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At least 1,531 records · Page 85Linked to original sources
PubMed2003

Hot alkali-labile linkages in the walls of the forage grass Phalaris aquatica and Lolium perenne and their relation to in vitro wall digestibility.

The factors affecting in vitro dry matter digestibility (IVDMD) of fully mature internodes of 150 lines of the forage grass, Phalaris aquatica, and internodes of 100 lines of perennial ryegrass (Lolium perenne), harvested just after anthesis, were investigated. The relationships between IVDMD and the contents of acetyl bromide lignin, and ester-ether linkages between lignin and wall polysaccharides, measured by hydroxycinnamic acids (HCAs) released by 4 M NaOH at 170 degrees C respectively, were determined. The regression analysis gave r(2)=0.05 and 0.03 for the relation between IVDMD and lignin content and r(2)=0.51 and 0.53 for the relation between IVDMD and the content of hot alkali-labile HCA (predominantly ferulic acid) for phalaris and ryegrass, respectively. These observations are interpreted in terms of the restricted accessibility of polysaccharide hydrolysing enzymes to their substrates in the forage cell walls by the covalent cross-linking of wall polymers through HCAs.

Animal Feed↗
PubMed1999

Proton spin-lattice relaxation time measurements of solid wood and its constituents as a function of pH: part II.

The proton spin-lattice relaxation times (T1H) for isolated cuoxam lignin and fully bleached cellulose were measured as a function of pH in the solid-state. These experiments provided the opportunity to examine for possible macromolecular connectivities that may be present between lignin and carbohydrates within softwood. These studies have shown that the molecular mobilities of the isolated polymeric constituents of wood are affected by the ionization of their functional groups at different pHs. The shapes of the plots of T1H as a function of pH for the two isolated polymers were dramatically different, while those for softwood were similar. This fact provides evidence supporting the notion that in wood, lignin and carbohydrates are intimately associated with each other.

Cellulose↗
PubMed2001

Influence of process variables in the ethanol pulping of olive tree trimmings.

A central composition design was developed to study the influence of process variables (temperature, pulping time and ethanol concentration) on the properties of the pulp produced (yield and holocellulose, alpha-cellulose and lignin contents) and the pH of the resulting wastewater, in the ethanol pulping of olive tree trimmings. The proposed equations reproduce the experimental results for the dependent variables with errors less than 5% for the holocellulose and alpha-cellulose contents, yield and wastewater pH, and less than 15% for the lignin content. Obtaining pulp with acceptably high yield (37.6%), high holocellulose and alpha-cellulose contents (above 88.8% and 46.9%, respectively), and low lignin contents (below 7.2%), entails operating at a pulping temperature of 200 degrees C, using an ethanol concentration of 75% and a pulping time of 60 min.

Biotechnology↗
PubMed2002

The effect of aeration on the biotransformation of lignocellulosic wastes by white-rot fungi.

The mineralisation and the humification of organic matter (OM) in sterile horticultural plant wastes inoculated with Coriolus versicolor or Phanerochaete flavido-alba was investigated under different aeration rates in order to determine their efficacy as potential inoculants for composting. The change in elemental composition, lignin content and OM fractions was analysed during a 90-day incubation. Both fungi degraded 30% of lignin at low aeration rates. Different aeration rates led to significant changes in OM mineralisation induced by C. versicolor, but did not have noticeable effect on P. flavido-alba activity. The mineralisation was more effectively carried out by P. flavido-alba than by C. versicolor. Lignin degradation and the linked humification process were equally achieved by the two fungi and were enhanced in aerated conditions. The fungi analysed may facilitate the composting of lignocellulosic wastes by means of an increase in substrate bioavailability and OM humification.

Air↗
PubMedDate not supplied

Thermoset phenolic matrices reinforced with unmodified and surface-grafted furfuryl alcohol sugar cane bagasse and curaua fibers: properties of fibers and composites.

Composites based on phenolic matrices and unmodified and chemically modified sugar cane bagasse and curaua fibers were prepared. The fibers were oxidized by chlorine dioxide, mainly phenolic syringyl and guaiacyl units of the lignin polymer, followed by grafting furfuryl alcohol (FA), which is a chemical obtained from a renewable source. The fibers were widely characterized by chemical composition analysis, crystallinity, UV-vis diffuse reflectance spectroscopy, SEM, DSC, TG, tensile strength, and 13C CP-MAS NMR. The composites were analyzed by SEM, impact strength, and DMA. The SEM images and DMA results showed that the oxidation of sugar cane bagasse fibers followed by reaction with FA favored the fiber/matrix interaction at the interface. The same chemical modification was less effective for curaua fibers, probably due to its lower lignin content, since the reaction considered touches mainly the lignin moiety. The tensile strength results obtained showed that the fibers were partially degraded by the chemical treatment, decreasing then the impact strength of the composites reinforced with them. In the continuity of the present project, efforts has been addressed to the optimization of fiber surface modification, looking for reagents preferably obtained from renewable resources and for chemical modifications that intensify the fiber/matrix interaction without loss of mechanical properties.

Alcohols↗
PubMed2004

Peroxidase-catalyzed coupling of phenol in the presence of model inorganic and organic solid phases.

Peroxidase-catalyzed oxidative coupling reactions of phenol in aqueous systems variously containing silica sand, cellulose, lignin, and polymethylstyrene were investigated. These four solid phase materials represent a broad spectrum of different natural geosorbent types in terms of their physicochemical characteristics. Each solid was found to influence peroxidase-catalyzed phenol coupling, either by mitigation of enzyme inactivation, by participation in cross-coupling, or by a combination of these two activities. Mitigation of enzyme inactivation was observed for those three of the four model solids found to adsorb the enzyme effectively; i.e., cellulose, silica sand, and lignin. Two solids, polymethylstyrene and lignin, were found to participate significantly in cross-coupling reactions. It is postulated that relatively hydrophilic solids can mitigate peroxidase inactivation by forming enzyme-solid associations. Aromatic structures or unsaturated C-C bonds were found to be features of the solid-phase materials that allowed them to participate in cross-coupling. The results have important implications for process feasibility assessment and the engineering design of soil/sediment remediation systems employing enzymatic coupling schemes.

Biodegradation, Environmental↗
PubMed2001

Mode of action of hot-water dip in reducing decay of lemon fruit.

A hot-water dip for 2 min at 52-53 degrees C prevented decay for at least one week in lemon fruit inoculated with Penicillium digitatum. The mode of action of hot water in reducing decay was investigated by studying the effects of this treatment on the pathogen and on the resistance mechanisms of the fruit. The hot-water dip had a transient inhibitory effect on the pathogen, arresting its growth for 24-48 h. During this lag period, the combined effects of the pathogen and the hot-water dip induced the build up of resistance in the peel. Lignin production in the inoculated sites began within 24 h after inoculation or wounding. When inoculation was followed by the hot-water dip, lignin accumulation continued for a week. Inoculated lemons that were not dipped in hot water rotted completely within 3 days after inoculation and their lignin content did not rise or even decreased. The scoparone concentration in the inoculated sites of hot dipped fruit started to rise 24 h after treatment and reached a level sufficient to inhibit the pathogen within 2 days after treatment. Parallel to scoparone accumulation, scopoletin was detected in inoculated and heat-treated lemons. Without the pathogen challenge or wounding, heat treatment by itself was not able to induce any of the above-mentioned defensive effects. Our data do not support the involvement of ethanol-extractable aldehydes, associated in the literature with wound gum, or of citral in decay inhibition in hot-water dipped lemons.

Acyclic Monoterpenes↗
PubMed2001

Tissue-specific patterns of lignification are disturbed in the brown midrib2 mutant of maize (Zea mays L.).

Despite recent progress, several aspects of lignin biosynthesis, including variation in lignin composition between species and between tissues within a given species, are still poorly understood. The analysis of mutants affected in cell wall biosynthesis may help increase the understanding of these processes. We have analyzed the maize brown midrib2 (bm2) mutant, one of the four bm mutants of maize, using pyrolysis-mass spectrometry (Py-MS) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). Vascular tissues from the leaf blade and leaf sheath from different parts of the plant were investigated and compared to the corresponding samples from a wild-type plant of the same genetic background (inbred line A619). Multivariate analysis revealed that the bm2 mutant had reduced amounts of di- and trimeric lignin derivatives, notably species with m/z 272 and m/z 330, and that the ratio of guaiacyl residues to polysaccharides was reduced in the bm2 mutant. In addition, differences in cell wall composition between different parts of the plant (blade versus sheath, young versus old tissue) were much less pronounced in the bm2 mutant. These changes suggest that the functional Bm2 gene is important for the establishment of tissue-specific cell wall composition.

Cell Wall↗
PubMed2004

Abiotic degradation of lignified cell walls by carbonate and copper salt.

This study reports on the destructuration of Wheat straw and Spruce wood cell walls after maceration in potassium carbonate or sodium hydroxide at pH = 10 in the presence of copper acetate. The alkaline treatments had a predominant impact on the wheat straw cell wall components over copper acetate. Either K-carbonate or Na-hydroxide extracted from wheat straw a particular lignin fraction rich in condensed C-C linkages, leading to the unmasking of new ether-linked sub-structures in the cell wall. This unmasking was increased in the presence of copper salt but only in the nonextracted Wheat straw sample incubated in carbonate and not in the corresponding extractive-free sample. This difference was related to the leaching of compounds from the nonextracted cell wall, which could sustain oxidative activity of copper by hindering its precipitation into inactive hydroxide and/or carbonate species. In Spruce wood samples, copper salt was the principal factor impacting on the lignin structure over alkali alone. Its effect was, however, only detected at the level of C-C linked dimers. These results confirmed that unmasking of lignin sub-structures also occurred in Spruce wood, but probably through mechanisms different from that evidenced in Wheat straw.

Carbonates↗
PubMed2003

Significant increases in pulping efficiency in C4H-F5H-transformed poplars: improved chemical savings and reduced environmental toxins.

The gene encoding ferulate 5-hydroxylase (F5H) was overexpressed in poplar (Populus tremula x Populus alba) using the cinnamate-4-hydroxylase (C4H) promoter to drive expression specifically in cells involved in the lignin biosynthetic pathway and was shown to significantly alter the mole percentage of syringyl subunits in the lignin, as determined by thioacidolysis. Analysis of poplar transformed with a C4H-F5H construct demonstrated significant increases in chemical (kraft) pulping efficiency from greenhouse-grown trees. Compared to wild-type wood, decreases of 23 kappa units and increases of >20 ISO brightness units were observed in trees exhibiting high syringyl monomer concentrations. These changes were associated with no significant modification in total lignin content and no observed phenotypic differences. C4H-F5H-transformed trees could increase pulp throughputs at mills by >60% while concurrently decreasing chemicals employed during processing (chemical pulping and bleaching) and, consequently, the amount of deleterious byproducts released into the environment.

Arabidopsis Proteins↗
PubMed2006

Chemical composition of abaca (Musa textilis) leaf fibers used for manufacturing of high quality paper pulps.

The chemical composition of leaf fibers of abaca (Musa textilis), which are commonly used for high-quality paper pulp production, was thoroughly studied. The results revealed that the lignin content was 13.2% of the total fiber. The analysis of abaca fibers by pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC/MS) released predominantly compounds arising from lignin and p-hydroxycinnamic acids, with high amounts of 4-vinylphenol. The latter compound was demonstrated to arise from p-coumaric acid by pyrolysis of abaca fibers in the presence of tetramethylammonium hydroxide, which released high amounts of p-coumaric acid (as the methyl derivative). Products from p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) propanoid units, with a predominance of the latter (H:G:S molar ratio of 1.5:1:4.9), were also released after Py-GC/MS of abaca fibers. Sinapyl and coniferyl acetates, which are thought to be lignin monomer precursors, were also found in abaca. The extractives content of the abaca fiber (0.4%) was low, and the most predominant compounds were free sterols (24% of total extract) and fatty acids (24% of total extract). Additionally, significant amounts of steroid ketones (10%), triglycerides (6%), omega-hydroxyfatty acids (6%), monoglycerides (4%), fatty alcohols (4%), and a series of p-hydroxycinnamyl (p-coumaric and ferulic acids) esterified with long chain alcohols and omega-hydroxyfatty acids were also found, together with minor amounts of steroid hydrocarbons, diglycerides, alpha-hydroxyfatty acids, sterol esters, and sterol glycosides.

Gas Chromatography-Mass Spectrometry↗
PubMed2006

In vitro bile acid binding activity within flour fractions from oat lines with typical and high beta-glucan amounts.

Whole flours from four oat lines with different amounts of beta-glucan (4.8-8.1%) were examined for their antioxidant activity and total phenolic and lignin concentrations. These data, along with the beta-glucan percentages, were compared with bile acid (BA) binding. Only the lignin concentrations of the flours significantly (P < 0.01) correlated with the BA binding values. The oat flours also were fractionated into bran, protein concentrate, starch, layer above starch, and soluble beta-glucan (SBG)-free flour, and their BA binding capacities were evaluated. The bran fractions were the only fractions that bound greater BA than did the whole oat flours on dry matter basis. Extraction of the soluble beta-glucan to create the SBG-free flour significantly (P < 0.01) decreased the BA binding of the remaining flour. These data suggest that BA binding of the oat flours involves the synergistic interactions of the oat components, with beta-glucan and lignin (insoluble fiber) having a great impact.

Antioxidants↗
PubMed2004

Lignification and related enzymes in Glycine max root growth-inhibition by ferulic acid.

Changes in soluble and cell wall bound peroxidase (POD, EC 1.11.1.7) activity, phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity, and lignin content in roots of ferulic acid-stressed soybean (Glycine max (L.) Merr.) seedlings and their relationships with root growth were investigated. Three-day-old soybean seedlings were cultivated in half-strength Hoagland nutrient solution containing 1.0 mM ferulic acid for 24-72 hr. Length, fresh weight, and dry weight of roots decreased, while soluble and cell wall bound POD activity, PAL activity, and lignin content increased after ferulic acid treatment. These enzymes probably participate in root growth reduction in association with cell wall stiffening related to the formation of cross-linking among cell wall polymers and lignin production.

Body Weight↗
PubMed2025

Rice transcription factor bHLH25 confers resistance to multiple diseases by sensing H2O2.

Hydrogen peroxide (H2O2) is a ubiquitous signal regulating many biological processes, including innate immunity, in all eukaryotes. However, it remains largely unknown that how transcription factors directly sense H2O2 in eukaryotes. Here, we report that rice basic/helix-loop-helix transcription factor bHLH25 directly senses H2O2 to confer resistance to multiple diseases caused by fungi or bacteria. Upon pathogen attack, rice plants increase the production of H2O2, which directly oxidizes bHLH25 at methionine 256 in the nucleus. Oxidized bHLH25 represses miR397b expression to activate lignin biosynthesis for plant cell wall reinforcement, preventing pathogens from penetrating plant cells. Lignin biosynthesis consumes H2O2 causing accumulation of non-oxidized bHLH25. Non-oxidized bHLH25 switches to promote the expression of Copalyl Diphosphate Synthase 2 (CPS2), which increases phytoalexin biosynthesis to inhibit expansion of pathogens that escape into plants. This oxidization/non-oxidation status change of bHLH25 allows plants to maintain H2O2, lignin and phytoalexin at optimized levels to effectively fight against pathogens and prevents these three molecules from over-accumulation that harms plants. Thus, our discovery reveals a novel mechanism by which a single protein promotes two independent defense pathways against pathogens. Importantly, the bHLH25 orthologues from available plant genomes all contain a conserved M256-like methionine suggesting the broad existence of this mechanism in the plant kingdom. Moreover, this Met-oxidation mechanism may also be employed by other eukaryotic transcription factors to sense H2O2 to change functions.

Hydrogen Peroxide↗
PubMed2000

Comparison of degradation state and stability of different humic acids by means of chemolysis with tetramethylammonium hydroxide.

In the chemolysis products of extracted humic acids (HAs) and tetramethylammonium hydroxide, different compounds can be identified which allow a description of the sources of soil organic matter (SOM). It is possible to draw conclusions concerning stability, degree of intramolecular cross-linking and degradation of aliphatic and lignin components from the distinctive product ratios. The ratio of lignin derived acidic phenolic derivatives and their analogous aldehydes and the ratio of phenylpropenoic acids and analogous benzoic acids provide comparably good parameters for the characterization of the state of degradation of lignin compounds to relatively stable HA building blocks. Regarding the aliphatic chemolysis products, alpha,omega-dicarboxylic acid and methoxy fatty acid contents indicate an intramolecular cross-linking state within the HA molecules and the degree of stable aliphatic constituent parts. High contents of unsaturated fatty acids can be considered as an indicator of an easy degradable humic skeleton because with their double bonds they represent active sites for further transformations. The suitability of the carbon preference index as an indicator of a biogenic carbon source can be confirmed. It is remarkable how the results obtained from extracted humic acids are in accordance with the expectations for the different SOMs derived from land use.

Fatty Acids↗
PubMed1966

Experimental induction of vascular tissue in an undifferentiated plant callus.

1. By the implantation of wedges containing indol-3-ylacetic acid and sucrose into blocks of undifferentiated bean-callus tissue it has been possible to induce the formation of xylem and phloem cells. 2. The differentiation has been investigated cytologically and measured chemically. 3. The optimum concentrations of the nutrients in the wedge, which gave differentiation closely resembling the vascular development found in the stem of the intact plant, was 0.1mg. of indol-3-ylacetic acid/l. and 2% sucrose. 4. The ratios of the xylose/arabinose concentrations of the tissues increased in the differentiated callus tissue compared with those of the undifferentiated tissue. A similar increase has been found for the ratios determined for xylem tissue compared with those for cambium. 5. The lignin content of the differentiated tissue compared with the undifferentiated tissue was greater in both the callus and stem tissue. 6. Chemical analysis of lignin showed that in the differentiated callus tissue it consisted of sub-units based on p-hydroxybenzaldehyde and vanillin. This was compared with the lignin obtained from undifferentiated callus tissue and that obtained from the tissues of the intact stem. 7. The results of the investigation have been discussed with reference to the problems of cell growth and differentiation and related to the changing patterns of the ultrastructure of the cell during its development.

Arabinose↗
PubMed1996

Lignocellulose degradation by Phanerochaete chrysosporium: gene families and gene expression for a complex process.

Phanerochaete chrysosporium completely degrades lignocellulose. The most recalcitrant component, lignin, is oxidized by the radical products of lignin and manganese peroxidases, whereas cellulose and hemicellulose are hydrolysed. Both peroxidases and cellulases exist as complex families at both the DNA and protein levels. The lignin peroxidases may function principally when mycelium-bound and, therefore, undetectable in culture supernatants. Moreover, methods for the study of P. chrysosporium must be applicable to solid substrate as well as liquid-culture conditions. For these reasons, detailed studies of gene expression, made possible by the reverse transcriptase-polymerase chain reaction method, are essential. Such studies reveal that gene families are subject to differential expression. The cellulase system has some differences from that of Trichoderma reesei; the distinction made between the activities of exocellobiohydrolases and endoglucanases needs to be re-appraised in both species. Current studies also seek to reconstruct the systems of degradation of lignocellulose and its individual components by heterologous expression of individual proteins in recombinant systems, and their use in mechanistic studies singly and in combinations.

Base Sequence↗
PubMed1998

Brown-midrib maize (bm1)--a mutation affecting the cinnamyl alcohol dehydrogenase gene.

Brown-midrib (bm) mutants of maize have modified lignin of reddish-brown colour. Although four independent bm loci are known, only one of the mutant genes has been previously identified. We report here that maize bm1, one of the less characterised mutants, shows severely reduced CAD activity in lignified tissues, resulting in the production of a modified lignin. Both the total lignin content and the structure of the polymer are altered by the mutation. We further describe the isolation and characterisation of the maize CAD cDNA and mapping of the CAD gene. CAD maps very closely to the known location of bm1 and co-segregates with the bm1 locus in two independent recombinant inbred populations. These data strongly support the premise that maize bm1 directly affects expression of the CAD gene.

Alcohol Oxidoreductases↗