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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Effect of Mechanical Wounding on Lignin Biosynthesis in Soybean Hypocotyls

Chen, Yung-Tai 18 June 2003 (has links)
In our study, the decrease of H2O2 levels in wounding-treated tissues of soybean ( Glycine Max ) hypocotyls is accompanied by the enhancement of the POD activity. The POD activity was significantly enhanced 0.5 d after wounding treatment. The laccase activity was significantly enhanced 1-2 d after wounding treatment. The enhancement of POD by mechanical wounding occurred a day earlier than laccase. The increase in activities of POD and laccase is correlated with a rise in lignin contents in wounding-treated tissues. We suggest that in control tissues, laccase might play major role on the lignin biosynthesis, hence, POD by utilizing H2O2 play the major role on the lignin biosynthesis during the wounding process.

Effect of harpinpss on lignin biosynthesis in tobacco leaves during hypersensitive response

Jan, Jen-Ting 20 June 2003 (has links)
Harpinpss, a pathogenic protein, encoded by hrpZ in the hrp gene cluster from Pswudomonas syringae pv. syringae, can induce the hypersensitive response in tobacco (Nicotiana tabacum L. cv. Xanthi). The lesion area on the tobacco leaves was visible 6 h after inoculation with harpin, and was evident 12 h after inoculation. The lignin content in harpin-treated tobacco leaves was about 2.5-fold as compared with the controls 24 h after inoculation. There were six isozymes of POD (pI 9.5, pI 8.7, pI 5.3, pI 4.4, pI 3.7, and pI 3.5) and seven isozymes of laccase (pI 9.4, pI 8.6, pI 7.8, pI 5.4, pI 4.5, pI 3.8, and pI 3.6) identified by isoelectric point in extracts of harpin-inoculated tobacco leaves. POD isozymes (pI 4.4, pI 5.3 and pI 8.7) and laccase isozyme (pI 7.8) only appeared in harpin-inoculated tissues. The increased POD isozymes (pI 4.4, pI 8.7, pI 9.5) are correlated with the rise of transcripts of these enzymes confirmed by the method of reverse transcriptase-polymerase chain reaction (RT-PCR).

Étude de l'oxydation de différents composés phénoliques par la laccase de Myceliophtora thermophila application à la fonctionnalisation du chitosane /

Issa, Nizar Girardin, Michel Muniglia, Lionel January 2009 (has links) (PDF)
Thèse de doctorat : Procédés biotechnologiques et alimentaires : INPL : 2009. / Titre provenant de l'écran-titre.

Enzymes : the new water/wastewater treatment chemical

Garcia, Hector A. 15 June 2011 (has links)
Pharmaceuticals and personal care products (PPCPs) are detected routinely in raw and treated municipal wastewater. Conventional wastewater treatment processes are not effective in removing PPCP; therefore, treated wastewater discharges are one of the main entry points for PPCPs into the aquatic environment, and eventually into drinking water supplies. The use of laccase-catalyzed oxidation for removing low concentrations of PPCPs from municipal wastewater after primary treatment is investigated. Oxybenzone was selected as a representative PPCP. Like many other PPCPs, oxybenzone is not recognized directly by the laccase enzyme. Therefore, mediators were used to expand the oxidative range of laccase, and the efficacy of this laccase-mediator system in primary effluent was evaluated. Eight potential mediators were investigated. The greatest oxybenzone removal efficiencies were observed when 2,2’-azino-bis(3-ethylbenzthiazoline-6sulphonic acid) (ABTS), a synthetic mediator, and acetosyringone (ACE), a natural mediator, were present. An environmentally relevant concentration of oxybenzone (10 µg/L) in primary effluent was removed below the detection limit after two hours of treatment with ABTS, and 95% was removed after two hours of treatment with ACE. Several mediator/oxybenzone molar ratios were evaluated at two different initial oxybenzone concentrations. Higher mediator/oxybenzone molar ratios were required at the lower (environmentally relevant) oxybenzone concentrations, and ACE required higher molar ratios than ABTS to achieve comparable oxybenzone removal. The oxidation mechanisms and kinetics of the ACE mediator was evaluated. A better understanding of the mediator oxidation process would lead to a better design of the laccase-mediator system. An alternative laccase-mediator treatment configuration, which allows the enzyme and mediator to react prior to coming in contact with the target PPCP, was investigated. This treatment configuration shows promise for further development since it might reduce laccase and mediator requirements. Oxidation byproducts generated by the laccase-mediator system were characterized and compared to those generated during ozonation. Enzymatic treatment generated byproducts with higher mass to charge (m/z) ratios, likely due to oxidative coupling reactions. The results of this study suggest that, with further development, a laccase-mediator system has the potential to extend the treatment range of laccase to PPCPs not directly recognized by the enzyme, even in a primary effluent matrix. / text

Dye decolourization by immobilized laccase and impact of auxiliary chemicals on dye decolourization

Champagne, Paul-Philippe 16 June 2009 (has links)
Textile dyes are molecules designed to impart a permanent colour to textile fabrics. They pose an environmental problem because they are toxic and they decrease the aesthetic value of rivers and lakes. Current technologies for dye removal cannot remove all classes of dyes and two or more technologies are usually combined to achieve statisfactory decolourization efficiencies. Lignin-degrading enzymes like laccases are potential technologies for dye decolourization and decolourization with immobilized laccase has been intensively investigated. The majority of those studies however have focused on dye disappearance and several reported that significant dye adsorption had occured during the dye removal, making the role of the enzyme unclear. Moreover, textile wastewaters contain auxiliary chemicals that can impact enzymatic dye decolourization and very few studies have evaluated the impact of those substances on laccase. This research evaluated the feasibility of treating dye-contaminated textile wastewaters with an immobilized laccase system. The first sub-objective was to examined the decolourization of Reactive blue 19 (an anthraquinone dye) by Trametes versicolor laccase immobilized on controlled porosity carrier (CPC) silica beads and the second was to analyze the kinetic effects of a non-ionic surfactant Merpol, sodium sulfate, and sodium chloride on laccase decolourization of Reactive blue 19. Decolourization of Reactive blue 19 by immobilized laccase was mainly enzymatic although dye some adsorption occurred. Decolourization led to less toxic by-products from azo and indigoid dyes whereas increased toxicity was observed for anthraquinone dyes. The feasibility of immobilizing laccase on poly(methyl methacrylate) (PMMA) through its sugar residues with a simple procedure was demonstrated and the mass of enzyme immobilized compared well with other commercial acrylic supports. The decolorization of Reactive blue 19 by laccase was inhibited by the non-ionic surfactant, Merpol by substrate depletion. A model describing this inhibition was developed and was validated by a saturated equilibrium binding experiment. While sodium sulfate (ionic strength) had no effect on either ABTS oxidation or dye decolourization, sodium chloride inhibited laccase during dye decolourization and the type and nature of the inhibition depended on the substrate. With ABTS, the inhibition was hyperbolic non-competitive whereas it was parabolic mixed with Reactive blue 19. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2009-06-16 16:58:47.753

Pcr Cloning And Heterologous Expression Of Scytalidium Thermophilum Laccase Gene In Aspergillus Sojae

Koclar, Gulden 01 December 2005 (has links) (PDF)
In this study, Scytalidium thermophilum laccase gene was first cloned into E. coli and then heterologously expressed in A. sojae. S. thermophilum is a thermophilic fungus with an important role in determining selectivity of compost produced for growing Agaricus bisporus. S. thermophilum laccase gene was first cloned by Novo Nordisk Bio Tech, Inc. in 1998. This laccase gene (lccS) has an open reading frame of 2092bp. It is composed of five exons punctuated by four small introns. The coding region, excluding intervening sequences is very GC-rich (60.8% G+C) and encodes a preproenzyme of 616 amino acids: a 21 amino acid signal peptide and a 24 amino acid predicted propeptide. lccS gene was amplified using specific primers to exclude the signal and pro-peptide coding regions and ligated to expression vector pAN52-4. The recombinant plasmid was used to transform Aspergillus sojae ATCC11906 (pyrG-). Heterologuos expression was observed in glucose-containing media, under the control of the glyceraldehydes 3-phosphate dehydnogenese promoter and the secretion signal of glucoamylase gene. Laccase gene is an important step towards the high level expression of this enzyme in a GRAS eucaryotic host and for further biotransformation and enzyme engineering studies. In this study also bioinformatic analysis of N-terminal and C-terminal propeptide cleavage sites of fungal proteins including laccases were studied.

Isolierung und Charakterisierung von Laccasen und Peroxidasen aus Basidiomyceten der Ordnung Agaricales /

Heinzkill, Marion. January 1995 (has links) (PDF)
Universiẗat, Diss.--Kaiserslautern, 1995.

Chemo-enzymatic modification of high-kappa kraft pulps with laccase

Chandra, Richard P. January 2003 (has links)
Thesis (Ph. D.)--Institute of Paper Science and Technology, Georgia Institute of Technology, 2005. / Includes bibliography.

Levantamento de macrofungos (filo Basidiomycota, subfilo Agaricomycotina) do nordeste do Rio Grande do Sul e avaliação do seu potencial ligninolítico

Rosa, Letícia Osório da 19 April 2013 (has links)
Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-16T13:42:16Z No. of bitstreams: 1 Dissertacao Leticia Osorio da Rosa.pdf: 17230782 bytes, checksum: 3f0328e46773e7a61e1fd2e792a3c366 (MD5) / Made available in DSpace on 2014-06-16T13:42:16Z (GMT). No. of bitstreams: 1 Dissertacao Leticia Osorio da Rosa.pdf: 17230782 bytes, checksum: 3f0328e46773e7a61e1fd2e792a3c366 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico

Levantamento de macrofungos (filo Basidiomycota, subfilo Agaricomycotina) do nordeste do Rio Grande do Sul e avaliação do seu potencial ligninolítico

Rosa, Letícia Osório da 19 April 2013 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico

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