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PubMed2006

Characterization of Klason lignins by reversed-phase high-performance liquid chromatography using wide-pore octadecylsilica and stepwise gradients of dimethylformamide in water.

RP-HPLC using stepwise gradients of N,N-dimethylformamide (DMF) in a phosphate-buffered (pH 3.00) aqueous mobile phase and a wide-pore (30 nm) octadecylsilica column has been applied to the analysis of a variety of lignins--organocell lignin, dioxane lignin, Björkman lignin, and Klason lignins from both softwoods and hardwoods, respectively, in order to demonstrate the usefulness of the approach for their characterization. Tandem combination of spectrophotometric diode array detection and fluorimetric detection was used to acquire more detailed information about the chromatographic behavior of lignins. The results show that a ten-step gradient can reveal distinct features of lignins and humic substances. Combination of good solvating properties of DMF for lignins together with a wide-pore RP sorbent improves surface interactions of the analytes and suppresses the influence of size exclusion effects. Thus it provides reproducibility of characterization profiles and robustness of the method. The calculated repeatability of the retention time of selected peaks was +/- 0.46% RSD. The reproducibility of the data within one week (set of seven data) was +/- 1.1% RSD. These data are also representative of the other well-shaped peaks of analyzed substances.

Buffers↗
PubMed2001

Repression of O-methyltransferase genes in transgenic tobacco affects lignin synthesis and plant growth.

Among the different enzymatic steps leading to lignin biosynthesis, two methylation reactions introduce the methyl groups borne by guaiacyl (G) and syringyl (S) units. Tobacco possesses a complex system of methylation comprising three classes of CCoAOMTs (caffeoyl-CoA-O-methyltransferases) and two classes of COMTs (caffeic acid OMTs). Antisense plants transformed with the CCoAOMT sequence alone or fused to COMT I sequence have been produced and compared to ASCOMT I plants in order to study the specific role of each OMT isoform in lignin biosynthesis, plant development and resistance to pathogens. Tobacco plants strongly inhibited in OMT activities have been selected and analyzed. Whereas antisense COMT I plants exhibited no visual phenotype, CCoAOMT repression was shown to strongly affect the development of both single and double transformants: a reduction of plant growth and the alteration of flower development were observed in the most inhibited plants. Lignin analysis performed by Klason and thioacidolysis methods, showed a decrease in the lignin quantity and changes in the lignin structure of ASCCoAOMT and ASCCoAOMT/ASCOMT I transgenics but not in ASCOMT I plants. Inhibition of COMT I in single as well as in double transformed tobacco was demonstrated to decrease S unit synthesis and to provoke the accumulation of 5-hydroxyguaiacyl lignin units. ASCCoAOMT/ASCOMT I tobacco was affected in lignin amount and composition, thus demonstrating additive effects of inhibition of both enzymes. The changes of lignin profiles and the phenotypical and molecular alterations observed in the different transgenic lines were particularly prominent at the later stages of plant development.

Lignin↗
PubMed2003

Structural and compositional modifications in lignin of transgenic alfalfa down-regulated in caffeic acid 3-O-methyltransferase and caffeoyl coenzyme A 3-O-methyltransferase.

Isolated lignins from alfalfa deficient in caffeic acid 3-O-methyltransferase contained benzodioxanes resulting from the incorporation of the novel monomer, 5-hydroxyconiferyl alcohol. Due to the high level incorporated into the soluble lignin fraction and the use of sensitive NMR instrumentation, unique structural features were revealed. A new type of end-unit, the 5-hydroxyguaiacyl glycerol unit, was identified. It was possible to establish that coniferyl alcohol, sinapyl alcohol, and the novel 5-hydroxyconiferyl alcohol can cross-couple with the 5-hydroxyguaiacyl units that are formed in the lignin, the latter giving rise to extended chains of benzodioxane units. There is also evidence that 5-hydroxyconiferyl alcohol couples with normal (guaiacyl or syringyl) lignin units. Lignin in the alfalfa deficient in caffeoyl CoA 3-O-methyltransferase was structurally similar to the control lignin but the transgenic exhibited a dramatic decrease in lignin content (approximately 20%) and modest increase in cellulose (approximately 10%) reflecting a 30% increase in cellulose:lignin ratio. The compositional changes in both transgenics potentially allow enhanced utilization of alfalfa as a major forage crop by increasing the digestibility of its stem fraction.

Down-Regulation↗
PubMed2003

The unmasking of lignin structures in wheat straw by alkali.

This study reports on the structural modifications of wheat straw cell wall promoted by potassium carbonate and sodium hydroxide that lead to the unmasking of some lignin structures. The first impact of the treatments was the extraction of a particular fraction of lignin enriched in C-C linked structures compared to the mean composition in reference wheat straw. Concomitantly, an apparent increase in the amount of lignin monomers released by the cleavage of alkyl-aryl ether bonds was observed in alkali-extracted samples. By summing the amount of ether linked monomers analyzed by thioacidolysis in the solubilized lignin to that found in the extracted wheat straw, an excess of up to 37% is apparent, relative to the corresponding amount in the reference wheat straw. Other modifications of the cell wall were also found. Indeed, a fraction of uronic acids was lost during the treatments and a new fractionation pattern of the lignin-carbohydrate complexes was evidenced. It can thus be concluded that a significant proportion of lignin within the cell wall was unmasked after (i) the selective removal of a particular lignin fraction, (ii) a partial saponification of the esterified fraction of lignin with uronic acids and (iii) a modification of the interactions between the cell wall constituents.

Carbonates↗
PubMed2001

Hydroxymethylation and oxidation of Organosolv lignins and utilization of the products.

Organosolv lignins obtained from Eucalyptus grandis, sugarcane bagasse and Picea abies by Acetosolv, Formacell and Organocell processes were characterized, fractionated and converted to hydroxymethylated and oxidized products. The reactivity of lignins with formaldehyde did not improve significantly with the fractionation. Both eucalyptus Acetosolv (EAc) and eucalyptus Formacell (EFo) lignins retained high heterogeneity in relation to the molecular weight distribution but not in relation to structural units. The temperatures of the exothermic peaks and the apparent activation energies for the cross-linking are different for hydroxymethylated lignins and phenol, with similar cure temperatures of the resols. Chemical oxidation using cobalt(II) and manganese(II) salts furnished oxidized lignins with improved chelating properties. These chelating agents can remove up to 14% of Mn present in pulps, decreasing the peroxide consumption in the bleaching process. The products obtained can be also used as oxidized phenols and controlled-release matrices. Oxidation of Acetosolv bagasse lignin with polyphenol oxidase furnishes lignins with chelating capacity 110% higher than that of original lignin.

Cellulose↗
PubMedDate not supplied

A new analysis of the depolymerized fragments of lignin polymer using ToF-SIMS.

Lignin in plant cell walls is a complex, irregular polymer built from phenylpropanoid C6-C3 units that are connected via various C-C and C-O linkages. A recent study using time-of-flight secondary ion mass spectrometry (ToF-SIMS) with Ga primary ion bombardment showed that lignin polymers can be characterized by specific positive ions possessing a substituted aromatic ring (so-called guaiacyl or syringyl rings), which are the basic building units of lignin. To study the relationship between the characteristic ions of lignin and the common interunit linkages, various lignin dimer model compounds were investigated using ToF-SIMS. The resulting dimer spectra showed that the characteristic ions with a guaiacyl ring at m/z 137 and 151 result from rupture of most common interunit linkages, not only 8-O-4' linkages, which are the most abundant in lignin, but also 8-1', 8-5', and 8-8'. There was no evidence of rupture of 5-5' linkages. These results show that ToF-SIMS offers a new tool for the direct analysis of the depolymerized fragments of lignin polymers. The mechanisms for the fragmentation of lignin dimer models in ToF-SIMS were proposed that allow ToF-SIMS fragmentation rules to be deduced. Adduct ions such as [M + 13]+ ([M + CH]+) were also produced in fragmentation of the dimers and are thought to arise from the combination of the molecules with their stable fragments.

Biocompatible Materials↗
PubMed2002

Lignin deposition and associated changes in anatomy, enzyme activity, gene expression, and ruminal degradability in stems of tall fescue at different developmental stages.

Stem tissues of tall fescue (Festuca arundinacea Schreb.) were sampled at three elongation stages and three reproductive stages. Anatomical analysis showed the deposition of guaiacyl (G) and syringyl (S) lignin during plant development and the formation of a lignified sclerenchyma ring. A dramatic increase in Klason lignin content was found from elongation stage to reproductive stage. Lignin composition analyzed by gas chromatography-mass spectrometry revealed that S lignin content and S/G ratio increased with stem development, but contents of p-hydroxyphenyl (H) and G lignins decreased during the same period. S lignin content and S/G ratio also increased from the younger upper internode down to the older basal internode of the stem, but G and H lignin decreased in parallel. Relative O-methyltransferase activities increased during stem development and in parallel with the lignification process of stem. The pattern of enzyme activity during development varied with the choice of substrate, with highest activities seen when substrates were caffeoylaldehyde and 5-hydroxyferulic acid, and lowest activities were seen when caffeic acid and 5-hydroxyconiferyl alcohol were used as substrates. The expression of caffeic acid O-methyltransferase and cinnamyl alcohol dehydrogenase genes increased during the stem elongation stage and remained at high levels during the reproductive stages. The changes at anatomical, metabolic, and molecular levels during plant development were closely associated with lignification and degradability. This study provides an integrated picture of the molecular and chemical events that accompany changes in lignin deposition and ruminal degradability.

Alcohol Oxidoreductases↗
PubMed2003

Controlled release of the herbicide, fluometuron, from matrix granules based on fractionated organosolv lignins.

An organosolv lignin and several of its fractions were used to prepare controlled release matrix granules with fluometuron using a melt process. Release profiles of fluometuron from these granules and a commercial granular formulation were studied in vitro. The release rates of fluometuron were considerably reduced from all lignin-based granules as compared to the commercial formulation. The release rates markedly varied with the lignin fraction used in the fluometuron-lignin matrix systems with the corresponding times for 50% release (T(50)) values ranging from 2.37 to 11.2 days. The variation in release rate of fluometuron was related to the high proportion of low molecular weight lignin and its associated water soluble lignin in the lignin-based granules, in terms of the hydrophobicity of matrix, the content, and release rate of soluble lignin. The release kinetics were fitted to the generalized model for up to 60% release of fluometuron; the kinetics of fluometuron were of the anomalous type for all matrixes in which release rates increased following a delay.

Chemical Fractionation↗
PubMed1999

Physicochemical and structural characterization of alkali soluble lignins from oil palm trunk and empty fruit-bunch fibers.

Six alkali soluble lignin fractions were extracted from the cell wall materials of oil palm trunk and empty fruit-bunch (EFB) fibers with 5% NaOH, 10% NaOH, and 24% KOH/2% H(3)BO(3). All of the lignin fractions contained rather low amounts of associated neutral sugars (0.8-1.2%) and uronic acids (1.1-2.0%). The lignin fractions isolated with 5% NaOH from the lignified palm trunk and EFB fibers gave a relatively higher degree of polymerization as shown by weight-average molecular weights ranging between 2620 and 2840, whereas the lignin fractions isolated with 10% NaOH and 24% KOH/2% H(3)BO(3) from the partially delignified palm trunk and EFB fibers showed a relatively lower degree of polymerization, as shown by weight-average molecular weights ranging between 1750 and 1980. The results obtained by alkaline nitrobenzene oxidation showed that all of the lignin preparations contained a high proportion of noncondensed syringyl units with small amounts of noncondensed guaiacyl and fewer p-hydroxyphenyl units. The lignin fraction extracted with 5% NaOH from the lignified EFB fiber was mainly composed of beta-O-4 ether-linked units. Small amounts of 5-5', beta-5, and beta-beta' carbon-carbon linkages were also found to be present between the lignin structural units. Further studies showed that uronic, p-hydroxybenzoic, and ferulic acids in the cell walls of palm fibers were esterified to lignin.

Alkalies↗
PubMed2000

Lignin structure in a mutant pine deficient in cinnamyl alcohol dehydrogenase.

Cinnamyl alcohol dehydrogenase (CAD) activity is deficient in loblolly pine (Pinus taeda L.) harboring a mutated allele of the cad gene (cad-n1). We compared lignin structure of CAD-deficient and wild-type pines, both types segregating within full-sib families obtained by controlled crosses. The type and frequency of lignin building units and distribution of interunit bonds were determined from the GC-MS analysis of thioacidolysis monomers and dimers. While the lignin content was only slightly reduced, the lignin structure was dramatically modified by the mutation in both mature and juvenile trees. Lignins from CAD-deficient pine displayed unusually high levels of coniferaldehyde and dihydroconiferyl alcohol. In addition, biphenyl and biphenyl ether bonds were in large excess in these abnormal lignins. These results suggest that the CAD-deficient pines efficiently compensate for the shortage in normal lignin precursors by utilizing nontraditional wall phenolics to construct unusual lignins particularly enriched in resistant interunit bonds.

Alcohol Oxidoreductases↗
PubMed1999

NMR characterization of lignins in Arabidopsis altered in the activity of ferulate 5-hydroxylase.

Nuclear magnetic resonance (NMR) of isolated lignins from an Arabidopsis mutant deficient in ferulate 5-hydroxylase (F5H) and transgenic plants derived from the mutant by overexpressing the F5H gene has provided detailed insight into the compositional and structural differences between these lignins. Wild-type Arabidopsis has a guaiacyl-rich, syringyl-guaiacyl lignin typical of other dicots, with prominent beta-aryl ether (beta-O-4), phenylcoumaran (beta-5), resinol (beta-beta), biphenyl/dibenzodioxocin (5-5), and cinnamyl alcohol end-group structures. The lignin isolated from the F5H-deficient fah1-2 mutant contained only traces of syringyl units and consequently enhanced phenylcoumaran and dibenzodioxocin levels. In fah1-2 transgenics in which the F5H gene was overexpressed under the control of the cauliflower mosaic virus 35S promoter, a guaiacyl-rich, syringyl/guaiacyl lignin similar to the wild type was produced. In contrast, the isolated lignin from the fah1-2 transgenics in which F5H expression was driven by the cinnamate 4-hydroxylase promoter was almost entirely syringyl in nature. This simple lignin contained predominantly beta-aryl ether units, mainly with erythro-stereochemistry, with some resinol structures. No phenylcoumaran or dibenzodioxocin structures (which require guaiacyl units) were detectable. The overexpression of syringyl units in this transgenic resulted in a lignin with a higher syringyl content than that in any other plant we have seen reported.

Arabidopsis↗
PubMed2005

Topochemical studies on modified lignin distribution in the xylem of Poplar (Populus spp.) after wounding.

BACKGROUND AND AIMS: Information on the influence of wounding on lignin synthesis and distribution in differentiating xylem tissue is still scarce. The present paper provides information on cell modifications with regard to wall ultrastructure and lignin distribution on cellular and subcellular levels in poplar after wounding. METHODS: Xylem of Populus spp. close to a wound was collected and processed for light microscopy, transmission electron microscopy and cellular UV microspectrophotometry. Cell wall modification with respect to lignin distribution was examined at different stages of wound tissue development. Scanning UV microspectrophotometry and point measurements were used to determine the lignin distribution. KEY RESULTS: Xylem fibres within a transition zone between differentiated xylem laid down prior to wounding and the tissues formed after wounding developed distinctively thickened secondary cell walls. Those modified walls and cell corners showed, on average, a higher lignin content and an inhomogeneous lignin distribution within the individual wall layers. CONCLUSIONS: The work presented shows that wounding of the xylem may induce a modified wall architecture and lignin distribution in tissues differentiating at the time of wounding. An increasing lignin content and distinctively thickened walls can contribute to improved resistance as part of the compartmentalization process.

Cell Differentiation↗
PubMed1995

Informed strain improvement for lignin degradation by Phanerochaete chrysosporium.

The effect of breeding from the white rot fungus Phanerochaete chrysosporium ME446 on performance for lignin mineralization was examined. This model for informed strain improvement without mutagenesis is based on abundant restriction fragment length polymorphisms (RFLPs). Under optimized conditions for lignin mineralization, extracellular manganese peroxidase (MnP) but not lignin peroxidase (LiP) could be detected, so measurement of LiP activity is not a valid assay for lignin degradation. Mineralization of 14C-labelled synthetic lignin (14C-DHP) was used to compare the performance of the wild-type strain ME446 with those of sets of progeny strains. Meiotic progeny from strain ME446, heterokaryotic progeny of crosses between such strains, and meiotic progeny of one heterokaryotic strain were examined. In each case, a minority of strains performed more efficiently than the parental strain ME446. The greatest range of lignin-mineralization performance (70-fold) was found within the set of initial progeny of ME446 and the narrowest was within the set of secondary homokaryotic strains. This is consistent with the view that a moderate number of determinants contribute to lignin mineralization performance. However, performance did not correlate with the possession of any single allele of those for 38 previously defined RFLP markers. The results show that lignin mineralization performance can be improved by cycles of crosses and fruiting, without mutagenesis.

Basidiomycota↗
PubMed1990

Lignin-solubilizing ability of actinomycetes isolated from termite (Termitidae) gut.

The lignocellulose-degrading abilities of 11 novel actinomycete strains isolated from termite gut were determined and compared with that of the well-characterized actinomycete, Streptomyces viridosporus T7A. Lignocellulose bioconversion was followed by (i) monitoring the degradation of [14C]lignin- and [14C]cellulose-labeled phloem of Abies concolor to 14CO2 and 14C-labeled water-soluble products, (ii) determining lignocellulose, lignin, and carbohydrate losses resulting from growth on a lignocellulose substrate prepared from corn stalks (Zea mays), and (iii) quantifying production of a water-soluble lignin degradation intermediate (acid-precipitable polymeric lignin). The actinomycetes were all Streptomyces strains and could be placed into three groups, including a group of five strains that appear superior to S. viridosporus T7A in lignocellulose-degrading ability, three strains of approximately equal ability, and three strains of lesser ability. Strain A2 was clearly the superior and most effective lignocellulose decomposer of those tested. Of the assays used, total lignocellulose weight loss was most useful in determining overall bioconversion ability but not in identifying the best lignin-solubilizing strains. A screening procedure based on 14CO2 evolution from [14C-lignin]lignocellulose combined with measurement of acid-precipitable polymeric lignin yield was the most effective in identifying lignin-solubilizing strains. For the termite gut strains, the pH of the medium showed no increase after 3 weeks of growth on lignocellulose. This is markedly different from the pattern observed with S. viridosporus T7A, which raises the medium pH considerably. Production of extracellular peroxidases by the 11 strains and S. viridosporus T7A was followed for 5 days in liquid cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomycetales↗
PubMed2003

Reduction of genotoxic effects of the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine by dietary lignin in mammalian cells cultured in vitro.

In the present study the protective effect of several lignin polymers against the genotoxic effect of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was tested in hamster lung V79 cells and human colon Caco-2 cells. Preculturing of cells with sublethal, nongenotoxic concentrations of the lignins A, B, and C (50 microg/ml) was found to decrease significantly the level of DNA strand breaks in both hamster and human cells treated with MNNG. Lignin A also reduced MNNG-induced gene mutations in V79 cells. As in addition to alkyl lesions MNNG gives rise to hydroxyl free radicals (OH) and nitrogen-centered free radicals (NR), we tried to determine whether antimutagenicity of lignin A was connected only with the well-known ability of lignin to bind MNNG molecules or also with its antioxidative effects. The use of the modified comet assay technique proved that preculturing of hamster V79 cells with lignin A resulted in a significant decrease of the level of DNA strand breaks originating from oxidized DNA bases. Therefore, we suggest that the antimutagenic effect of lignin A against MNNG is associated with both adsorptive and antioxidative action. This study also showed that the presence of lignin A neither helped to renew DNA replication nor influenced the kinetics of DNA rejoining in MNNG-treated V79 cells.

Animals↗
PubMed2004

Lignin-stimulated reduction of oxidative DNA lesions in testicular cells and lymphocytes of sprague-dawley rats in vitro and ex vivo.

Lignin biopolymers constitute 30% of plant biomass and belong to the most abundant organic polymers on earth. We showed previously that this important component of dietary fiber exhibited a protective effect against the overall DNA damage induced by H2O2 or N-methyl-N'-nitro-N-nitrosoguanidine in hamster lung cells and human foreskin cells cultured in vitro. The objective of the present work was to examine DNA-protective effects of lignin in rat testicular cells and rat peripheral blood lymphocytes using in vitro and ex vivo experiments. H2O2 and visible light-excited methylene blue (MB) were used as DNA-damaging agents. Testicular cells were chosen because the germinal epithelium of testes is one of the most proliferately active tissues potentially susceptible to DNA-damaging effects. As a second target peripheral blood lymphocytes were chosen because dietary lignin or its metabolites circulate in the animal organism probably through the blood system. For the in vitro experiments, isolated cells were preincubated with lignin for 2 h before treatment with one of the oxidative agents. In ex vivo experiments, the cells were exposed to H2O2 or visible light-excited MB after isolation from rats fed either a common diet or a lignin-supplemented diet. The water-soluble, sulfur-free lignin used in experiments was obtained by fractionation of hardwood hydrolysate. The level of direct single-strand DNA breaks in H2O2-treated cells was measured by the classical comet assay, and the level of oxidative DNA lesions in visible light-treated cells was measured by a modified comet assay. We found that lignin reduced DNA lesions induced by H2O2 or visible light-excited MB both in vitro and ex vivo. The major conclusion of our study is that lignin polymer obtained by fractionation of hardwood hydrolysate manifested a specific type of antimutagenic effect.

Animals↗
PubMed2006

Obtainment of chelating agents through the enzymatic oxidation of lignins by phenol oxidase.

Oxidation of lignin obtained from acetosolv and ethanol/water pulping of sugarcane bagasse was performed by phenol oxidases: tyrosinase (TYR) and laccase (LAC), to increase the number of carbonyl and hydroxyl groups in lignin, and to improve its chelating capacity. The chelating properties of the original and oxidized lignins were compared by monitoring the amount of Cu2+ bound to lignin by gel permeation chromatography. The Acetosolv lignin oxidized with TYR was 16.8% and with LAC 21% higher than that of the original lignin. For ethanol/water lignin oxidized with TYR was 17.2% and with LAC 18% higher than that of the original lignin.

Agaricales↗
PubMed2003

Effects of lignin on nitrification in soil.

The effects of two lignins isolated from black liquor from pulping process on nitrification in soils after addition of urea, (NH4)2SO4 and (NH4)2HPO4 were investigated by incubation at 20 or 30 degrees C for 7 or 14 d. The effects of lignin on nitrous oxide emissions from soil were also determined. Results showed that both lignins were more effective for inhibiting nitrification of NH4(+)-N as (NH4)2SO4 or (NH4)2HPO4 as compared to urea-N. The effectiveness of lignin on nitrification was markedly affected by different soil type and temperature. Nitrous oxide emissions from soil declined when lignin was used. Urea plus 20 and 50 g/kg lignin reduced N2O emissions by about 83% and 96%. respectively, while (NH4)2HPO4 plus 20 and 50 g/kg lignin respectively reduced emissions by 83% and 93%. Because of its low cost and nonhazardous characteristics, lignin has potential value as a fertilizer amendment to improve N fertilizer efficiency.

Conservation of Natural Resources↗