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PubMed1999

Accuracy of Klason lignin and acid detergent lignin methods as assessed by bomb calorimetry.

An accurate method for estimation of lignin concentration is important for prediction of the digestible energy content of livestock feeds. The accuracy of lignin concentration estimates based on the Klason lignin and acid detergent lignin methods was compared. Ten diverse forage samples were analyzed for protein, carbohydrates, lipids, organic acids, ash, lignin (by both methods), and gross energy. The accuracy of the two lignin concentration estimates was examined by comparing the measured forage gross energy to a gross energy value calculated from the compositional analysis. Use of the acid detergent lignin estimate in this gross energy calculation accounted for 68-84% of the forage gross energy compared to 85-97% of the gross energy using Klason lignin. These results indicate that while Klason lignin estimates are substantially higher than acid detergent lignin estimates, Klason lignin is the more accurate lignin method and does not overestimate lignin because gross energy recoveries were less than 100%.

Animal Feed↗

PubMedDate not supplied

Controlled release of aldicarb from lignin loaded ionotropic hydrogel microspheres.

Aldicarb loaded microspheres of carboxymethyl cellulose, CMC, of various compositions were prepared with the crosslinking action of Al(III). Into these microspheres, lignin was introduced as a filler to further regulate the rate of release. The encapsulation efficiency was low (4.15-13.00%) due to the high water solubility of aldicarb. Release into aqueous media was quite rapid and almost complete within 24h. Initial stages of the release (60% of AS released) was investigated to determine the release mechanism and it was found that release from the microspheres was governed by Fickian diffusion. Among the various parameters, the ratio of lignin to CMC and aldicarb to CMC were found to be influential on the rate of release from the crosslinked CMC-lignin microspheres. The soil behaviour confirmed the delayed release effect of the controlled release formulation compared to Temik (a commercial preparation of aldicarb), especially when lignin was incorporated.

Aldicarb↗

PubMed1996

Analysis of Lignin-Polysaccharide Complexes Formed during Grass Lignin Degradation by Cultures of Pleurotus Species.

A brown material, precipitable with ethanol, was formed during wheat straw and lignin degradation by liquid cultures of different species of Pleurotus. Fourier transform infrared spectroscopy and cross-polarization and magic-angle-spinning (sup13)C nuclear magnetic resonance spectroscopy showed that most of the precipitable material was formed from exopolysaccharide secreted by the fungus but it also contained an aromatic fraction. The results of acid hydrolysis, methylation analysis, and Smith degradation indicated that the major exopolysaccharide produced by these fungi is a (1(symbl)3)-(beta)-glucan branched at C-6 every two or three residues along the main chain. The presence of lignin or straw in the culture medium had little effect on the composition and structure of the extracellular polysaccharide. Cross-polarization and magic-angle-spinning (sup13)C nuclear magnetic resonance spectroscopy provided an estimation of the aromatic content of the lignin-polysaccharide complexes, assigning 20% of the total (sup13)C signal in the material recovered from cultures of Pleurotus eryngii in lignin medium to aromatic carbon. Analytical pyrolysis indicated that the aromatic fractions of the lignin-polysaccharide complexes were derived from lignin, since products characteristic of pyrolytic breakdown of H (p-hydroxyphenylpropane), G (guaiacylpropane), and S (syringylpropane) lignin units were identified. These complexes cannot be fractionated by treatment with polyvinylpyrrolidone or extraction with lignin solvents, suggesting that the two polymers were chemically linked. Moreover, differences in composition with respect to the original lignin indicated that this macromolecule was modified by the fungi during the process of formation of the lignin-polysaccharide complexes.

Journal Article↗

PubMed1996

Elucidation of factors associated with the maturity-related decline in degradability of big bluestem cell wall.

Big bluestem (Andropogon gerardii) forage samples were collected from three ungrazed, annually burned pastures at 38, 58, and 97 d after burning. Cell wall material received five treatments: chlorite delignification, chlorite delignification plus alkali extraction, NaOH, NaOCH3 in methanol, or NaBH4. Untreated and treated cell walls were analyzed for carbohydrate composition (glucose, xylose, arabinose, galactose, and uronic acids), acetyl bromide lignin, acid detergent lignin, alkali-labile phenolics (p-coumaric and ferulic acids), acetyl groups, and 24- and 72-h in vitro degradabilities of neutral monosaccharides. A number of compositional features, notably concentrations of xylose, core lignin as measured by acetyl bromide lignin, alkali-labile phenolics, and acetyl groups, were well related to the decline in cell wall degradability that occurred with increasing maturity of big bluestem. p-Coumaric acid increased with increasing maturity to a greater extent than did ferulic acid. Acid detergent lignin was not well related to degradability of the cell wall for either the untreated or chemically treated cell walls. Chemical treatments failed to identify any particular cell wall component as being most inhibitory. However, all treatments improved in vitro degradability of the carbohydrate fraction, indicating that components contributing to the undegradability of big bluestem cell wall are sensitive to chemical alteration. Treatments involving alkali were most effective for improving degradability of big bluestem cell walls.

Aging↗

PubMed2000

Investigation of aqueous biphasic systems for the separation of lignins from cellulose in the paper pulping process.

In efforts to apply a polymer-based aqueous biphasic system (ABS) extraction to the paper pulping process, the study of the distribution of various lignin and cellulosic fractions in ABS and the effects of temperature on system composition and solute partitioning have been investigated. The partitioning of three lignin species (Indulin AT, Indulin C, and Reax 85A) have been studied in ABS prepared from stock solutions of 40% (w/w) poly(ethylene glycol) (PEG)-2000 and increasing concentrations of K2CO3, (NH4)2SO4, and NaOH. The partitioning of these lignins is affected by the free energy of hydration of the salt forming the ABS, the tie line length, and the dissociation of the sulfonic acid and hydroxyl groups of the distributed solutes. The partitioning of fibrous cellulose and diethylaminoethyl cellulose have been studied in 40% (w/w) PEG-2000-(NH4)2SO4 ABS. The hydrophilic nature of these species is important in terms of their phase preference when designing a polymer-based aqueous biphasic extraction process for use in a paper pulping process. Both cellulosic samples do not dissolve, but rather report to the salt-rich phase of an ABS. In both chemical pulping and Organosolv pulping, temperatures in excess of 120 degrees C are needed to solubilize the lignin from the cellulose fraction of wood. To study the effects of temperature on the phase diagram and solute partitioning, phthalic acid and NH499TcO4 (as system probes) have been partitioned in 40% (w/w) PEG-2000-(NH4)2SO4 ABS at known tie line lengths as a function of temperature. Temperature does not appear to affect the partitioning results beyond the expected increase in phase divergence as temperature is increased. The PEG-2000 polymer itself appears to be stable to chemical pulping conditions.

Cellulose↗

PubMed2002

Identification of QTLs influencing wood property traits in loblolly pine ( Pinus taeda L.). II. Chemical wood properties.

Chemical wood property traits were analyzed for the presence of quantitative trait loci (QTLs) in a three-generation outbred pedigree of loblolly pine ( Pinus taeda L.). These traits were assayed using pyrolysis molecular beam mass spectrometry and include mass spectrum peak intensities associated with carbohydrates, alpha-cellulose and hemicellulose sugars, and lignin. Models for projection to latent structures (PLS) were used to also estimate the chemical composition of cell walls (i.e., alpha-cellulose, galactan and lignin) from mass spectrum data using multivariate regression. Both earlywood and latewood fractions from the fifth annual ring were analyzed for each trait. An interval mapping approach designed for an outbred pedigree was used to estimate the number of QTLs, the magnitude of QTL effects, and their genomic position. Eight unique QTLs influencing cell wall chemistry were detected from multiple peak intensities and/or PLS estimates using the one- and two-QTL models. Significant differences in chemical contents were observed among the populations from North Carolina vs Oklahoma, and results from QTLxenvironment analyses suggest that QTLs interact with environmental location. QTLs should be verified in larger experiments and in different genetic and environmental backgrounds. QTL mapping will help towards eventually identifying genes having a major effect on chemical wood properties.

Journal Article↗

PubMed2004

Fractional and physico-chemical characterization of hemicelluloses from ultrasonic irradiated sugarcane bagasse.

The present study was undertaken to investigate the extractability of the hemicelluloses from bagasse obtained by ultrasound-assisted extraction methods. The results showed that the ultrasonic treatment and sequential extractions with alkali and alkaline peroxide under the conditions given led to a release of over 90% of the original hemicelluloses and lignin. This fact as well as the sugar composition and structural features of the isolated seven hemicellulosic fractions indicated that ultrasonication attacked the integrity of cell walls, cleaved the ether linkages between lignin and hemicelluloses, and increased accessibility and extractability of the hemicelluloses. Increasing alkali concentration from 0.5 to 2M and alkaline peroxide percentage from 0.5% to 3.0% resulted in degradation of hemicellulosic backbone as shown by a decrease in their molecular weights from 43,580 to 14,470 and 30,180 to 18,130gmol(-1), respectively. However, there were no significant differences in the structural features of the seven sequential alkali- or alkaline peroxide-soluble hemicellulosic fractions, which are composed mainly of L-arabino-(4-O-methyl-D-glucurono)-D-xylans. Ferulic and p-coumaric acids were found to be chemically linked with hemicelluloses.

Cellulose↗

PubMedDate not supplied

Helicoidal pattern in secondary cell walls and possible role of xylans in their construction.

The helicoidal organization of secondary cell walls is overviewed from several examples. Both the plywood texture and the occurrence of characteristic defects strongly suggest that the wall ordering is relevant of a cholesteric liquid-crystal assembly that is rapidly and strongly consolidated by lignification. A preferential localization of glucuronoxylans, major matrix components, and in vitro re-association experiments emphasize their preeminent role: (1) during the construction of the composite as directing the cellulose microfibrils in a helicoidal array; (2) during the lignification of the composite as a host structure for lignin precursors.

Cell Wall↗

PubMed2003

Wood properties of Scots pines (Pinus sylvestris) grown at elevated temperature and carbon dioxide concentration.

Impacts of elevated temperature and carbon dioxide concentration ([CO2]) on wood properties of 15-year-old Scots pines (Pinus sylvestris L.) grown under conditions of low nitrogen supply were investigated in open-top chambers. The treatments consisted of (i) ambient temperature and ambient [CO2] (AT+AC), (ii) ambient temperature and elevated [CO2] (AT+EC), (iii) elevated temperature and ambient [CO2] (ET+AC) and (iv) elevated temperature and elevated [CO2] (ET+EC). Wood properties analyzed for the years 1992-1994 included ring width, early- and latewood width and their proportions, intra-ring wood density (minimum, maximum and mean, as well as early- and latewood densities), mean fiber length and chemical composition of the wood (cellulose, hemicellulose, lignin and acetone extractive concentration). Absolute radial growth over the 3-year period was 54% greater in AT+EC trees and 30 and 25% greater in ET+AC and ET+EC trees, respectively, than in AT+AC trees. Neither elevated temperature nor elevated [CO2] had a statistically significant effect on ring width, early- and latewood widths or their proportions. Both latewood density and maximum intra-ring density were increased by elevated [CO2], whereas fiber length was increased by elevated temperature. Hemicellulose concentration decreased and lignin concentration increased significantly in response to elevated temperature. There were no statistically significant interaction effects of elevated temperature and elevated [CO2] on the wood properties, except on earlywood density.

Carbon Dioxide↗

PubMed2004

Profiling of oligolignols reveals monolignol coupling conditions in lignifying poplar xylem.

Lignin is an aromatic heteropolymer, abundantly present in the walls of secondary thickened cells. Although much research has been devoted to the structure and composition of the polymer to obtain insight into lignin polymerization, the low-molecular weight oligolignol fraction has escaped a detailed characterization. This fraction, in contrast to the rather inaccessible polymer, is a simple and accessible model that reveals details about the coupling of monolignols, an issue that has raised considerable controversy over the past years. We have profiled the methanol-soluble oligolignol fraction of poplar (Populus spp.) xylem, a tissue with extensive lignification. Using liquid chromatography-mass spectrometry, chemical synthesis, and nuclear magnetic resonance, we have elucidated the structures of 38 compounds, most of which were dimers, trimers, and tetramers derived from coniferyl alcohol, sinapyl alcohol, their aldehyde analogs, or vanillin. All structures support the recently challenged random chemical coupling hypothesis for lignin polymerization. Importantly, the structures of two oligomers, each containing a gamma-p-hydroxybenzoylated syringyl unit, strongly suggest that sinapyl p-hydroxybenzoate is an authentic precursor for lignin polymerization in poplar.

Lignin↗

PubMed1999

Manganese deficiency can replace high oxygen levels needed for lignin peroxidase formation by Phanerochaete chrysosporium.

The combined effects of Mn and oxygen on lignin peroxidase (LIP) activity and isozyme composition in Phanerochaete chrysosporium were studied by using shallow stationary cultures grown in the presence of limited or excess N. When no Mn was added, LIP was formed in both N-limited and N-excess cultures exposed to air, but no LIP activity was observed at Mn concentrations greater than 13 mg/liter. In oxygen-flushed, N-excess cultures, LIP was formed at all Mn concentrations, and the peak LIP activity values in the extracellular fluid were nearly identical in the presence of Mn concentrations ranging from 3 to 1,500 mg/liter. When the availability of oxygen to cultures exposed to air was increased by growing the fungus under nonimmersed liquid conditions, higher levels of Mn were needed to suppress LIP formation compared with the levels needed in shallow stationary cultures. The composition of LIP isozymes was affected by the levels of N and Mn. Addition of veratryl alcohol to cultures exposed to air did not eliminate the suppressive effect of Mn on LIP formation. A deficiency of Mn in N-excess cultures resulted in lower biomass and a lower rate of glucose consumption than in the presence of Mn. In addition, almost no activity of the antioxidant enzyme Mn superoxide dismutase was observed in Mn-deficient, N-excess cultures, but the activity of this enzyme increased as the Mn concentration increased from 3 to 13 mg/liter. No Zn/Cu superoxide dismutase activity was observed in N-excess cultures regardless of the Mn concentration.

Benzyl Alcohols↗

PubMed2000

[Effects of dietary fiber on some indices of the activity of the gastrointestinal tract in rats].

Now nobody doubts of necessity and importance of inclusion of vegetative food fibres (as the separately isolated biopolymers--lignin, cellulose, gemicellulose, pectine substances; in composition of a food fibres complex or introduction last in traditional products of nutrition) in a daily human diet. Is proved by experimental researches, that the investigated kinds of food fibres are non-toxic, do not influence on internal structure, are well perceived by animals and can be recommended as the additive in a human diet.

Animals↗

PubMed2005

Fractionation of corn stover by hot-water and aqueous ammonia treatment.

The efficiency of biomass utilization can be significantly improved by fractionation of biomass. A two-stage percolation process was investigated for pretreatment and fractionation of corn stover. The two-stage process is composed of hot water treatment followed by treatment with aqueous ammonia, both applied in a flow-through (percolation) reactor. The first stage processing is intended for hemicellulose removal whereas the second stage is intended for delignification. The pretreated material was nearly pure cellulose and both reagents are cheap and environmentally friendly. The conditions that achieve satisfactory level of biomass fractionation and acceptable enzymatic hydrolysis were identified in terms of reaction temperature, flow rate (retention time) and reaction time for each stage. With proper operation of two-stage treatment, fractionation of biomass was achieved to the extent that the xylan fraction is hydrolyzed with 92-95% conversion, and recovered with 83-86% yields; and the lignin removal is 75-81%. The remaining solid after two-stage treatment contained 78-85% cellulose. The two-stage treatments enhanced the enzymatic digestibility to 90-96% with 60 FPU/g of glucan, and 87-89% with 15 FPU/g of glucan. In two-stage treatment, the composition and digestibility data indicate that the lignin content in the biomass is one of the major factors controlling the enzymatic digestibility.

Ammonia↗

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↗

PubMed1997

Chemical Composition of Hypodermal and Endodermal Cell Walls and Xylem Vessels Isolated from Clivia miniata (Identification of the Biopolymers Lignin and Suberin).

The occurrence of the biopolymers lignin and suberin was investigated with hypodermal (HCW) and endodermal cell walls (ECW) and xylem vessels (XV) isolated from Clivia miniata Reg. roots. Both biopolymers were detected in HCW and ECW, whereas in XV, typical aliphatic suberin monomers were missing and only representative lignin monomers such as guaiacyl (G) and syringyl (S) units could be detected. The absolute amounts of lignin were about one order of magnitude higher compared with suberin in both HCW and ECW. The ratios of the two aromatic lignin units (G/S) decreased from 39 in XV and 10 in HCW to about 1 in ECW, indicating significant differences in lignin structure and function between the three investigated samples. Additionally, compared with the detectable lignin-derived aromatic units G and S, significantly higher amounts of esterified p-coumaric acid-derived aromatic monomers were obtained with HCW, but not with ECW. This is interpreted as a functional adaption of HCW toward pathogen defense at the root/soil interface. The final aim of this study was to provide a thorough chemical characterization of the composition of HCW, ECW, and XV, which in turn will form the basis for a better understanding of the relevant barriers toward the passive, radial, and apoplastic diffusion of solutes from the soil across the root cortex into the root cylinder.

Journal Article↗

PubMed1999

Effect of lignin on growth and tyrosinase activity of fungi from the genus Aspergillus.

The effect of lignin hydrolyzate (a waste product of the pulp and paper industry) on the growth and tyrosinase activity of several strains of fungi of the genus Aspergillus was studied. During fungal growth lignin was degraded with the formation of soluble aromatic products. Accumulation of these products in the growth medium leads to a 60-100-fold increase in tyrosinase synthesis. The intensity of tyrosinase synthesis depends on the composition of the growth medium. The ratio between lignin and glucose concentrations seems to be the main factor; the activity was maximal at the ratio 2:1.

Aspergillus↗

PubMed2001

Modification of lignin for the production of new compounded materials.

The cell walls of woody plants are compounded materials made by in situ polymerization of a polyphenolic matrix (lignin) into a web of fibers (cellulose), a process that is catalysed by polyphenoloxidases (laccases) or peroxidases. The first attempt to transform the basic strategy of this natural process for use in human craftsmanship was the ancient lacquer method. The sap of the lacquer tree (Rhus verniciflua) contains large amounts of a phenol (urushiol), a polysaccharide and the enzyme laccase. This oil-in-water emulsion solidifies in the presence of oxygen. The Chinese began using this phenomenon for the production of highly creative artwork more than 6,000 years ago. It was the first example of an isolated enzyme being used as a catalyst to create an artificial plastic compound. In order to apply this process to the production of products on an industrial scale, an inexpensive phenol must be used, which is transferred by an enzyme to active radicals that react with different components to form a compounded material. At present, the following approaches have been studied: (1) In situ polymerization of lignin for the production of particle boards. Adhesive cure is based on the oxidative polymerization of lignin using phenoloxidases (laccase) as radical donors. This lignin-based bio-adhesive can be applied under conventional pressing conditions. The resulting particle boards meet German performance standards. By this process, 80% of the petrochemical binders in the wood-composite industry can be replaced by materials from renewable resources. (2) Enzymatic copolymerization of lignin and alkenes. In the presence of organic hydroperoxides, laccase catalyses the reaction between lignin and olefins. Detailed studies on the reaction between lignin and acrylate monomers showed that chemo-enzymatic copolymerization offers the possibility to produce defined lignin-acrylate copolymers. The system allows control of the molecular weights of the products in a way that has not been possible with chemical catalysts. This is a novel attempt to enzymatically induce grafting of polymeric side chains onto the lignin backbone, and it enables the utilization of lignin as part of new engineering materials. (3) Enzymatic activation of the middle-lamella lignin of wood fibers for the production of wood composites. The incubation of wood fibers with a phenol oxidizing enzyme results in oxidative activation of the lignin crust on the fiber surface. When such fibers are pressed together, boards are obtained which meet the German standards for medium-density fiber boards (MDF). The fibers are bound together in a way that comes close to that by which wood fibers are bound together in naturally grown wood. This process will, for the first time, yield wood composites that are produced solely from naturally grown products without any addition of resins.

Biopolymers↗

PubMed2005

Lignin primary structures and dirigent sites.

Although lignin is the second most abundant plant substance in vascular plants, its mode of synthesis is still the subject of much debate. However, recent progress has provided crucial evidence to support the theory that lignin primary structure is controlled at the proteinaceous level. Evidence for control over lignin assembly has been demonstrated with the discovery of monomer-invariant aryl-O-ether linkages in lignins that upon alkaline cleavage release the corresponding monomers in equimolar amounts, regardless of monolignol composition. Current evidence would indicate that there are only a few native lignin primary structures, the entire sequences of which now need to be fully determined. A provisional mechanistic model is proposed to account for macromolecular lignin assembly through the participation of proteins harboring arrays of dirigent (monolignol radical binding) sites.

Binding Sites↗