Reductive biological treatment of textile effluents

Abstract

Azo dyes are synthetic organic colorants which are extensively used in textile, food and cosmetic industries. A large fraction of these dyes is released into the environment even after conventional wastewater treatments. This is a worldwide problem and particularly a problem in regions where textile industries release large quantities of coloured wastewater to water courses. In an attempt to develop a biological treatment for colour removal we isolated several ascomycete yeast strains from contaminated soil based on its capacity to decolourize soluble azo dyes. In a study with four selected strains the growth rates, pH effect, temperature effect and decolourizing capacity were compared. We have demonstrated that the colour loss was due to a reductase activity, expressed constitutively, which could transform azo dyes into colourless amines [1]. The fate of the formed amines and the use of alternative carbon sources were also investigated.

[1] Ramalho, P.A., Scholze, H., Cardoso, M.H., Ramalho, M.T., Oliveira-Campos, A.M. 2002 Improved conditions for the aerobic reductive decolourization of azo dyes by Candida zeylanoides. Enz Microbiol Technol 31: 848-854.