Biodegradation of commercial textile reactive dye mixtures by industrial effluent adapted bacterial consortium VITPBC6: a potential technique for treating textile effluents.

Textile industries release major fraction of dyestuffs in effluents leading to a major environmental concern. These effluents often contain more than one dyestuff, which complicates dye degradation. In this study ten reactive dyes (Reactive Yellow 145, Reactive Yellow 160, Reactive Orange 16, Reactive Orange 107, Reactive Red 195, Reactive Blue 21, Reactive Blue 198, Reactive Blue 221, Reactive Blue 250, and Reactive Black 5) that are used in textile industries were subjected to biodegradation by a bacterial consortium VITPBC6, formulated in our previous study. Consortium VITPBC6 caused single dye degradation of all the mentioned dyes except for Reactive Yellow 160. Further, VITPBC6 efficiently degraded a five-dye mixture (Reactive Red 195, Reactive Orange 16, Reactive Black 5, Reactive Blue 221, and Reactive Blue 250). Kinetic studies revealed that the five-dye mixture was decolorized by VITPBC6 following zero order reaction kinetic; Vmax and Km values of the enzyme catalyzed five-dye decolorization were 128.88 mg L-1 day-1 and 1003.226 mg L-1 respectively. VITPBC6 degraded the dye mixture into delta-3,4,5,6-Tetrachlorocyclohexene, sulfuric acid, 1,2-dichloroethane, and hydroxyphenoxyethylaminohydroxypropanol. Phytotoxicity, cytogenotoxicity, microtoxicity, and biotoxicity assays conducted with the biodegraded metabolites revealed that VITPBC6 lowered the toxicity of five-dye mixture significantly after biodegradation.

Enzymatic biodegradation, kinetic study, and detoxification of Reactive Red-195 by Halomonas meridiana isolated from Marine Sediments of Andaman Sea, India.

Azo dyes are a significant class of hazardous chemicals that are extensively utilised in diverse industries. Industries that manufacture and consume reactive azo dyes generate hyper-saline wastewater. The ability of halotolerant bacteria to thrive under extreme environmental conditions thus makes them a potential candidate for reactive azo dye degradation. An efficient halotolerant bacterium (isolate SAIBP-6) with the capability to degrade 87.15% of azo dye Reactive Red 195 (RR-195) was isolated from sea sediment and identified as Halomonas meridiana SAIBP-6. Strain SAIBP-6 maintained potential decolourisation under a wide range of environmental conditions viz. 35-45°C temperature, 50-450 mg/L RR-195, pH 7-9, and 50-150 g/L NaCl. However, maximum decolourisation occurred at 40°C, 200 mg/L RR-195 dye, pH 9, and 50 g/L NaCl, under static conditions. Tyrosinase and azoreductase were responsible for dye degradation. The reaction catalysed by these enzymes followed zero-order kinetics. The maximum velocity (Vmax) of the enzymatic reaction was 4.221 mg/(L.h) and the Michaelis constant (Km) was 517.982 mg/L. Strain SAIBP-6 also efficiently decolourised Reactive Black-5 and Reactive Yellow-160 dye. The biodegradation process was further studied with the help of UV-Vis spectral scan, ultra-high performance liquid chromatography (UPLC), fourier-transform infra-red spectroscopy (FT-IR), and proton nuclear magnetic resonance (1H NMR) analysis. Finally, cytogenotoxicity assay conducted with the meristematic root tip cells of Allium cepa and phytotoxicity assay conducted with the seeds of Vigna mungo led to the inference that strain SAIBP-6 significantly reduced the toxicity of RR-195 after biodegradation.

Bioremediation of reactive orange 16 by industrial effluent-adapted bacterial consortium VITPBC6: process optimization using response surface methodology (RSM), enzyme kinetics, pathway elucidation, and detoxification.

Textile effluent is one of the most hazardous industrial pollutant sources. It is generated in huge volumes and contains a wide array of toxicants. Reactive azo dyes, which are xenobiotic compounds, are predominantly utilized by textile industries for dyeing cotton, viscose, wool, and silk. The conventional physicochemical treatments used by industrial effluent treatment plants are ineffective in dye degradation. The present study thus attempted to find a potential treatment for reactive azo dyes. A novel bacterial consortium VITPBC6 was constructed with the most potent and compatible reactive orange 16 (RO-16) decolorizing isolates of tannery and textile effluents, and the isolates were identified as Bacillus flexus VITSP6, Bacillus paraflexus VITSPB7, Bacillus megaterium VITSPB9, Bacillus firmus VITEPB1, B. flexus VITEPB2, and Bacillus aryabhattai VITEPB3. The physicochemical factors of RO-16 decolorization were optimized by response surface methodology. Consortium VITPBC6 was able to tolerate a high concentration of RO-16 up to 800 mg L-1. A cocktail of enzymes including azoreductase, tyrosinase, laccase, lignin peroxidase, and manganese peroxidase was involved in RO-16 degradation by VITPBC6. Consortium VITPBC6 degraded RO-16 following zero-order reaction. The enzymes of consortium VITPBC6 had a Vmax of 352 mg L-1 day-1 for RO-16 degradation; however, the Km value was high. VITPBC6 biodegraded RO-16 resulting in the formation of small aromatic compounds. Lastly, different toxicity assays conducted with untreated RO-16 and its corresponding biodegraded metabolite revealed that the toxicity of biodegraded metabolites was significantly lower than the untreated dye.

A study on the utility of immobilized cells of indigenous bacteria for biodegradation of reactive azo dyes.

Azo dyes are recalcitrant compounds used as a colorant in various industries. The pollution caused by their extensive usage has adversely affected the environment for years. The existing physicochemical methods for dye pollution remediation are rather inefficient and hence there is a dearth of low-cost, potential systems capable of dye degradation. The current research studies the biodegradation potential of immobilized bacterial cells against azo dyes Reactive Orange 16 (RO-16) and Reactive Blue 250 (RB-250). Two indigenous dye degrading bacteria Bacillus sp. VITAKB20 and Lysinibacillus sp. KPB6 was isolated from textile sludge sample. Free cells of Bacillus. sp. VITAKB20 degraded 92.38% of RO-16 and that of Lysinibacillus sp. KPB6 degraded 95.36% of RB-250 within 72 h under static conditions. Upon immobilization with calcium alginate, dye degradation occurred rapidly. Bacillus. sp. VITAKB20 degraded 97.5% of RO-16 and Lysinibacillus sp. KPB6 degraded 98.2% of RB-250 within 48 h under shaking conditions. Further, the nature of dye decolorization was biodegradation as evident by high-performance liquid chromatography (HPLC), and Fourier-transform infrared spectroscopy (FTIR) results. Phytotoxicity and biotoxicity assays revealed that the degraded dye products were less toxic in nature than the pure dyes. Thus, immobilization proved to be a highly likely alternative treatment for dye removal.

Biodecolorization and Biodegradation of Azo Dye Reactive Orange-16 by Marine Nocardiopsis sp.

BACKGROUND: Azo dyes are xenobiotic compounds that have bioaccumulated in the environment due to escalated industrial development. These are hazardous in nature, possessing carcinogenic and mutagenic effects on human beings. OBJECTIVES: The perspective of the present study was to isolate and to determine azo dye (Reactive Orange-16) degrading potential of marine actinobacteria isolated from sediment samples of Port Blair, India. MATERIAL AND METHODS: Actinobacteria with dye decolorization potential were isolated from sea sediment samples. The actinobacterial isolate with the highest dye decolorizing percentage was identified with the help of phenotypic, biochemical and molecular studies. The different physico-chemical parameters for dye decolorization were also optimized. The nature of decolorization by the potent isolate was determined with the help of High Performance Liquid chromatography (HPLC) and Fourier Transformed Infrared spectroscopy (FTIR) techniques. Further the toxicity of RO-16 decolorized products was investigated with the help of phytotoxcity assay. RESULTS: Out of six actinobacterial isolates, VITVAMB 1 possessed the most efficient RO-16 decolorization property. It decolorized 85.6% of RO-16 (250 mg L-1) within 24hrs. Isolate VITVAMB 1 was identified to be Nocardiopsis sp. Maximum dye decolorization occurred at pH 8, temperature 35°C, 3% salt concentration and a dye concentration of 50 mg L-1. CONCLUSIONS: The nature of decolorization by Nocardiopsis sp. was biodegradation. Additionally, the degraded dye metabolites were found to be less toxic than pure dye. The high decolorization potential of VITVAMB 1 and the low toxicity of its degradation products make it a prospective dye removal system. The marine origin of VITVAMB 1 also makes it an attractive source for novel azo dye reducing enzymes.