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Ver el documento (formato PDF)   Papinutti, Víctor Leandro.  "Enzimas ligninolíticas en Fomes sclerodermeus"  (2003)
Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires

White rot fungi are the only organisms capable to mineralize the lignin to CO2. These fungi posses at least three enzymes impicated in the process: lignin peroxidase, manganese dependent peroxidase and laccase. The screening of 13 strains of white-rot fungi showed that F. sclerodermeus was the more efficient ligninase producer fungus and the decolorization of the polymeric dye poly R was fast. Lip activity was not detected in any of the media tested. Optimal media conditions for laccase and MnP production in synthetic liquid media were found. The Doehlert uniform factorial experimental design was applied to study the effect of MnSO4, CuSO4 and asparagine. Among the aromatic compounds evaluated in GA medium, vanillin and fenilic acid were the more efficient laccase and MnP inducers. On the other hand, in semidefined medium (YPG) aromatic compounds had not effect on any activity. Under this conditions only copper and Mn increased laccase and MnP activities, respectively. Solid state fermentation on wheat or soy bran, high laccase and MnP were produced. Neither aromatic compounds, MnSO4 nor CuSO4 increased none of the activities. The effect on known ligninolytic inducers was studied on a crystalline cellulose (CC) based medium. Cellulolytic activities decreased 3-fold when CuSO4 or MnSO4 were added to the medium. MnP activity was only detected in the media containing MnSO4 as inducer, while the laccase activity was constitutiver expressed under all the conditions tested, and it was increased to a major extent when copper was added to the medium. Wood blocks of poplar incubated during six months with F. sclerodermeus registered dry weight losses of 51%. Differential hydrolysis of the wood blocks revealed that the remaining content of cellulose and lignin were 58 y 56%, respectively. On the other hand, the hydrosolubles increased 3-fold, due to the degradation products. Observation of the wood showed the degradation of parenchyma rays and thinning of the cell walls. Growing on sawdust medium, enzyme activities were produced only with poplar, whereas on cedar laccase and MnP were inhibited. Laccase and MnP produced in YPG medium by F. sclerodcrmeus were purified to electrophoretic homogeneity and characterized biochemically. Two isoenzymes of laccase (Lac I y Lac II) and two MnP (MnP I y MnP II) were found. Isoforms of both systems showed slight differences in their isoelectric points. Laccase activity produced on wheat bran based medium revealed three bands in PAGE with differential patterns of inactivation. Among the compounds tested, the CuSO4 1,25 mM was the best stabilizer. The combination of both CuSO4 and glycerol 0,2% further increased the stability of the enzyme. Laccase activity produced in the optimized conditions was used in assays of decoloration and detoxification of the fungicide malachite green. P. chrysosporium was used as biotest, this Fungus showed a high sensitivity to the fungicide, while degradation by F. sclerodermeus laccase rendered a not toxic compound. The presence of I-HBT accelerated the detoxification. The detoxification response of other white-rot fungi was similar to that observed for P. chrysosporium.
Título : Enzimas ligninolíticas en Fomes sclerodermeus     =    Lignin modifying enzymes in Fomes sclerodermeus
Autor : Papinutti, Víctor Leandro
Director : Forchiassin, Flavia
Año : 2003
Editor : Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Filiación : Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales
Departamento de BIodiversidad y Biología Experimental
Grado obtenido : Doctor en Ciencias Biológicas
Ubicación : Preservación - http://digital.bl.fcen.uba.ar/gsdl-282/cgi-bin/library.cgi?a=d&c=tesis&d=Tesis_3584_Papinutti
Idioma : Español
Area Temática : Biología /Micología
URL al Documento : 
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