The fungus Pycnoporus sanguineus MUCL 51321 white rot isolated in Gabon showed a high ability to decolorize and degrade two synthetic dyes. On solid and liquid media, the fungus had different enzyme activities (laccase and manganese (Mn) peroxidase) in the presence of different substrates. At concentrations of 0.05 g/L (Orange G) and 0.3 g/L (reactive blue 4), the respective rates of decolorization of 81% and 97% were observed after 15 days of incubation in liquid media. In the same time interval, changes on the spectra (UV-vis and FTIR) and chromatograms (HPLC) showed that these decolorizations were due to the degradation of dyes by fungus with the production of new compounds. The study revealed the possibility of the use of this fungal strain in the microbial degradation process of synthetic dyes. Aldrich (Sigma-Aldrich, St. Louis, MO, USA). All reagents used were of the analytical grade. Journal of Bior emediation & Biodegradation Culture ConditionsThe composition of the solid growth medium used was as follows: 0.2% glucose, 0.2% malt extract, 0.01% MgSO 4 , 0.01% MnCl 2 , 0.03% NH 4 NO 3 , 0.026% KH 2 PO 4 , 0.026% Na 2 HPO 4 , 0.01% CaCl 2 .2H 2 O, 0.0001% FeC1 3 .6H 2 O, 0.0001% ZnCl 2 , 1.6% and 1.6% agar in 1 L of distilled water. The pH was adjusted to 5.5 with hydrochloric acid (0. 5 N) before autoclaving (at 121°C for 15 min). The culture medium was transferred into 4 Erlenmeyer flasks (200 mL each) and each reagent (enzymatic revelation) or dye, depending on its final concentration was added. The mixture was shaken, then about 15 mL were distributed in a Petri dish (diameter 8.5 mm); each test was replicated three times. 50 mL of liquid culture media in flasks of 100 mL were constituted in almost the same way as the solid culture media described above, except for the absence of agar. Each test was conducted three times. Decolorization experimentsDyes decolorization on solid medium: Solid culture media contained different concentrations of each dye (0.05 g/L to 1.5 g/L). Various controls were also prepared: some Petri dishes with fungus alone and others with dye alone to assess possible abiotic decolorization. One square portion of agar (1 cm of diameter) containing the fungus was placed at the centre of each Petri dish. The fungal growth diameters and the halos of decolorization were measured every day during one week at constants temperature (30°C) and humidity (75%). After these measures, different ratios and rates (decolorization or inhibition) were determined as described by . The optimum temperature of decolorization was evaluated using different growth temperatures (15, 22, 30, 35, 40 and 45°C). Moreover, the optimal concentrations for decolorization (0.05 g/L for the Orange G and 0.3 g/L for the RB4) were obtained after one week. All tests were conducted three times (averages are presented with the corresponding standard deviations).Dyes decolorization on liquid culture medium: For each Erlenmeyer flask (100 mL) containing liquid culture medium (50 mL) and dye (0.05 g/L Orange G or 0.3...