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PubMed2001

Fractional and structural characterization of lignins isolated by alkali and alkaline peroxide from barley straw.

A sequential treatment of dewaxed barley straw with sodium hydroxide, different concentrations of hydrogen peroxide, and potassium hydroxide/sodium borate degraded various proportions of the original lignin and solubilized different amounts of the original hemicelluloses. The isolated lignin fractions were subjected to comprehensive structural characterization by UV, FT-IR, and (13)C NMR spectroscopy, and their chemical compositions were analyzed by alkaline nitrobenzene oxidation. All of the lignin fractions were typical of grass lignins and had weight-average molecular weights between 1750 and 2190. It was found that the peroxide treatment at low concentrations (< or =2.0%) resulted in a slight increase in the amount of carboxyl groups, whereas the treatment at a relatively high concentration of alkaline peroxide, such as at 3.0% H(2)O(2), led to a noticeable oxidation of the lignins, as shown by an increase of carboxyl groups. Moreover, the results obtained indicated that the successive treatments with alkali and alkaline peroxide under the conditions used did not significantly affect the beta-O-4 structures of lignins. Substantial amounts of etherified ferulic acids were cleaved by the sequential treatments with alkaline peroxide, as shown in the (13)C NMR spectra. The results underscore the structural differences between alkali- and alkaline peroxide-soluble lignins from barley straw.

Hordeum↗
PubMed2004

Straw bio-degradation by acidogenic bacteria and composite fungi.

A composite microbial system, including a strain of Candida tropicalis (W3), a strain of Lactobacillus plantarm(WY3) and three strains of basidiomycete pL104, pL113 and C33, was chosen to degrade corn straw. The final pH was acid owing to the inoculation of acidogenic bacteria, and under this condition the composite fungi system could produce complex enzyme to destroy the compact structure of corn straw. The experimental results showed that the biomass of composite fungi could reach up to maximum when the pH value was 4.5. Through the bio-degradation by combining acidogenic bacteria with the composite fungi system, the cellulose, hemi-cellulose and lignin degradation rates of corn straw powder were 26.36%, 43.30% and 26.96%, respectively. And the gross crude protein content increased 60.41%. This study provided the evidence for the feasibility of developing a composite microbial system with high capability of degrading straw lignocelluloses in order to make reasonable use of straw resource and protect rural eco-environment.

Agriculture↗
PubMed2006

Covalent linkages between cellulose and lignin in cell walls of coniferous and nonconiferous woods.

Covalent linkages between wall polysaccharides and lignin, especially linkage between cellulose and lignin were discussed by carboxymethylation technique of whole cell walls of coniferous and nonconiferous woods. Hydroxyl groups of plant cell walls polysaccharides were highly substituted, but not those of lignin by carboxymethyl groups under the used conditions, and separated into water-soluble and insoluble fractions by water extraction. Carboxymethylated wall polysaccharides linked covalently with lignin were distributed into the water-insoluble fractions. Composition of carboxymethylated sugar residues in the both fractions was analyzed quantitatively by 1H NMR spectroscopy after hydrolyzation with D2SO4 in D2O. More than half of cellulose linked covalently with lignin in coniferous wood, but only one-sixth of cellulose was involved in the linkage in nonconiferous wood. The major noncellulosic wall polysaccharides of coniferous wood also linked significantly with lignin. On the other hand, noncellulosic wall polysaccharides of nonconiferous wood were involved slightly in the covalent linkage with lignin. The situation of linkage between wall polysaccharides containing cellulose and lignin was visualized by scanning electron micrographs.

Cell Wall↗
PubMed1994

Whole grains--impact of consuming whole grains on physiological effects of dietary fiber and starch.

Much of the present research on the physiological effects of dietary fiber and starch has been done on sources isolated from the parent material, and it is not clear whether they have the same effects if fed in the intact or whole grain. For dietary fiber, physiological effect depends on extent of fermentation in the large intestine, and this is influenced by chemical composition, solubility, physical form, and presence of lignin or other compounds. All of these factors are altered by isolation of a fiber source from the whole grain, and hence effects of eating fiber vary. Similarly, physical form and presence in the whole grain will affect digestibility of starch in the small intestine, which in turn influences the glycemic response and colonic effects determined by the extent of malabsorption and entry into the colon. Starch that enters the colon is fermented and produces short-chain fatty acids, particularly butyrate, which is necessary to maintain a healthy mucosa. Hence, their presence within the whole grain may have important implications for health for both dietary fiber and starch. Evidence indicates that such effects are beneficial and that whole-grain consumption should be encouraged.

Dietary Carbohydrates↗
PubMed1971

Lignofibrils on the external cell wall surface of cultured plant cells.

Small strands and bundles of strands extend from the outside surface of suspension-cultured cells of Daucus, Ipomoea, and Phaseolus into the medium. This fibrous cell coat is present in all samples from various growth stages but appears to increase in quantity in the order Ipomoea < Phaseolus < Daucus. The bundles are often many microns in length and display great variation in frequency, size, and form. Identification of the composition of the strands and bundles as lignin is consistent with the following observations: alkaline nitrobenzene oxidation of the strands to compounds which resemble monomers of wood lignin; resistance of the strands to pronase, trypsin, pectinase, and lipase; strong irreversible adsorption of heavy metals; deposition of silver granules by treatment with silver nitrate-hexamine reagent; extraction of the bundles with aqueous dioxane (Björkman procedure); presence in quantity of a structured form of Klason lignin; and existence of material giving a positive test with the Wiesner reagent. Large individual strands (lignofibrils) from Phaseolus show the form of a flat ribbon with very thin branches at irregular intervals. This form does not vary with preparatory techniques, although its electron opacity does. Intercellular spaces display considerable structure and sometimes contain sheets of fibrillar material merging with both the middle lamella between the cells and the surface bundles facing the medium. These sheets are probably another form of association of the lignofibrils. It is suggested that natural fibrous lignin may be a much commoner component of plant tissue than suspected hitherto.

Cell Fractionation↗
PubMedDate not supplied

Structural differences between the lignin-carbohydrate complexes present in wood and in chemical pulps.

Lignin-carbohydrate complexes (LCCs) were prepared in quantitative yield from spruce wood and from the corresponding kraft and oxygen-delignified pulps and were separated into different fractions on the basis of their carbohydrate composition. To obtain an understanding of the differences in lignin structure and reactivity within the various LCC fractions, thioacidolysis in combination with gas chromatography was used to quantify the content of beta-O-4 structures in the lignin. Periodate oxidation followed by determination of methanol was used to quantify the phenolic hydroxyl groups. Furthermore, size exclusion chromatography (SEC) of the thioacidolysis fractions was used to monitor any differences between the original molecular size distribution and that after the delignification processes. Characteristic differences between the various LCC fractions were observed, clearly indicating that two different forms of lignin are present in the wood fiber wall. These forms are linked to glucomannan and xylan, respectively. On pulping, the different LCCs have different reactivities. The xylan-linked lignin is to a large extent degraded, whereas the glucomannan-linked lignin undergoes a partial condensation to form more high molecular mass material. The latter seems to be rather unchanged during a subsequent oxygen-delignification stage. On the basis of these findings, a modified arrangement of the fiber wall polymers is suggested.

Acetone↗
PubMed1981

An examination of factors which may affect the water holding capacity of dietary fibre.

1. Dietary fibre has a water holding capacity (WHC) and this is a function of the fibre source and method of measurement. Water can be associated with fibre either as trapped water or bound water. This makes it difficult to predict the ability of fibre to influence stool weight in humans. 2. Examination of various fibre concentrates for chemical composition, as neutral detergent fibre (NDF), acid detergent fiber (ADF) and lignin; structure, by scanning electron microscopy; WHC, by centrifugation, suggests that WHC is more a function of fibre structure than chemical composition. Cereal fibre and vegetable fibre have a different chemical composition and are structurally very distinct. Structure is also dependent on the method of fibre preparation. 3. Measurement of WHC by centrifugation gives an estimate of the water which can be bound and also trapped by the fibre. The amount of trapped water will depend on the structure of the fibre whereas bound water will depend on the chemical composition.

Cellulose↗
PubMed2004

Characterization of the radical scavenging activity of lignins--natural antioxidants.

The present work is devoted to studies of the radical scavenging properties of lignins, which are recognized as efficient antioxidants of natural origin. Radical scavenging efficiency of a series of lignins isolated from deciduous and coniferous wood species and 10 lignin related monomeric compounds were examined against 1,1-diphenyl-2-picrylhydrazyl (DPPH*) radical in homogeneous conditions using ESR and spectrophotometry methods. Some structure-activity relationships are proposed, pointing out the importance of the non-etherified OH phenolic groups, ortho-methoxy groups, hydroxyl groups and the double bond between the outermost carbon atoms in the side chain for increasing scavenger activity. Analysis of rate constants for the lignins-DPPH* interaction revealed the contribution of polymer molecular weight and pi-polyconjugation systems. The pi-conjugation systems of lignins operate as catalysts/activators of the interaction with DPPH*. Heterogeneity in terms of component composition (carbohydrate admixtures) and polydispersity is the factor which can decrease drastically the antioxidant efficiency of isolated lignins. The connection of the antibacterial effect of kraft lignin with radical scavenging activity of its soluble fraction was assumed.

Antioxidants↗
PubMed1980

The composition and dissolution of phytobezoars.

The plant fiber content (cellulose, hemicellulose, lignin, and tannins) in phytobezoars was determined. Phytobezoars were found to have a high concentration of polymerized tannins composed mainly of leucoanthocyanins and catechins. Unripe fruit was found to have a high concentration of the tannin monomers. It is concluded that the formation of phytobezoars is due to the polymerization of these tannin monomers. On the ingestion of unripe fruit, the hydrochloric acid of the stomach initiates the polymerization, resulting in a tannin-cellulose-hemicellulose-protein complex. This complex disintegrated in a crude preparation of cellulase. Cellulase is a simple and effective method of treating human gastric phytobezoars.

Bezoars↗
PubMed2001

Ripening-related changes in raspberry cell wall composition and structure.

Cell walls were prepared from the fruit of two cultivars of raspberry at three stages of ripening; green, white and red (ripe). The cultivars. Glen Clova and Glen Prosen, are subjectively classified, at harvest by growers, as soft and firm fruit, respectively. The cell walls were analysed for neutral sugar composition, uronic acid content, degree of methyl esterification, lignin and ferulic acid-derived dehydrodimers. Solid-state 31C NMR and diffuse reflectance infrared (DRIFT) spectra were acquired for the cell wall residues. For both cultivars the progression from green to white produced minimal changes, save for a reduction in pectin. NMR analyses indicated that the solubilized pectin was acetylated. Progression to the red (ripe) stage, in both cultivars, was accompanied by a reduction in the ordered cellulose and a dramatic reduction in pectin content and the degree of methyl-esterification. Significantly, the softer fruit (Glen Clova) exhibited greater reductions in both parameters, implicating increased pectin hydrolysis, as one of the main factors contributing to the difference in firmness between the cultivars. A relative increase in cell wall-associated protein was seen at the red stage. The nature and function of the protein(s) are, as yet unknown.

Cell Wall↗
PubMed2003

Variations in the cell wall composition of maize brown midrib mutants.

Most studies published thus far on the four brown midrib (bm) mutants (bm1, bm2, bm3, and bm4) in maize (Zea mays L.) have focused on one or two individual mutants, and comparisons between studies have been difficult because of variation in genetic backgrounds, maturity, and source of tissue. Detailed analyses of the stalks of the four bm single mutants and a bm1-bm2 double mutant in a common genetic background (inbred A619) revealed structural and compositional changes in their isolated cell walls and lignins compared to the wild-type inbred. 2D-NMR revealed a significant presence of benzodioxane units in the bm3 isolated lignin. 1D (13)C NMR revealed increased aldehyde levels in the bm1 and bm1-bm2 mutants compared to the wild-type inbred. The bm3 and bm1-bm2 mutants contained less Klason lignin in the isolated cell walls. The bm1, bm3, and bm1-bm2 mutants contained approximately 50% less esterified p-coumaric acid with noticeably elevated levels of ferulate in the bm3 mutant. A difference among bm mutants in the solubility of p-coumaric acid-lignin complexes during cellulase enzyme treatment was also discovered, suggesting that the bm mutations might also differ in the structural organization of lignin.

Aldehydes↗
PubMed2004

Functional reclassification of the putative cinnamyl alcohol dehydrogenase multigene family in Arabidopsis.

Of 17 genes annotated in the Arabidopsis genome database as cinnamyl alcohol dehydrogenase (CAD) homologues, an in silico analysis revealed that 8 genes were misannotated. Of the remaining nine, six were catalytically competent for NADPH-dependent reduction of p-coumaryl, caffeyl, coniferyl, 5-hydroxyconiferyl, and sinapyl aldehydes, whereas three displayed very low activity and only at very high substrate concentrations. Of the nine putative CADs, two (AtCAD5 and AtCAD4) had the highest activity and homology (approximately 83% similarity) relative to bona fide CADs from other species. AtCAD5 used all five substrates effectively, whereas AtCAD4 (of lower overall catalytic capacity) poorly used sinapyl aldehyde; the corresponding 270-fold decrease in k(enz) resulted from higher K(m) and lower k(cat) values, respectively. No CAD homologue displayed a specific requirement for sinapyl aldehyde, which was in direct contrast with unfounded claims for a so-called sinapyl alcohol dehydrogenase in angiosperms. AtCAD2, 3, as well as AtCAD7 and 8 (highest homology to sinapyl alcohol dehydrogenase) were catalytically less active overall by at least an order of magnitude, due to increased K(m) and lower k(cat) values. Accordingly, alternative and/or bifunctional metabolic roles of these proteins in plant defense cannot be ruled out. Comprehensive analyses of lignified tissues of various Arabidopsis knockout mutants (for AtCAD5, 6, and 9) at different stages of growth/development indicated the presence of functionally redundant CAD metabolic networks. Moreover, disruption of AtCAD5 expression had only a small effect on either overall lignin amounts deposited, or on syringyl-guaiacyl compositions, despite being the most catalytically active form in vitro.

Alcohol Dehydrogenase↗
PubMed1988

Effect of cooking, pH and polyphenol level on carbohydrate composition and nutritional quality of a sorghum (Sorghum bicolor (L.) Moench) food, ugali.

1. The present work was undertaken to study the effects of cooking, pH and polyphenol level on carbohydrate composition and nutritional quality of sorghum (Sorghum bicolor (L.) Moench). Three different sorghum varieties; Dabar, Feterita and Argentine containing zero, intermediate to low and high levels of polyphenols respectively were used in the study. From these varieties uncooked, uncooked acidified, cooked, and cooked acidified diets were prepared. Diets were characterized with regard to resistant starch (RS), dietary fibre (DF), acid-detergent fibre (ADF) and amino acid content. Raw materials were further analysed for content and composition of non-starch polysaccharides and Klason lignin. The nutritional properties were studied in balance trials with rats. True protein digestibility (TD), biological value (BV), net protein utilization, digestible amino acids, digestible energy (DE) and digestible DF were used as criteria in the nutritional study. 2. Cooking at neutral and acid pH resulted in significantly higher assayed values for DF. Increase in DF could be accounted for by formation of RS. Approximately 50% of RS was recovered in the faeces. 3. In vitro values for protein associated with ADF and in vivo balance values using rats suggest that an endosperm protein fraction, kafirins, was made unavailable during cooking. This resulted in reduced TD and increased BV. It is assumed that unavailable kafirins serve as a nitrogen source for microflora in the hind-gut. 4. Dietary polyphenols changed the excretory route for N from urine to faeces. This resulted in lower TD and higher BV in Argentine (high in polyphenols) than in Dabar and Feterita (low in polyphenols), although dietary lysine (first limiting amino acid) was the same in the three varieties. 5. Variation in DE of the diets was attributed to DF, RS and the amount of faecal protein, which in turn were influenced by undigested kafirins and polyphenols.

Animals↗
PubMed1991

Gastrointestinal implications in pigs of wheat and oat fractions. 1. Digestibility and bulking properties of polysaccharides and other major constituents.

The present work was undertaken to study the gastrointestinal effects of wheat and oat dietary fibre (DF) using 40-50 kg pigs cannulated in the terminal ileum. The variables studied were: chemical characteristics of the DF, ileal and faecal digestibility of nutrients and bulking properties of polysaccharides and other major constituents. The wheat products studied included refined wheat flour and wheat fractions rich in the following botanical components: aleurone, pericarp/testa and bran. The oat products used were rolled oats and oat bran. The products varied considerably in DF content (g/kg dry matter) and composition; non-starch polysaccharides (NSP) and Klason lignin content ranged from 34 and 1 g/kg respectively in wheat flour, to 465 and 92 g/kg in pericarp/testa. The main NSPs in the wheat were arabinoxylans (AX) (64-69%) and cellulose (15-31%) and in oats mixed linked beta(1----3; 1----4-D-glucans (beta-glucans; 46-63%) and AX (28-32%). The lowest content of soluble NSP was found in the lignified wheat fractions (bran and pericarp/testa) and the highest in oat bran. Eight diets were produced using the wheat and oat products and studied in two series of experiments using wheat flour as the DF-depleted control. The diets in Expt 1 were based on wheat flour and three iso-DF enriched diets prepared by adding DF from the fractions rich in wheat aleurone, pericarp/testa or bran. In Expt 2, oat bran was added to wheat flour to achieve the same DF intake level as in Expt 1. This series also included diets based on rolled oats and rolled oats plus oat bran. Starch was almost completely digested in the small intestine (0.97-1.00). However, there was a tendency to a slightly lower digestibility of oat starch compared with wheat starch. The recovery of wheat NSP in ileal digesta was 82-104% compared with 64-66% for oats. The low recovery of NSP in oat diets was primarily due to the low recovery of beta-glucans (25-36%). In the large intestine NSP and starch residues were extensively degraded. For the DF-depleted control diets or diets based on oats, 8-17% NSP survived breakdown while in the diets enriched with aleurone, pericarp/testa or bran fractions, NSP recovery was 33, 50 and 38% respectively. Fermentative breakdown of carbohydrates in the large intestine was estimated to contribute between 10 and 24% of the energy for maintenance. Energy derived from the inflow of organic acids from the ileum contributed an additional 1-4% of maintenance energy.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed1989

Disappearance of hemicellulosic monosaccharides and alkali-soluble phenolic compounds of normal and brown midrib sorghum x sudangrasses fed to heifers and sheep.

Eight yearling Holstein heifers (330 kg) were utilized in two 4 x 4 Latin squares. Diets were normal and brown midrib genotypes of Redlan x Greenleaf and Redlan x Piper varieties of ensiled first-cutting sorghum-sudangrass harvested at early head stage of maturity. Composition of hemicellulosic monosaccharides and alkali-soluble lignin phenolic compounds in feeds and corresponding digestibilities were estimated. Arabinose, xylose, and uronic acids were more digestible in brown midrib genotypes than in normal genotypes. p-Coumaric acid disappearance was higher in heifers consuming normal genotypes than in those on brown midrib mutants. In a second experiment, four Suffolk wethers with ruminal, duodenal, and ileal cannulae were utilized in a 4 x 4 Latin square design. Diets were second-cutting sorghum-sudangrass harvested at prehead stage of maturity as baled hay. Digestibilities were determined in the same manner as for heifers. Brown midrib genotypes had higher hemicellulosic monosaccharides, galactose, and uronic acids than did normal genotypes. Xylose content of the brown midrib mutant of Redlan x Piper was higher than that of the corresponding normal genotype. Total tract galactose digestibility was higher in brown midrib genotypes than in normal genotypes. Total tract hemicellulose digestibility (estimated by summing fractional digestibilities of hemicellulosic monosaccharides) was higher in brown midrib mutants than in normal genotypes.

Animal Feed↗
PubMed2000

[Role of the iodine microelement in nutrition and prophylaxis of various diseases].

The article describes various iodine deficiency-related disorders. Iodine deficiency is the chief cause of goiter, mental retardation and other disorders. It is an acute problem the whole mankind face, Ukraine included. In this country, the following territories are biogeochemical provinces: Zhitomir, Lvov, Ternopol, Volyn regions and other regions of Ukraine, and some regions of the Crimea as well. It is necessary that food rations be supplemented with different iodine preparations with the view of preventing iodine deficiency. Concentrates of food fibre recovered from cell walls of various plant raw stuff and containing complexes of structural carbohydrates and lignin can be used in combination with iodine compositions in dealing with the above problem.

Animals↗