Chemical Composition Of Lignin Research Articles

Distribution and Chemical Composition of Lignin in Secondary Xylem of Cactaceae.

Cactaceae family has heterogeneity in the accumulation of lignocellulose due to the diversity of shapes and anatomy of the wood. Most studies focus on fibrous and dimorphic species; but the non-fibrous species are poorly studied. The aims of this work were to analyze the syringyl/guaiacyl ratio of lignin and its distribution in secondary xylem, especially in non-fibrous species. The syringyl/guaiacyl (S/G) ratio was quantified from 34 species of cacti by nitrobenzene oxidation of free-extractive wood. The distribution of lignocellulose in wood sections stained with safranin O/fast green was determined with epifluorescence microscopy. The S/G ratio was heterogeneous; most of the non-fibrous species had a higher percentage of syringyl, while the fibrous ones accumulate guaiacyl. Fluorescence emission showed that vessel elements and wide-band tracheids had similar tonalities. It is hypothesized that the presence of a higher percentage of syringyl in most cacti is part of the defense mechanism against pathogens, which together with the succulence of the stem represent adaptations that contribute to survival in their hostile environments.

Characterization of lignocellulose of Opuntia (Cactaceae) species using FTIR spectroscopy: possible candidates for renewable raw material

Opuntia is mainly cultivated for its fruit and cladodes, but the chemical composition of lignocellulose in this genus is unknown. The aims of this study were to quantify the extracts in different organic solvents and water, to quantify the lignocellulosic compounds, to compare the syringyl/guaiacyl ratio of lignin, and to calculate the crystallinity index of cellulose. The mature cladodes of three Opuntia species were dehydrated and milled; with the powder, sequential solvent extractions were performed based on TAPPI T-222 om-02 standard. Lignin Klason, cellulose, and hemicellulose were quantified. Fourier transform infrared spectra were obtained from cellulose and lignin samples to calculate the syringyl/guaiacyl ratio and the crystalline cellulose index. The percentages of water ranged from 89 to 92%; the Kruskal-Wallis analysis showed significant differences (p < 0.05) in the extracts with ethanol/benzene, cellulose, and hemicelluloses. Opuntia ficus-indica had the highest amount of cellulose (32.6%) and hemicelluloses (9.8%). The syringyl/guaiacyl ratio was 1.59 to 2.12, due to the presence of 60% of syringyl. The crystallinity index revealed percentages higher than 60% of crystalline cellulose. The lignocellulosic percentages and the chemical composition of lignin and cellulose allow Opuntia species to be used in the production of cellulose nanofibers and biofuels.

Exploring the flexibility of cellulase cocktail obtained from mutant UV-8 of Talaromyces verruculosus IIPC 324 in depolymerising multiple agro-industrial lignocellulosic feedstocks

Effective management and the valorization of agro-industrial lignocellulosic feedstocks can only be realized if a versatile cellulase cocktail is developed that can release glucose at affordable cost irrespective of biomass type. In the present study the flexibility of using cellulase cocktail obtained from mutant UV-8 of Talaromyces verruculosus IIPC 324 in depolymerizing multiple agro-industrial lignocellulosic feedstocks was explored.Five different dilute acid pretreated biomasses were evaluated and cellulase loading was done at 25 mg protein/g cellulose content. After 72 h of hydrolysis at 55 °C and pH 4.5, corn cob and rice straw emerged as the easiest and toughest substrates with saccharification yield of 83.9 ± 1.17 and 35.5 ± 1.16% respectively from their cellulose fraction. Addition of PEG 6000 could retain >65% of all mono-component enzymes present in cellulase cocktail.Structural elucidation of biomasses gave an insight about key features responsible for variable recalcitrance in the different agro-industrial feedstock. Cellulose hydrolysis showed a significant negative correlation in the order of Cr I > S/G ratio > ash content. The chemical composition of lignin had a major impact on enzyme-lignin interactions. Higher H lignin content and lower S/G ratio promoted enzyme desorption, thereby increasing the likelihood of their recycling and reuse.

Fermentative Conversion of Two-Step Pre-Treated Lignocellulosic Biomass to Hydrogen

Fermentative hydrogen production via dark fermentation with the application of lignocellulosic biomass requires a multistep pre-treatment procedure, due to the complexed structure of the raw material. Hence, the comparison of the hydrogen productivity potential of different lignocellulosic materials (LCMs) in relation to the lignocellulosic biomass composition is often considered as an interesting field of research. In this study, several types of biomass, representing woods, cereals and grass were processed by means of mechanical pre-treatment and alkaline and enzymatic hydrolysis. Hydrolysates were used in fermentative hydrogen production via dark fermentation process with Enterobacter aerogenes (model organism). The differences in the hydrogen productivity regarding different materials hydrolysates were analyzed using chemometric methods with respect to a wide dataset collected throughout this study. Hydrogen formation, as expected, was positively correlated with glucose concentration and total reducing sugars amount (YTRS) in enzymatic hydrolysates of LCMs, and negatively correlated with concentrations of enzymatic inhibitors i.e., HMF, furfural and total phenolic compounds in alkaline-hydrolysates LCMs, respectively. Interestingly, high hydrogen productivity was positively correlated with lignin content in raw LCMs and smaller mass loss of LCM after pre-treatment step. Besides results of chemometric analysis, the presented data analysis seems to confirm that the structure and chemical composition of lignin and hemicellulose present in the lignocellulosic material is more important to design the process of its bioconversion than the proportion between the cellulose, hemicellulose and lignin content in this material. For analyzed LCMs we found remarkable higher potential of hydrogen production via bioconversion process of woods i.e., beech (24.01 mL H2/g biomass), energetic poplar (23.41 mL H2/g biomass) or energetic willow (25.44 mL H2/g biomass) than for cereals i.e., triticale (17.82 mL H2/g biomass) and corn (14.37 mL H2/g biomass) or for meadow grass (7.22 mL H2/g biomass).

High resolution fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for the characterisation of enzymatic processing of commercial lignin

Lignin and lignin components of woody biomass have been identified as an attractive alternative to fossil fuels. However, the complex composition of this plant polymer is one of the drawbacks that limits its exploitation. Biocatalysis of lignin to produce platform chemicals has been receiving great attention as it presents a sustainable approach for lignin valorisation. Aligned with this area of research, in the present study we have applied ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to identify the preferred lignin substrates of a ligninolytic enzyme, a laccase produced by the terrestrial fungus Trametes versicolor. A commercial lignin was incubated with the laccase and acetosyringone (a laccase mediator) for up to 168 h and direct infusion electrospray FT-ICR MS enabled the identification of thousands of molecular species present in the complex lignin sample at different incubation time points. Significant changes in the chemical composition of lignin were detected upon laccase treatment, which resulted in a decrease in the molecular mass distribution of assigned species, consistent with laccase lytic activity. This reduction was predominantly in species classified as lignin-like (based on elemental ratios) and polymeric in nature (>400 Da). Of particular note was a fall in the number of species assigned containing sulfur. Changes in the chemical composition/structure of the lignin polymer were supported by FT-IR spectroscopy. We propose the use of FT-ICR MS as a rapid and efficient technique to support the biotechnological valorisation of lignin as well as the development and optimization of laccase-mediator systems for treating complex mixtures.

Exploiting plant long-distance signalling mechanisms in agriculture

Lignin and lignin components of woody biomass have been identified as an attractive alternative to fossil fuels. However, the complex composition of this plant polymer is one of the drawbacks that limits its exploitation. Biocatalysis of lignin to produce platform chemicals has been receiving great attention as it presents a sustainable approach for lignin valorisation. Aligned with this area of research, in the present study we have applied ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to identify the preferred lignin substrates of a ligninolytic enzyme, a laccase produced by the terrestrial fungus Trametes versicolor. A commercial lignin was incubated with the laccase and acetosyringone (a laccase mediator) for up to 168 h and direct infusion electrospray FT-ICR MS enabled the identification of thousands of molecular species present in the complex lignin sample at different incubation time points. Significant changes in the chemical composition of lignin were detected upon laccase treatment, which resulted in a decrease in the molecular mass distribution of assigned species, consistent with laccase lytic activity. This reduction was predominantly in species classified as lignin-like (based on elemental ratios) and polymeric in nature (>400 Da). Of particular note was a fall in the number of species assigned containing sulfur. Changes in the chemical composition/structure of the lignin polymer were supported by FT-IR spectroscopy. We propose the use of FT-ICR MS as a rapid and efficient technique to support the biotechnological valorisation of lignin as well as the development and optimization of laccase-mediator systems for treating complex mixtures.

Changes in the chemical composition of lignin in the leaves of coffee plants supplied with silicon and infected with Hemileia vastatrix

Coffee leaf rust, caused by the fungus Hemileia vastatrix , is considered the main disease of coffee in Brazil. Aiming to find alternatives to control this disease, this study investigated, at the metabolic level, the possible effect of silicon (Si) on coffee resistance to coffee leaf rust. The analytical pyrolysis was used to evaluate possible changes in the chemical composition of lignin on the leaves of coffee plants supplied with Si and inoculated with H. vastatrix . There was no significant increase in the foliar Si concentration for plants sup­plied with this element, consequently, there was no reduction on coffee leaf rust symptoms. Eight com­pounds derived from lignin from the p -hidroxifenila precursor (H) were identified, seven from the precursor guaiacyl (G) and one from the precursor syringyl (S) on leaves of plants supplied or non-supplied with Si and non-inoculated or inoculated with H. vastatrix . For the inoculated plants supplied with Si, there was a ten­dency of occur higher concentrations of the compounds vanillin and caffeine compared to plants non- -supplied with Si and non-inoculated. Plants supplied with Si, regardless of inoculation with H. vastatrix , showed higher values for S/G ratio when compared to non-supplied plants. Even though there was an increase in the concentrations of vanillin and caffeine and higher S/G ration on the leaves of plants supplied with Si and infected with H. vastatrix , this fact did not result in reduction in the symptoms of coffee leaf rust.

Influence of lignin source and esterification on properties of lignin-polyethylene blends

Lignins from pulp mills and biorefineries will gain increasing commercial importance in the next years. Their utilisation in polyolefin blends is of growing research interest as it offers a value-added usage of lignin as well as substitution of non-renewable resources. However, the low compatibility of lignin and polyolefins restrains a satisfying blend production and leads to poor mechanical properties. This can be overcome by modifying lignin prior to its incorporation into polymers in order to reduce its polarity. In this study, five lignins from different raw material sources and production processes were esterified with acetic, propionic and butyric anhydride and subsequently mixed with polyethylene with a weight ratio of 1:1. The paper provides a comprehensive and systematic evaluation of the influence of esterification as well as chemical composition of lignins on mechanical properties and, for the first time, water absorption of lignin-polyethylene blends. Properties of blends were found to improve upon lignin esterification. Compared to blends with unmodified lignin, a progressive increase of tensile (+45%) and flexural (+30%) strength could be observed with increasing length of the ester carbon chain. Lignin source and chemical composition affect water absorption of blends, but show no significant effect on mechanical properties as similar values were observed for blends produced with the respective lignin esters.

木质素在树脂胶粘剂中的应用进展

木质素是自然界中可再生芳香族聚合物，可替代苯酚用于高附加值化加工。此外，石油和天然气等化石资源面临着日渐枯竭的严重形势。木质素作为部分替代化石原料展现出良好的应用前景。要实现木质素的利用，必须首先充分了解木质素的组成与结构特征。本文以木质素的化学组成为出发点，分析比较了木质素的分离提取、应用等方法与技术，重点阐述了木质素结构研究最新进展，展望了木质素应用的发展方向。 Lignin is a renewable aromatic polymer in nature, and it can be used in the process of high added value. In addition, the oil and natural gas are facing the serious situation of increasingly exhausted. Lignin as a part of alternative fossil raw materials shows a good application prospect. In order to realize the use of lignin, firstly, we must understand the composition and structure of lignin. Stating from the chemical composition of lignin, this paper analyzed and compared some methods and techniques for separation as well as extraction, and application of lignin extraction, focused on the latest progress in the structure of lignin, and forecasted the development direction of lignin ap-plication.

Fractionation of five technical lignins by selective extraction in green solvents and characterisation of isolated fractions

Lignins from softwood, hardwood, grass and wheat straw were fractionated by selective extraction at ambient temperature using green solvents like acetone/water solutions of 10, 30, 50, 70 and 90% (v/v) acetone and ethyl acetate. A comparison between the isolated fractions and unfractionated lignins was made in terms of extraction yield, lignin solubility factor, molecular weight distribution and functional group composition. Low molecular weight (LMW) lignin fractions with narrow dispersity are obtained by extraction with ethyl acetate and acetone–water solution containing 30% acetone, with yields depending on the type and the functional group content of lignins. A significant amount (56%) of the organosolv hardwood lignin with low molecular weight (Mw=1868g/mol) and low dispersity was isolated from ethyl acetate. Insoluble fractions with very high molecular weight (Mw between 10 and 17kg/mol) are obtained in low yield from acetone–water solutions with 50, 70 and 90% acetone. LMW lignins are in general less condensed and have lower aliphatic hydroxyl content than parent lignins while the HMW fractions have a higher content of condensed hydroxyls. Principal component analysis on the chemical composition of lignins and isolated fractions determined from 31P NMR data showed the high heterogeneity of the technical lignins. Partial least squares models based on FT-IR spectral data were developed to predict the functional group content determined by quantitative 31P NMR analysis of technical lignins and lignin fractions. This approach can be used to develop simple, rapid and accurate analytical tools to monitor and control the selective fractionation of lignin.

Litter decay rates are determined by lignin chemistry

Litter decay rates are often correlated with the initial lignin:N or lignin:cellulose content of litter, suggesting that interactions between lignin and more labile compounds are important controls over litter decomposition. The chemical composition of lignin may influence these interactions, if lignin physically or chemically protects labile components from microbial attack. We tested the effect of lignin chemical composition on litter decay in the field during a year-long litterbag study using the model system Arabidopsis thaliana. Three Arabidopsis plant types were used, including one with high amounts of guaiacyl-type lignin, one with high aldehyde- and p-hydroxyphenyl-type lignin, and a wild type control with high syringyl-type lignin. The high aldehyde litter lost significantly more mass than the other plant types, due to greater losses of cellulose, hemicellulose, and N. Aldehyde-rich lignins and p-hydroxyphenyl-type lignins have low levels of cross-linking between lignins and polysaccharides, supporting the hypothesis that chemical protection of labile polysaccharides and N is a mechanism by which lignin controls total litter decay rates. 2D NMR of litters showed that lignin losses were associated with the ratio of guaiacyl-to-p-hydroxyphenyl units in lignin, because these units polymerize to form different amounts of labile- and recalcitrant-linkages within the lignin polymer. Different controls over lignin decay and polysaccharide and N decay may explain why lignin:N and lignin:cellulose ratios can be better predictors of decay rates than lignin content alone.

Chemical Characterization of Lignin and Lipid Fractions in Industrial Hemp Bast Fibers Used for Manufacturing High-Quality Paper Pulps

The chemical composition of lignin and lipids of bast fibers from industrial hemp (Cannabis sativa) used for high-quality paper pulp production was studied. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) of fibers showed a lignin with a p-hydroxyphenyl:guaiacyl:syringyl unit (H:G:S) molar proportion of 13:53:34 (S/G ratio of 0.64). p-Hydroxycinnamic acids, namely, p-coumaric and ferulic acids, were found in only trace amounts. Among the lipids, the main compounds identified by GC/MS of the hemp fibers extracts were series of n-alkanes, free and esterified sterols and triterpenols, waxes, and long-chain n-fatty acids. Other compounds such as n-aldehydes, n-fatty alcohols, steroid hydrocarbons, and steroid and triterpenoid ketones as well as steryl glycosides were also found.

Chemical characterization of lignin and lipid fractions in kenaf bast fibers used for manufacturing high-quality papers.

The chemical composition of lignin and lipids of bast fibers from kenaf (Hibiscus cannabinus) used for high-quality paper pulp production was studied. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) of fibers showed a lignin with a high syringyl/guaiacyl ratio (5.4) and minor amounts of p-hydroxyphenyl units. Simultaneously, sinapyl and coniferyl acetates were also identified, indicating that this lignin is partially acetylated. p-Hydroxycinnamic acids were found in only trace amounts. The main lipids identified by GC/MS of extracts from kenaf fibers were series of long-chain n-fatty acids, waxes, n-alkanes, and n-fatty alcohols. Free and esterified sterols and triterpenols, steroid hydrocarbons, and steroid and triterpenoid ketones, as well as steryl glycosides, were also found. Finally, the fate of the main constituents of kenaf fibers in alkaline pulping was also investigated.