The influence of the various carbon and nitrogen sources on the decolorization of reactive black 5 (RB 5) by Funalia trogii was examined using a classical method of medium optimization. Of the carbon sources examined as effective co-substrates, fructose, glycerol, and starch were found to be satisfactory, whereas lactose and sucrose were not. When ammonium tartrate, yeast extract, and peptone were used as nitrogen sources, the decolorization rate was high. An optimal pH is important for fungal growth, and our system operated best at a pH 5-6. By combining a Latin square design with a classical method of medium optimization, the essential medium components were identified using liquid culture experiments. Morphological changes of F trogii were found to be significantly related to decolorization, and changes in fractal dimension followed RB 5-decolorizing enzyme activity. (c) 2006 Elsevier Inc. All rights reserved.