Solid-state 13C NMR study of palm trunk cell walls

Trunk material from the oil palm Elaeis guineensis was dissected into parenchyma and vascular bundle fractions, which were individually examined by ¹³C solid-state nuclear magnetic resonance at low field (25 MHz). Cross-polarisation and magic-angle spinning were used with dipolar dephasing to reveal the aromatic carbons of lignin free from interference by carbohydrate. The lignin contents of the parenchyma and vascular bundles were found to be 240 g kg^?1 and 130 g kg^?1, respectively. The lignin appeared to contain a high proportion of aryl ether-linked syringyl units, but little or no ferulic or p-coumaric acid. The cellulose of both fractions had a high proportion of the crystalline component. The acetyl content was c 6 mol %C. The in-vitro digestibility of the two fractions was measured using the rumen liquor-pepsin method and was found to be low compared with forage materials: 19.5% in the parenchyma and only 11.1% in the vascular bundles.     

Comparison of common lignin methods and modifications on forage and lignocellulosic biomass materials

BACKGROUND: A variety of methods have been developed for estimating lignin concentration within plant materials. The objective of this study was to compare the lignin concentrations produced by six methods on a diverse population of forage and biomass materials and to examine the relationship between these concentrations and the portions of these materials that are available for utilisation by livestock or for ethanol conversion. RESULTS: Several methods produced lignin concentrations that were highly correlated with the digestibility of the forages, but there were few relationships between these methods and the available carbohydrate of the biomass materials. The use of Na₂SO₃ during preparation of residues for hydrolysis resulted in reduced lignin concentrations and decreased correlation with digestibility of forage materials, particularly the warm‐season grasses. CONCLUSION: There were several methods that were well suited for predicting the digestible portion of forage materials, with the acid detergent lignin and Klason lignin method giving the highest correlation across the three types of forage. The continued use of Na₂SO₃ during preparation of Van Soest fibres needs to be evaluated owing to its ability to reduce lignin concentrations and effectiveness in predicting the utilisation of feedstuffs and feedstocks. Because there was little correlation between the lignin concentration and the biomass materials, there is a need to examine alternative or develop new methods to estimate lignin concentrations that may be used to predict the availability of carbohydrates for ethanol conversion. Copyright © 2011 Society of Chemical Industry     

Lignin in the ‘cell contents’ fraction of tropical forages

In several tropical forage species the neutral detergent extraction used to determine cell wall and cell contents fractions solubilised a substantial UV‐absorbing polymeric fraction which appeared to be a soluble lignin–carbohydrate complex. A crude product was isolated from spear grass (Heteropogon contortus) with a yield of 30 g kg^?1. In other forages an acetyl bromide method was used to estimate lignin extractable by neutral detergent. For eight species of tropical grasses this gave the following values: Aristida calcyna, 38; Mitchell grass (Astrebla squarrosa), 37; Chloris gayana, 31; Eragrostis sp, 37; spear grass, 49; Iseilema membranaceum, 35; Panicum maximum, 36; Sorghum sp, 42; Themeda triandra, 79 g kg^?1. The levels in two legumes were: Alysicarpus bupleurifolius, 29; Macroptilium atropurpureum, 27 g kg^?1 dry matter. Sequential extractions on spear grass and Mitchell grass showed that most of the 50% dioxan‐soluble fraction was also soluble in neutral detergent, raising the possibility that ‘dioxan lignin’, on which studies of forage lignin structure in other species have been conducted, would be found in the cell contents fraction rather than in the fibre fractions on which lignin analyses have been performed. Addition of dioxan extractives reduced the in vitro neutral detergent fibre (NDF) digestibility of spear grass and Mitchell grass. © 2002 Society of Chemical Industry     

Chemical composition of some forages and various residues from feeding value determinations

NDF, ADF, ‘cellulose’ and IVOMD residues, from feeding value determinations, were prepared from some forages, including straw, alkali-treated straw, grass and lucerne samples. The crude protein, cellulose, hemicellulose, uronic acid, Klason lignin, lignin and ash contents of these residues and the corresponding original forage samples were determined together with the relative composition of the neutral sugar constituents after acid hydrolysis. Cellulose, hemicellulose and Klason lignin were the main components in the NDF fractions but substantial amounts of crude protein (1–6%) also remained. Cellulose and Klason lignin were the main components in the ADF fractions, but 7–14% of the fractions was hemicellulose and 1–4% crude protein. Cellulose was the main component in the ‘cellulose’ fractions, but they also contained 8–13% hemicellulose, 2–7% Klason lignin and 2–11% ash. The composition of the IVOMD residues showed that cellulose and hemicellulose had been dissolved to about the same amounts (70–80%) and that most of the Klason lignin remained.     

Chemical and in vivo evaluation of a brown midrib mutant of Zea mays. I. Fibre, lignin and amino acid composition and digestibility for sheep

Two types of corn (maize) were used which were genetically identical except for a mutant gene (bm₁) in one which reduced the type and amount of lignin produced compared with the normal plant (Tr). The Tr plant appeared to have only slightly lower digestibilities of dry matter and fibre for sheep even though the protein contents of the cornstalks, normally less in the Tr, were equalised by supplementation with soya bean protein. Comparing the acid-detergent method of fibre and lignin determination with an acid-pepsin method revealed that the former method gave values considerably lower than the latter. The alkali—lignin contents of the bm₁ were higher than the acid—detergent lignins which must under-estimate the true lignin content. The acid—pepsin method gave fibre and lignin concentrations which were more closely correlated with rumen digestion of the diets as shown by dry matter loss of the diets suspended into the rumen in nylon bags. This technique also revealed there was a significant increase in the rate of rumen digestion after 69 to 74 h of incubation. Digestion of lignin on the Tr diet could be explained by loss of ferulic and p-coumaric acids. The reduced lignin and p-coumaric acid content of the bm corn was associated in young plants with a low phenylalanine content but normal tyrosine content suggesting that the genetic block in lignin synthesis in this plant may occur between prephenic acid and phenylalanine.     

Digestion of the dry matter, nitrogen, phosphorus, sulphur, calcium and detergent-fibre fractions of the seed and pod of Stylosanthes humilis contained in terylene bags in the bovine rumen

The rates of digestion of the separated seed and pods of Stylosanthes humilis in Terylene bags in the rumen of cattle were studied. The rates of disappearance of dry matter, N, P, S, Ca and detergent fibre fractions and lignin were examined. The magnitude of the errors of determination were assessed statistically for dry matter digestion. Four bag replications were necessary to detect differences of 20% between samples. The cell contents constituted 80% of the seed dry matter, but only 20% of the pod dry matter. Lignin content of seed was negligible (0.5%), but was high in pods (18%). The seed was rapidly digested (77% of dry matter after 48 h). This was largely due to almost complete digestion of the cell contents. The pod was only slightly digested (14% at 48 h). Protein and phosphorus appeared to be selectively solubilised, but calcium was only slowly solubilised in both seed and pod. The cell-wall constituents present were compared to the concentrations of hemicellulose and cellulose found in seed and pod by more definitive chemical methods.     

Changes in cell-wall carbohydrates and lignin of some forage-type millets as affected by growth stage

Changes in the cell-wall carbohydrates and lignin of bajra (Pennisetum typhoides), jowar (Sorghum vulgare) and napier (Pennisetum purpureum)–bajra hybrids (NB₂₁) as affected by growth stage are reported. With growth of the plants the concentrations of α-cellulose and hemicellulose increased in the stems. In bajra and jowar this increase was gradual up to 60–70 days growth stage followed by a decline and a subsequent rise towards maturity. In contrast, in NB₂₁, α-cellulose continued to rise gradually throughout the growth period. The concentration of hemicellulose was much higher in the stems than in the leaves of NB₂₁. With the ageing of the plants the lignin content increased in all these forage crops. In NB₂₁ the stems contained more lignin than the leaves at all stages of maturity. Fluctuations in the contents of lignin, cellulose and hemicellulose followed similar trends indicating that possibly they are components of a common matrix in the cell wall. In NB₂₁ the water-soluble carbohydrates continued to rise throughout the growth period unlike other forage crops. The protein content decreased as the NB₂₁ plants matured. The protein content of the leaves of these plants was always higher than that of the stems. The oxalates gradually declined with the maturation of the plants.     

Physico-chemical characterisation and tensile mechanical properties of Agave americanaL. fibres

In this paper, the physico-chemical and mechanical properties of Agave americana L. fibre are studied to explore the possibilities of using this fibre in textile industry. Three different processings for extracting fibres from the leaf of Agave americana L. plant were investigated: (i) raw fibres manually extracted, (ii) fibres extracted by retting leaves in seawater and (iii) fibres extracted after hydrolysis treatment of the leaves in distilled water. Chemical composition (cellulose, lignin and hemicellulose contents), physical properties (density, fineness and crystallinity) as well as mechanical properties of the resultant fibres were measured. The chemical composition reveals that the Agave americana L. fibre has a cellulose content at the order of 62% which is similar to that of other lignocellulosic fibres. The distilled water extracted fibres developed the highest cellulose content. Lignin content of Agave americana L. fibre is low compared to other natural fibres (2.4%) and seawater-extracted fibres generated the lowest lignin content (2.12%). Fourier transform infrared spectra (FTIR) and x-ray diffractometry of all extracted fibres revealed the same chain conformation. X-ray diffractograms showed that cellulose I is the main crystalline constituent. Concerning physical and mechanical properties, raw fibres were characterised by the lowest density (0.9) and the highest crystallinity (51.2%), they are also stronger and less extensible than the other two fibres. In this paper, we attempt to study the effect of extraction in water on the mechanical and physical properties of Agave americana L. fibres.     

Analysis of carbohydrates in the jute plant (Corchorus capsularis)

Jute plants (Corchorus capsularis) were fractionated into bark and stick. Jute fibre was produced from the bark by retting in water. Polysaccharides and lignin (estimated as Klason lignin) were the major constituents of the three jute fractions. Glucose, fructose, sucrose, six low-molecular weight sugar alcohols (glycerol, erythritol, threitol, rhamnitol, arabinitol, and mannitol), and two inositols (myo-inositol and scyllitol) were identified and quantified in the bark; all these compounds, except rhamnitol were also measured in the stick. Cellulose, xylans and pectins were major polysaccharide constituents in the three jute fractions. During fibre production by retting, extractives and pectic polysaccharides were solubilised or degraded, producing a fibre material enriched in cellulose and xylans.     

Quantitative and qualitative study of spelt and wheat fibres in varying milling fractions

The fibre composition of four spelt genotypes and of three wheat genotypes was studied on three grindings: bran, whole bare grains flour for all genotypes, and whole hulled grains flour for spelt only. Insoluble fibre and soluble fibre contents were measured after removal of proteins, starch and ashes from the sample (Lee, Prosky, & De Vries, 1992). Cellulose, hemicellulose and lignin contents were measured according to the same principles with different chemical degradations of the sample (Van Soest & Wine, 1967). Spelt and wheat bran and whole grain flour displayed significant statistical differences for hemicellulose and cellulose contents. Variability amongst the spelt genotypes was much higher than amongst the wheat genotypes. The study also highlighted the special profile of the true baking variety Ressac and the richness in fibres of the landrace 140. Finally, various methods of measurement were compared and a combination of these methods was proposed for cereal grains dietary fibre analysis.     

Yield and composition of cell wall residues isolated from various feedstuffs used for non-ruminant farm animals

The contents of cell wall residue were measured in 14 common feedstuffs used for non-ruminant farm animals by utilising a technique involving pronase and α-amylase treatments. Comparison with the contents of neutral detergent fibre (NDF) revealed that the NDF procedure underestimated cell wall contents in the dicotyledonous plant materials. The losses of cell wall material due to the neutral detergent solution were correlated (r=0.931, P<0.01) with the amount of pectic substances present in the cell wall residues of the dicotyledonous plant materials. Cell wall residues were analysed for starch, crude protein, polysaccharides, condensed tannins, sulphuric acid lignin, acetyl bromide lignin, and ash. Condensed tannins in the cell wall residues of sorghum, rapeseed meal and field bean resulted in a large protein contamination (11.3–26.6%) of these residues and to an overestimation of their lignin content. Compositions of polysaccharides are discussed from chemical and nutritonal viewpoints.     

Roughages for ruminants--net energy value in relation to chemical composition

The use of net energy values as measures of the nutritive value of roughages is discussed and reference is made to the principal energy-yielding substrates present. Using data obtained for twelve dried grasses the relationships between net energy values for maintenance and for fattening and single constituents of the dry matter are examined. A comparison of the energy values determined for seven forages, with values predicted from their contents of crude protein, crude fibre or lignin has also been made. These studies suggest that the determination of hemicellulose, cellulose or lignin contents offers little advantage over the determination of acid-detergent fibre or of crude fibre for predicting energy values. Predictions of energy values based upon in vitro digestibility determinations have been found to compare favourably with those based upon chemical analysis. The determination of in vitro digestibility has the added advantage that it may also give some guide to voluntary intake and hence reflect more fully the nutritive value of a roughage.     

Lignin Impact on Fibre Degradation: 1—Quinone Methide Intermediates Formedfrom Lignin DuringIn VitroFermentation ofCorn Stover*

Experiments were conducted to determine whether formation of quinone methide intermediates from lignin occurs during ruminal fermentation of corn stover, as indicated by nucleophilic addition reaction with sulphur-containing reducing agents. Corn stover leaf and stem fractions harvested at full maturity were incubated in buffered ruminal fluid without reducing agents or with (NH₄)₂SO₄ (S-control), Na₂S.9H₂O, cysteine-HCl (cysHCl), or cysHCl plus Na₂S.9H₂O; and in only buffer with or without cysHCl plus Na₂S.9H₂O. Mixed reducing agents (cysHCl plus Na₂S.9H₂O) enhanced ( P< 0.001) in vitro fibre degradation after 48 h, tended to increase solubilisation of fibre ( P =0.07) and dry matter ( P =0.06) in buffer alone, and elevated ( P< 0.001) S-content of residual fibre. In vitro incorporation of S into the undegraded fibre was determined for corn stover fractions of varying lignin compositions that were harvested at two maturities (early dent and full maturity) in 2 years. Extent of fibre degradation was correlated with extent of S-incorporation ( r =-0.54, P< 0.001), and with lignin methoxyl content ( r =-0.84, P< 0.001). The negative association of lignin methoxyl content with digestibility is explained by the relative likelihood of quinone methide intermediate formation from guaiacyl and syringyl units in lignin.     

Metabolic changes of biochemical constituents in developing fennel seeds (Foeniculum vulgare)

Fennel (Foeniculum vulgare) is the major spice/condimental crop of Haryana, generally used in India for preparing pickles and in vegetable cooking. Flowers were tagged at anthesis, fennel seeds (local variety) were collected at 1-week intervals after 40 days from anthesis for studying biochemical constituents. Moisture and protein contents decreased significantly with the advancement of seed development. Oil content ranged from 68 to 135·7 g kg^?1 (dry weight basis), which increased with seed development. The oil content was greater in mature seeds. The presence of phytate (11·35–13·10 mg g^?1) was also observed, which affects the availability of Zn and Fe. Fennel seeds were found to be a rich source of micro- and macroelements. Neutral detergent fibre, acid detergent fibre, cellulose and lignin contents increased significantly with the advancement of seed development. Oleic and linoleic fatty acids were found to be major fatty acids and variable proportions of different fatty acids were observed.     

Storage of fresh and ensiled forages by freezing affects fibre and crude protein fractions

The effect of freezing on fibre and crude protein fractions of forages was determined. Fresh and ensiled lucerne and fresh bromegrass were processed immediately after collection or stored at ?25°C for 1 day or 1, 6 or 12 months before drying at 55°C. Samples were frozen quickly by submersion in liquid nitrogen or slowly at ?25°C. Samples which were not frozen were processed immediately or after 1 h delay at room temperature. All treatments were replicated (n = 3). Samples were analysed for crude protein (CP), trichloroacetic acid soluble CP (TSCP), phosphate buffer soluble CP (BSCP), neutral detergent insoluble CP (NDCP), acid detergent insoluble CP (ADCP), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent sulphuric acid lignin (lignin) and ash. Freezing decreased BSCP and increased NDCP by more than 40% for bromegrass. Freezing also changed NDF, ADF, lignin, ash, CP and ADCP in different ways depending on forage type and length of time frozen. No significant effects were observed for method of freezing or a 1-h delay in processing. An additional experiment showed that freeze-drying resulted in less insoluble protein than ovendrying. Prior freezing of forages appeared inconsistently to change the extent of gaseous loss during drying, and resulted in precipitation of protein. These changes also affected fibre estimates. Fresh forages should not be frozen and thawed before analysis of protein or fibre fractions.     

New potato fibre for improvement of texture and colour of wheat bread

The aim of this project was to compare the functional properties of five fibre fractions by baking of wheat bread by substitution 0, 4, 8 and 12 w/w% of wheat flour using dry potato pulp (Fibre 1), a commercial potato fibre (Fibre 2), two fibre prepared from potato pulp by enzymatic hydrolysis (Fibre 3 and 4), and one solubilised fibre (Fibre 5). The effect of chemical composition of fibre on texture, colour, specific weight and volume of wheat bread was studied using objective methods for measurement of texture characteristics, colour (L, a, b) and sensory analysis. Dry potato pulp, Potex (Fibre 2) and two enzymatically prepared fibre powders (Fibre 3 and 4) with a high concentration of lignin and insoluble non-starch polysaccharides (INCP) had a detrimental effect on bread quality by substitution of more than 8% of the wheat flour by fibre. The detrimental effect was mainly due to increased hardness, deformation energy, modulus and gumminess. Multiple linear regression analysis with forward selection was used for determination of the relationship between quality characteristics and of soluble non-starch polysaccharides (SNSP), insoluble non-starch polysaccharides (INCP), cellulose and lignin. The enzymatic solubilised fibre (Fibre 5) with a high concentration of soluble fibre and a low concentration of cellulose and lignin could be used for substitution of at least 12% wheat flour for baking of bread with an attractive colour, delicious texture and flavour.     

Lignification of switchgrass (Panicum virgatum) and big bluestem (Andropogon gerardii) plant parts during maturation and its effect on fibre degradability

Five cultivars of switchgrass (Panicum virgatum L) and four cultivars of big bluestem (Andropogon gerardii Vitman) were harvested at vegetative, boot and heading stages of maturity. Leaf and stem fractions were analysed for detergent fibre composition and 48-h ruminal in-vitro degradability, ester- and ether-linked non-core lignin phenolic acids, and core lignin composition. Big bluestem leaves contained more neutral detergent fibre than switchgrass, but general composition of the fibre did not differ. Stem fibre of switchgrass had relatively lower levels of cellulose and lignin at the vegetative stage than observed in big bluestem. Esterified and etherified p-coumaric and ferulic acid concentrations were generally higher in switchgrass plant parts. Yield of nitrobenzene oxidation products from core lignin was greater for switchgrass leaves, but very little difference in composition was noted. Leaf tissue contained lower concentrations of all lignin components than stems. Maturation resulted in increased total lignification, but all components did not respond in the same manner. Variation for all measures of lignification seemed to be as great within species as between the grass species. Degradability of fibre declined with maturation. The only species difference was that switchgrass fibre was more degradable at the vegetative stage. Relationships between lignification and fibre degradability were in agreement with some, but not all, previously reported relationships. Concentration of core lignin was only a significant predictor of fibre degradability when the relationship was examined across maturity stages. Within a stage of maturity, lignin composition was more closely related to fibre degradability than was concentration. However, the best predictors of fibre digestibility differed among species, plant part and maturity.     

Chemical,nutritive, deoxynivalenol and zearalenone content of corn relative to the site of inoculation with different isolates of Fusarium graminearum

Kernels from two samples of 18 ears of corn were hand-shelled into three fractions (Fl, F2 and F3) relative to the site (F3) where the ears had previously been inoculated with one of four isolates of Fusarium graminearum (Schwabe). F3 and Fl were from the nearest and remotest parts of the ear, respectively, to the inoculation site. Ears of uninoculated control corn were processed in the same manner. The resulting 30 samples were analysed, after grinding (20 mesh), for deoxynivalenol (DON), zearalenone (ZEA), ergosterol (EGS), dry matter (DM), 200 kernel weight, Kjeldahl nitrogen (N), ether extract, ash, sugar, starch, acid and neutral detergent fibre (ADF, NDF, respectively), cellulose, hemicellulose and lignin. The true metabolisable energy (TME), TME corrected to zero N balance (TME_n), true available amino acid (TAAA) and true DM digestibility (TDMD) contents of these samples and corn to which 4, 16 or 64 mg purified DON kg^?1 were added, were determined using adult White Leghorn chickens. The DON, ZEA, EGS, N and ash contents were higher (P<0.001), and ether extract, TME and TME_n values were lower (p<0.01) in F3 than in Fl. Higer avilabilites accured for aspartic and glutamic acids, isoleucine, leucine and histidine in F2 and F3 than F1 (P<0.05). Carbohydrate and fibre values varied little (p>0.05) among fractions either within or among incoulation treatments. Sources of Fusarium inoculate influenced (P<0.05) the DON, ZEA, N, fat and TDMD of the corn. The TME_n and total TAAA of corn decreased (P<0.001) when purified DON was added. Moderate relationships (r=0.57?0.73) occurred between DON and ZEA, EGS and N. In general, these results are similar to those for wheat, and indicate that chemical and nutritive content of feedingstuffs may be increased when they are infected by toxigenic fungi.     

Sources of error in dietary fibre analysis

The following error sources in the present dietary fibre (DF) analytical methods were investigated: (1) the omission of the protease treatment of samples may modify the results by increasing the Klason lignin fraction and altering the content and/or distribution of polysaccharides; (2) some soluble dietary fibre (SDF) constituents can be retained in the insoluble dietary fibre (IDF) matrix affecting the insoluble and soluble fraction distribution; (3) protein, ash and blank corrections in gravimetric analysis involve a lack of precision, over- or undervaluing the actual DF contents; (4) the Klason lignin fractions obtained by acid hydrolysis of DF residues are made up of different components and artifacts besides lignin.

These studies included both new observations and additional quantitative evidence on error sources previously mentioned in the literature. In some cases the published methods were modified to emphasize the methodological errors.     

Preparation and characterisation of dietary fibre from sugar beet pulp

Dried sugar beet pulp was ground and washed with 95% ethanol in order to obtain a colourless and odourless product which could be used as dietary fibre after drying and sieving. Sugar beet fibre had the same chemical composition as the initial pulp: 26–32% of hemicelluloses, 22–24% cellulose, 21.5–23% uronic acids, ～1–2% lignin, ～7–8% protein, 7.5–12% ash and ～0.5% residual sucrose. The main physicochemical properties such as density, cation exchange capacity (～0.6 meq g^?1) and water holding capacity (24–32 g g^?1) were determined. The water holding capacity of sugar beet fibre was only slightly affected by pH and ionic strength (adjusted by NaCl or CaCl₂) but it held less water in the H⁺ form than in the salt form, Na⁺ or Ca²⁺.