonic wood features a much higher mechanical strength in a wet environment (20-times higher tensile strength and 12-times greater compression resistance), significant scalability (≈2 m long sample), and largely reduced processing times (1-6.5 h vs 4-14 h) compared with delignification methods. Additionally, this in situ lignin-modified wood structure is easily patterned through a photocatalytic oxidation process. This photocatalytic production of photonic wood paves the way for the large-scale manufacturing of sustainable biosourced functional materials for a range of applications, including energy-efficient buildings, optical management, and fluidic, ionic, electronic, and optical devices.

Structural Changes in Milled Wood Lignin (MWL) of Chinese Quince (Chaenomeles sinensis) Fruit Subjected to Subcritical Water Treatment.

Subcritical water treatment has received considerable attention due to its cost effectiveness and environmentally friendly properties. In this investigation, Chinese quince fruits were submitted to subcritical water treatment (130, 150, and 170 °C), and the influence of treatments on the structure of milled wood lignin (MWL) was evaluated. Structural properties of these lignin samples (UL, L130, L150, and L170) were investigated by high-performance anion exchange chromatography (HPAEC), FT-IR, gel permeation chromatography (GPC), TGA, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), 2D-Heteronculear Single Quantum Coherence (HSQC) -NMR, and 31P-NMR. The carbohydrate analysis showed that xylose in the samples increased significantly with higher temperature, and according to molecular weight and thermal analysis, the MWLs of the pretreated residues have higher thermal stability with increased molecular weight. The spectra of 2D-NMR and 31P-NMR demonstrated that the chemical linkages in the MWLs were mainly β-O-4′ ether bonds, β-5′ and β-β′, and the units were principally G- S- H- type with small amounts of ferulic acids; these results are consistent with the results of Py-GC/MS analysis. It is believed that understanding the structural changes in MWL caused by subcritical water treatment will contribute to understanding the mechanism of subcritical water extraction, which in turn will provide a theoretical basis for developing the technology of subcritical water extraction.

Comparative studies on lignin structures in normal and tension wood of Populus × euramericana cv. “74/76”

Tension wood is a type of defect of wood, however, it has some especial character and structure. In this study, cellulase lignin structures in normal and tension wood of Poplar 107 (Populus × euramericana cv. ‘74/76’) were compared using ultraviolet (UV), Fourier transform infrared (FT-IR), Raman and magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) and elemental analysis. The results showed that the lignins in both normal and tension wood were dominated by syringyl units, followed by guaiacyl and p-hydroxyphenyl units. The FT-IR result presented that the relative intensity of syringyl units in normal and tension wood were 0.87 and 0.90. The contents of aliphatic hydroxyl, methoxyl, condensed phenolic hydroxyl and carboxyl of lignin in tension wood were higher than those of phenolic hydroxyl groups and β-5. The contents of β-O-4, β-β and β-1 in tension wood were similar with those in normal wood. The average per-C9-unit formulae of the lignin in normal and tension wood of Poplar 107 were C9H7.21O1.79 (OH)1.17_x0001_(OCH3)1.55 and C9H7.23O1.76(OH)1.25_x0001_(OCH3)1.62, respectively.

Wood and bark lignin contents of trees from deciduous forests of eastern India

Abstract Lignin is a polyphenolic compound found in plant tissues, especially wood and bark. The lignin content determines the quality of wood biochar in agroecological uses, and is used in the production of synthetic resins and adhesives. Despite its importance in plant physiology and its agricultural and industrial utility, there exists a wide gap of knowledge of lignin contents of tropical hardwood trees of South Asia, except for a few species. We present here the first estimation of lignin content in wood and bark of 48 species from tropical deciduous forests of India. We show that some species are characterized by greater wood lignin (WL) compared with bark lignin (BL) content, contrary to the generalization held for hardwood trees, and suggest a plausible correspondence between the WL to BL ratio and timber quality.

Recovering Wood Waste to Produce Briquettes Enriched with Commercial Kraft Lignin

Aiming to use lignocellulosic biomass as energy source, one of the process that may aggregate values is the densification process, which allows the production of bioenergy using solid fuels, mainly for reducing transportation costs. In this research, solid fuel from co-briquetting of wood residues from sawmill using commercial kraft lignin as binder was investigated. The effects of compression pressure (900, 1200 and 1500 PSI) and briquette formulation (varying wood and kraft lignin proportion) on the quality and characteristics of briquettes were evaluated. The main findings were that briquetting of wood residues with kraft lignin resulted in an improvement of bulk density, strength rupture modulus, low heating value (LHV) and high heating value (HHV). The briquettes using 4% and 6% of kraft lignin, and submitted to 1200 to 1500 PSI, presented higher bulk density and strength resistance, respectively. On the other hand, the heating values showed the highest results with the addition of 2% lignin at 900 PSI, being the legal range for additives in briquettes for many countries such as in European Union.

Anatomy and cell wall chemistry of tension wood in Hibiscus cannabinus

Hibiscus cannabinus (kenaf) is well known as a source for textile fibers and as an alternate source for cellulosic fibers for paper and pulp industry. Formation of reaction xylem alters the chemical properties of fibers, which may affect its uses. To the best of our knowledge, there are no reports on the occurrence of reaction xylem in kenaf. The present study examines reaction xylem (i.e. tension wood and its opposite side) formed in response to bending of stems in Kenaf by anatomical, histochemical and biochemical methods. The reaction xylem found on the upper side of leaning stems showed an eccentric growth pattern, thin walls, shorter and wider fibers without gelatinous layer, decrease of vessel or ray density as compared to wood formed on opposite sides. Histochemical localization of lignin using Weisner reaction and Maule’s test indicated presence of more syringyl units in the fiber wall of tension wood. Gravimetric quantification of cell wall polymers showed relatively more amount of holocellulose and hemicellulose in tension wood (69 and 46 %, respectively) compared to those of opposite wood (63 and 42 %, respectively). There was no significant difference noticed in the klason lignin content between opposite (17.4 %) and tension wood (16.7 %). Lignin characterization by the thioacidolysis method revealed that the tension wood lignin in kenaf was composed of more amount of syringyl and p-hydroxyphenyl monomers compared to that of opposite side wood. This analysis also suggests that the tension wood lignin is rich in β-aryl ether linkages in syringyl units resulting in high S/G ratio.