Remazol Brilliant Blue R (RBBR) dye was used as substrate to evaluate ligninolytic activity in 125 basidiomycetous fungi isolated from tropical ecosystems. The extracellular RBBR decolorizing activity produced when selected fungi were grown in solid media and in soil contaminated with organochlorines was also evaluated. A total of 106 fungi decolorized the RBBR during the growth in malt extract agar (MEA, 2%); 96 fungi showed a mycelia growth and decolorization activity stronger than the P. chrysosporium used as reference. Extracellular extracts of 35 selected fungi grown on solid medium with sugar cane bagasse (BGS) were evaluated for RBBR decolorization and peroxidase activity. All fungi showed peroxidase activities, but 5 of those were unable to decolorize the RBBR. Different patterns of ligninolytic enzymes were detected in 12 fungi extracts. Mn-dependent peroxidase (MnP) was produced by Peniophora cinerea, Psilocybe castanella, three strains of Trametes villosa, T. versicolor, Melanoporia nigra and Trichaptum byssogenum. All 12 fungi had laccase activity. Trogia buccinalis showed the highest RBBR decolorization and did not produce MnP activity. RBBR decolorization without MnP production was also observed for three strains of Lentinum tested. Higher levels of peroxidase and laccase cannot be related to high RBBR decolorization. RBBR decolorization by extracellular extract was also detected during the growth of P. castanella, L. crinitus, P. cinerea and two strains of T. Villosa in pentachlorophenol-and hexachlorobenzene-contaminated soils. These fungi showed higher RBBR decolorization when grown in the presence of organochlorine compounds than when in non contaminated soil.
Pleurotus ostreatus ("shimeji") is produced in Brazil on a commercial scale using various lignocellulosic residues. Efforts have been made to reuse the culture residue to obtain products of greater aggregate value such as enzymes or in processes of bioremediation. We evaluated the Remazol brilliant blue R (RBBR) degradation potential of extracts from solid substrate colonized by P. ostreatus and extracts from residue of the "shimeji" mushroom yield. Colonized substrates and residue were provided by Toyobo do Brasil Ltda. Extraction was performed with sodium acetate buffer (50 mM, pH 4.6). RBBR decolorization was monitored at 592 nm and peroxidase and laccase activities were measured by monitoring the oxidation of ABTS. Horseradish peroxidase was used as reference. The time of growth of P. ostreatus influenced RBBR degradation and peroxidase and laccase activities. Concentration of 1 mM H2O2 and pH 4.0 were the best for RBBR decolorization. Complete RBBR decolorization was obtained with the addition of only one aliquot of 50 µL of 1 mM H2O2. The stability of the extracts was higher when they were kept under refrigeration than when stored frozen. The potential application of the ligninolytic complex derived from P. ostreatus and mushroom residue for xenobiotic degradation was demonstrated.
The potential of Trametes villosa and Pycnoporus sanguineus to decolorize reactive textile dyes used for cotton manufacturing in the State of Minas Gerais, Brazil, was evaluated. Growth and decolorization halos were determined on malt extract agar containing 0.002g L -1 of the dye. T. villosa decolorized all 28 of the tested dyes while P. sanguineus decolorized only 9. The effect of culture conditions (shaking and dye and nitrogen concentration) on the degradation of Drimaren Brilliant Blue dye was evaluated during growth of the fungi in liquid synthetic medium. Shaking favored degradation and decolorization was not repressed by nitrogen. In pure culture, T. villosa and P. sanguineus decolorized synthetic effluent consisting of a mixture of 10 dyes. Higher decolorization of the synthetic effluent was observed when a mixed culture of the two fungi was used. This study demonstrated differences between tropical basidiomycete species in terms of their ability to degrade reactive dyes, and reinforces the potential of this group of fungi for the decolorization of textile effluents.
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