RESUMEN
The development of value-added wood-derived polymer products is of significant importance. Of particular interest is the synthesis of advanced bioactive cellulosic materials. In the present research, novel cellulosic honeycomb films are reported. Cellulose was reacted with dimethylthexylsilyl chloride to form regioselective 2,6-di-O-thexyldimethylsilyl cellulose followed by substitution of the C3 with functionalized poly(ethylene glycol) (PEG). The free end of the PEG side chains of the regioselective 3-O-poly(ethylene glycol)-2,6-di-O-thexyldimethylsilyl cellulose served as an attachment point for bioactive molecules. As an example, Fmoc-Gly-OH was linked to the free end of PEG to produce 3-O-Fmoc-Gly-poly(ethylene glycol)-2,6-di-O-thexyldimethylsilyl cellulose. Honeycomb films were produced through film casting under a humid airflow. AFM analysis revealed the directed self-assembly of the 3-O-Fmoc-Gly-poly(ethylene glycol)-2,6-di-O-thexyldimethylsilyl cellulose wherein the pendent 3-O-Fmoc-Gly-poly(ethylene glycol) groups allocated preferentially around the edges of the honeycomb pores.
Asunto(s)
Aminoácidos/química , Celulosa/química , Membranas Artificiales , Polietilenglicoles/químicaRESUMEN
Phage therapy is a potentially beneficial approach to food preservation and storage. Sustained delivery of bacteriophage can prevent bacterial growth on contaminated food surfaces. Using coaxial electrospinning bacteriophage can be encapsulated in electrospun fibers with high viability. The resulting bio-based electrospun fibers may have potential as a food packaging material. In the present work, T4 bacteriophage (T4 phage) was incorporated into core/shell electrospun fibers made from poly(ethylene oxide) (PEO), cellulose diacetate (CDA), and their blends. Fibers prepared using PEO as the shell polymer showed an immediate burst release of T4 phage upon submersion in buffer. The blending of CDA with PEO significantly decreased the rate of phage release, with no released T4 phage being detected from the solely CDA fibers. Increasing the PEO molecular weight increased the electrospun fiber diameter and viscosity of the releasing medium, which resulted in a relatively slower T4 phage release profile. SEM analyses of the electrospun fiber morphologies were in good agreement with the T4 phage release profiles. Depending on the PEO/CDA ratio, the post-release electrospun fiber morphologies varied from discontinuous fibers to minimally swollen fibers. From these results it is suggested that the T4 phage release mechanism is through solvent activation/polymer dissolution in the case of the PEO fibers and/or by diffusion control from the PEO/CDA blend fibers.
Asunto(s)
Bacteriófago T4/química , Celulosa/análogos & derivados , Embalaje de Alimentos/métodos , Polietilenglicoles/química , Cápsulas , Celulosa/química , Interacciones Hidrofóbicas e Hidrofílicas , Solubilidad , Viscosidad , Agua/químicaRESUMEN
Preparation of moisture-responsive Kraft lignin-based materials by electrospinning blends of Kraft lignin fractions with different physical properties is presented. The differences in thermal mobility between lignin fractions are shown to influence the degree of interfiber fusion occurring during oxidative thermostabilization of electrospun nonwoven fabrics, resulting in different material morphologies including submicrometer fibers, bonded nonwovens, porous films, and smooth films. The relative amount of different lignin fractions and degree of fiber flow and fiber fusion is shown to influence the tendency for the electrospun materials to be transformed into moisture-responsive materials capable of reversible changes in shape. Material characterization by scanning electron microscopy and atomic force microscopy as well characterization of the chemical and physical properties of Kraft lignin fractions by dynamic rheology, 1H and 13C NMR, and gel permeation chromatography combined with multiangle laser light scattering are presented. A proposed mechanism underlying moisture-responsiveness, shape change, and shape recovery is discussed based on the differences in chemical structure and physical properties of Kraft lignin fractions.
Asunto(s)
Lignina/química , Lignina/síntesis química , Agua/química , Biocombustibles , Ensayo de Materiales , Microscopía de Fuerza Atómica , Microscopía Electrónica de Rastreo , Resonancia Magnética Nuclear BiomolecularRESUMEN
DypB, a dye-decolorizing peroxidase from the lignolytic soil bacterium Rhodococcus jostii RHA1, catalyzes the peroxide-dependent oxidation of divalent manganese (Mn(2+)), albeit less efficiently than fungal manganese peroxidases. Substitution of Asn246, a distal heme residue, with alanine increased the enzyme's apparent k(cat) and k(cat)/K(m) values for Mn(2+) by 80- and 15-fold, respectively. A 2.2 Å resolution X-ray crystal structure of the N246A variant revealed the Mn(2+) to be bound within a pocket of acidic residues at the heme edge, reminiscent of the binding site in fungal manganese peroxidase and very different from that of another bacterial Mn(2+)-oxidizing peroxidase. The first coordination sphere was entirely composed of solvent, consistent with the variant's high K(m) for Mn(2+) (17 ± 2 mM). N246A catalyzed the manganese-dependent transformation of hard wood kraft lignin and its solvent-extracted fractions. Two of the major degradation products were identified as 2,6-dimethoxybenzoquinone and 4-hydroxy-3,5-dimethoxybenzaldehyde, respectively. These results highlight the potential of bacterial enzymes as biocatalysts to transform lignin.
Asunto(s)
Bacterias/enzimología , Lignina/metabolismo , Manganeso/metabolismo , Peroxidasas/metabolismo , Sitios de Unión , Biocatálisis , Cromatografía Líquida de Alta Presión , Cristalografía por Rayos X , Hidrólisis , Modelos Moleculares , Oxidación-Reducción , Peroxidasas/químicaRESUMEN
Development of value-added micropatterned porous materials from naturally abundant polymers, such as cellulose, are of growing interest. In this paper, regioselectively modified amphiphilic cellulose azide, 3-O-azidopropoxypoly(ethylene glycol)-2,6-di-O-thexyldimethylsilyl cellulose, with different degrees of substitution (DS) and degrees of polymerization (DP) of the poly(ethylene glycol) (PEG) side chain, was synthesized and employed in the formation of honeycomb-patterned films. With the variation of the DP and/or DS, the amphiphilicity of the polymer and the pore size of the formed films changed accordingly. It was found that amphiphilicity of the cellulose azide played a significant role in the formation of honeycomb films. Balanced amphiphilicity was of particular importance in the formation of uniform honeycomb films. Via the Cu(I)-catalyzed alkyne-azide [2 + 3] cycloaddition reaction, fluorescent avidin and quantum dots were attached to the films. By means of confocal microscopy, it was confirmed that the functional azido group was preferentially allocated inside the pores. This provides a platform for the development of advanced honeycomb materials with site-specific functionalities, such as biosensors.
Asunto(s)
Azidas/química , Celulosa/química , Polietilenglicoles/química , Tensoactivos/síntesis química , Avidina , Reacción de Cicloadición , Colorantes Fluorescentes , Microscopía Confocal , Microscopía Electrónica de Rastreo , Estructura Molecular , Polimerizacion , Porosidad , Puntos Cuánticos , Estereoisomerismo , Propiedades de SuperficieRESUMEN
A series of ionic responsive poly(N-isopropylacrylamide) (PNIPAM) surface-modified lignin nanofiber mats were prepared by aqueous surface-initiated atom transfer radical polymerization (SI-ATRP). PNIPAM brushes with various molecular weights, thickness, and grafting densities were immobilized on electrospun lignin nanofiber mats by adjusting initial monomer concentration and surface initiator density. ATR-FTIR, SEM, TGA, XPS, and water contact angle measurements confirmed successful surface modification. Analysis of the PNIPAM-modified lignin nanofiber mats (Lig-PN) found that the lower critical solution temperature (LCST) was similar to that of PNIPAM and demonstrated ionic responsive characteristics. With increasing ionic concentration, the water contact angles of the Lig-PN increased correspondingly. AFM images showed that the PNIPAM on the lignin nanofiber mat surface expanded in water and contracted in 0.5 M Na(2)SO(4).
Asunto(s)
Acrilamidas/química , Lignina/química , Nanofibras , Polímeros/química , Resinas Acrílicas , Iones , Polimerizacion , Propiedades de Superficie , Temperatura , AguaRESUMEN
Several lignin model polymers and their derivatives comprised exclusively of ß-O-4 or 8-O-4' interunitary linkages were synthesized to better understand the relation between the thermal mobility of lignin, in particular, thermal fusibility and its chemical structure; an area of critical importance with respect to the biorefining of woody biomass and the future forest products industry. The phenylethane (C6-C2)-type lignin model (polymer 1) exhibited thermal fusibility, transforming into the rubbery/liquid phase upon exposure to increasing temperature, whereas the phenylpropane (C6-C3)-type model (polymer 2) did not, forming a char at higher temperature. However, modifying the Cγ or 9-carbon in polymer 2 to the corresponding ethyl ester or acetate derivative imparted thermal fusibility into this previously infusible polymer. FT-IR analyses confirmed differences in hydrogen bonding between the two model lignins. Both polymers had weak intramolecular hydrogen bonds, but polymer 2 exhibited stronger intermolecular hydrogen bonding involving the Cγ-hydroxyl group. This intermolecular interaction is responsible for suppressing the thermal mobility of the C6-C3-type model, resulting in the observed infusibility and charring at high temperatures. In fact, the Cγ-hydroxyl group and the corresponding intermolecular hydrogen bonding interactions likely play a dominant role in the infusibility of most native lignins.
Asunto(s)
Lignina/química , Polímeros/química , Madera/química , Enlace de Hidrógeno , Espectroscopía de Resonancia Magnética , Espectroscopía Infrarroja por Transformada de Fourier , TemperaturaRESUMEN
Value-added materials from naturally abundant polymers such as cellulose are of significant importance. In particular, cellulosic open-framework structures with controlled chemical functionality of the internal surface have great potential in many biosensor applications. Although various cellulose derivatives can form porous honeycomb structured materials, solubility issues and problems with film formation exist. To address this, we have generated robust cellulosic open-framework structures that can be post-functionalized through site-specific modification. Regioselectively modified amphiphilic cellulose azides, 3-O-azidopropoxypoly(ethylene glycol)-2,6-di-O-thexyldimethylsilyl cellulosics, were synthesized, and honeycomb-patterned films were readily produced by the simple breath figures method. Changing the degree of polymerization (DP) of the pendent ethylene glycol (EG(DP)) groups from 22 to 4 increased the corresponding honeycomb film pore diameters from ~1.2 to ~2.6 µm, enabling the potential tuning of pore size. Moreover, these novel azido-functionalized honeycomb films were easily functionalized using Cu(I)-catalyzed alkyne-azide [2 + 3] cycloaddition reaction; biotin was "clicked" onto the azide functionalized cellulosic honeycomb films without any effect to the film structure. These results indicate this system may serve as a platform for the design and development of biosensors.
Asunto(s)
Técnicas Biosensibles , Celulosa/síntesis química , Polímeros/síntesis química , Alquinos/química , Azidas/química , Técnicas Biosensibles/instrumentación , Técnicas Biosensibles/métodos , Biotina/química , Catálisis , Celulosa/análogos & derivados , Química Clic , Cobre/química , Diseño de Equipo , Glicol de Etileno/química , Espectroscopía de Resonancia Magnética , Estructura Molecular , Polimerizacion , Porosidad , Estereoisomerismo , Propiedades de SuperficieRESUMEN
To assess the effects that the physical and chemical properties of lignin might have on the enzymatic hydrolysis of pretreated lignocellulosic substrates, protease treated lignin (PTL) and cellulolytic enzyme lignin (CEL) fractions, isolated from steam and organosolv pretreated corn stover, poplar, and lodgepole pine, were prepared and characterized. The adsorption of cellulases to the isolated lignin preparations corresponded to a Langmuir adsorption isotherm. It was apparent that, rather than the physical properties of the isolated lignin, the carboxylic acid functionality of the isolated lignin, as determined by FTIR and NMR spectroscopy, had much more of an influence when lignin was added to typical hydrolysis of pure cellulose (Avicel). An increase in the carboxylic content of the lignin preparation resulted in an increased hydrolysis yield. These results suggested that the carboxylic acids within the lignin partially alleviate non-productive binding of cellulases to lignin. To try to confirm this possible mechanism, dehydrogenative polymers (DHP) of monolignols were synthesized from coniferyl alcohol (CA) and ferulic acid (FA), and these model compounds were added to a typical enzymatic hydrolysis of Avicel. The DHP from FA, which was enriched in carboxylic acid groups compared with the DHP from CA, adsorbed a lower mount of cellulases and did not decrease hydrolysis yields when compared to the DHP from CA, which decreased the hydrolysis of Avicel by 8.4%. Thus, increasing the carboxylic acid content of the lignin seemed to significantly decrease the non-productive binding of cellulases and consequently increased the enzymatic hydrolysis of the cellulose.
Asunto(s)
Biomasa , Ácidos Carboxílicos/análisis , Lignina/química , Pinus/química , Populus/química , Zea mays/química , Biotecnología/métodos , Celulasas/metabolismo , Hidrólisis , Lignina/aislamiento & purificación , Lignina/metabolismo , Espectroscopía de Resonancia Magnética , Pinus/metabolismo , Populus/metabolismo , Espectroscopía Infrarroja por Transformada de Fourier , Zea mays/metabolismoRESUMEN
Douglas-fir was SO(2)-steam pretreated at different severities (190, 200, and 210°C) to assess the possible negative effect of the residual and isolated lignins on the enzymatic hydrolysis of the steam pretreated substrates. When various isolated lignins were added to the Avicel hydrolysis reactions, the decrease in glucose yields ranged from 15.2% to 29.0% after 72 h. It was apparent that the better hydrolysis yields obtained at higher pretreatment severities were more a result of the greater accessibly of the cellulose rather than any specific change in the non-productive binding of the lignin to the enzymes. FTIR and (13)C NMR characterization indicated that the lignin in the steam pretreated substrates became more condensed with increasing severity, suggesting that the cellulases were adsorbed to the lignin by hydrophobic interactions. Electrostatic interactions were also involved as the positively charged cellulase components were preferentially adsorbed to the lignins.
Asunto(s)
Celulasa/metabolismo , Celulosa/metabolismo , Lignina/aislamiento & purificación , Pseudotsuga/química , Vapor , Adsorción , Hidrólisis , Lignina/química , Espectroscopía de Resonancia Magnética , Péptido Hidrolasas , Solubilidad , Análisis Espectral , TemperaturaRESUMEN
The effect of dihydric alcohol (nonsolvent) addition on the rheological and microstructural behavior of cellulose acetate (CA) in a ternary CA, N,N-dimethylacetamide (DMA), nonsolvent system was investigated. Increasing the dihydric alcohol concentration led to enhanced steady shear viscosity and dynamic viscoelastic properties that were dependent on CA concentration. Changing the dihydric alcohol from 1,2-ethanediol to 1,4-butanediol and 1,6-hexanediol increased the moduli and decreased the concentration of nonsolvent at which the sol-gel transition occurred. At 10 wt % CA concentration the modulus and gel morphology of the 1,2-ethanediol and 1,4-butanediol systems were quite similar and distinctly different from that of 1,6-hexanediol. In the former, the gel morphologies were more heterogeneous, evident of more extensive coarsening, and likely obtained via nucleation and growth and spinoidal decomposition of off-critical mixtures. The latter exhibited more uniform dense network morphology, indicative of a spinoidal decomposition of near-critical mixtures. The gels were fractal in nature and exhibited different fractal dimensions in-line with the observed differences in microstructure; D â¼ 1.87 ± 0.02 (1,2-ethanediol and 1,4-butanediol) and D â¼ 1.97 ± 0.02 (1,6-hexanediol). However, at 15 wt % CA content, the gels exhibited more similar viscoelastic behavior and gel microstructures; D â¼ 1.97 ± 0.02 for all three dihydric alcohol systems.
Asunto(s)
Celulosa/análogos & derivados , Transición de Fase , Acetamidas/química , Celulosa/química , Elasticidad , Glicol de Etileno/química , Geles , Glicoles/química , ViscosidadRESUMEN
Advanced solid-state NMR was employed to investigate differences in chemical structure and heterogeneity between milled wood lignin (MWL) and residual enzyme lignin (REL). Wiley and conventional milled woods were also studied. The advanced NMR techniques included 13C quantitative direct polarization, various spectral-editing techniques, and two-dimensional 1H-13C heteronuclear correlation NMR with 1H spin diffusion. The 13C chemical shift regions between 110 and 160 ppm of two lignins were quite similar to those of two milled woods. REL contained much more residual carbohydrates than MWL, showing that MWL extraction more successfully separated lignin from cellulose and hemicelluloses than REL extraction; REL was also of higher COO, aromatic C-C, and condensed aromatics but of lower aromatic C-H. At a spin diffusion time of 0.55 ms, the magnetization was equilibrated through the whole structure of MWL lignin, but not through that of REL, indicating that REL is more heterogeneous than MWL.
Asunto(s)
Lignina/química , Resonancia Magnética Nuclear Biomolecular/métodos , Pinus taeda/química , Madera/química , Lignina/aislamiento & purificación , Lignina/metabolismo , Extractos Vegetales/química , Extractos Vegetales/aislamiento & purificaciónRESUMEN
The effect of hydrophilic and hydrophobic interactions on the rheological and microstructural behavior of cellulose acetate (CA) in a ternary CA, N,N-dimethylacetamide (DMA), nonsolvent (alcohol) system was examined. Increasing nonsolvent concentration increased the viscosity and dynamic viscoelastic properties of the system. At a critical nonsolvent concentration, a sol-gel transition was observed, which was dependent on nonsolvent structure. Increasing the available hydrogen bonding groups within the nonsolvent led to higher modulus (stronger gels) and a sol-gel transition at lower nonsolvent concentration. Likewise, increasing the alkyl chain length (hydrophobicity) of the nonsolvent also enhanced the viscoelastic properties; however, hydrogen bonding, specifically the ability to hydrogen bond donate was critical for gel formation. For all gels studied, the elastic modulus shifts to higher values with increasing hydrophilicity and hydrophobicity of the nonsolvent and exhibits a power-law behavior with nonsolvent content. All of the gels exhibit similar fractal dimensions; however, confocal images of the different systems reveal distinct differences. Increasing the hydrophilicity of the nonsolvent led to a more uniform denser gel microstructure, whereas increasing the hydrophobicity resulted in a larger more heterogeneous network structure despite the increase in moduli.
Asunto(s)
Celulosa/análogos & derivados , Interacciones Hidrofóbicas e Hidrofílicas , Reología , Celulosa/química , Celulosa/ultraestructura , Elasticidad , Geles , Enlace de Hidrógeno , Microscopía Confocal , Espectroscopía Infrarroja por Transformada de Fourier , ViscosidadRESUMEN
Copolymerization of N-isopropylacrylamide (NIPAM) with technical hardwood kraft lignin (HWKL) was achieved by atom transfer radical polymerization (ATRP) using a selectively modified lignin-based macroinitiator. The degree of polymerization (DP) of polyNIPAM graft side chains was affected by varying the ratio of the DMF/water solvent system from 5:0 to 0:5, and an estimated DP(NIPAM) of >40 was obtained using a ratio of 1:4 (v/v). The thermal decomposition temperature of the lignin-g-polyNIPAM copolymers significantly increased with increasing DP(NIPAM). Likewise, the solubility of the lignin-g-polyNIPAM copolymers in water changed depending on copolymer structure. In both the water-soluble and suspended copolymers, at temperatures above 32 degrees C, the g-polyNIPAM component underwent the typical hydrophilic-to-hydrophobic transition, resulting in the precipitation of the copolymer.
Asunto(s)
Acrilamidas/química , Materiales Biocompatibles/síntesis química , Lignina/química , Polímeros/síntesis química , Materiales Biocompatibles/química , Espectroscopía de Resonancia Magnética , Estructura Molecular , Polímeros/química , Espectroscopía Infrarroja por Transformada de Fourier , TemperaturaRESUMEN
Regioselective copolymerization of N-isopropylacrylamide (NIPAM) onto cellulose was achieved by atom transfer radical polymerization (ATRP) using a regioselectively modified 6- O-bromoisobutyryl-2,3-di- O-methyl cellulose macroinitiator. Varying the ratio of NIPAM to macroinitiator to ligand to transition metal in a Cu(I)Br/ N, N, N', N'', N'''-pentamethyldiethylenetriamine (PMDETA) catalyst system affected graft yield and degree of polymerization. ATRP proceeded to completion without any trace of the macroinitiator, and a degree of polymerization (DP) of polyNIPAM up to 46.3 was obtained. Increasing the DP of the NIPAM component increased both the thermal decomposition temperature and the glass transition temperature of the copolymer. The grafting of NIPAM also affected the solubility properties of the methylcellulose. The 6- O-polyNIPAM-2,3-di- O-methyl cellulose formed a stable suspension in water at room temperature and underwent a hydrophillic-to-hydrophobic transition and copolymer precipitation when the temperature was raised above 30 degrees C.
Asunto(s)
Acrilamidas/química , Celulosa/química , Polímeros/síntesis química , Catálisis , Metilcelulosa/química , Transición de Fase , SolubilidadRESUMEN
The use of single wall carbon nanotubes (SWCNTs) in current and future applications depends on the ability to process SWCNTs in a solvent to yield high-quality dispersions characterized by individual SWCNTs and possessing a minimum of SWCNT bundles. Many approaches for the dispersion of SWCNTs have been reported. However, there is no general assessment which compares the relative quality and dispersion efficiency of the respective methods. Herein we report a quantitative comparison of the relative ability of "wrapping polymers" including oligonucleotides, peptides, lignin, chitosan, and cellulose and surfactants such as cholates, ionic liquids, and organosulfates to disperse SWCNTs in water. Optical absorption and fluorescence spectroscopy provide quantitative characterization (amount of SWCNTs that can be suspended by a given surfactant and its ability to debundle SWCNTs) of these suspensions. Sodium deoxy cholate (SDOCO), oligonucleotides (GT)(15), (GT)(10), (AC)(15), (AC)(10), C(10-30), and carboxymethylcellulose (CBMC-250K) exhibited the highest quality suspensions of the various systems studied in this work. The information presented here provides a good framework for further study of SWCNT purification and applications.
Asunto(s)
ADN de Cadena Simple/química , Nanotubos de Carbono/química , Tensoactivos/química , Absorción , Imidazolinas/química , Espectrofotometría InfrarrojaRESUMEN
The effect of increasing water composition on the rheological and microstructural behavior of a ternary cellulose acetate (CA)/N,N-dimethylacetamide (DMA)/water system is examined. Addition of water to the CA/DMA system results in enhanced steady shear viscosity and dynamic viscoelastic properties and ultimately to phase-separated gel formation. The changes in dynamic rheological behavior of the system during gelation correlate well with the combined solubility parameter (delta) and, in particular, the Hansen hydrogen-bonding solubility parameter index (delta(h)) of the solvent system, suggesting hydrogen-bonding interactions may be the major route initiating the sol-gel process. For all gels studied, the elastic modulus and the critical stress to yield shifts to higher values with increasing CA concentration and/or water content. In addition, the elastic modulus exhibits a power-law behavior with water content, with the same power-law exponent observed for gels containing different CA concentrations. Addition of water leads to formation of a denser gel network, as evidenced from direct visualization of the gel microstructure through confocal microscopy.
Asunto(s)
Acetamidas/química , Celulosa/análogos & derivados , Solventes/química , Agua/química , Celulosa/química , Elasticidad , Geles/química , Enlace de Hidrógeno , Reología , ViscosidadRESUMEN
Thin film honeycomb materials were prepared from regioselectively modified celluloses. The method uses water condensation at the surface of a cellulosic solution as an ordered template to form honeycomb structures. Pore size and distribution is controlled by several factors, one of which is the hydrophilicity of the cellulosic used. The amphiphilic nature of the celluloses was modified with varying lengths of ethylene glycol side chains using 2,6-thexyldimethylsilyl cellulose. It was found that the side chains do affect the honeycomb formation, with longer ethylene glycol chains leading to increased pore uniformity but having little influence on the pore size.
Asunto(s)
Celulosa/análogos & derivados , Compuestos de Organosilicio/química , Acetamidas/química , Rastreo Diferencial de Calorimetría , Celulosa/química , Glicoles de Etileno/química , Furanos/química , Sustancias Macromoleculares/química , Microscopía Electrónica de Rastreo , Modelos Químicos , Conformación Molecular , Espectroscopía Infrarroja por Transformada de Fourier , Temperatura , Agua/químicaRESUMEN
Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy was applied to intact and isolated loblolly pine wood samples to identify potential structural changes induced by tree age, milling, lignin extraction, or naturally occurring mutations. Special attention was paid to ketone and aldehyde as well as nonpolar alkyl groups, which could be observed at low concentrations (<2 in 1000 C) using improved spinning-sideband suppression with gated decoupling. Carbonyl structures were present in intact wood, and there are more keto groups than aldehydes. Their concentrations increased from juvenile to mature wood and with milling time, whereas extraction did not alter the C=O fraction. Significant amounts of aldehyde and dihydroconiferyl alcohol residues were present in coniferyl aldehyde dehydrogenase-deficient wood, confirming solution-state NMR spectra of the corresponding lignin. These results demonstrate the utility of solid-state NMR as an assay for changes in the lignin structure of genetically modified plants.
Asunto(s)
Lignina/análisis , Espectroscopía de Resonancia Magnética , Pinus taeda , Madera/química , Alcoholes/análisis , Aldehídos/análisis , Cetonas/análisis , Lignina/química , Mutación , Pinus taeda/química , Pinus taeda/genética , Plantas Modificadas Genéticamente/químicaRESUMEN
Twenty-one organosolv ethanol lignin samples were prepared from hybrid poplar (Populus nigra xP. maximowiczii) under varied conditions with an experimental matrix designed using response surface methodology (RSM). The lignin preparations were evaluated as potential antioxidants. Results indicated that the lignins with more phenolic hydroxyl groups, less aliphatic hydroxyl groups, low molecular weight, and narrow polydispersity showed high antioxidant activity. Processing conditions affected the functional groups and molecular weight of the extracted organosolv ethanol lignins, and consequently influenced the antioxidant activity of the lignins. In general, the lignins prepared at elevated temperature, longer reaction time, increased catalyst, and diluted ethanol showed high antioxidant activity. Regression models were developed to enable the quantitative prediction of lignin characteristics and antioxidant activity based on the processing conditions.