Azoreductase Activity Research Articles

Performance of a novel Built-in Static Magnetic Field – Biological Aerated Filter (BSMF–BAF) for treating high-salt textile dyeing wastewater

High-salt textile dyeing wastewater is difficult to treat. Magnetic fields can enhance the biodegradation capacity and extreme environmental adaptabilities of microorganisms. Thus, magnetically enhanced bioreactors are expected to improve the treatment efficiency and stability of high-salt textile dyeing wastewater. Accordingly, a novel Built-in Static Magnetic Field – Biological Aerated Filter (BSMF–BAF) was constructed and investigated for treating actual high-salt textile dyeing wastewater in this study. Two other BAFs packed with traditional and magnetic ceramsite carriers, respectively, were simultaneously operated for comparison. The removal of color, chemical oxygen demand (COD), suspended solid (SS) and acute toxicity were monitored. The activities of key enzymes and microbial community structure were analyzed to reveal possible mechanisms for improving the treatment efficiency of traditional BAF using the BSMF. The results showed that the BSMF–BAF possessed the highest removal efficiencies of color, COD, SS and acute toxicity among the three BAFs. The BSMF induced significant increases in the activities of azoreductase and lignin peroxidase, which were responsible for the degradation of azo compounds in the wastewater and the detoxification of toxic intermediates, respectively. Additionally, the BSMF induced the relative enrichment of potentially effective bacteria and fungi, and it maintained a relatively high abundance of fungi in the microbial community, resulting in a high treatment efficiency.

Sequence similarity network analysis of drug- and dye-modifying azoreductase enzymes found in the human gut microbiome

Drug metabolism by human gut microbes is often exemplified by azo bond reduction in the anticolitic prodrug sulfasalazine. Azoreductase activity is often found in incubations with cell cultures or ex vivo gut microbiome samples and contributes to the xenobiotic metabolism of drugs and food additives. Applying metagenomic studies to personalized medicine requires knowledge of the genes responsible for sulfasalazine and other drug metabolism, and candidate genes and proteins for drug modifications are understudied. A representative gut-abundant azoreductase from Anaerotignum lactatifermentan DSM 14214 efficiently reduces sulfasalazine and another drug, phenazopyridine, but could not reduce all azo-bonded drugs in this class. We used enzyme kinetics to characterize this enzyme for its NADH-dependent reduction of these drugs and food additives and performed computational docking to provide the groundwork for understanding substrate specificity in this family. We performed an analysis of the Flavodoxin-like fold InterPro family (IPR003680) by computing a sequence similarity network to classify distinct subgroups of the family and then performed chemically-guided functional profiling to identify proteins that are abundant in the NIH Human Microbiome Project dataset. This strategy aims to reduce the number of unique azoreductases needed to characterize one protein family in the diverse set of potential drug- and dye-modifying activities found in the human gut microbiome.

Decolorization and detoxification of Brilliant Crocein GR by a newly enriched thermophilic consortium

The environmental pollution caused by azo dyes at high temperatures has become an urgent problem. However, little attention has been paid to decolorizing azo dyes by thermophilic consortiums. In this study, a thermophilic bacterial consortium (BCGR-T) mainly composed of two genera, namely, Caldibacillus (70.90%) and Aeribacillus (17.63%) was first enriched, which can decolorize Brilliant Crocein GR (BCGR) at high temperatures (50–75 °C), pH values of 6∼8, dye concentrations (100–400 mg/L) and salinities (1–5%, w/v). The enzyme activity results showed that the azoreductase activity was nearly 8.8 times that of the control (p < 0.01), and the intracellular lignin peroxidase was also highly expressed with enzyme activity of 5.64 U (min−1 mg−1 protein) (p < 0.05), indicated that both azoreductase and intracellular lignin peroxidase played an important part in the decolorization process. Furthermore, seven new intermediate metabolic products, including aniline, phthalic acid, 2-carboxy benzaldehyde, phenylacetic acid, benzoic acid, toluene, and 4-methyl-hexanoic acid, were identified. In addition, functional genes related with the azo dye decolorization, such as those encoding the azoreductase, laccase, FMN reductase, NADPH-/NADH-quinone oxidoreductases and NADPH-/NADH dehydrogenases, catechol dioxygenase, homogentisate 1,2-dioxygenase, protocatechuate 3,4-dioxygenase, gentisate 1,2-dioxygenase, azobenzene reductase, naphthalene 1,2-dioxygenase, benzoate/toluate 1,2-dioxygenase, and anthranilate 1,2-dioxygenase and so on were found in the metagenome of the consortium BCGR-T. Finally, a new decolorization pathway of the thermophilic consortium BCGR-T was proposed. In addition, the phototoxicity of BCGR decreased after decolorization. Overall, the thermophilic consortium BCGR-T could be a promising candidate in the treatment of high concentration azo dye wastewater at high temperatures.

Unveiling the azo-reductase mechanism in Pseudomonas putida for efficient decolorization of textile Reactive dyes: an in-silico study

The textile industry utilizing affordable azo dyes is a high threat to aquatic life and causes environmental problems due to their toxicity. Biodegradation of azo dyes employing microbes and enzymes has proved to be an efficient method for treating industrial effluent. This study used the novel microbial consortium to decolorize reactive azo dyes (Reactive Red 120; Reactive Black 5 and Reactive Blue 13), and its azo-reductase activity was evaluated. The metagenomic analysis of the consortium identified azo-reductase-producing bacterial species. The molecular docking revealed that PpAzoR from Pseudomonas putida had the highest binding affinities for all the three dyes such as Reactive Black 5 (−9.3 kcal/mol), Reactive Blue 13 (−9.8 kcal/mol) and Reactive Red 120 (−10.7 kcal/mol). The structural rigidity and stability of the docked complex were confirmed through MD simulations evaluated across multiple descriptors from the simulation trajectories. Further, MMPBSA analysis validated the results that binding of the ligands, i.e. dye molecules Reactive Black (RB5), Reactive Blue (RB13) and Reactive Red (RR120) binding with the Azoreductase (PpAzoR) to the screened Azo-dyes was spontaneous. Based on molecular dynamics simulations for 100 ns, RR 120 showed the highest binding affinity (−411.336 ± 46.799 KJ/mol), followed by RB5 (−288.012 ± 33.371 KJ/mol). The dyes (RR120 and RB5) exhibited stable interactions with the target azoreductase (PpAzoR). The present study provides insights that PpAzoR shows the highest decolorization potency, which could be interpreted as a potential dye-degrading protein based on dye-degrading assay findings. Communicated by Ramaswamy H. Sarma

Visualization of an Endogenous Mitochondrial Azoreductase Activity under Normoxic Conditions Using a Naphthalimide Azo-Based Fluorogenic Probe.

In this paper, we demonstrate the existence of an endogenous mitochondrial azoreductase (AzoR) activity that can induce the cleavage of N═N double bonds of azobenzene compounds under normoxic conditions. To this end, 100% OFF-ON azo-based fluorogenic probes derived from 4-amino-1,8-naphthalimide fluorophores were synthesized and evaluated. The in vitro study conducted with other endogenous reducing agents of the cell, including reductases, demonstrated both the efficacy and the selectivity of the probe for AzoR. Confocal experiments with the probe revealed an AzoR activity in the mitochondria of living cells under normal oxygenation conditions, and we were able to demonstrate that this endogenous AzoR activity appears to be expressed at different levels across different cell lines. This discovery provides crucial information for our understanding of the biochemical processes occurring within the mitochondria. It thus contributes to a better understanding of its function, which is implicated in numerous pathologies.

Metagenomic analysis of a bioreactor biofilm treating raw textile effluent and biochemical characterization of a novel azoreductase gene

Azo dyes are potent synthetic carcinogens that are widely used in the textile industries and their discharge into the surface water has detrimental consequences for human and ecosystem health. Oxidoreductases have been found to be involved in the metabolism of various xenobiotic compounds including azo dyes. Therefore, in this study shotgun metagenomic sequencing (SGMS) was used to bioprospect novel oxidoreductase genes in the biofilm of a fixed-film bioreactor treating raw textile effluent. According to the SGMS taxonomic and functional annotation, the bacteria found to be dominant in the bioreactor biofilm exhibited versatility and possessed genes that are capable of degrading azo dyes as well as other xenobiotics. A novel azoreductase gene (BM-AzoR) derived from the bioreactor biofilm metagenome was found to encode a previously uncharacterized FMN-dependent NADH azoreductase. In silico analysis of BM-AzoR gene encoded enzyme suggests that it is a thermostable and hydrophilic monomeric protein. The purified BM-AzoR is a flavin protein showing an optimal enzyme activity at pH 5 and 55 °C, respectively. The purified enzyme showed a specific azoreductase activity of 1.348 ± 0.12 U mg−1 in the presence of flavin mononucleotide (FMN) and preferred nicotinamide adenine dinucleotide (NADH) over nicotinamide adenine dinucleotide phosphate (NADPH) as an electron donor. A molecular docking analysis validated the in vitro results by identifying Methyl Red as the best substrate for the BM-AzoR. The purified enzyme retained its activity in a variety of metal ions and solvents, indicating its potential application in azo dye bioremediation.

The global anaerobic metabolism regulator fnr is necessary for the degradation of food dyes and drugs by Escherichia coli.

This work has broad relevance due to the ubiquity of dyes containing azo bonds in food and drugs. We report that azo dyes can be degraded by human gut bacteria through both enzymatic and nonenzymatic mechanisms, even from a single gut bacterial species. Furthermore, we revealed that environmental factors, oxygen, and L-Cysteine control the ability of E. coli to degrade azo dyes due to their impacts on bacterial transcription and metabolism. These results open up new opportunities to manipulate the azoreductase activity of the gut microbiome through the manipulation of host diet, suggest that azoreductase potential may be altered in patients suffering from gastrointestinal disease, and highlight the importance of studying bacterial enzymes for drug metabolism in their natural cellular and ecological context.

Evaluation of Bioremediation Potentiality of Bacillus mojavensis Isolated from Wastewater for the Elimination of Reactive Yellow 145 and Methyl Orange.

Textile industry waste has become one of the largest polluters in the world. In recent years, there has been a growing awareness of the need for sustainable and eco-friendly practices for the treatment of dye-laden effluents. Overall, this study highlights the potential of bioremediation as a sustainable solution for wastewater treatment. The Bacillus mojavensis isolated from wastewater and identified using 16S rRNA degraded reactive yellow 145 and methyl orange in 36h of incubation, this decolorization was affected by pH, temperature, dye concentration, glucose concentration, source of nitrogen, type of dye, and agitation. Our study found that the optimal conditions for total decolorization of dyes were achieved by incubating B. mojavensis at 46°C, pH 9, with 1g/L of glucose and 2g/L of peptone. The azoreductase activity, FT-IR analysis, and UV-visible spectrum before and after total decolorization indicated that it was a dye degradation rather than biosorption in surface Celle. In addition, the study of phytotoxicity show the metabolites of degradation are not phytotoxic in Lens esculenta seeds. In conclusion, our results suggest the use of this bacterium as an environmentally friendly and also cost-effective method, making it an attractive option for industries looking to reduce their environmental impact.

Production, partial purification and characterization of intracellular Azoreductase from bacterial isolates during biodecolorization of textile dye Acid Maroon V

Azoreductase is an important enzyme for the reduction of the azo linkage of dye during the biodecolorization process. In the present study, the production of intracellular azoreductase from bacterial cultures Enterobacter dissolvens AGYP1 (ED) and Pseudomonas aeruginosa AGYP2 (PA) was achieved during biodecolorization of synthetic textile dye Acid Maroon V. When compared with PA, the enzyme activity of ED was 2.31 times greater. The partial purification of azoreductase revealed specific activity of the dialyzed enzyme 51.72 U mg-1 protein (ED) and 33.06 U mg1 protein (PA). Methyl Red served as the best substrate for the azoreductase enzyme with superior activity at optimal pH 7 and temperature 30 °C. 75-80% of azoreductase enzyme activity was maintained when Mg+2 and Ca+2 were present. The azoreductase activity was considerably increased with NADH as the most suitable electron donor. The kinetic study showed consequent Michaelis-Menten constant (Km) and maximal velocity (Vmax) values of 50 μM and 2222 U ml-1 (ED) and 250 μM and 1000 U ml-1 (PA), respectively

Foliar application of growth regulators and nutrients for enhanced yield attributes of guava cv Lalit

Azoreductase is an important enzyme for the reduction of the azo linkage of dye during the biodecolorization process. In the present study, the production of intracellular azoreductase from bacterial cultures Enterobacter dissolvens AGYP1 (ED) and Pseudomonas aeruginosa AGYP2 (PA) was achieved during biodecolorization of synthetic textile dye Acid Maroon V. When compared with PA, the enzyme activity of ED was 2.31 times greater. The partial purification of azoreductase revealed specific activity of the dialyzed enzyme 51.72 U mg-1 protein (ED) and 33.06 U mg1 protein (PA). Methyl Red served as the best substrate for the azoreductase enzyme with superior activity at optimal pH 7 and temperature 30 °C. 75-80% of azoreductase enzyme activity was maintained when Mg+2 and Ca+2 were present. The azoreductase activity was considerably increased with NADH as the most suitable electron donor. The kinetic study showed consequent Michaelis-Menten constant (Km) and maximal velocity (Vmax) values of 50 μM and 2222 U ml-1 (ED) and 250 μM and 1000 U ml-1 (PA), respectively

Homologous overexpression of azoreductase (azoA) in Enterococcus sp. L2 moderated growth and azo dye decolorization while gaining an oxidative and heavy metal stress resistance: A trade-off

Heavy metals as co-pollutants significantly restrict the efficiency of bioremediation of azo dye-containing effluents wherein bacterial survival is a prerequisite. An exposure to quinones and oxidative stress via H 2 O 2 could induce the azoreductase activity in Enterococcus sp. L2 which could link the AzoA to its stress management system. Therefore, we underpinned the physiological and stress tolerance features by homologous over-expression of the azoA gene in its native strain. AzoA overexpression increased 3.4 folds azoreductase specific activity and enhanced quinone reduction profile. AzoA overexpression in native strain led to a delay in the early log phase growth and reactive violet 5R decolorization while gaining an advantageous stress resistance towards oxidative and heavy metals such as copper and chromium. This was confirmed by the 32 folds higher survival upon exposure to 20 mM H 2 O 2 supported by H 2 DCFA staining. Additionally, the genetically modified strain significantly tolerated 3 mM Cu(II) and 0.3 mM Cr(VI) supporting the development of a robust azo dye bioremediation strain. • Azo dye, quinones and H 2 O 2 enhanced azoreductase activity of Enterococcus sp. L2. • Homologous cloning in strain L2 resulted in 3.4 folds over-expression of AzoA gene. • AzoA over-expression in strain L2 moderated growth and dye decolorization. • AzoA over-expression in strain L2 increased oxidative stress (H 2 O 2 ) resistance. • AzoA over-expression in strain L2 enhanced heavy metal (Cu 2+ and Cr 6+ ) tolerance.

Eco-sustainable bioremediation of industrial azodye micropollutants by extremophilic plant growth promoting bacterium Halomonas desertis G11

Application of extremophilic plant growth promoting bacteria (PGPB) and their enzymes in bioremediation have been received increasing interest due to their eco-friendly nature and effectiveness for bio treatment of diverse industrial micro pollutants. In this work, the azo-dye decolorization potential of halophilic PGPB Halomonas desertis G11 was evaluated and optimized using central composite experimental design and response surface methodology. Interestingly, the increase of pH and NaCl concentration accelerated the dye decolorization. The model predicted a maximum removal of BEZACTIV blue S-2G dye (80%) at optimal operating conditions (dye concentration of 50 mg/L, inoculum size of 1.0%, pH of 8.2, NaCl of 5.0% and incubation time of 10 days). The experimental design model predictions are in good agreement with the experimental data, thereby providing the soundness of the developed model. The biodecolorization under pressures of high salinity and alkalinity seems to be correlated to azoreductase activity. The gene encoding FMN-dependent NADH azo-reductase from halophilic bacterium H. desertis G11 was identified and the structure and catalytic mechanism of dye decolorizing enzyme were elucidated. Results of this study provide evidence for the potential application of this azoreductase producing extremophilic bacterium as a novel candidate in the biological treatment of sediments and wastewaters contaminated by azo-dyes.

Synthesis of magnetic hydrochar from Fenton sludge and sewage sludge for enhanced anaerobic decolorization of azo dye AO7

A novel magnetic hydrochar synthesized from Fenton sludge (FS) and sewage sludge (SS) was employed in the anaerobic decolorization of acid orange 7 (AO7). The stable presence of Fe3O4 in magnetic hydrochar was confirmed by physicochemical characterization. The degradation efficiency of AO7 in the anaerobic system with the addition of hydrochar prepared in an optimal proportion (SS:FS=1:3, named as HC-1:3) could reach 98.55%, which was 1.91 times higher than the control system. Particularly, superior electrical conductivity, electron transport system activity and azo reductase activity of the sludge in anaerobic system with HC-1:3 were achieved. The redox of Fe(Ⅲ)/Fe(Ⅱ) in anaerobic system was realized by dissimilatory iron-reducing bacteria enriched with HC-1:3. According to the six-cycle batch experiments and 120-day continuous-flow UASB experiments, the addition of HC-1:3 into the anaerobic system facilitated the diversity of microbiological community and increased the ecological stability of anaerobic system. The possible electron transfer mechanism involving in the magnetic hydrochar-based anaerobic system for AO7 removal was speculated preliminarily. The as-prepared magnetic hydrochar not only showed a promising future in anaerobic system for recalcitrant contaminants degradation, but also provided a new approach for the resource utilization of FS and SS.

Radiosynthesis and in silico bioevaluation of 131 I-Sulfasalazine as a highly selective radiotracer for imaging of ulcerative colitis.

This study demonstrated the tracking of ulcerative colitis, which is considered a stressful immune disease. Although there are many ways to test for this disease including dependence on gases, dyes, and painful anal endoscopy, these treatment modalities have many disadvantages. Hence, it is the utmost need of time to discover new methods to detect this chronic immune disease and to avoid the defects of traditional methodologies. Sulfasalazine (SSD) was labeled with iodine-131 (half-life: 8days, Energy: 971keV) under optimum reaction conditions including the amount of reducing agent, pH factor, chloramine-T (Ch-T) amount, and incubation period. Characterization was performed using 1 H/ 13 C-NMR, ESI-MS, and HPLC (UV/ Radio) techniques. The biodistribution study was performed in normal and ulcerative mice models, and in silico molecular docking study was performed to evaluate the possible mechanism of action to target peroxisome proliferator-activated receptor gamma (PPARγ). The high radiolabeling yield of [131 I]-sulfasalazine ([131 I]-SSD) was achieved ≥90% through the direct labeling method with radioactive iodine-131 in the presence of chloramine-T (100μg). The radiotracer [131 I]-SSD was observed to be stable in normal saline and freshly eluted serum up to 12hr at ambient temperature (37℃±2℃). The radiotracer [131 I]-SSD showed the highest uptake in the targeted organ (i.e., ulcerative colon) which was observed to be ≥75% injected dose per gram (% ID/g) organ for 24hr postinjection (p.i). Furthermore, in silico data collected from molecular modeling analysis of SSD and [131 I]-SSD with antimicrobial protein (PDB code: 3KEG) and peroxisome proliferator-activated receptor gamma (PPARγ) (PDB code: 4XTA) showed azoreductase activity and high binding potential for PPAR-γ site, respectively. The results of biological studies obtained in this study enlighten the usefulness of radiotracer [131 I]-SSD as a potential imaging agent for ulcerative colitis.

Studies on decolourisation of azo dye Orange G by bacterium isolated from dye contaminated sites

ABSTRACT In the present study, an azo dye decolourising bacterium, Pseudomonas aeruginosa; JKAK, was isolated and characterised based on morphological, biochemical and 16S rDNA sequence analysis. The strain decolourised 99.12% of 200 mg/L Orange G dye in just 16 h. JKAK also decolourised up to 800 mg/L of the dye by 76.78% in 24 h. The optimum pH and temperature for decolourisation were 8.5 and 40°C, respectively. Also, this strain could decolourise over 90% of the dye in presence of 30 g/L NaCl in less than 20 h. Furthermore, it could decolourise 92.1%, 91.7% and 34.6% of the dye, after 20, 28 and 52 h in the presence of Lead, Zinc and Cobalt ions, respectively. Consortium of JKAK with previously isolated strains of bacteria AK1, AK2 and VKY1 decolourised the dye completely in 12 h. The cell-free extract of JKAK showed azoreductase activity of 0.9 µmoles/min/mg protein. The HPLC and LCMS analysis of the decolourised medium indicated the presence of azo bond breakage products 8-amino-6-hydroxynaphthaline-1,3-disulfonate and aniline. About 42% reduction in phytotoxicity was observed in the decolourised samples. Overall, due to the high decolourising capacity over a wide range of conditions, this strain could be effectively applied for the treatment of textile effluents.

Wasteful Azo Dyes as a Source of Biologically Active Building Blocks.

In this work, an environment-friendly enzymatic strategy was developed for the valorisation of dye-containing wastewaters. We set up biocatalytic processes for the conversion of azo dyes representative of the main classes used in the textile industry into valuable aromatic compounds: aromatic amines, phenoxazinones, phenazines, and naphthoquinones. First, purified preparations of PpAzoR azoreductase efficiently reduced mordant, acid, reactive, and direct azo dyes into aromatic amines, and CotA-laccase oxidised these compounds into phenazines, phenoxazinones, and naphthoquinones. Second, whole cells containing the overproduced enzymes were utilised in the two-step enzymatic conversion of the model mordant black 9 dye into sodium 2-amino-3-oxo-3H-phenoxazine-8-sulphonate, allowing to overcome the drawbacks associated with the use of expensive purified enzymes, co-factors, or exquisite reaction conditions. Third, cells immobilised in sodium alginate allowed recycling the biocatalysts and achieving very good to excellent final phenoxazine product yields (up to 80%) in water and with less impurities in the final reaction mixtures. Finally, one-pot systems using recycled immobilised cells co-producing both enzymes resulted in the highest phenoxazinone yields (90%) through the sequential use of static and stirring conditions, controlling the oxygenation of reaction mixtures and the successive activity of azoreductase (anaerobic) and laccase (aerobic).

Bioremedial approach of Pseudomonas stutzeri SPM-1 for textile azo dye degradation.

The optimization of the bacterium Pseudomonas stutzeri SPM-1, obtained from textile wastewater dumping sites of Surat, Gujarat was studied for the degradation of the textile azo dye Procion Red-H3B. The strain showed significant activities of azoreductase (95%), laccase (76%) and NADH-DCIP reductase (88%) at 12, 10 and 8h of growth, respectively, indicating the evidence for reductive cleavage of the dye. The optimization was carried on phenanthrene enrichment medium followed by exposing it to variable environmental factors and nutritional sources. The complete decolourization of dye (50mg/L) happened within 20h of incubation at pH 8 and temperature 32 ± 0.2°C under microaerophilic condition. Decolourization was monitored with the shifting of absorbance peak in UV-Vis spectrophotometry and HPLC analysis. The changes in the functional groups were confirmed by the presence of new peaks in FT-IR data. GC-MS analysis helped in recognizing the degraded dye compounds thus elucidating the proposed pathway for Procion Red-H3B. The potential of bioremediation process was completed by phytotoxicity test using two plants Vigna radiata and Cicer arietinum. Our study concludes that the strain Pseudomonas stutzeri SPM-1, with its rapid decolourization efficiency holds noteworthy prospective in industrial application for textile wastewater treatment.

Environment friendly degradation and detoxification of Congo red dye and textile industry wastewater by a newly isolated Bacillus cohnni (RKS9)

Textile industry wastewater (TIWW) is a major source of environmental pollution causing serious threats to all life forms and thus, it must be adequately treated before its final discharge for the safety of environment and public health. In the present study, a potential bacterial strain (RKS9) was isolated from textile (wastewater & sludge) sample for the effective treatment of TIWW resulting in a significant reduction in pollution parameters such as ADMI color (93.87%), COD (77.35%), BOD (86.02%), TDS (66.75%), TOC (67.25%), TSS (60.34%), and phenol (68.55%) within 48 h. This bacterium also decolorized 99% of Congo red dye (100 mg L −1 ) within 12 h and removed 59.76%, 40.51%, 52.71% and 26.51% cadmium, chromium, lead and nickel, respectively from the TIWW. The activities of azoreductase, laccase, lignin peroxidase (LiP) and manganese peroxidase (MnP) was monitored and metabolites produced during the treatment of dye and TIWW were also analyzed by FT-IR and GC–MS. The phytotoxicity of the untreated and treated TIWW was assessed by seed germination and seedling growth parameters of Phaseolus mungo L. and results showed a significant reduction in the toxicity of the treated TIWW, suggesting that the isolated bacterium RKS9 has a remarkable potential to effectively decolorize/detoxify TIWW. • Textile industry wastewater (TIWW) has different dyes as residual pollutants. • TIWW causes severe environmental and health threats. • Bacteria Bacillus cohnni was used to treat CR dye and TIWW. • FT-IR and GC–MS were used to characterize TIWW pollutants and metabolites. • Toxicity of untreated and treated TIWW was evaluated by seed germination test.

Microbial degradation of Procion Red by Pseudomonas stutzeri

The bacterium Pseudomonas stutzeri SPM-1, obtained from textile wastewater dumping sites of Surat, Gujarat was studied for the degradation of the textile azo dye Procion Red—H3B. The optimization was carried on the phenanthrene enrichment medium followed by exposing it to variable environmental factors and nutritional sources. The complete decolorization of dye (50 mg/L) happened within 20 h of incubation at pH 8 and temperature 32 ± 0.2 °C under microaerophilic conditions. Decolourization was monitored with the shifting of absorbance peak in UV–Vis spectrophotometry and HPLC analysis. The physicochemical studies of effluent before and after the treatment revealed 85%, 90%, and 65% decline in BOD, COD, and TOC levels. The strain showed significant activities of azoreductase (95%), laccase (76%), and NADH-DCIP reductase (88%) at 12 h, 10 h, and 8 h of growth respectively indicating evidence for reductive cleavage of the dye. The changes in the functional groups were confirmed by the presence of new peaks in FT-IR data. GC–MS analysis helped in recognizing the degraded dye compounds thus elucidating the proposed pathway for degradation of Procion Red—H3B. The potential of the bioremediation process was concluded by a phytotoxicity test using two plants, Vigna radiata and Cicer arietinum. Our study demonstrates that the strain Pseudomonas stutzeri SPM-1 has rapid decolorization efficiency and holds a noteworthy perspective in industrial application for textile wastewater treatment.

Mycoremediation of azo dyes using Cyberlindnera fabianii yeast strain: Application of designs of experiments for decolorization optimization.

This study investigated the dye decolorization capacity of three yeast strains. Cyberlindnera fabianii was shortlisted for its high decolorization capacity and was further tested on various azo dyes. Based on the color of the biomass, and the UV-Vis analysis, Acid Red 14 was selected as a model dye, to examine the enzymatic biodegradation. The results showed significant increase in the intracellular and extracellular activities of laccase, tyrosinase, manganese peroxidase, and azoreductase. Phytotoxicity assessment indicated that the AR14 biodegradation by-products were not phytotoxic compared to the original dye molecules. Regarding the decolorization optimization, the screening of factors using the Plackett-Burman design showed that pH, dye concentration, and shaking speed had significant effects. These factors and their combined effect were evaluated using response surface methodology with the Box-Behnken model. The pH was the most significant factor, followed by dye concentration. The analysis of the contour plot and the 3D response surface diagram showed that the decolorization was inversely proportional to the increase in the initial dye concentration, but proportional to the initial pH and shaking speed. At optimal conditions (pH=5.154, AR14=50mg/L), C.fabianii could decolorize more than 97% of AR14 within 12hr. PRACTITIONER POINTS: Cyberlindnera fabianii is a successful candidate for dye mycoremediation. Oxidase and reductase are the key enzymes involved in the biodegradation of azo dyes. By-products of Acid red 14 biodegradation are not phytoxic compared to the original dye. Design of experience tools enables to determine optimum conditions for efficient decolorization.