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At least 1,603 records · Page 89Linked to original sources
PubMed2005

The ectopic expression of phenylalanine ammonia lyase with ectopic accumulation of polysaccharide-linked hydroxycinnamoyl esters in internode parenchyma of rice mutant Fukei 71.

Both polysaccharide-linked hydroxycinnamoyl esters (PHEs) and lignin are biosynthesized via the phenylpropanoid pathway. In the abnormal internode parenchyma of the rice (Oryza sativa L.) mutant Fukei 71, which has a defective recessive gene (d50), the biosynthesis of lignin and PHEs differs. . The polysaccharide-linked ferulate and p-coumarate have been shown to accumulate to high levels in the irregularly shaped and collapsed internode parenchyma cells of Fukei 71 without an accompanying overaccumulation of lignin as a result of the defective d50 gene. In the present study we demonstrated that in this abnormal parenchyma tissue of Fukei 71 the expression of phenylalanine ammonia lyase (PAL) and glutamine synthetase (GS) were ectopically induced with the ectopic accumulation of PHEs, suggesting that the d50 gene may play a role as a controlling element in the biosynthesis of PHEs during cell-wall formation in the grasses.

Base Sequence↗
PubMed2003

Mechanical, chemical and X-ray analysis of wood in the two tropical lianas Bauhinia guianensis and Condylocarpon guianense: variations during ontogeny.

Mechanical and chemical properties as well as microfibril angles of wood tissues from different ontogenetic stages are determined for the neotropical lianas Bauhinia guianensis and Condylocarpon guianense. The mechanical properties include the elastic moduli under bending and under dynamic torsion. The chemical analyses cover (i) the content of cellulose, lignin and hemicelluloses fractions, (ii) the monomeric composition of the uncondensed lignin, and (iii) the composition of the hemicelluloses with respect to neutral monosaccharides. By comparing the wood properties of these lianas with the corresponding properties of wood from self-supporting deciduous trees, common characteristics and differences are revealed. Additionally, the changes in the lignin and polysaccharides fractions as well as the variations in microfibril orientation that occur during ontogeny of the two liana species are discussed with regard to their implications for the mechanical properties of wood.

Apocynaceae↗
PubMed2005

Biosoftening of coir fiber using selected microorganisms.

Coir fiber belongs to the group of hard structural fibers obtained from coconut husk. As lignin is the main constituent of coir responsible for its stiffness, microbes that selectively remove lignin without loss of appreciable amounts of cellulose are extremely attractive in biosoftening. Five isolated strains were compared with known strains of bacteria and fungi. The raw fiber treated with Pseudomonas putida and Phanerocheate chrysosporium produced better softened fiber at 30+/-2 degrees C and neutral pH. FeSO4 and humic acid were found to be the best inducers for P. chrysosporium and P. putida, respectively, while sucrose and dextrose were the best C-sources for both. Biosoftening of unretted coir fibers was more advantageous than the retted fibers. Unlike the weak chemically softened fiber, microbial treatment produced soft, whiter fibers having better tensile strength and elongation (44.6-44.8%) properties. Scanning electron microscopy photos showed the mycelia penetrating the pores of the fiber, removing the tylose plug and degrading lignin.

Cocos↗
PubMed1995

Reductions catalyzed by a quinone and peroxidases from Phanerochaete chrysosporium.

A quinone produced from veratryl alcohol by lignin peroxidase from the white rot fungus Phanerochaete chrysosporium was tested for its ability to mediate reduction. The quinone (2-hydroxymethyl-5-methoxy-1,4-benzoquinone), reduced chemically or by cellobiose:quinone reductase isolated from cultures of the fungus, mediated the reduction of cytochrome c in reactions containing either Mn(III), a manganese-dependent peroxidase, Mn(II) and H2O2, or lignin peroxidase and H2O2. Formation of the semiquinone, the species responsible for reducing cytochrome c, was observed by electron spin resonance spectroscopy in these reactions. The production of the quinone was observed in the extracellular fraction of cultures grown under nutrient nitrogen-deficient conditions (2.4 mM ammonium tartrate) for over 10 days, starting on Day 2, but not under nutrient nitrogen-sufficient conditions. These results suggest that a quinone produced by lignin peroxidase can serve as a physiological mediator of reductive reactions catalyzed by the fungal peroxidases.

Benzoquinones↗
PubMed1989

Trametes versicolor ligninase: isozyme sequence homology and substrate specificity.

The substrate specificity of three ligninase isozymes from the white-rot fungus Trametes versicolor has been investigated using stereochemically defined synthetic dimeric models for lignin. The isozymes have been found to attack non-phenolic beta-O-4 as well as beta-1 lignin model compounds. This finding confirms the classification of the isozymes from T. versicolor as ligninases. The amino-terminal residues of the three isozymes from T. versicolor have been determined using Edman degradation. Minor differences found between the sequences suggest the existence of several structural genes for ligninase in T versicolor. Comparisons have been made with the sequences of three previously reported ligninases from Phanerocompaete chrysosporium, another lignin-degrading fungus. One of the sequences from P. chrysosporium is distinctly more similar to the T. versicolor isozymes than to the other two sequences from P. chrysosporium.

Amino Acid Sequence↗
PubMed1993

Dietary fibre: its composition and role in protection against colorectal cancer.

Dietary fibre has a complex and highly variable composition. Although some dietary fibres may protect against colorectal cancer, it is unlikely that all are equally protective. Dietary fibre is principally composed of plant cell walls, but it also includes components obtained from cell walls (e.g. cellulose, pectin, and lignin), and non-starch polysaccharides (NSPs) from other sources (e.g. seaweeds and micro-organisms). The AOAC and Englyst methods are commonly used to determine the total amount of dietary fibre in foods. Most of the cell walls in food plants are from parenchyma cells, which are extensively degraded by bacteria in the colon. Cell types with walls containing the hydrophobic polymers lignin, suberin, or cutin also occur in food plants in small numbers, but they may be important in preventing colorectal cancer. Lignin, and possibly the other polymers, protect these walls from degradation. Epidemiological, human intervention, and animal studies can be used to try to identify the most protective dietary fibres. Epidemiological studies are difficult to interpret because usually only the total amount of dietary fibre eaten is reported. Intervention studies indicate that wheat bran dietary fibre may be protective. The results of animal carcinogenesis studies are variable, but sources of insoluble dietary fibres, including wheat bran, appear more protective than soluble dietary fibres, and some dietary fibres appear to enhance carcinogenesis. Possible mechanisms for protection by dietary fibres can be divided into two groups: those where the dietary fibre is acting directly, and those which result from the dietary fibre being degraded by colonic bacterial enzymes and the products fermented. Possible direct mechanisms include the binding of carcinogens to undegradable dietary fibres, and the absorption of water by undegradable dietary fibre resulting in increased faecal bulk and shortened transit times. Possible indirect mechanisms include the lowering of the colon pH by the short-chain fatty acids produced by bacterial fermentation, and the specific effects of butyrate. There are also a number of possible mechanisms by which some dietary fibres may enhance carcinogenesis. Use of better defined dietary fibres will increase our understanding of the role of dietary fibres in modulating colorectal cancer.

Animals↗
PubMed1996

Studies on the role of specific dietary fibres in protection against colorectal cancer.

Although dietary fibre is generally thought to protect against the development of colorectal cancer, some of the results of animal and epidemiological studies are equivocal. We believe that this may be because the term dietary fibre covers a range of complex materials and some may protect but others may not. Dietary fibre is mainly composed of plant cell walls which vary in composition and properties according cell type and plant species. In addition to polysaccharides, the walls of some plant cell types contain the hydrophobic polymers lignin or suberin. Two groups of mechanisms have been proposed for the way dietary fibres may protect against colorectal cancer: those in which the dietary fibre may act directly and those in which the dietary fibre may have an indirect effect as a consequence of it being degraded by colonic bacterial enzymes and the products fermented. Direct mechanisms include the adsorption of carcinogens onto undegraded dietary fibres which pass out of the intestinal tract in the faeces. we have shown that different types of plant cell walls adsorbed a range of carcinogens, including heterocyclic aromatic amines, to different extents. Cell walls that contained lignin or suberin adsorbed hydrophobic carcinogens particularly well. Furthermore, the presence of lignin, and probably suberin, in the walls makes them resistant to degradation in the colon. Wheat bran, which is a good source of dietary fibre, contains some cell types with lignified walls. We used Fischer-344 rats to test the ability of wheat bran to protect against the formation of aberrant crypts (which are considered to be precursors to colon cancer) caused by the heterocyclic aromatic amine, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Our results indicate that wheat bran protects and probably does so by a direct mechanism.

Adsorption↗
PubMed1994

A novel type of peroxidase gene from the white-rot fungus Trametes versicolor.

The wood-decaying fungus Trametes versicolor secretes a large number of peroxidase isozymes, presumed to partake in the degradation of lignin. From enzymic studies, two types of peroxidases have been distinguished: lignin peroxidases and manganese peroxidases. We here report the finding of a T. versicolor peroxidase gene, PG V, which displays several features not observed in previously studied peroxidase genes from white-rot fungi, such as a high number of introns (12). Eight of the 12 introns have positions equivalent to introns of peroxidase genes from another white-rot fungus, Phanerochaete chrysosporium. The gene structure of PG V appears to be primarily related to known lignin peroxidase genes, while the encoded mature 339-residue protein has several characteristics in common with manganese peroxidases. Analyses further indicate that PG V encodes a Ser instead of an Asn at a position regarded as invariant within the enzyme superfamily, with the side chain involved in hydrogen bonding with the distal His.

Amino Acid Sequence↗
PubMed1984

Advances in microbial delignification.

Microbial delignification is a new field of applied research. The progress will therefore run parallel to the development of new basic knowledge on the physiological demands of white-rot fungi to degrade lignin and on new knowledge on enzyme mechanisms involved in lignin degradation. In the last few years both basic and applied research on microbial conversion of lignocellulosic materials have vastly expanded. In certain areas, such as microbial delignification, considerable progress has recently been made. Basidiospores from Sporotrichum pulverulentum and some CEL(-) mutants have been obtained. Crossing of mycelium from single basidiospore cultures of wild-type and CEL(-) mutants will eventually give rise to much better CEL(-) mutants than those which have been used in the past. An understanding of which enzymes are the most important for lignin degradation to take place is also beginning to develop. This review discusses present knowledge and future possibilities in this field.

Journal Article↗
PubMed2006

Characterization of two new multiforms of Trametes pubescens laccase.

Electrochemical properties of two multiforms of laccase from Trametes pubescens basidiomycete (LAC1 and LAC2) have been studied. The standard redox potentials of the T1 sites of the enzymes were found to be 746 and 738 mV vs. NHE for LAC1 and LAC2, respectively. Bioelectroreduction of oxygen based on direct electron transfer between each of the two forms of Trametes pubescens laccase and spectrographic graphite electrodes has been demonstrated and studied. It is concluded that the T1 site of laccase is the first electron acceptor, both in solution (homogeneous case) and when the enzymes are adsorbed on the surface of the graphite electrode (heterogeneous case). Thus, the previously proposed mechanism of oxygen bioelectroreduction by adsorbed fungal laccase was additionally confirmed using two forms of the enzyme. Moreover, the assumed need for extracellular laccase to communicate directly and electronically with a solid matrix (lignin) in the course of lignin degradation is discussed. In summary, the possible roles of multiforms of the enzyme based on their electrochemical, biochemical, spectral, and kinetic properties have been suggested to consist in broadening of the substrate specificity of the enzyme, in turn yielding the possibility to dynamically regulate the process of lignin degradation according to the real-time survival needs of the organism.

Catalysis↗
PubMed2005

Colour removal of anaerobically treated pulp and paper mill effluent by microorganisms in two steps bioreactor.

In the present study sequential anaerobic and aerobic treatment in two steps bioreactor was performed for removal of colour in the pulp and paper mill effluent. In anaerobic treatment, colour (70%), lignin (25%), COD (42%), AOX (15%) and phenol (39%) were reduced in 15 days. The anaerobically treated effluent was separately applied in bioreactor in presence of fungal strain, Paecilomyces sp., and bacterial strain, Microbrevis luteum. Data of study indicated reduction in colour (95%), AOX (67%), lignin (86%), COD (88%) and phenol (63%) by Paecilomyces sp. where as M. luteum showed removal in colour (76%), lignin (69%), COD (75%) AOX (82%) and phenol (93%) by day third when 7 days anaerobically treated effluent was further treated by aerobic microorganisms. Change in pH of the effluent, and increase in biomass of microorganisms substantiated results of the study, which was concomitant to the treatment method.

Anaerobiosis↗
PubMed2005

Biocatalytic decolourisation of molasses by Phanerochaete chrysosporium.

Bioremediation potential of Phanerochaete chrysosporium strains NCIM 1073, NCIM 1106 and NCIM 1197 to decolourise molasses in solid and liquid molasses media was studied. Strains varied in the pattern of molasses decolourisation on solid medium by Giant colony method. Under submerged cultivation conditions, strain NCIM 1073 did not decolourise molasses while, strains NCIM 1106 and NCIM 1197 could decolourise molasses up to 82% and 76%, respectively. Under stationary cultivation conditions, none of the strains could decolourise molasses. This was overcome by increasing the surface area of the culture in flat bottom glass bottles under stationary cultivation conditions. Under submerged cultivation conditions, growth was more or less same in all strains. However, the lignin peroxidase and manganese peroxidase activities were significantly less in the strain NCIM 1073. Under stationary cultivation conditions, none of the strains could produce enzymes lignin peroxidase, manganese peroxidase and laccase. However, all of them could produce lignin peroxidase and manganese peroxidase when cultivated in flat bottom glass bottles under stationary cultivation conditions.

Biodegradation, Environmental↗
PubMed2003

White-rot fungi and their enzymes for the treatment of industrial dye effluents.

White-rot fungi produce various isoforms of extracellular oxidases including laccase, Mn peroxidase and lignin peroxidase (LiP), which are involved in the degradation of lignin in their natural lignocellulosic substrates. This ligninolytic system of white-rot fungi (WRF) is directly involved in the degradation of various xenobiotic compounds and dyes. This review summarizes the state of the art in the research and prospective use of WRF and their enzymes (lignin-modifying enzymes, LME) for the treatment of industrial effluents, particularly dye containing effluents. The textile industry, by far the most avid user of synthetic dyes, is in need of ecoefficient solutions for its colored effluents. The decolorization and detoxification potential of WRF can be harnessed thanks to emerging knowledge of the physiology of these organisms as well as of the biocatalysis and stability characteristics of their enzymes. This knowledge will need to be transformed into reliable and robust waste treatment processes.

Basidiomycota↗
PubMed2006

Computational analysis of the Phanerochaete chrysosporium v2.0 genome database and mass spectrometry identification of peptides in ligninolytic cultures reveal complex mixtures of secreted proteins.

The white-rot basidiomycete Phanerochaete chrysosporium employs extracellular enzymes to completely degrade the major polymers of wood: cellulose, hemicellulose, and lignin. Analysis of a total of 10,048 v2.1 gene models predicts 769 secreted proteins, a substantial increase over the 268 models identified in the earlier database (v1.0). Within the v2.1 'computational secretome,' 43% showed no significant similarity to known proteins, but were structurally related to other hypothetical protein sequences. In contrast, 53% showed significant similarity to known protein sequences including 87 models assigned to 33 glycoside hydrolase families and 52 sequences distributed among 13 peptidase families. When grown under standard ligninolytic conditions, peptides corresponding to 11 peptidase genes were identified in culture filtrates by mass spectrometry (LS-MS/MS). Five peptidases were members of a large family of aspartyl proteases, many of which were localized to gene clusters. Consistent with a role in dephosphorylation of lignin peroxidase, a mannose-6-phosphatase (M6Pase) was also identified in carbon-starved cultures. Beyond proteases and M6Pase, 28 specific gene products were identified including several representatives of gene families. These included 4 lignin peroxidases, 3 lipases, 2 carboxylesterases, and 8 glycosyl hydrolases. The results underscore the rich genetic diversity and complexity of P. chrysosporium's extracellular enzyme systems.

Carboxylic Ester Hydrolases↗
PubMed2003

Properties and functional significance of Saccharomyces cerevisiae ADHVI.

The completion of the Saccharomyces cerevisiae genome project has provided the opportunity to explore for new genes of the medium-chain dehydrogenase/reductase enzyme superfamily. Our group has recently identified a new gene, the YMR318C open reading frame, which coded for a Zn-containing NADP(H)-dependent alcohol dehydrogenase (ADHVI). ADHVI has been purified to homogeneity from over expressing yeast cells, and found to be a homodimer of 40 kDa subunits. The enzyme showed a strict specificity for NADP(H) and high activity with a variety of long chain aliphatic and bulky substrates. Aldehydes exhibited 50-12000 times higher catalytic efficiency than the corresponding alcohols. Substrates with high k(cat)/K(m) were: pentanal, veratraldehyde and cinnamaldehyde. The ADHVI expression was strongly induced when galactose was the sole carbon source in the culture medium. Phylogenetic trees include ADHVI in the cinnamyl alcohol dehydrogenase (CADH) family. In contrast to the plant CADH, involved in lignin biosynthesis, this is not the function for ADHVI, since yeast does not synthesize lignin. ADHVI may be physiologically involved in several steps of the lignin degradation pathway, initiated by other microorganisms, in the synthesis of fusel alcohols, products derived from the aminoacidic metabolism, and in the homeostasis of NADP(H). Disruption of ADH6 was not lethal for the yeast, under laboratory conditions.

Aldehyde Dehydrogenase↗
PubMed2001

Two cinnamoyl-CoA reductase (CCR) genes from Arabidopsis thaliana are differentially expressed during development and in response to infection with pathogenic bacteria.

Cinnamoyl-CoA reductase (CCR; EC 1.2.1.44) catalyses the conversion of cinnamoyl-CoAs into their corresponding cinnamaldehydes, i.e. the first step of the phenylpropanoid pathway specifically dedicated to the monolignol biosynthetic branch. In previous work, we described the isolation and characterisation of the first cDNA encoding CCR in Eucalyptus (Lacombe, E., Hawkins, S., Van Dorsselaere, J., Piquemal, J., Goffner, D., Poeydomenge, O., Boudet, A.M., Grima-Pettenati, J., 1997. Cinnamoyl CoA reductase, the first committed enzyme of the lignin branch biosynthetic pathway: cloning, expression and phylogenetic relationships. Plant Journal 11, 429--441) and shown the role of this enzyme in controlling the carbon flux into lignins (Piquemal, J., Lapierre, C., Myton, K., O'Connell, A., Schuch, W., Grima-Pettenati, J., Boudet, A.M., 1998. Down-regulation of cinnamoyl-CoA reductase induces significant changes of lignin profiles in transgenic tobacco plants. Plant Journal 13, 71--83). Here, we report the characterisation of two functionally and structurally distinct cDNA clones, AtCCR1 and AtCCR2 (81.6% protein sequence identity) in Arabidopsis thaliana. The two recombinant proteins expressed in Escherichia coli are able to use the three cinnamoyl-CoAs tested but with different levels of efficiency. AtCCR1 is five times more efficient with feruloyl-CoA and sinapoyl-CoA than AtCCR2. In addition, the two genes are differentially expressed during development and in response to infection. AtCCR1 is preferentially expressed in tissues undergoing lignification. In contrast, AtCCR2, which is poorly expressed during development, is strongly and transiently induced during the incompatible interaction with Xanthomonas campestris pv. campestris leading to a hypersensitive response. Altogether, these data suggest that AtCCR1 is involved in constitutive lignification whereas AtCCR2 is involved in the biosynthesis of phenolics whose accumulation may lead to resistance.

Aldehyde Oxidoreductases↗
PubMed1999

Binding capacity of various fibre to pesticide residues under simulated gastrointestinal conditions.

The purpose of this study was to compare the effect of the nature and quantity of various dietary fibre (cellulose, hemicellulose, pectin, lignin) in diets on the binding capacity to pesticides azinphos-methyl (AZM), chlorpropham (CLP), chlorothalonil (CKL), permethrin (PER) as estimated by solubility under conditions of pH and temperature simulating those in the gastrointestinal tract (incubated at pH 2 for 30 min at 37 degrees C, then at pH 7 for 60 min). The ratios of fibre to pesticides were determined in omnivorous diets. In this model, the binding capacity of lignin was equal to hemicellulose for PER, AZM and CLP, but it was significantly higher for CKL. Hemicellulose bound more CKL, AZM and CLP than did cellulose. Although pectin appreciably decreased all pesticides, its effect was lower than other fibres with one exception--cellulose-CKL. In the presence of equal amounts of fibre, lignin exerted the most significant effect on pesticide solubility. Hemicellulose and cellulose bind to the same extent PER and AZM. The effect of pectin was significant only on CKL and AZM when compared to the control.

Adult↗
PubMed2003

Stacking transgenes in forest trees.

Huge potential exists for improving plant raw materials and foodstuffs via metabolic engineering. To date, progress has mostly been limited to modulating the expression of single genes of well-studied pathways, such as the lignin biosynthetic pathway, in model species. However, a recent report illustrates a new level of sophistication in metabolic engineering by overexpressing one lignin enzyme while simultaneously suppressing the expression of another lignin gene in a tree, aspen. This novel approach to multi-gene manipulation has succeeded in concurrently improving several wood-quality traits.

Biolistics↗