Biodegradation of Direct Red 5B, a textile dye by newly isolated Comamonas sp. UVS

Soil samples collected from the vicinity of "Manpasand textile industry", located near Ichalkaranji, India were studied for screening and isolation of bacterial strains capable of degradation of textile dyes. A potential strain was selected on the basis of rapid dye degradation and later identified as Comamonas sp. UVS. Comamonas sp. UVS showed 100% decolorization of Direct Red 5B (DR5B) dye at 40 degrees C and pH 6.5. The maximum Direct Red 5B concentration decolorized was 1,100 mg/l in nutrient broth within 125 h. A numerical simulation with the Michaelis-Menten kinetics model gives an optimal value of 16.01+/-0.36 mg dye/g cell/h for maximum rate (V(max)) and 7.97+/-0.21 mg/l for the Michaelis constant (K(m)). The induction in the activities of laccase and LiP was observed during decolorization. These enzymes were inhibited by the addition of sodium azide. The biodegradation was monitored by UV-vis, FTIR spectroscopy and HPLC. The GCMS analysis indicated the presence of 7-benzoylamino-3-diazenyl-4-hydroxy-naphthalene-2-sulfonic acid in degraded product of the dye. The germination of Triticum aestivum seeds was inhibited with DR5B treatment but not with the treatment of dye degradation products.