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At least 865 records · Page 48Linked to original sources
PubMed2002

H(2)O(2) generation during the auto-oxidation of coniferyl alcohol drives the oxidase activity of a highly conserved class III peroxidase involved in lignin biosynthesis.

Characterization of lignified Zinnia elegans hypocotyls by both alkaline nitrobenzene oxidation and thioacidolysis reveals that coniferyl alcohol units are mainly found as part of 4-O-linked end groups and aryl-glycerol-beta-aryl ether (beta-O-4) structures. Z. elegans hypocotyls also contain a basic peroxidase (EC 1.11.1.7) capable of oxidizing coniferyl alcohol in the absence of H(2)O(2). Results showed that the oxidase activity of the Z. elegans basic peroxidase is stimulated by superoxide dismutase, and inhibited by catalase and anaerobic conditions. Results also showed that the oxidase activity of this peroxidase is due to an evolutionarily gained optimal adaptation of the enzyme to the microM H(2)O(2) concentrations generated during the auto-oxidation of coniferyl alcohol, the stoichiometry of the chemical reaction (mol coniferyl alcohol auto-oxidized/mol H(2)O(2) formed) being 0.496. These results therefore suggest that the H(2)O(2) generated during the auto-oxidation of coniferyl alcohol is the main factor that drives the unusual oxidase activity of this highly conserved lignin-synthesizing class III peroxidase.

Chromatography, High Pressure Liquid↗
PubMed2000

Antimicrobial intermediates of the general phenylpropanoid and lignin specific pathways.

The minimum inhibitory concentration (MIC) of the major intermediates of the general phenylpropanoid and lignin specific pathways of plants were determined employing a range of yeasts and bacteria. Of the three main classes of compounds tested, the hydroxycinnamaldehydes were the most effective, possessing notable antifungal and antibacterial activity. Determination of the minimum killing concentration (MKC) of the hydroxycinnamaldehydes revealed MIC/MKC ratios suggesting these compounds to be fungicidal, but not bactericidal, in their mode of action. In contrast, the hydroxycinnamic acids and hydroxycinnamyl alcohols possessed little antimicrobial activity, with the exception of the hydroxycinnamic acids, which were antibacterial.

Anti-Bacterial Agents↗
PubMed2001

Cell-wall architecture and lignin composition of wheat developed in a microgravity environment.

The microgravity environment encountered during space-flight has long been considered to affect plant growth and developmental processes, including cell wall biopolymer composition and content. As a prelude to studying how microgravity is perceived - and acted upon - by plants, it was first instructive to investigate what gross effects on plant growth and development occurred in microgravity. Thus, wheat seedlings were exposed to microgravity on board the space shuttle Discovery (STS-51) for a 10 day duration, and these specimens were compared with their counterparts grown on Earth under the same conditions (e.g. controls). First, the primary roots of the wheat that developed under both microgravity and 1 g on Earth were examined to assess the role of gravity on cellulose microfibril (CMF) organization and secondary wall thickening patterns. Using a quick freeze/deep etch technique, this revealed that the cell wall CMFs of the space-grown wheat maintained the same organization as their 1 g-grown counterparts. That is, in all instances, CMFs were randomly interwoven with each other in the outermost layers (farthest removed from the plasma membrane), and parallel to each other within the individual strata immediately adjacent to the plasma membranes. The CMF angle in the innermost stratum relative to the immediately adjacent stratum was ca 80 degrees in both the space and Earth-grown plants. Second, all plants grown in microgravity had roots that grew downwards into the agar; they did not display "wandering" and upward growth as previously reported by others. Third, the space-grown wheat also developed normal protoxylem and metaxylem vessel elements with secondary thickening patterns ranging from spiral to regular pit to reticulate thickenings. Fourthly, both the space- and Earth-grown plants were essentially of the same size and height, and their lignin analyses revealed no substantial differences in their amounts and composition regardless of the gravitational field experienced, i.e. for the purposes of this study, all plants were essentially identical. These results suggest that the microgravity environment itself at best only slightly affected either cell wall biopolymer synthesis or the deposition of CMFs, in contrast to previous assertions.

Cell Membrane↗
PubMed2001

Removal of estrogenic activities of bisphenol A and nonylphenol by oxidative enzymes from lignin-degrading basidiomycetes.

Bisphenol A (BPA) and nonylphenol (NP) were treated with manganese peroxidase (MnP) and laccase prepared from the culture of lignin-degrading fungi. Laccase in the presence of 1-hydroxybenzotriazole (HBT), the so-called laccase-mediator system, was also applied to remove the estrogenic activity. Both chemicals disappeared in the reaction mixture within a 1-h treatment with MnP but the estrogenic activities of BPA and NP still remained 40% and 60% in the reaction mixtures after a 1-h and a 3-h treatment, respectively. Extension of the treatment time to 12 h completed the removal of estrogenic activities of BPA and NP. The laccase has less ability to remove these activities than MnP, but the laccase-HBT system was able to remove the activities in 6 h. A gel permeation chromatography (GPC) analysis revealed that main reaction products of BPA and NP may be oligomers formed by the action of enzymes. Enzymatic treatments extended to 48 h did not regenerate the estrogenic activities, suggesting that the ligninolytic enzymes are effective for the removal of the estrogenic activities of BPA and NP.

Basidiomycota↗
PubMed2003

Toxic by-products from the combustion of Kraft lignin.

Lignin samples, sub-product in the Kraft process of cellulose from eucalyptus wood, were burnt in a laboratory scale furnace at different residence temperatures and with distinct fuel-rich atmospheres. The yields of CO, CO(2), eight light hydrocarbons (methane, ethylene, ethane, propylene, acetylene, butane, etc.) and 60 semi-volatile+volatile compounds (benzene, toluene, ethylbenzene, styrene, indene, naphthalene, dibenzofuran, phenanthrene, chrysene, etc.) were determined, with nominal reactor temperatures between 800 and 1100 degrees C and residence times of the volatiles evolved and formed between 4 and 7 s. The collection of the gases and volatiles evolved was carried out with a Tedlar bag and by XAD-4 resin respectively, comparing the data obtained in both cases. The emission factor (mg/kg) of the CO was between 2500 and 90000, and under the poor-oxygen atmosphere, the emission factors of many by-toxic products were greater than 100 mg/kg. A pyrolysis run was also performed, obtaining emission factors between 30 and 3000 mg/kg, facilitating its identification. The behaviour of different compounds in the combustion runs was discussed considering three groups in accordance with their stability vs. oxygen, and two groups vs. temperature.

Air Pollutants↗
PubMed2002

ZL-DHP lignin model compound at the air-water interface.

In this paper we present our surface chemistry studies of enzymatically polymerized, poly-coniferyl alcohol lignin model compound (dehydrogenate polymer a.k.a. ZL-DHP) at the air-water interface. Using the CHCl(3)/MeOH (5:1 v/v) spreading solvent, we found an average molecular area of ZL-DHP of approximately 1200 A(2). The monolayer expresses a high compressibility with a collapsed area of 500 A(2) and collapsed surface pressure of 28 mN m(-1). In the range of applied surface pressures, ZL-DHP polymer have no phase changes, as shown by the very high linearity (R=0.994) of absorbance vs. surface pressure cure. There was no symmetry transitions observed as shown by absence of shifts of absorption peak maximums.

Air↗
PubMed2003

Modulation of interleukin-8 and nitric oxide synthase mRNA levels by interferon-gamma in macrophages stimulated with lignin derivatives and lipopolysaccharides.

It has been shown that interferon-gamma (IFN-gamma) plays a role in the regulation of interleukin-8 (IL-8), nitric oxide (NO), and tumor necrosis factor-alpha (TNF-alpha) secretion by macrophages stimulated with lignin derivatives, such as EP3, and lipopolysaccharides (LPS) [Cytokine 11 (1999) 571]. To examine the mechanism by which IFN-gamma affects secretion of these factors, EP3- or LPS-stimulated macrophages were treated with different concentrations of IFN-gamma, and mRNA levels of IL-8, nitric oxide synthase (NOS) and TNF-alpha were determined by Northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). As reported previously, stimulation of macrophages by EP3 or LPS dramatically induced the expression of IL-8, NOS, and TNF-alpha mRNAs. IFN-gamma clearly decreased the level of IL-8 mRNA in stimulated macrophages, although it did not affect the IL-8 mRNA level in unstimulated macrophages. In contrast, IFN-gamma appeared to increase the level of NOS mRNA both in unstimulated and stimulated macrophages. IFN-gamma, which increased the amount of TNF-alpha mRNA in unstimulated macrophages, showed no significant effect on the high level of TNF-alpha mRNA in stimulated macrophages. These results suggest that IFN-gamma causes changes in IL-8 and NO secretion by stimulated macrophages through its effects on the level of IL-8 and NO mRNA, respectively. Effects of IFN-gamma on TNF-alpha secretion by stimulated macrophages may be mediated by a different mechanism.

Animals↗
PubMed2001

Slow-release effect of N-functionalized kraft lignin tested with Sorghum over two growth periods.

Biomass production of fodder sorghum (Sorghum sp.) has been tested in a field trial over two harvesting periods under natural meteorological conditions using ammoxidized kraft lignin (AKL) as a slow-release fertilizer and urea as conventional reference. In the course of the first growth cycle, plants treated with urea gave higher biomass yields because of the better solubility of urea in the initial phase. However, during the second cycle AKL treated plants performed better than urea treated sorghum, indicating that nitrogen from AKL became readily available.

Biomass↗
PubMed2002

Bio-degradation of lignin in olive pomace by freshly-isolated species of Basidiomycete.

The solid waste (pomace) from olive oil processing cannot be used directly as an animal feed, but it was thought that an appropriate series of fermentations might improve its nutritional value. As a first step, typical samples of pomace were subjected, after an alkaline pre-treatment, to delignification by Phanerochaete chrysosporium (ATCC 19343), Oxysporus sp., Schizophyllum commune, Hyphoderma sp. or Ganoderma sp.; the last four species being freshly isolated from decaying wood collected in a woodland in Jordan. The relative activity of the species was judged by the levels of ligninase or laccase secreted and the extent of lignin degradation under a range of experimental conditions. Oxysporus sp. (ca. 69%) and S. commune (ca. 53%) gave significantly higher levels of breakdown of the lignified material than the other recent isolates. P. chrysosporium (ca. 60%) was not as active as in previously reported studies, and it may be that culturing the fungus on a standard laboratory medium had reduced its ability to generate ligninase. Further work is needed to establish whether the delignified pomace could be further processed into a feed for poultry.

Basidiomycota↗
PubMed2000

The reactivity of phenolic and non-phenolic residual kraft lignin model compounds with Mn(II)-peroxidase from Lentinula edodes.

Three phenolic model compounds representing bonding patterns of residual kraft lignin were incubated with manganese peroxidase from Lentinula edodes. Extensive degradation of all the phenolic models, mainly occurring via side-chain benzylic oxidation, was observed. Among the tested model compounds the diphenylmethane alpha-5 phenolic model was found to be the most reactive, yielding several products showing oxidation and fragmentation at the bridging position. The non-phenolic 5-5' biphenyl and 5-5' diphenylmethane models were found unreactive.

Biodegradation, Environmental↗
PubMed1995

Veratryl alcohol oxidation by lignin peroxidase.

Lignin peroxidase (LiP) from the white rot fungus Phanerochaete chrysosporium catalyzes the H2O2-dependent oxidation of veratryl alcohol (VA), a secondary metabolite of the fungus, to veratryl aldehyde (VAD). The oxidation of VA does not seem to be simply one-electron oxidation by LiP compound I (LiPI) to its cation radical (VA.+) and the second by LiP compound II (LiPII) to VAD. Moreover, the rate constant for LiPI reduction by VA (3 x 10(5) M-1 s-1) is certainly sufficient, but the rate constant for LiPII reduction by VA (5.0 +/- 0.2 s-1) is insufficient to account for the turnover rate of LiP (8 +/- 0.4 s-1) at pH 4.5. Oxalate was found to decrease the turnover rate of LiP to 5 s-1, but it had no effect on the rate constants for LiP with H2O2 or LiPI and LiPII, the latter formed by reduction of LiPI with ferrocyanide, with VA. However, when LiPII was formed by reduction of LiPI with VA, an oxalate-sensitive burst phase was observed during its reduction with VA. This was explained by the presence of LiPII, formed by reduction of LiPI with VA, in two different states, one that reacted faster with VA than the other. Activity during the burst was sensitive to preincubation of LiPI with VA, decaying with a half-life of 0.54 s, and was possibly due to an unstable intermediate complex of VA.+ and LiPII. This was supported by an anomalous, oxalate-sensitive, LiPII visible absorption spectrum observed during steady state oxidation of VA. The first order rate constant for the burst phase was 8.3 +/- 0.2 s-1, fast enough to account for the steady state turnover rate of LiP at pH 4.5. Thus, it was concluded that oxalate decreased the turnover of LiP by reacting with VA.+ bound to LiPII. The VA.+ concentration measured by electron spin resonance spectroscopy (ESR) was 2.2 microM at steady state (10 microM LiP, 250 microM H2O2, and 2 mM VA) and increased to 8.9 microM when measured after the reaction was acid quenched. Therefore, we assumed the presence of two states of VA.+ bound to LiPII, one ESR-active and one ESR-silent. The ESR-silent species, which could be detected after acid quenching, would be responsible for the burst phase. Both of the VA.+ species disappeared in the presence of 5 mM oxalate. The ESR-active species reached a maximum (3.5 microM) at 0.5 mM VA under steady state. From these studies, a mechanism for VA oxidation by LiP is proposed in which a complex of LiPII and VA.+ reacts with an additional molecule of VA, leading to veratryl aldehyde formation.

Basidiomycota↗
PubMedDate not supplied

Modification of high lignin content kraft pulps with laccase to improve paper strength properties. 1. Laccase treatment in the presence of gallic acid.

Laccase was reacted with gallic acid in the presence of a high-kappa (91) kraft pulp. The result was a modified pulp with 34%, 20%, and 72% improvements in burst, tensile, and wet tensile strength compared to untreated control samples. Fully bleached pulps were not responsive to the laccase treatment, indicating lignin was the major target for the fiber modification. The results indicate that the strength increases were a combined effect of improvements of hydrogen bonding between fibers and creation of phenoxy radical cross-links within the sheet.

Gallic Acid↗
PubMedDate not supplied

Modification of high-lignin kraft pulps with laccase. Part 2. Xylanase-enhanced strength benefits.

The effects of xylanase pretreatment of high lignin content softwood (SW) kraft pulp on subsequent pulp treatment with laccase in combination with gallic acid were investigated. Although xylanase pretreatment was ineffective in enhancing the laccase-facilitated biografting of gallic acid to kraft fibers, it was beneficial for subsequent treatment with laccase exclusively. Treating pulp fibers with xylanase followed by laccase provided a collective 25% and 46% increase in dry and wet tensile strength properties, respectively.

Endo-1,4-beta Xylanases↗
PubMed2003

Quantitative 2D HSQC (Q-HSQC) via suppression of J-dependence of polarization transfer in NMR spectroscopy: application to wood lignin.

A quantitative method to record (1)H-(13)C correlation NMR spectra (Q-HSQC) is presented. The suppression of (1)J(CH)-dependence is achieved by modulating the polarization transfer delays of HSQC. In addition, the effect of homonuclear couplings, as well as relaxation during the pulse sequence are discussed. We developed the Q-HSQC approach for the quantitative analysis of wood lignin, a complex polymer where it has been difficult to obtain reliable data on the relative amounts of different structural units. The current method is applicable to a variety of complex mixtures, where normal 1D (1)H- and (13)C-NMR methods fail.

Lignin↗
PubMed2001

Degradation of lignin in wheat straw during growth of the oyster mushroom (Pleurotus ostreatus) using off-line thermochemolysis with tetramethylammonium hydroxide and solid-state (13)C NMR.

The oyster mushroom (Pleurotus ostreatus) is widely cultivated on wheat straw (Triticum aestivum); however, there is a need to better understand the relationship between the chemical composition of the compost and mushroom growth. Wheat straw was degraded over a period of 63 days by P. ostreatus during which time it was sampled at weekly intervals. Off-line thermochemolysis with tetramethylammonium hydroxide and solid-state (13)C NMR were then used in the molecular characterization of the undegraded wheat straw and the degraded samples. The degraded wheat straw samples had a lower proportion of syringyl- to guaiacyl-derived moieties and cinnamyl- to guaiacyl-derived moieties than the undegraded control. There were increases in both guaiacyl and syringyl acid to aldehyde ratios with composting time, which showed that side-chain oxidation has been mediated by P. ostreatus. The (13)C NMR spectra confirmed the increase in carboxyl content but indicated that the overall lignin and methoxyl contents remained relatively constant, although some nonsystematic variations were observed. The spectra also showed a decrease in amorphous noncellulosic polysaccharides in relation to the crystalline cellulose upon degradation.

Carbon Isotopes↗
PubMed2005

Rapid prediction of acid detergent fiber, neutral detergent fiber, and acid detergent lignin of rice materials by near-infrared spectroscopy.

A rapid predictive method based on near-infrared spectroscopy (NIRS) was developed to measure acid detergent fiber (ADF), neutral detergent fiber (NDF), and acid detergent lignin (ADL) of rice stem materials. A total of 207 samples were divided into two subsets, one subset (approximately 136 samples) for calibration and cross-validation and the other subset for independent external validation to evaluate the calibration equations. Different mathematical treatments were applied to obtain the best calibration and validation results. The highest coefficient of determination for calibration (R2) and coefficient of determination for cross-validation (1-VR) were 0.968 and 0.949 for ADF, 0.846 and 0.812 for NDF, and 0.897 and 0.843 for ADL, respectively. Independent external validation still gave a high coefficient of determination for external validation (r2) and a low standard error of performance (SEP) for the three parameters; the best validation results were SEP = 0.933 and r2 = 0.959 for ADF, SEP = 2.228 and r2 = 0.775 for NDF, and SEP = 0.616 and r2 = 0.847 for ADL, indicating that NIR gave a sufficiently accurate prediction of ADF and ADL content of rice material but a less satisfactory prediction for NDF. This study suggested that routine screening for these forage quality parameters with large numbers of samples is possible with NIRS in early-generation selection in rice-breeding programs.

Calibration↗
PubMed2005

Tetramethylammonium hydroxide (TMAH) thermochemolysis of lignin: behavior of 4-O-etherified cinnamyl alcohols and aldehydes.

The thermochemolytic behavior of 4-O-etherified cinnamyl alcohols and aldehydes in lignin was investigated in the presence of tetramethylammonium hydroxide (TMAH) (315 degrees C/4 s), using veratrylglycol-beta-(coniferyl alcohol) ether (1a), veratrylglycol-beta-(sinapyl alcohol) ether (1b), and veratrylglycol-beta-(coniferyl aldehyde) ether (2). The methylated products were monitored with gas chromatography-mass spectrometry. Dimers 1a and 1b provided the coniferyl and sinapyl alcohol dimethyl ethers consisting of three isomers, respectively. Coniferyl alcohol dimethyl ether isomers were also observed in the TMAH thermochemolysis pyrolysates of a bulk dehydrogenation polymer of coniferyl alcohol and a Japanese cedar (Cryptomeria japonica) wood. Coniferyl aldehyde methyl ether was not provided from TMAH thermochemolyses of coniferyl aldehyde, 2, a dehydrogenation polymer of coniferyl aldehyde, and the cedar wood. The former three provided veratryl aldehyde in a large abundance, instead of coniferyl aldehyde methyl ether. Sinapyl aldehyde provided 3,4,5-trimethoxybenzaldehyde in a large abundance and sinapyl aldehyde methyl ether in a trace abundance. The results showed that TMAH thermochemolysis is an effective tool to obtain information on cinnamyl alcohol end groups, but is not applicable to analysis of cinnamyl aldehyde end groups.

Acrolein↗
PubMed2001

Utilisation of lignocellulosic wastes for lignin peroxidase production by semi-solid-state cultures of Phanerochaete chrysosporium.

In the present work, the production of ligninolytic enzymes by semi-solid-state cultures of Phanerochaete chrysosporium BKM-F-1767 (ATCC 24725), employing different lignocellulosic wastes as support, was investigated. The waste materials employed were grape seeds, wheat straw and wood shavings. Maximum lignin peroxidase activities of 1,620 +/- 123 U/l,364 +/- 35 U/l and 571 +/- 42 U/l were attained, respectively. Nevertheless, low manganese-dependent peroxidase activities were found, being insignificant in the grape seed cultures. Moreover, the in vivo decolourisation of a model dye compound, the polymeric dye Poly R-478 (polyvinylamine sulfonate anthrapyridone), by the above-mentioned cultures was monitored to assess the degrading capability of the extracellular liquid secreted by such cultures. The percentage of biological decolourisation attained by grape seed and wood shaving cultures was around 74% and 63%, respectively, whereas it was rather low (40%) in the wheat straw ones.

Carbohydrates↗