Differential catalytic action ofBrevibacillus laterosporuson two dissimilar azo dyes Remazol red and Rubine GFL

Molecular characterization of azoreductase and its potential for the decolorization of Remazol Red R and Acid Blue 29

Azoreductase is a reductive enzyme that efficiently biotransformed textile azo dyes. This study demonstrated the heterologous overexpression of the azoreductase gene in Escherichia coli for the effective degradation of Remazol Red-R and Acid-Blue 29 dyes. The AzK gene of Klebsiella pneumoniae encoding a ≈22 kDa azoreductase enzyme was cloned into the pET21+C expression vector. The inoculum size of 1.5%, IPTG concentration of 0.5 mM, and incubation time of 6 h were optimized by response surface methodology a statistical tool. The crude extract showed 76% and 74%, while the purified enzyme achieved 94% and 93% decolorization of RRR and AB-29, respectively in 0.3 h. The reaction kinetics showed that RRR had a Km and Vmax value of 0.058 mM and 1416 U mg-1, respectively at an NADH concentration of 10 mM. HPLC and GC-MS analyses showed that RRR was effectively bio-transformed by azoreductase to 2-[3-(hydroxy-amino) benzene-1-sulfonyl and AB-29 to aniline and 3-nitrosoaniline. This study explored the potential of recombinant azoreductase isolated from K. pneumoniae in the degradation of toxic textile azo dyes into less toxic metabolites.

Synergistic effect of biological and advanced oxidation process treatment in the biodegradation of Remazol yellow RR dye

The current study investigated the efficiency of synergistic biological and Advanced Oxidation Process (AOPs) treatment (B-AOPs) using Aeromonas hydrophila SK16 and AOPs-H2O2 in the removal of Remazol Yellow RR dye. Singly, A. hydrophila and AOPs showed 90 and 63.07% decolourization of Remazol Yellow RR dye (100 mg L-1) at pH 6 and ambient temperature within 9 h respectively. However, the synergistic B-AOPs treatments showed maximum decolorization of Remazol Yellow RR dye within 4 h. Furthermore, the synergistic treatment significantly reduced BOD and COD of the textile wastewater by 84.88 and 82.76% respectively. Increased levels in laccase, tyrosinase, veratryl alcohol oxidase, lignin peroxidase and azo reductase activities further affirmed the role played by enzymes during degradation of the dye. UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) and gas chromatography-mass spectroscopy (GC-MS) confirmed the biotransformation of dye. A metabolic pathway was proposed based on enzyme activities and metabolites obtained after GC-MS analysis. Therefore, this study affirmed the efficiency of combined biological and AOPs in the treatment of dyes and textile wastewaters in comparison with other methods.

Biodegradation and detoxification of Direct Black G textile dye by a newly isolated thermophilic microflora

The biodegradation and detoxification of azo dye - Direct Black G (DBG) with a newly isolated thermophilic microflora was investigated in the present study. It was found this microflora can decolorize DBG at a wide range of pH from 5 to 10, and grow well under high concentration of dye (600 mg·L^-1) and salinity (50 g·L^-1). Its decolorization ratio could reach 97% with 8 h of incubation at optimal conditions. The induction of laccase, manganese peroxidase, lignin peroxidase and azoreductase suggests their synergetic involvements in the degradation process of DBG. In addition, the phytotoxicity analysis indicated the thermophilic microflora converted toxic dye DBG into low toxicity metabolites. PCR-DGGE analysis revealed that there are nine different bacteria presented in this microflora. Furthermore, a new degradation pathway of DBG degradation by this microflora was proposed based on the intermediates identified by LC-ESI-MS/MS.

Biodegradation and detoxification of textile dye Disperse Red 54 by Brevibacillus laterosporus and determination of its metabolic fate

Bioremediation is one of the milestones achieved by the biotechnological innovations. It is generating superior results in waste management such as removal of textile dyes, which are considered xenobiotic compounds and recalcitrant to biodegradation. In the present bioremedial approach, Brevibacillus laterosporus was used as an effective microbial tool to decolorize disperse dye Disperse Red 54 (DR54). Under optimized conditions (pH 7, 40°C), B. laterosporus led to 100% decolorization of DR54 (at 50 mg L(-1)) within 48 h. Yeast extract and peptone, supplemented in medium enhanced the decolorization efficiency of the bacterium. During the decolorization process, activities of enzymes responsible for decolorization, such as tyrosinase, veratryl alcohol oxidase and NADH--DCIP reductase were induced by 1.32-, 1.51- and 4.37-fold, respectively. The completely different chromatographic/spectroscopic spectrum of metabolites obtained after decolorization confirmed the biodegradation of DR54 as showed by High pressure liquid chromatography, High pressure thin layer chromatography and Fourier transform infrared spectroscopy. Gas chromatography-Mass spectroscopy studies suggested the parent dye was biodegraded into simple final product, N-(1λ(3)-chlorinin-2-yl)acetamide. Phytotoxicity study suggested that the metabolites obtained after biodegradation of DR54 were non-toxic as compared to the untreated dye signifying the detoxification of the DR54 by B. laterosporus.

Bacterial–yeast consortium as an effective biocatalyst for biodegradation of sulphonated azo dye Reactive Red 198

A novel bacterial–yeast consortium (Brevibacillus laterosporusandGalactomyces geotrichum) acts as a proficient biocatalyst.

Degradation of a xenobiotic textile dye, Disperse Brown 118, by Brevibacillus laterosporus

The toxic textile dye, Disperse Brown 118, was degraded by Brevibacillus laterosporus. 96% decolorization was achieved within 48 h at pH 7, 40 °C at 50 mg dye l(-1) accompanied by significant increases in the activities of veratryl alcohol oxidase, tyrosinase and NADH-DCIP reductase. HPTLC and FT-IR spectroscopy confirmed biodegradation after dye decolorization. As identified by GC-MS, biodegradation products of Disperse Brown 118 were N-carbamoyl-2-[(8-chloroquinazolin-4-yl)oxy] acetamide and N-carbamoyl-2-(quinazolin-4-yloxy)acetamide which were much less toxic than parent dye as evidenced by phytotoxicity tests.