Screening of dye-decolorizing activity of isolated yeasts from the ecoregion of Las Yungas (Tucumán, Argentina)

PAJOT H.F.; FARIÑA J.I.; FIGUEROA L.I.C.

Rio de Janeiro

Congreso; 11th International Congress on Yeast (ICY); 2004

International Commission on Yeasts

Effluent discharge from textile and dyestuff industries is a cause of health concern and colour removal has become a research topic receiving great attention in water-pollution control. The disposal of dye-containing efluents into receiving waters irreversible damages the environment by affecting photosynthetic activity and generating toxic and/or carcinogenic effects of proper dyes and other auxiliary chemicals. Microbial decolourization is nowadays seen as a cost-effective method being considered as a promising ‘ecofriendly’ alternative to the conventional physico-chemical colour removal techniques. In contrast to the anaerobic microbial processes which may lead to carcinogenic aromatic amines, those involving fungal ligninolytic enzymes with low substrate-specificity make the possessing microorganisms suitable for aerobic dye degradation avoiding hazardous product formation. The aim of this study was to investigate the ability of several yeasts isolated from the unexploited ecoregion of Las Yungas to decolorize commercial azo dyes. To this end, the optimization of a screening and selection scheme was accomplished as described below. Samples were collected from Phoebe porphyria trees in “Las Yungas” and aseptically transported to the laboratory. One gram of sample was suspended in sterile distilled water and a suitable dilution spread on YM agar medium. Isolation at 26ºC resulted in 65 yeast strains. Among 4 different solid culture media, Normal Decolourization Medium (NDM) was the optimal for the screening of decolourization ability on agar plates. Primary screening involving single or combined 6 different azo dyes was carried out at 26ºC for 72 h for the isolated yeasts. Two parameters were considered to score the decolorizing ability: 1) the colourless halo surrounding the colony and, 2) the colouring intensity of the colony. Seventeen yeasts were selected for their high decolorizing ability and one of these was further subjected to decolourization assays in liquid NDM containing 200 mg/l of either Vilmafix Blue RR-BB or Vilmafix Red 7B-HE to evaluate the culture kinetics of dye disappearance. After 72 h the extent of colour removal was 89 and 93%, respectively. Concluding, the present work provides preliminary evidence on the potential use of yeasts for the removal of industrial azo dyes under aerobic conditions.