The decolorization of Remazol Brilliant Blue R (RBBR), Poly R-478 and Poly S-119 by fungi and bacteria isolated from composting piles and the relationship of this ability to other ligninolytic activity tests was analyzed. Poly S-119 decolorizing capability was the most widespread among all tested microorganisms, followed by poly R-478, with RBBR being the most difficult to decolorize. Decolorizing ability was strongly correlated to ligninase production according to Sundman test. However, no relationship was found between this capability and laccase, tyrosinase, oxidase, polyphenoloxidase or peroxidase activities. Three mesophile fungi, one thermophile fungus, and one bacterium were able to significantly decolorize all the dyes. The mesophile fungi had the higher decolorization efficiency with more than 95% for Poly R-478 and Poly S-119 and more than 50% for RBBR. The thermophile fungus decolorized 12, 14 and 40% of Poly R-478, RBBR and Poly S-119, respectively, and the bacterium decolorized 24, 45 and 96% of Poly R-478, RBBR and Poly S-119, respectively. This is the first report of non-filamentous aerobic bacteria showing dye decolorization in axenic culture. These microorganisms can be potential candidates for use in biodecolorization processes. (c) 2006 Elsevier Inc. All rights reserved.