Recebido em 27/5/04; aceito em 26/10/04; publicado na web em 28/2/05 BIODEGRADATION OF TEXTILE EFFLUENTS BY Pleurotus sajor-caju. Effluents generated by the textile industry are of environmental concern because of the presence of dyes with complex molecular structure, which confer them recalcitrant characteristics. Indigo is one of the most widely used dyes within the textile sector and studies have suggested that edible fungi may be capable of its biodegradation. A textile effluent was mixed with sugarcane bagasse and inoculated with Pleurotus sajorcaju, the decolorization being evaluated after 14 days, when the process was observed. Enzymatic activities of laccase, peroxidase and manganese peroxidase were determined, the production of these ligninolytic enzymes being evident and a synergism among them being likely in the decolorizing process.

Manganese peroxidase (MnP) is a ligninolytic enzyme that is involved in the removal of lignin from the cell wall of plants. This removal facilitates the access of hydrolytic enzymes to the carbohydrate polymers that are hydrolyzed to simple sugars, which allows the subsequent fermentation to obtain bioproducts, such as ethanol. In this work, response surface methodology (RSM) was employed to optimize the culture conditions on unexpensive substrate for MnP secretion by Trametes villosa. Three independent variables were evaluated (i.e., temperature, moisture content and pH). The crude extract containing MnP was used in the delignification experiment and it caused a reduction in lignin content for all residues tested: 35.05 ± 1.45 (%) for the sugar cane bagasse; 63.11 ± 0.06 (%) for the sisal fiber and 39.61 ± 0.39 (%) for the coconut shell, under the reaction conditions tested after 4 hours of fermentation. The preliminary results exhibited the potential application of this enzyme in the removal of lignin from plant residues. However, the conditions should be evaluated and optimized for each residue type.

The Americana Municipal Treatment Station, Sa˜o Paulo, Brazil, manages 400 l of effluent s )1 , from domestic and textile origin, which produces an average of 20 t of sludge per day. The decolourization of the effluent and sludge by three strains of Pleurotus (Pleurotus sajor-caju F2, F6 and Pleurotus ostreatus) was evaluated. The strains of P. sajorcaju F2 and F6 were able to decolourize the sludge, while P. ostreatus was less efficient. Detoxification was appraised with three bioassays comprising the cnidarian Hydra attenuata, the alga Selenastrum capricornutum and lettuce seeds. After exposure to fungi, effluent toxicity decreased but not that of its sludge. Strain P. sajor-caju F6 presented signs of toxicity shown by electron microscopy in the presence of the effluent. The three strains produced high amounts of manganese-peroxidase (Mn-P) and laccase in the presence of the sludge. Although P. ostreatus produced large amount of Mn-P and laccase enzymes, these enzymes did not result in decolourization of the sludge, suggesting that other factors are likely to be involved. Carbon content decreased only in the treatment with P. ostreatus.

Ganoderma lucidum is a medicinal mushroom with different forms of bioactivity that has been used in popular medicine for centuries. This study aimed to test the application of agricultural wastes (fruit shells, leaves, and bracts) from the endemic Brazilian palm tree Syagrus coronata (licuri) as substrates for the production of G. lucidum basidiomata and ligninolytic enzymes via solid-state fermentation. The best culture conditions were the same for all substrates (pH 6.5, carbon-to-nitrogen ratio = 40, and temperature 30°C) and were established from preliminary assays. The yield was not significantly different for bracts (33.53 g/kg) and leaves (37.48 g/kg), nor for the biological efficiency in these same substrates: bracts, 3.35%; leaves, 3.75%. The highest laccase (13.80 U/L) and manganese peroxidase (14.92 U/L) activities were achieved after 14 and 28 days of incubation, respectively, using bracts as the substrate. Licuri residues are then potential substrates to be used in the bioconversion process for mycelia, basidiomata, and ligninolytic enzyme production by G. lucidum.

Lytic enzymes are widely used in industrial biotechnology as they are able to hydrolyze the bacterial cell wall. One application of these enzymes is the clarification of the culture broth for the production of xanthan gum, because of its viability in viscous media and high specificity. The screening process for filamentous fungi producing lytic enzymes, the optimization of production of these enzymes by the selected microorganism, and the optimization of the application of the enzymes produced in the clarification of culture broth are presented in this article. Eleven fungal isolates were tested for their ability to produce enzymes able to increase the transmittance of the culture broth containing cells of Xanthomonas campestris. To optimize the secretion of lytic enzymes by the selected microorganism the following variables were tested: solid substrate, initial pH, incubation temperature, and addition of inducer (gelatin). Thereafter, secretion of the enzymes over time of incubation was assessed. To optimize the clarification process a central composite rotational design was applied in which the pH of the reaction medium, the dilution of the broth, and the reaction temperature were evaluated. The isolate identified as Aspergillus tamarii was selected for increasing the transmittance of the broth from 2.1% to 54.8%. The best conditions for cultivation of this microorganism were: use of coconut husk as solid substrate, with 90% moisture, at 30°C for 20 days. The lytic enzymes produced thereby were able to increase the transmittance of the culture broth from 2.1% to 70.6% at 65°C, without dilution and without pH adjustment.

Exclusively Brazilian, the Caatinga biome has been thus far a place of very few studies on the Basidiomycetes fungi. Due to its semiarid climate, fungi found in the region are likely to carry lignolytic enzymes which hold biotechnological potential to be used in industrial processes of agro-industrial residue bioconversion. This study performed a response surface statistical planning to optimize the secretion of enzymes such as laccase (Lac), lignin peroxidase (LiP) and manganese peroxidase (MnP) by Lentinus crinitus. Three variables were under analysis: different concentrations of barley and cassava residue, pH and temperature. MnP enzyme showed the highest enzymatic activity rate (23.5 IU/L). Additionally, MnP had the best results of enzyme secretion for substrate composition of 50% barley and 50% cassava, at pH 7 and temperature at 28˚C for a 28-day incubation period. However, further studies are pivotal to test the efficiency in lignin bioconversion by the enzymes synthesized in this work and also to establish their usage pattern on a large scale.

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