Tissue cultured shrub plants of Blumea malcolmii were found to decolorize Malachite green, Red HE8B, Methyl orange, Reactive Red 2 and Direct Red 513 at 20 mg L(-1) concentration to varying extent within three days. A significant induction in the activities of lignin peroxidase, tyrosinase, DCIP (2,6-dichlorophenol-indophenol) reductase, azoreductase and riboflavin reductase in the roots was observed during the decolorization of Direct Red 5B, which indicated their crucial role in the metabolism of the dye. HPLC (High Performance Liquid Chromatography) and FTIR (Fourier Transform Infrared Spectroscopy) analysis of the samples before and after decolorization of the dye confirmed the phytotransformation of Direct Red 5B. The GC-MS (Gas Chromatography Mass Spectroscopy) analysis of the products led us to the identification of three metabolites formed after phytotransformation of the dye as 4-(4-amino-phenylazo)-benzene sulfonic acid, 3-amino-7-carboxyamino-4-hydroxy-naphthalene-2-sulfonic acid and 7-carboxyamino-naphthalene-2-sulfonic acid. (C) 2009 Elsevier Ltd. All rights reserved.