Biochemical characteristics of a textile dye degrading extracellular laccase from a Bacillus sp. ADR.

Bacillus sp. ADR secretes an extracellular laccase in nutrient broth, and this enzyme was purified up to 56-fold using acetone precipitation and DEAE-cellulose anion exchange chromatography. The molecular weight of purified laccase was estimated to be 66 kDa using sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified laccase oxidized 2,6-dimethoxy phenol, o-tolidine, hydroquinone, L-DOPA and guaiacol. The optimum pH for oxidation of o-tolidine, 2,6-dimethoxy phenol and guaiacol were 3.0, 4.0 and 5.0, respectively. The purified laccase contained 2.7 mol/mol of copper. The laccase was stable up to 40 °C and within the pH range of 7.0-9.0. Well-known inhibitors of multicopper oxidases such as, sodium azide, L-cysteine and dithiothreitol showed significant inhibition of laccase activity. The purified enzyme decolorized structurally different azo dyes with variable decolorization rates and efficiencies of 68-90%. This study is useful for understanding the precise use of Bacillus sp. ADR in the decolorization of textile dyes containing industrial wastewater.

Rapid biodegradation and decolorization of Direct Orange 39 (Orange TGLL) by an isolated bacterium Pseudomonas aeruginosa strain BCH.

A newly isolated novel bacterium from sediments contaminated with dyestuff was identified as Pseudomonas aeruginosa strain BCH by 16S rRNA gene sequence analysis. The bacterium was extraordinarily active and operative over a wide rage of temperature (10-60 degrees C) and salinity (5-6%), for decolorization of Direct Orange 39 (Orange TGLL) at optimum pH 7. This strain was capable of decolorizing Direct Orange 39; 50 mg l(-1) within 45 +/- 5 min, with 93.06% decolorization, while maximally it could decolorize 1.5 g l(-1) of dye within 48 h with 60% decolorization. Analytical studies as, UV-Vis spectroscopy, FTIR, HPLC were employed to confirm the biodegradation of dye and formation of new metabolites. Induction in the activities of lignin peroxidases, DCIP reductase as well as tyrosinase was observed, indicating the significant role of these enzymes in biodegradation of Direct Orange 39. Toxicity studies with Phaseolus mungo and Triticum aestivum revealed the non-toxic nature of degraded metabolites.

Coordinate action of exiguobacterial oxidoreductive enzymes in biodegradation of reactive yellow 84A dye.

A novel bacterial species identified as Exiguobacterium sp. RD3 degraded the diazo dye reactive yellow 84A (50 mg l(-1)) within 48 h at static condition, at 30 degrees C and pH 7. Lower salinity conditions were found to be favorable for growth and decolorization. Enzymatic activities of an H(2)O(2) independent oxidase along with laccase and an azoreductase suggest their prominent role during the decolorization of reactive yellow 84A. Presence of an H(2)O(2) independent oxidase in Exiguobacterium sp. RD3 was confirmed and hydrogen peroxide produced was detected by a coupled iodometric assay. Azoreductase activity was prominent in presence of cofactors NADH and NADP in mineral salt medium. Considerable depletion of COD of the dye solution during degradation of dye was indicative of conversion of complex dye into simple oxidizable products. Products of degradation were analyzed by HPLC, FTIR and GCMS. A possible product of the degradation was identified by GCMS. Degradation of dye resulted with significant reduction of phytotoxicity, confirming the environmentally safe nature of the degradation metabolites.