Browsing by Author "FERRER, I"

Now showing 1 - 6 of 6
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    DECOLORIZATION OF KRAFT EFFLUENT BY FREE AND IMMOBILIZED LIGNIN PEROXIDASES AND HORSERADISH-PEROXIDASE
    (1991) FERRER, I; DEZOTTI, M; DURAN, N
    Color removal from Kraft effluent by lignin peroxidase and horseradish peroxidase was compared. Free lignin peroxidase and horseradish peroxidase removed color from kraft effluent. Immobilization of lignin peroxidase type III, lyophilized fungal culture and horseradish peroxidase on CNBr-Sepharose 4B improved the decolorization by factor of 2.9, 4.5 and 2.6, respectively in 48 h. Lignin peroxidase type I was effective only in the immobilized form in decolorization. In general, the immobilized form all the studied systems exhibited an average value around of 30% polymer consumption and very little of depolymerization. Lignin peroxidases and lyophilized fungal culture were shown to have considerable potential for treating Kraft effluents.
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    ISOLATION AND PHOTOOXIDATION OF LYSOZYME FRAGMENTS
    (1981) FERRER, I; SILVA, E
    Reduction of the 4 disulfide bonds and further carboxymethylation of lysozyme followed by its reaction with CNBr brings about L-I, (aa [amino acids] 1-12) and L-II-III (aa 13-129) peptides. When breaking the polypeptidic chain by CNBr action and freeing the peptides formed through S-S bonds reduction and carboxymethylation, 3 peptides are obtained corresponding to L-I (aa 1-12), L-II (aa 13-105) and L-III (aa 106-129). L-II-III, L-III and L-II peptides were separately subjected to photo-oxidation in presence of riboflavin in 0.05 M phosphate buffer, pH 7.0. The kinetic analysis of Trp photo-oxidation in L-II-III peptides shows that these residues keep, to a great extent, the degree of exposure they had in native lysozyme. L-II peptide also presents Trp residues with a different degree of exposure. Presence of Tyr photo-oxidation in L-II and L-II-III peptides (this does not take place in native lysozyme) suggests a relationship between photo-oxidation selectivity and the degree of exposure of certain amino acid residues in spatial configuration.
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    LIGNIN PEROXIDASE FROM CHRYSONILIA-SITOPHILA - HEAT-DENATURATION KINETICS AND PH STABILITY
    (1992) FERRER, I; ESPOSITO, E; DURAN, N
    Many practical applications utilizing lignin peroxidases from Chrysonilia sitophila (TFB-27441 strain) have been proposed. However, more information regarding the stability of these enzymes was required to design and develop these technologies. Heat- and pH-denaturation studies were conducted on purified lignin peroxidase and on crude culture of lignin peroxidase from C. sitophila. The culture produced in a 15-l bioreactor with Fries medium was utilized to obtain purified lignin peroxidases. LIG-I, LIG-II, and LIG-III were tested in the range 28-50-degrees-C, and LIG-III was found to be the most stable in the temperature range tested. The observed k(D) values at 28, 35, and 50-degrees-C were 0.058, 0.095, and 0.111 h-1, respectively. Increasing the LIG-III concentration by 2.3-fold increased thermal stability by around twofold. The heat-denaturation kinetics under these conditions for all lignin peroxidases and for the crude culture were first-order. LIG-I and LIG-II appeared as the most representative enzymes in the crude culture, since similar k(D) values were obtained. The pH stability showed the same trends.
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    LIGNINASES FROM CHRYSONILIA-SITOPHILA (TFB-27441 STRAIN)
    (1987) DURAN, N; FERRER, I; RODRIGUEZ, J
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    STUDY OF A PHOTOINDUCED LYSOZYME-RIBOFLAVIN BOND
    (1985) FERRER, I; SILVA, E
    Irradiation of lysozyme in the presence of riboflavin results in the formation of a lysozyme-riboflavin adduct. Reduction and carboxymethylation of the 4 disulfide bonds as well as the chemical modification of the Tyr residues and the photochemical alteration of the His residue in lysozyme, do not affect the formation of the photo-induced lysozyme-riboflavin bond. When the lysozyme-riboflavin adduct was subjected to mild acid hydrolysis and ion exchange chromatography, the retention of a compound containing 14C-riboflavin was observed. Free 14C-riboflavin, on the contrary, is not retained by the column. The photo-oxidation of free Trp in the presence of 14C-riboflavin, gave a compound which bound to the ion exchange resin like the above-mentioned derivative. The photo-oxidation of the Trp residues in lysozyme and in peptides obtained from lysozyme showed very high quantum yields, and these values were directly related to the incorporation of 14C-riboflavin in these samples.