DCIP Reductase Research Articles

Mechanistic insights on enzyme mediated-metabolite cascade during decolourization of Reactive Blue 13 using novel microbial consortium

Understanding the role of oxido-reductase enzymes followed by deciphering the functional genes and their corresponding proteins are crucial for the speculation of molecular mechanism for azo dye degradation. In the present study, decolourization efficiency of developed microbial consortium was tested using 100 mgL−1 reactive blue 13 (RB13) and the results showed ∼92.67% decolourization of RB13 at 48 h of incubation. The fourier-transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) and gas chromatography–mass spectrometry (GC-MS) analysis were performed to identify the metabolites formed during RB13 degradation, followed by hypothesizing the metabolic pathway. The GC-MS analysis showed formation of 1,4-dihydronaphthalen-1-ol and 1,3,5-triazin-2-amine as the final degraded compounds after enzymatic breakdown of RB13 dye. The activity of different oxido-reductase enzymes was determined, and the results showed that NADH DCIP reductase and azo reductase had higher activity than other enzymes. It clearly indicated the degradation was initiated with the enzymatic cleavage of azo bond of RB13. Further, the functional genes were annotated against the database of clusters of orthologous groups (COGs) and kyoto encyclopedia of genes and genomes (KEGG). It provided valuable information about the role of crucial functional genes and their corresponding proteins correlated with dominant bacterial species in degradation of RB13. Hence, the present research is the first systematic study that correlated the formation of degradation compounds with the functional genes/enzymes and their corresponding bacterial species responsible for RB13 degradation.

Biodegradation and Detoxification of Azo Dyes by Halophilic/Halotolerant Microflora Isolated From the Salt Fields of Tibet Autonomous Region China.

This study aimed to decolorize azo dyes in high-salt industrial wastewater under high-salt and low oxygen conditions using extreme halophilic/halotolerant bacteria screened from the salt fields of Tibet, which consisted of Enterococcus, unclassified Enterobacteriaceae, Staphylococcus, Bacillus, and Kosakonia. Under the optimal conditions, 600 mg/l Congo red, Direct Black G (DBG), Amaranth, methyl red, and methyl orange could be completely decolorized in 24, 8, 8, 12, and 12 h, respectively. When the DBG concentration was 600 mg/l, NADH–DCIP, laccase, and azo reductase were confirmed to be the primary reductase and oxidase during the degradation process, and the degradation pathways were verified. The microflora could not only tolerate changes in salt concentrations of 0–80 g/l, but also displayed strong degradative ability. Under high-salt concentrations (≥ 60 g/l NaCl), NADH–DCIP reductase was primarily used to decolorize the azo dye. However, under low salt concentrations (≤ 40 g/l NaCl), azo reductase began to function, and manganese peroxidase and lignin peroxidase could cooperate to participate in DBG degradation. Additionally, the halophilic/halophilic microflora was shown to convert the toxic DBG dye to metabolites of low toxicity based on phytotoxicity analysis, and a new mechanism for the microflora to degrade DBG was proposed based on intermediates identified by liquid chromatography-mass spectrometry (LC–MS). This study revealed that the halophilic/halophilic microflora has effective ecological and industrial value for treating wastewater from the textile industry.

Methyl Orange Biodegradation by Immobilized Consortium Microspheres: Experimental Design Approach, Toxicity Study and Bioaugmentation Potential.

Simple SummaryAn efficient immobilized bacterial consortium of Raoultella planticola, Ochrobactrum thiophenivorans, Bacillus flexus, and Staphylococcus xylosus was used to degrade MO under high salinity conditions. The biodegradation efficiency was confirmed by UV−visible spectrophotometric analysis, FTIR, and the assaying of degradative enzymes. The cytotoxicity of such metabolic byproducts was evaluated on two human normal cell lines. In addition, the immobilized consortium showed the synergistic interaction between immobilized consortium and indigenous microorganism for degrading MO in artificially contaminated agricultural and industrial effluents.Methyl orange (MO) is categorized among the recalcitrant and refractory xenobiotics, representing a significant burden in the ecosystem. To clean-up the surrounding environment, advances in microbial degradation have been made. The main objective of this study was to investigate the extent to which an autochthonous consortium immobilized in alginate beads can promote an efficient biodegradation of MO. By employing response surface methodology (RSM), a parametric model explained the interaction of immobilized consortium (Raoultella planticola, Ochrobactrum thiophenivorans, Bacillus flexus and Staphylococcus xylosus) to assimilate 200 mg/L of MO in the presence of 40 g/L of NaCl within 120 h. Physicochemical analysis, including UV-Vis spectroscopy and FTIR, and monitoring of the degrading enzymes (azoreductase, DCIP reductase, NADH reductase, laccase, LiP, MnP, nitrate reductase and tyrosinase) were used to evaluate MO degradation. In addition, the toxicity of MO-degradation products was investigated by means of phytotoxicity and cytotoxicity. Chlorella vulgaris retained its photosynthetic performance (>78%), as shown by the contents of chlorophyll-a, chlorophyll-b and carotenoids. The viability of normal lung and kidney cell lines was recorded to be 90.63% and 99.23%, respectively, upon exposure to MO-metabolic outcomes. These results reflect the non-toxicity of treated samples, implying their utilization in ferti-irrigation applications and industrial cooling systems. Moreover, the immobilized consortium was employed in the bioremediation of MO from artificially contaminated agricultural and industrial effluents, in augmented and non-augmented systems. Bacterial consortium remediated MO by 155 and 128.5 mg/L in augmented systems of agricultural and industrial effluents, respectively, within 144 h, revealing its mutual synergistic interaction with both indigenous microbiotas despite differences in their chemical, physical and microbial contents. These promising results encourage the application of immobilized consortium in bioaugmentation studies using different resources.

Application of a downflow microaerophilic fixed film (DFMFF) reactor for the treatment of dye house effluents using a developed bacterial consortium

The present study describes a downflow microaerophilic fixed film (DFMFF) reactor based treatment of dye house effluents. The major characteristics of the two effluents E-2 and E-5 under study were; chemical oxygen demand (COD) 4680-16,266 mg L−1, biological oxygen demand (BOD) 1575–3151 mg L−1 and American Dye Manufacturers' Institute (ADMI) color index of 10,794–21,413. DFMFF reactor was packed with ultra-high molecular weight polyethylene (UHMWPE) shredding. The developed consortium was allowed to grow and form bio-film on packed UHMWPE. Degradation of the effluents at a various hydraulic retention time (HRT) and organic loading rate (OLR) was studied. Batch mode studies in the reactor showed > 80% removal of BOD and COD at OLR of 4.3 kg L−1 day−1 of E-2 and 2.4 kg L−1 day−1 of E-5 at 48 h HRT. Fourier Transform Infrared Spectroscopy (FTIR) and High Performance Liquid Chromatography (HPLC) analysis confirmed biodegradation and obtained results indicated significant induction of oxidoreductive enzyme activities of azoreductase, NADH–DCIP reductase and laccase enzymes. Reduction in phytotoxicity and microbial toxicity was observed after the treatment of both the effluents. The reactor was also operated on continuous mode for treatment of E-2 under sequential anaerobic–aerobic phase and charcoal treatment. Results of sequential effluent treatment resulted in a reduction of > 99% of COD, BOD and ADMI along with > 88% of solids removal from the effluent. The resulting effluent was clear and meets the discharge criteria so as to release into the sewers. .

Biotreatment of paper mill effluent using alkaliphilic Rhizobium sp. NCIM 5590 isolated from meteoric alkaline Lonar Lake, Buldhana District, Maharashtra, India

AbstractBacterial strain Rhizobium sp. was isolated from littoral soil of meteoric alkaline Lonar Lake and used to treat paper mill waste water. The bacterium was found to fix 125.7 nmol of C2H4 formed ml−1 culture media in 72 hr by ARA (acetylene reduction assay). The optimum pH for its growth was 12, whereas the optimum temperature was 40°C. The bacterium could tolerate salt concentrations up to 4%. The collected paper mill effluent used two dyes in combination, namely Acid Orange 7 (AO) and Acid Yellow 17 (AY) to produce brown paper, eventually producing coloured effluent containing unbound AO and AY. Rhizobium sp. was found to be efficient for decolorization of both AO and AY individually, as well as in a mixture of AO and AY, suggesting the ability of this strain for treating paper mill effluent. The strain was found to be efficient in reducing up to 85% of the colour from undiluted paper mill effluent within 18 hr. In addition, biotreatment also was effective in reducing COD, metals and toxicity from the waste water. Induction in the enzymes azo reductase and DCIP reductase indicated their possible involvement in biotreatment of paper mill effluent. The effluent toxicity before and after treatment was studied using Allium cepa root cells, evaluating various biochemical parameters to assess the toxicity, including lipid peroxidation, protein oxidation, antioxidant enzyme status (catalase, superoxide dismutase) and genotoxicity assays using single cell gel electrophoresis (SCGE).

Biodegradation of reactive green dye (RGD) by indigenous fungal strain VITAF-1

Present study demonstrates the decolourization and degradation of reactive green dye (RGD) by indigenous fungal strain VITAF-1 isolated from dye contaminated sites of Tirupur district, T.N, India. The intensive metabolic activity of VITAF-1 led to 97.9% decolourization of RGD within 48 h at 30 ± 2 °C temperature in Minimal Salt Media (MSM). VITAF-1 had a strong capability to decolourize elevated concentrations of reactive green dye (250 mg L−1–1500 mg L−1) over a pH range of 3.0–9.0. Induction of oxidoreductive enzymes like laccase, LiP and DCIP reductase confirmed their potential role in degradation. Decolourization assay with living and dead biomass of VITAF-1 revealed its ability in absorbing RGD. The degradation capability of the isolate VITAF-1 was monitored using UV–Vis spectrophotometer, HPLC and FTIR analysis, further the degraded product was identified as benzoic acid, 2(-1-oxopropyl) by GC-MS. 18S rRNA gene sequencing confirmed the fungal strain VITAF-1 to be the nearest neighbour of Aspergillus sp.

Efficient decolorization and detoxification of textile industry effluent by Salvinia molesta in lagoon treatment

Salvinia molesta, an aquatic fern was observed to have a potential of degrading azo dye Rubine GFL up to 97% at a concentration of 100mg/L within 72h using 60±2g of root biomass. Both root as well as stem tissues showed induction in activities of the enzymes such as lignin peroxidase, veratryl alcohol oxidase, laccase, tyrosinase, catalase, DCIP reductase and superoxide dismutase during decolorization of Rubine GFL. FTIR, GC-MS, HPLC and UV–visible spectrophotometric analysis confirmed phytotransformation of the model dye into smaller molecules. Analysis of metabolites revealed breakdown of an azo bond of Rubine GFL by the action of lignin peroxidase and laccase and formation of 2-methyl-4-nitroaniline and N-methylbenzene-1, 4-diamine. Anatomical tracing of dye in the stem of S. molesta confirmed the presence of dye in tissues and subsequent removal after 48h of treatment. The concentration of chlorophyll pigments like chlorophyll a, chlorophyll b and carotenoid was observed during the treatment. Toxicity analysis on seeds of Triticum aestivum and Phaseolus mungo revealed the decreased toxicity of dye metabolites. In situ treatment of a real textile effluent was further monitored in a constructed lagoon of the dimensions of 7m×5m×2m (total surface area 35m2) using S. molesta for 192h. This large scale treatment was found to significantly reduce the values of COD, BOD5 and ADMI by 76%, 82% and 81% considering initial values 1185, 1440mg/L and 950 units, respectively.

Ipomoea hederifolia rooted soil bed and Ipomoea aquatica rhizofiltration coupled phytoreactors for efficient treatment of textile wastewater

Ipomoea aquatica, a macrophyte was found to degrade a highly sulfonated and diazo textile dye Brown 5R up to 94% within 72 h at a concentration of 200 mg L−1. Induction in the activities of enzymes such as azoreductase, lignin peroxidase, laccase, DCIP reductase, tyrosinase, veratryl alcohol oxidase, catalase and superoxide dismutase was observed in leaf and root tissue in response to Brown 5R exposure. There was significant reduction in contents of chlorophyll a (25%), chlorophyll b (17%) and carotenoids (30%) in the leaves of plants. HPLC, FTIR, UV–vis spectrophotometric and HPTLC analyses confirmed the biotransformation and removal of parent dye from solution. Enzymes activities and GC-MS analysis of degradation products lead to the proposal of a possible pathway of phytotransformation of dye. The proposed pathway of dye metabolism revealed the formation of Napthalene-1,2-diamine and methylbenzene. Toxicity study on HepG2 cell lines showed a 3 fold decrease in toxicity of Brown 5R after phytoremediation by I. aquatica. Hydrophytic nature of I. aquatica leads to its exploration in a combinatorial phytoreactor with Ipomoea hederifolia soil bed system. Rhizofiltration with I. aquatica and soil bed treatment by I. hederifolia treated 510 L of effluent effectively within 72 h. I. aquatica along with I. hederifolia could decolorize textile industry effluent within 72 h of treatment as evident from the significant reductions in the values of COD, BOD, solids and ADMI. Further on field trials of treatment of textile wastewater was successfully carried out in a constructed lagoon.

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.

Phytoremediation of sulfonated Remazol Red dye and textile effluents by Alternanthera philoxeroides: An anatomical, enzymatic and pilot scale study

Alternanthera philoxeroides Griseb. a macrophyte was found to degrade a highly sulfonated textile dye Remazol Red (RR) completely within 72 h at a concentration of 70 mg L−1. An induction in the activities of azoreductase and riboflavin reductase was observed in root and stem tissues; while the activities of lignin peroxidase, laccase and DCIP reductase were induced in leaf tissues. Some enzymes namely tyrosinase, veratryl alcohol oxidase, catalase and superoxide dismutase displayed an increase in their activity in all the tissues in response of 72 h exposure to Remazol Red. There was a marginal reduction in contents of chlorophyll a (20%), chlorophyll b (5%) and carotenoids (16%) in the leaves when compared to control plants. A detailed anatomical study of the stem during uptake and treatment revealed a stepwise mechanism of dye degradation. UV–vis spectrophotometric and high performance thin layer chromatographic analyses confirmed the removal of parent dye from solution. Based on the enzymes activities and gas chromatography-mass spectroscopic analysis of degradation products, a possible pathway of phytotransformation of RR was proposed which revealed the formation of 4-(phenylamino)-1,3,5-triazin-2-ol, naphthalene-1-ol and 3-(ethylsulfonyl)phenol. Toxicity study on Devario aequipinnatus fishes showed that the anatomy of gills of fishes exposed to A. philoxeroides treated RR was largely protected. The plants were further explored for rhizofiltration experiments in a pilot scale reactor. A. philoxeroides could decolorize textile industry effluent of varying pH within 96 h of treatment which was evident from the significant reductions in the values of American dye manufacturers' institute color, chemical oxygen demand, biological oxygen demand, total dissolved and total suspended solids.

Improved biodegradation of textile dye effluent by coculture

The present study demonstrates the de-colorization and degradation of textile effluent by coculture consisting of three bacterial species isolated from textile effluent contaminated environment with an aim to reduce the treatment time. The isolates were identified as Ochrobactrum sp., Pseudomonas aeruginosa and Providencia vermicola by 16S rRNA analysis. Their secondary structure was predicted and GC content of the sequence was found to be 54.39, 52.10, and 52.53%. The co-culture showed a prominent increase in the degradation activity due to the action of oxidoreductase enzymatic mechanism of laccase, NADH–DCIP reductase and azoreductase activity. The biodegradability index of 0.75 was achieved with 95% chemical oxygen demand (COD) reduction in 16h and 78 and 85% reduction in total organic carbon (TOC) and total solids was observed. Bioaccumulation of metals was identified by X-ray diffraction (XRD) analysis. The effective decolorization was confirmed from the results of UV–vis spectroscopy, high performance liquid chromatography and Fourier transformed infrared spectrometer analyzes. The possible degradation pathway was obtained from the analysis of liquid chromatography–mass spectroscopy analysis and the metabolites such as 2-amino naphthalene and N-phenyl-1.3,5 triazine were observed. The toxic nature of the effluent was analyzed using phyto-toxicity, cell-death assay and geno-toxicity tests.

Development of low cost upflow column bioreactor for degradation and detoxification of Blue HERD and textile effluent by Lysinibacillus sp. RGS immobilized on Loofa

Dyes and other toxic components of textile wastewater create severe hazards to receiving water. In the present study, Lysinibacillus sp. RGS, an effective dye degrading bacteria immobilized on Luffa cylindrica (Loofa) was used to decolorize sulphonated azo dye Blue HERD and 50% real textile effluent in an upflow column bioreactor. Blue HERD (200 mg L−1) and 50% real textile effluent were degraded at volumetric flow rate 40 mL h−1 and 15 mL h−1, respectively. Induction in reductive (NADH–DCIP reductase and azoreductase) as well as oxidative (laccase, tyrosinase and veratryl alcohol oxidase) enzymes proved enzymatic decolorization of Blue HERD and 50% textile effluent. Significant reduction in COD, BOD, TOC, hardness and alkalinity of decolorized samples of Blue HERD and 50% effluent confirmed mineralization. HPTLC, FTIR and GCMS analysis confirmed degradation of Blue HERD into simple intermediates during decolorization in bioreactor. Less toxic nature of metabolites was confirmed using genotoxicity, cytotoxicity and phytotoxicity tests.

Phytoremediation of textile effluent pretreated with ultrasound and bacteria

This study presents the phytoremediation of textile effluent pretreated with ultrasound irradiation and microbial treatment. The isolates such as Ochrobactrum sp., Pseudomonas aeruginosa and Providencia vermicola were used for the bacterial degradation and phytoremediation was done using Bouteloua dactyloides. The effect of sonication time on the performance of phytoremediation was evaluated. Ochrobactrum sp. showed better performance compared to other species and better results were observed with the effluent sonicated for a longer period. The pretreatment of textile effluent with Ochrobactrum sp. and sonication improved the phytoremediation and showed about 95% COD reduction at the end of 24h. The influence of oxidoreductive enzymes such as laccase, NADH–DCIP reductase and azoreductase during bacterial degradation was studied and the activity of catalase and peroxidase was identified during phytoremediation. The UV–visible and high performance liquid chromatography analysis confirmed the degradation of dye molecules. The possible metabolic pathway was identified through liquid chromatography-mass spectroscopy analysis. The X-ray diffraction (XRD) analysis showed the reduction in the heavy metals content of the treated effluent and the phytotoxicity analysis confirmed the less toxic nature of the treated effluent.

Optimization of triazo Acid Black 210 dye degradation by Providencia sp. SRS82 and elucidation of degradation pathway

The current work is aimed to evaluate the degradation of triazo textile dye Acid Black 210 (AB210) by Providencia sp. SRS82 that degrade 100mg/L dye within 90min under optimum conditions and was also found tolerant to as high as 2000ppm of dye AB210. Optimum conditions for decolourization and degradation of AB210 with the isolate were viz. temperature 30°C, pH 8, NaCl concentration 2.5% (w/v) and initial cell load of 8×108 cells/mL under static condition. Induction of intracellular and extracellular lignin peroxidase, intracellular laccase and tyrosinase, azoreductase, and DCIP reductase indicated their contribution in the biodegradation of AB210. The products obtained from Providencia sp. SRS82 degradation was monitored through UV–Vis spectrophotometer and were characterized by FTIR, HPTLC, HPLC, GC/MS and LCMS. The proposed metabolic pathway for the biodegradation of AB210 is elucidated for the first time, which showed production of 4 molecules of benzene, one of naphthalene and 4-aminophenyl-N-(4-amino phenyl) benzene sulphonamide. Microbial toxicity and cytotoxicity studies revealed the comparatively less toxic nature of metabolites generated after degradation of AB210. Providencia sp. SRS82 was found competent to degrade actual effluent and diverse dyes that could be present in textile industry effluent showing usefulness of the organism for possible commercial application.

Development of a low-cost, phyto-tunnel system using Portulaca grandiflora and its application for the treatment of dye-containing wastewaters.

A phyto-tunnel was developed using a drilled PVC pipe. It was planted with Portulaca grandiflora and used for the treatment of a textile effluent and a dye mixture. COD, BOD, TOC, conductivity, turbidity, total suspended solids and total dissolved solids of the textile effluent, and dye mixture were decreased by 57, 45, 43, 52, 76, 77 and 24% within 96h, and 49, 62, 41, 63, 58, 71 and 33%, within 60h, respectively, after treatment. The effluent and dye mixture were decolorized up to 87 and 90% within 96 and 60h, respectively. Significant induction in activities of lignin peroxidase, tyrosinase and DCIP reductase was observed in root tissues of the plants. FTIR, HPLC and HPTLC of untreated and treated samples showed the formation of new metabolites and preferential dye removal. Phytotoxicity studies revealed the non-toxic nature of the metabolites.

Evaluation of phytoremediation potential of Tagetes patula L. for the degradation of textile dye Reactive Blue 160 and assessment of the toxicity of degraded metabolites by cytogenotoxicity

Tagetes patula is an annual flowering plant belonging to family Asteraceae. The present study deals with in vitro decolorization and remediation of a textile dye Reactive Blue 160 by T. patula. There was considerable (∼90%) decolorization of the dye within 4d of incubation, as confirmed by UV–vis, HPLC and FTIR analysis. The enzymes responsible for the remediation were lignin peroxidase, tyrosinase, laccase and NADH–DCIP reductase which were found in root tissues of the plantlets. GC–MS analysis of the products revealed formation of six metabolites such as sodium benzenesulfonate, 6-chloro 1,3,5-triazine-2,4-diamine, disodium benzene-1,4-disulfonate, sodium 3-amino-4-hydroxybenzenesulfonate, 1-phenylmethanediamine and sodium 4-amino-3-carboxybenzenesulfonate after phytoremediation of Reactive Blue 160. Based on the FTIR and GC–MS results, the possible pathway for the biodegradation of Reactive Blue 160 has been traced. The non-toxic nature of the degraded products was confirmed by performing cytogenotoxicity tests on root tip cells of growing Allium cepa.

Development of a bioreactor for remediation of textile effluent and dye mixture: A plant–bacterial synergistic strategy

The objective of the present work was to develop a plant–bacterial synergistic system for efficient treatment of the textile effluents. Decolorization of the dye Scarlet RR and a dye mixture was studied under in vitro conditions using Glandularia pulchella (Sweet) Tronc., Pseudomonas monteilii ANK and their consortium. Four reactors viz. soil, bacteria, plant and consortium were developed that were subjected for treatment of textile effluents and dye mixture. Under in vitro conditions G. pulchella and P. monteilii showed decolorization of the dye Scarlet RR (SRR) by 97 and 84%, within 72 and 96 h respectively, while their consortium showed 100% decolorization of the dye within 48 h. In case of dye mixture G. pulchella, P. monteilii and consortium-PG showed an ADMI removal of 78, 67 and 92% respectively within 96 h. During decolorization of SRR G. pulchella showed induction in the activities of enzymes lignin peroxidase and DCIP reductase while P. monteilii showed induction of laccase, DCIP reductase and tyrosinase, indicating their involvement in the dye metabolism. High Performance Liquid Chromatography (HPLC), Fourier Transform Infra Red Spectroscopy (FTIR) and High Performance Thin Layer Chromatography (HPTLC) confirmed the biotransformation of SRR and dye mixture into different metabolites. Soil, bacteria, plant and consortium reactors performed an ADMI removal of 42, 46, 62 and 93% in the first decolorization cycle while it showed an average ADMI removal of 21, 27, 59 and 93% in the next three (second, third and fourth) decolorization cycles respectively for the dye mixture within 24 h. Consortium reactor showed an average ADMI removal of 95% within 48 and 60 h for textile effluents A and B respectively for three decolorization cycles, while it showed an average TOC, COD and BOD removal of 74, 70 and 70%, 66, 72 and 67%, and 70, 70 and 66% for three decolorization cycles of the dye mixture (second, third and fourth decolorization cycles), effluent A and effluent B respectively. Degradation of the textile effluents and dye mixture into different metabolites by the consortium reactor was confirmed using HPLC and FTIR. Phytotoxicity studies revealed the non-toxic nature of the metabolites of degradation of dye mixture, effluents A and B by consortium reactor. The developed consortial reactor system performed efficient treatment of the dye mixture and textile effluents, and can be used for treating large amounts of textile effluents when implemented as a constructed wetland by proper engineering approach.

Biotransformation studies of textile dye Remazol Orange 3R.

In the present study, biotransformation of Remazol Orange 3R (RO3R) was studied using well-known bacterial isolate Pseudomonas aeruginosa strain BCH. The dye was decolorized up to 98 % within 15 min. The induction in the level of various oxidoreductive enzymes viz. laccase, tyrosinase, veratryl alcohol oxidase and DCIP reductase were observed in the cells obtained after decolorization of RO3R, which supports their role in decolorization. The metabolites of RO3R obtained after biodegradation were identified and characterized by various analytical techniques viz, HPLC, FTIR, and GC–MS. The RO3R was transformed to the N-(7 amino 8 hydroxy-napthalen-2yl) actamide (m/z, 198), Acetamide (m/z, 59) and Napthalen-1-ol (m/z, 144).

Azo dye decolorization by Shewanella aquimarina under saline conditions

Decolorization of azo dyes under saline conditions was studied with Shewanella aquimarina, which demonstrated good growth at up to 7% NaCl. No inhibition on acid red 27 (AR27) decolorization was caused by 1–3% NaCl. Additionally, 14.5% AR27 (0.2mM) could still be removed in 12h in the presence of 10% NaCl. The relationship between specific decolorization rate and AR27 concentration followed Michaelis–Menten kinetics (Km=0.34mM, Vmax=6.44μmolmgcell−1h−1). Lactate and formate were efficient electron donors for AR27 decolorization. The initial decolorization rate was in direct proportion to biomass concentration (0.18–0.72gl−1). Compared to NaCl, slighter inhibitive effects were found with Na2SO4 whereas more severe inhibition was caused by NaNO3. Lower NaCl concentration stimulated azoreductase, laccase and NADH–DCIP reductase activities of cell extracts. AR27 decolorization products were found to be aromatic amines, which were less phytotoxic than the untreated dye.

Enzymatic degradation of textile dye Reactive Orange 13 by newly isolated bacterial strain Alcaligenes faecalis PMS-1

The aim of the present work is to evaluate degradation of textile dye Reactive Orange 13 (RO 13) by newly isolated bacterial strain. The bacterial isolate was identified as Alcaligenes faecalis PMS-1 based on 16S rDNA analysis. The isolate was able to decolorize cyanuric chloride based RO 13 under the static anoxic condition with an average decolorization rate of 24.75mgl−1h−1; which is approximately 38.13 times higher than the literature reported value. Kinetic study of decolorization experiments approximates the first-order reaction. The activation energy (Ea) and frequency factor (Ao) were calculated for decolorization reaction using Arrhenius equation. The maximum rate (Vmax) and Michaelis constant (Km) were found to be 27.1mgl−1h−1 and 105mgl−1, respectively by using Michaelis–Menten kinetics. Noteworthy induction of Veratryl Alcohol Oxidase, Tyrosinase and NADH–DCIP reductase enzymes were observed during decolorization of RO 13, which suggested the enzymatic decolorization and degradation of reactive dye. UV–Vis spectroscopy, FTIR and HPLC analysis confirmed decolorization of RO 13. Dye degradation pathway was determined through enzyme assay study and GC–MS analysis. The final products, naphthalene and 6-[(4-chloro-1,3,5-triazin-2-yl) amino]-2-iminonaphthalen-1(2H)-one were characterized by GC–MS analysis. The phytotoxicity study revealed the degradation of RO 13 into non-toxic product by PMS-1.