Universidade Catolica de Santos, Santos, SP, Brasil. Fundacao Centro Tecnologico de Minas Gerais, Belo Horizonte, MG, Brasil. Laboratorio de Quimica de Produtos Naturais, Centro de Pesquisas Rene Rachou, Fundacao Instituto Oswaldo Cruz, Belo Horizonte, MG, Brasil

ABSTRACT

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.

Key words: textile industry, synthetic effluent, reactive dyes

INTRODUCTION

In the State of Minas Gerais, the second largest textile pole in Brazil, most textile industries operate with pure cotton fibers or cotton fibers mixed with polyester. Few of these factories possess their own wastewater treatment plant, and most of the time the effluents are discharged into the water bodies without any treatment. In general, the difficulties encountered in the wastewater treatment resulting from dyeing operations lies in the wide variability of the dyes used and in the excessive color of the effluents. Many dyes and other substances present in textile effluents are not readily degraded during their permanency in traditional aerobic treatment systems (17, 26).

Although many physicochemical techniques of decolorization have been developed over the last 20 years, few have been implemented by the textile industries due to their high cost, low efficiency and inapplicability to a wide variety of dyes. A definitive solution of the color problem of textile effluents would provide a marked competitive advantage for this industrial sector. Since no single process is able to decolorize all textile effluents, a solution for each situation should be considered, possibly involving a combination of different methods (1). The success of a biological process for color removal from a given effluent depends in part on the utilization of microorganisms that effectively decolorize synthetic dyes of different chemical structures. Many bacteria, actinomycetes, yeast and metaphoric fungi are able to decolorize dyes, with color removal by these microorganisms being mainly attributed to adsorption of the dyes (1, 27).

Basidiomycetous fungi are able not only to decolorize but also to degrade and mineralize a broad spectrum of different dye structures (azo, anthraquinone, heterocyclic, triphenylmethane and polymeric dyes), in addition to numerous other toxic organic and recalcitrant compounds.

The enzymatic system involved in the degradation of pollutants by these fungi is nonspecific and even acts on mixtures of pollutants (12, 23, and 26). The objectives of the present study were 1) to evaluate the potential of native Brazilian basidiomycetes to degrade a broad spectrum of reactive synthetic dyes, 2) to analyze the decolorization of reactive dyes under different culture conditions (shaking and dye and nitrogen concentration), and 3) to determine the decolorization of a synthetic effluent by pure and mixed cultures of basidiomycetes.