Effect of basidiomycete fungi on the discoloration and phytotoxicity of synthetic dye and textile effluent
Abstract
The elimination of toxic wastes from industrial activities, mainly the textile industry, has induced the researchers to seek new techniques that reduce or eliminate the toxicity of these effluents. The textile effluent has a high chemical demand of oxygen and strong coloration, requiring an especific treatment. The aim of this study was to evaluated the decolorizationRemazol Brilliant Blue R (RBBR) and textile effluent using pre-selected cultures of basidiomycete fungi: Lentinula edodes, Pleurotusostreatus and Pleutotuspulmorarius, and phytotoxicity of the dye and effluent before and after treatment with fungi. The decolorization test was realized in a liquid medium and the absorbance determined in spectrophotometer. For the dye was used to two pH values (5.0 and 9.0) and concentration (0.1 gL-1 and 0.5 gL-1). Lactuca sativa L. seeds were exposed to dye samples and textile effluents and the parameters evaluated were the germination rate and root lenght. The fungus Pleurotuspulmonarius was the one with the best result on the decolorization of dye RBBR on the both values: pH and concentration. As the textile effluent there was no significant difference among the treatments. In some treatments with the dye germination rate decreased indicating toxicity after decolorization. However there was an increase in root growth in the presence of the dye treated with P.pulmonarius.
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Introduction
In recent years, studies on urban environmental problems have been gaining prominence, mainly because the evolution of urban centers and continued population growth have led to the emergence of some forms of pollution that have reached catastrophic dimensions, which can be observed through changes quality of soil, air and water [1].
The textile sector is one of the activities that contribute most to the environmental contamination, because it uses in its processes large volumes of water, besides several substances during the staining, such as caustic soda, gums, detergents, defoamers, chlorine, formols, emulsions, oils and resins, among others. This leads to the production of a complex, toxic and recalcitrant residue [2].
Approximately 8,000 different dyes and pigments are used industrially, representing an annual consumption of around 800 000 tonnes worldwide, of which approximately 10-15% is discharged into the environment [3].
The textile effluent has high chemical oxygen demand and coloration due to the presence of dyes, pigments and auxiliary chemicals, which causes that the effluent needs a specific treatment [4].
When not properly treated and released into water bodies, the effluents from the textile fiber dyeing process can modify the ecosystem, reducing the transparency of the water and the penetration of solar radiation, which can modify the photosynthetic activity and the solubility regime of gases [5].
With regard to the removal of textile dyes present in industrial effluents, new technologies have been sought to minimize the environmental damages they may cause. Although there are physical and chemical forms of treatment of textile effluents, microorganisms have been intensively studied for this purpose [6].
Studies indicate that lignin-degrading basidiomycete fungi are efficient in the degradation of several compounds, including dyes, presenting high action potential in the recovery of contaminated environments [7].
The extracellular enzymes present in these fungi (lignin peroxidase, manganese peroxidase and laccase) are an effective means of degradation of pollutants, presenting specific mechanisms of degradation of recalcitrant compounds. However, there is a demand for biological agents not only able to degrade these effluents more efficiently, but also to reduce their toxicity [8].
It is in this context, from the constant search for alternative methods of treatment of effluents, that the need arises to study new fungal species that have degradation capacity of dyes and textile effluents, aiming at the optimization of traditional treatment processes.
The present work was carried out with the objective of evaluating the discoloration of Remazol Brilliant Blue R dye and textile effluent using pre-selected basidiomycete fungi cultures and verify the phytotoxicity of the dye and effluent before and after treatment with fungi, with Lactuca sativa L.
Conclusion
The fungus Pleuriticpulmonarius was able to decolorize the RBBR dye, both at pH 5.0 and at pH 9.0 and at the two concentrations used, 0.1 gL-1 and 0.5 gL-1; Lentinula edodes obtained better discoloration in the treatment with the RBBR dye at pH 5.0 and 0.5 gL-1 and the fungus Pleurotusostreatus, in the treatments at pH 5.0 and 0.5 gL-1 and at pH 9.0 and 0.5 gL-1; The dye showed a phytotoxic effect after the discoloration, reducing the germination rate in some treatments. However, after treatment with the fungus Pleurotuspulmonarius, it induced root growth, which did not present a toxic effect for this parameter; The treatments with the textile effluent showed lower germination rates and, in contrast, higher promoter effect on root growth.