39 research outputs found

    Polymerization study of the aromatic amines generated by the biodegradation of azo dyes using the laccase enzyme

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    Four different azo dyes were decolorized (color reduction >90%) by bacteria isolated from a textile wastewater effluent. Dye decolorizing was carried out under microaerobic conditions until completion, after which the aromatic amine concentration was determined. A laccase from Myceliophthora thermophila was used to catalyze coupling reactions of the aromatic amines produced from decolorizing the dyes. The reaction was carried out with stirring (100 rpm) in a weak acidic buffer solution (pH 5.0) at 45 °C for 3 days. The presence of aromatic amines in the samples after bacterial decolorizing confirmed the azo bond was reduced in the process. In addition, the UV–vis spectrum was shifted significantly after the sequential bacterial-laccase treatment also indicating a chemical transformation of the dyes. After laccase treatment the solutions formed colored soluble and precipitated products. The particles sizes making up the precipitates formed after laccase treatment varied between 105 and 483 nm as determined by Photon Correlation Spectroscopy (PCS). The laccase treatment also reduced the COD of the dye solutions by ∼20%. We show that successive bacterial-laccase treatment is effective in decolorized azo dyes by reduction of the azo bonds, and promoting coupling reactions between the aromatic amines formed. Promoting coupling reactions between the aromatic amines using enzymes may prove useful for the physical removal and reuse of these amines.The authors would like to thank the Brazilian Foundation Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior of the Ministry of Education (CAPES) and the National Counsel for Technological and Scientific Development (CNPq) for providing grants to Elisangela Franciscon

    Single origin of sex chromosomes and multiple origins of B chromosomes in fish genus Characidium

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    Chromosome painting with DNA probes obtained from supernumerary (B) and sex chromosomes in three species of fish genus Characidium (C. gomesi, C. pterostictum and C. oiticicai) showed a close resemblance in repetitive DNA content between B and sex chromosomes in C. gomesi and C. pterostictum. This suggests an intraspecific origin for B chromosomes in these two species, probably deriving from sex chromosomes. In C. oiticicai, however, a DNA probe obtained from its B chromosome hybridized with the B but not with the A chromosomes, suggesting that the B chromosome in this species could have arisen interspecifically, although this hypothesis needs further investigation. A molecular phylogenetic analysis performed on nine Characidium species, with two mtDNA genes, showed that the presence of heteromorphic sex chromosomes in these species is a derived condition, and that their origin could have been unique, a conclusion also supported by interspecific chromosome painting with a CgW probe derived from the W chromosome in C. gomesi. Summing up, our results indicate that whereas heteromorphic sex chromosomes in the genus Characidium appear to have had a common and unique origin, B chromosomes may have had independent origins in different species. Our results also show that molecular phylogenetic analysis is an excellent complement for cytogenetic studies by unveiling the direction of evolutionary chromosome changes.This research was funded by grants from the State of Sao Paulo Research Foundation (FAPESP) to EAS (2013/02143-3), grants from National Council for Research and Development (CNPq) to FF (480449/2012-0), and by Coordenacao de Aperfeicoamento de Pessoal de Nıvel Superior (CAPES)
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