Potential of halophiles and alkaliphiles in bioremediation of azo dyes-laden textile wastewater: a review.

Azo dye-laden textile wastewater must be treated before release due to various health and environmental concerns. Bioremediation of textile wastewater, however, is a challenge owing to its alkaline and saline nature as mesophilic microbes, in general, are either not able to thrive or show less efficiency under such hostile environment. Thus, pre-treatment for neutralization or salinity removal becomes a prerequisite before applying microbes for treatment, causing extra economical and technical burden. Extremophilic bacteria can be the promising bioremediating tool because of their inherent ability to survive and show toxicants removal capability under such extreme conditions without need of pre-treatment. Among extremophiles, halophilic and alkaliphilic bacteria which are naturally adapted to high salt and pH are of special interest for the decolorization of saline-alkaline-rich textile wastewater. The current review article is an attempt to provide an overview of the bioremediation of azo dyes and azo dye-laden textile wastewater using these two classes of extremophilic bacteria. The harmful effects of azo dyes on human health and environment have been discussed herein. Halo-alkaliphilic bacteria circumvent the extreme conditions by various adaptations, e.g., production of certain enzymes, adjustment at the protein level, pH homeostasis, and other structural adaptations that have been highlighted in this review. The unique properties of alkaliphiles and halophiles, to not only sustain but also harboring high dye removal competence at high pH and salt concentration, make them a good candidate for designing future bioremediation strategies for the management of alkaline, salt, and azo dye-laden industrial wastewaters.

Promotion of anaerobic biodegradation of azo dye RR2 by different biowaste-derived biochars: Characteristics and mechanism study by machine learning.

The addition of biochar resulted in a 31.5 % to 44.6 % increase in decolorization efficiency and favorable decolorization stability. Biochar promoted extracellular polymeric substances (EPS) secretion, especially humic-like and fulvic-like substances. Additionally, biochar enhanced the electron transfer capacity of anaerobic sludge and facilitated surface attachment of microbial cells. 16S rRNA gene sequencing analysis indicated that biochar reduced microbial species diversity, enriching fermentative bacteria such as Trichococcus. Finally, a machine learning model was employed to establish a predictive model for biochar characteristics and decolorization efficiency. Biochar electrical conductivity, H/C ratio, and O/C ratio had the most significant impact on RR2 anaerobic decolorization efficiency. According to the results, the possible mechanism of RR2 anaerobic decolorization enhanced by different types of biochar was proposed.

Synthesis rifaximin with copper (Rif-Cu) and copper oxide (Rif-CuO) nanoparticles Considerable dye decolorization: An application of aerobic oxidation of eco-friendly sustainable approach.

In this study, rifaximin with copper (Cu) and copper oxide (CuO) nanoparticles (NPs) were synthesised. The resultant CuO nanoparticles were used to degrade Rhodamine B (RhB) and Coomassie Brilliant Blue (G250). Rifaximin copper and copper oxide nanoparticles were characterised using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), and gas chromatography-electrochemical mass spectrometry (GC-EI-MS). An FT-IR study confirmed the formation of Cu in the 562 cm-1 peak range. Rifaximin Cu and CuO Nanoparticles displayed UV absorption peaks at 253 nm and 230 nm, respectively. Coomassie Brilliant Blue G250 was completely decolourised in Cu nanoparticles at 100 %, and Rhodamine B was also decolourised in Rifaximin CuO nanoparticles at 73 %, although Coomassie Brilliant Blue G250 Rifaximin Cu nanoparticles absorbed a high percentage of dye decolorization. The aerobic oxidation of isopropanol conversion was confirmed by GC-MS analysis. Retention time of 27.35 and 30.32 was confirmed using Cu and CuO nanoparticles as the final products of 2-propanone. It is used in the textile and pharmaceutical industries for aerobic alcohol oxidation. Rifaximin CuO nanoparticles highly active in aerobic oxidation. The novelty of this study is that, for the first time, rifaximin was used for the synthesis of copper and copper oxide nanoparticles, and it successfully achieved decolorization and aerobic oxidation.

Enhanced Photocatalysis of Electrically Polarized Titania Nanosheets.

Titania (TiO2) nanosheets are crystals with controlled, highly ordered structures that improve the functionality of conventional TiO2 nanoparticles. Various surface modification methods have been studied to enhance the effectiveness of these materials as photocatalysts. Surface modifications using electrical polarization have attracted considerable attention in recent years because they can improve the function of titania without changing its composition. However, the combination of facet engineering and electrical polarization has not been shown to improve the functionality of TiO2 nanosheets. In the present study, the dye-degradation performance of polarized TiO2 nanosheets was evaluated. TiO2 nanosheets with a F/Ti ratio of 0.3 were synthesized via a hydrothermal method. The crystal morphology and structure were evaluated using transmission electron microscopy and X-ray diffraction. Then, electrical polarization was performed under a DC electric field of 300 V at 300 °C. The polarized material was evaluated using thermally stimulated current measurements. A dye-degradation assay was performed using a methylene blue solution under ultraviolet irradiation. The polarized TiO2 nanosheets exhibited a dense surface charge and accelerated decolorization. These results indicate that electrical polarization can be used to enhance the photocatalytic activity of TiO2.

Optimization and purification of laccase activity from Mammaliicoccus sciuri isolated from the soils of Similipal, Odisha, India: a kinetics study of crystal violet dye decolorization.

Four laccase-producing bacteria were found in soil samples from the Similipal Biosphere Reserve in Odisha, according to the current study. The isolates (SLCB1 to SLCB4) were evaluated for their laccase-producing ability in LB broth supplemented with guaiacol. The ABTS assay was performed to assess the laccase activity. The bacterium Mammaliicoccus sciuri shows the highest laccase activity i.e., 0.5125 U/L at the optimized conditions of pH 5.5, temperature 32.5 °C, ABTS concentration of 0.75 µl with an incubation time of 9 d. Laccase activity of M. sciuri grown in Sawdust was significantly increased in comparison to that in other agro wastes. The partially purified laccase enzyme after ammonium sulfate precipitation and dialysis showed a molecular weight of ∼58.5 kDa as determined by SDS-PAGE. A decolorization efficiency of 66.67% was recorded for the dye crystal violet after 1 h treatment with dialyzed laccase enzyme compared with phenol red, brilliant blue, and methylene blue.

CO2 Photoreduction Activity Enhancement and Unexpected Observation of Carbon Monoxide Adsorbates on the Surface of TiO2 Nanotube Arrays Synthesized in Formamide Electrolytes.

TiO2 nanotube arrays grown through electrochemical anodization in a formamide-based electrolyte (TNTA-FA) exhibited a whole host of unusual properties compared to nanotubes grown in the conventional ethylene glycol-based electrolyte (TNTA-EG). TNTA-FA exhibited shorter phonon lifetimes, lower lattice strain, more visible light absorption, lower work function, and a highly unusual adsorbate structure consisting of physisorbed and chemisorbed CO along with linearly adsorbed CO2 and various monodentate and bidentate carbonate species. The observation of adsorbed CO in the dark is highly unusual and indicates spontaneous deoxygenation of CO2 on the surface of TNTA-FA. The significance of this finding is that the formation of CO2•- is no longer the rate-limiting bottleneck for the reduction of CO2 on TNTA-FA surfaces as it is for all TiO2 surfaces. TNTA-FA samples are strongly colored (inclusive of a fluorescent green color) and consist of rounded, vertically oriented hollow cylinders as opposed to the honeycomb-like morphology of TNTA-EG arranged in an approximate triangular lattice. The photocatalytic activity was tested through the CO2 photoreduction and dye degradation tests. Formamide-based nanotubes outperformed the EG-based nanotubes by almost 1.7 and 2 times, respectively, in CO2 reduction and dye degradation tests done on methylene blue, brilliant green, and rhodamine B dyes. These results are attributed to stronger surface band bending in TNTA-FA which facilitates more efficient separation of photogenerated electron-hole pairs.

Kinetics of dye decolorization using heterogeneous catalytic system with immobilized Achromobacter xylosoxidans DDB6.

Textile effluents containing toxic dyes must be treated effectively before discharge to prevent adverse environmental impacts. Traditional physical and chemical treatment methods are costly and generate secondary pollutants. In contrast, biological treatment is a more suitable, clean, versatile, eco-friendly, and cost-effective technique for treating textile effluent. It is well established that indigenous microbial populations present in effluents can effectively degrade toxic dyes. In this regard, Achromobacter xylosoxidans DDB6 was isolated from the effluent sample to decolorize crystal violet (CV), Coomassie brilliant blue (CBB), and alizarin red (AR) by 67.20%, 28.58%, and 20.41%, respectively. The growth parameters of A. xylosoxidans DDB6 in media supplemented with 100 ppm of various dyes were determined using the modified Gompertz growth model. The immobilized cells in calcium alginate beads showed apparent decolorization rate constant of 0.27, 0.18, and 0.13 h-1 for CV, CBB, and AR, respectively. The immobilized cells in a packed bed reactor with an optimum flow rate of 0.5 mL/min were used to treat 100 ppm of CV with a percentage decolorization of 79.47% after three cycles. Based on the findings, A. xylosoxidans DDB6 could be effectively used for decolorization of various dyes.

An Inferred Ancestral CotA Laccase with Improved Expression and Kinetic Efficiency.

Laccases are widely used in industrial production due to their broad substrate availability and environmentally friendly nature. However, the pursuit of laccases with superior stability and increased heterogeneous expression to meet industry demands appears to be an ongoing challenge. To address this challenge, we resurrected five ancestral sequences of laccase BsCotA and their homologues. All five variants were successfully expressed in soluble and functional forms with improved expression levels in Escherichia coli. Among the five variants, three exhibited higher catalytic rates, thermal stabilities, and acidic stabilities. Notably, AncCotA2, the best-performing variant, displayed a kcat/KM of 7.5 × 105 M-1·s-1, 5.2-fold higher than that of the wild-type BsCotA, an improved thermo- and acidic stability, and better dye decolorization ability. This study provides a laccase variant with high application potential and presents a new starting point for future enzyme engineering.

Assessment of drying conditions for storage of a yeast-based decolorization solution for application in textile industrial wastewater treatment plants.

The textile industry produces harmful effluents that are discharged into the environment, damaging the aquatic and other ecosystems. A yeast-based solution for decolorization of textile industrial wastewater was produced and evaluated. Three yeast strains, Candida parapsilosis (HOMOGS20B), Yarrowia lipolytica (HOMOGST27AB) and Candida pseudoglaebosa (LIIIS36B), isolated from a textile wastewater treatment plant and previously selected for their dye decolorization capacity, were freeze-dried. Additionally, Yarrowia lipolytica (HOMOGST27AB) was also spray-dried. Skim milk powder and maltodextrin were used as cell protectors, and the freeze-dried products were stored at cold (4 °C) and room temperature for 210 days. The viability of the yeast cells and their decolorization capacity over time were assessed. Dried yeast cells maintained their viability, and decolorization capacity for at least 90 days of storage after spray- and freeze-drying with both cell-protecting agents. The dried yeast-based solution for decolorizing textile industrial wastewater combines stability, efficiency, and convenience of production for application in real industrial facilities.

Computer-aided discovery of a novel thermophilic laccase for low-density polyethylene degradation.

Polyethylene (PE) and industrial dyes are recalcitrant pollutants calling for the development of sustainable solutions for their degradation. Laccases have been explored for removal of contaminants and pollutants, including dye decolorization and plastic degradation. Here, a novel thermophilic laccase from PE-degrading Lysinibaccillus fusiformis (LfLAC3) was identified through a computer-aided and activity-based screening. Biochemical studies of LfLAC3 indicated its high robustness and catalytic promiscuity. Dye decolorization experiments showed that LfLAC3 was able to degrade all the tested dyes with decolorization percentage from 39% to 70% without the use of a mediator. LfLAC3 was also demonstrated to degrade low-density polyethylene (LDPE) films after eight weeks of incubation with either crude cell lysate or purified enzyme. The formation of a variety of functional groups was detected using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Damage on the surfaces of PE films was observed via scanning electron microscopy (SEM). The potential catalytic mechanism of LfLAC3 was disclosed by structure and substrate-binding modes analysis. These findings demonstrated that LfLAC3 is a promiscuous enzyme that has promising potential for dye decolorization and PE degradation.

Enzymatic degradation of azo dyes methylene blue and congo red with peroxidase purified from cauliflower using affinity chromatography technique: Kinetic study, optimization and metal binding activity.

The effective results of the enzymatic decolorization of industrial azo dyes found in wastewater, which cause serious health and environmental problems, with peroxidases have recently increased the interest in these enzyme sources. Redox-mediated decolorization of Methylene Blue and Congo Red azo dyes with cauliflower (Brassica oleracea var. botrytis L.) peroxidase (CPOD) purified in one step using 4-amino 3-bromo 2-methyl benzohydrazide molecule was investigated for the first time. The inhibition effect of this molecule, which is used as a ligand in affinity chromatography, on the CPOD enzyme was investigated. The Ki and IC50 values for this enzyme were calculated as 0.113 ± 0.012 mM and 0.196 ± 0.011 mM, respectively. With the affinity gel obtained by binding to the Sepharose-4B-l-tyrosine matrix of this molecule, which shows a reversible inhibition effect, the purification values of CPOD enzyme were determined as 562-fold with a specific activity of 50,250 U mg-1. The purity of the enzyme was checked by the SDS-PAGE technique and its molecular weight was determined. A single band at 44 kDa was observed for the CPOD enzyme. In dye decolorization studies, the effects of dye, enzyme, and hydrogen peroxide concentrations as well as time, pH, and temperature were investigated. The profiles of the optimum conditions for both dyes were similar, and the percentages of decolorization of Methylene Blue and Congo Red under these conditions were 89% and 83%, respectively, at the end of the 40 min reaction time. Again, when examining the effect of metal ions on enzyme activity, it was found that there was no significant negative change in CPOD.

Heterogeneous biocatalytic system for effective decolorization of textile dye effluent.

The current physicochemical methods for decolorizing toxic synthetic dyes are not sustainable to halt the environmental damage as they are expensive and often produce concentrated sludge, which may lead to secondary disposal problems. Biocatalysis (microbes and/or their enzymes) is a cost-effective, versatile, energy-saving and clean alternative. The most common enzymes involved in dye degradation are laccases, azoreductases and peroxidases. Toxic dyes could be converted into less harmful byproducts through the combined action of many enzymes or the utilization of whole cells. The action of whole cells to treat dye effluents is either by biosorption or degradation (aerobic or anaerobic). Using immobilized cells or enzymes will offer advantages such as superior stability, persistence against harsh environmental conditions, reusability and longer half-lives. This review envisages the recent strategies of immobilization and bioreactor considerations with the immobilized system as the effective treatment of textile dye effluents. Packed bed reactors are the most popular heterogeneous biocatalytic reactors for dye decolorization due to their efficiency and cost-effectiveness.

Efficient Azo Dye Biodecolorization System Using Lignin-Co-Cultured White-Rot Fungus.

The extensive use of azo dyes by the global textile industry induces significant environmental and human health hazards, which makes efficient remediation crucial but also challenging. Improving dye removal efficiency will benefit the development of bioremediation techniques for textile effluents. In this study, an efficient system for azo dye (Direct Red 5B, DR5B) biodecolorization is reported, which uses the white-rot fungus Ganoderma lucidum EN2 and alkali lignin. This study suggests that the decolorization of DR5B could be effectively enhanced (from 40.34% to 95.16%) within 48 h in the presence of alkali lignin. The dye adsorption test further confirmed that the alkali-lignin-enhanced decolorization of DR5B was essentially due to biodegradation rather than physical adsorption, evaluating the role of alkali lignin in the dye biodegradation system. Moreover, the gas chromatography/mass spectrometry analysis and DR5B decolorization experiments also indicated that alkali lignin carried an excellent potential for promoting dye decolorization and displayed a significant role in improving the activity of lignin-modifying enzymes. This was mainly because of the laccase-mediator system, which was established by the induced laccase activity and lignin-derived small aromatic compounds.

Citrus limon peroxidase-assisted biocatalytic approach for biodegradation of reactive 1847 colfax blue P3R and 621 colfax blue R dyes.

One of the big environmental problems in today's world is dye-contaminated toxic waste. Peroxidase is known as highly efficient for the degradation of various pollutants, including dyes. Environmental contamination caused by the discharge of dyes into water bodies is an onerous challenge that poses both human and ecological hazards. In the current studies, biocatalysts used for enzyme decolorization (1847 Colafx Blue P3R and 621 Colafx Blue) are regarded as an eco-friendly method utilizing commonly available low-cost material lemon peels (Citrus limon peroxidase). Peroxidase was extracted in a phosphate buffer of pH 7.0 and partially purified by 20-80% ammonium sulfate precipitation technique from Citrus limon peels. The soluble enzyme was characterized in terms of kinetic and thermodynamic parameters. The values of Km and Vmax (23.16 and 204.08 µmol/ml/min) were determined, respectively. The enzyme showed maximum activity at pH 5.0 and a temperature of 55 °C. Citrus limon efficiently degraded 1847 Colafx Blue P3R and 621 Colafx Blue R dyes with maximum degradation of 83 and 99%, respectively, with an initial dye concentration of 200 ppm at pH 4 and 35 °C temperature within 5-10 min of incubation time. The effect of the redox mediator on the degradation process was examined. Results showed that the peroxidase HOBT system efficiently enhanced the degradation of dyes from water. Hence, Citrus limon peroxidase is an efficient biocatalyst for the treatment of effluents.

Tailor-made novel electrospun polycaprolactone/polyethyleneimine fiber membranes for laccase immobilization: An all-in-one material to biodegrade textile dyes and phenolic compounds.

In spite of many works on the biodegradation of textile dyes and phenolic compounds, we propose a new, inexpensive, environmentally friendly, and sustainable material based on electrospun fiber and immobilized laccase. The polycaprolactone (PCL)/polyethyleneimine (PEI) electrospun fibers were optimized and prepared by electrospinning technique according to the operational parameters like PCL concentration (12 wt%), PEI concentration (10 wt%), voltage (16 kV), needle tip-collector distance (20 cm), and injection speed (0.7 mL/h). Next, characterization studies were performed to investigate the morphology and structure of the electrospun fibers without and with laccase. The crude laccase was obtained by cultivating the white rot fungus T. trogii (TT), and T. versicolor (TV). The resulting electrospun fibers showed a smooth surface with a mean diameter of around 560 nm, and larger diameters were observed after laccase immobilization. According to the results, immobilization increased the stability properties of laccase such as storage, and operational. For instance, the residual activity of the PCL/PEI/TTL and PCL/PEI/TVL after 10 repeated cycles, was 33.2 ± 0.2% and 26.0 ± 0.9%, respectively. After 3 weeks of storage, they retained around 30% of their original activity. Moreover, the PCL/PEI/TTL and PCL/PEI/TVL were found to possess high decolorization yield to remove Orange II and Malachite Green textile dyes from solutions imitating polluted waters. Among them, the PCL/PEI/TTL exhibited the highest decolorization efficiencies of Orange II and Malachite Green after 8 continuous uses at pH 5 and a temperature of 50 °C, reaching over 86%, and 46%, respectively. Moreover, PCL/PEI/TTL and PCL/PEI/TVL effectively degraded the 2,6-dichlorophenol phenolic compound at an optimal pH and temperature range and exhibited maximum removal efficiency of 52.6 ± 0.1% and 64.5 ± 7.6%, respectively. Our approach combines the advantageous properties of electrospun fiber material and immobilization strategy for the efficient use of industrial scale important enzymes such as laccase in various enzymatic applications.

Deciphering the alkaline stable mechanism of bacterial laccase from Bacillus pumilus by molecular dynamics simulation can improve the decolorization of textile dyes.

Laccases are considered promising tools for removing synthetic dyes from textile and tannery effluents. However, the alkaline pH in the effluents causes laccase instability, inactivation, and difficulty in its bioremediation. Based on a Bacillus pumilus ZB1 (BpLac) derived alkaline stable laccase, this study aimed to elucidate its alkaline stable mechanism at molecular level using molecular dynamics simulation. The effects of metal ions, organic solvents, and inhibitors on BpLac activity were assessed. BpLac formed more salt bridges and negatively charged surface in alkaline environment. Thereafter, pH-induced conformation changes were analyzed using GROMACS at pH 5.0 and 10.0. Among the identified residues with high fluctuation, the distance between Pro359 and Thr414 was stable at pH 10.0 but highly variable at pH 5.0. DSSP analysis suggested that BpLac formed more ß-sheet and less coil at pH 10.0. Principal component analysis and free energy landscape indicated that irregular coils formed at pH 5.0 benefit for activity, while rigid α-helix and ß-sheet structures formed at pH 10.0 contributed to alkaline stability. Breaking the α-helix near T1 copper center would not reduce alkaline stability but could improve dye decolorization by BpLac. Overall, these findings would advance the potential application of bacterial laccase in alkaline effluent treatment.

Immobilization of Horseradish Peroxidase on Magnetite-Alginate Beads to Enable Effective Strong Binding and Enzyme Recycling during Anthraquinone Dyes' Degradation.

The aim of this study was to investigate covalent immobilization of horseradish peroxidase (HRP) on magnetic nanoparticles (Mag) encapsulated in calcium alginate beads (MABs) for color degradation, combining easy and fast removal of biocatalyst from the reaction mixture due to its magnetic properties and strong binding due to surface alginate functional groups. MABs obtained by extrusion techniques were analyzed by optical microscopy, FEG-SEM and characterized regarding mechanical properties, magnetization and HRP binding. HRP with initial concentration of 10 mg/gcarrier was successfully covalently bonded on MABs (diameter ~1 mm, magnetite/alginate ratio 1:4), with protein loading of 8.9 mg/gcarrier, immobilization yield 96.9% and activity 32.8 U/g. Immobilized HRP on MABs (HRP-MABs) was then used to catalyze degradation of two anthraquinonic dyes, Acid Blue 225 (AB225) and Acid Violet 109 (AV109), as models for wastewater pollutants. HRP-MABs decolorized 77.3% and 76.1% of AV109 and AB225, respectively after 15 min under optimal conditions (0.097 mM H2O2, 200 mg of HRP-MABs (8.9 mg/gcarrier), 0.08 and 0.1 g/mg beads/dye ratio for AV109 and AB225, respectively). Biocatalyst was used for 7 repeated cycles retaining 75% and 51% of initial activity for AB225 and AV109, respectively, showing potential for use in large scale applications for colored wastewater treatment.

Environmental Impacts of Ecofriendly Iron Oxide Nanoparticles on Dyes Removal and Antibacterial Activity.

Biosynthesized nanoparticles have a promising future since they are a more environmentally friendly, cost-effective, repeatable, and energy-efficient technique than physical or chemical synthesis. In this work, Purpureocillium lilacinum was used to synthesize iron oxide nanoparticles (Fe2O3-NPs). Characterization of mycosynthesized Fe2O3-NPs was done by using UV-vis spectroscopy, transmission electron microscope (TEM), dynamic light scattering (DLS), and X-ray diffraction (XRD) analysis. UV-vis gave characteristic surface plasmon resonance (SPR) peak for Fe2O3-NPs at 380 nm. TEM image reveals that the morphology of biosynthesized Fe2O3-NPs was hexagonal, and their size range between 13.13 and 24.93 nm. From the XRD analysis, it was confirmed the crystalline nature of Fe2O3 with average size 57.9 nm. Further comparative study of photocatalytic decolorization of navy blue (NB) and safranin (S) using Fe2O3-NPs was done. Fe2O3-NPs exhibited potential catalytic activity with a reduction of 49.3% and 66% of navy blue and safranin, respectively. Further, the antimicrobial activity of Fe2O3-NPs was analyzed against pathogenic bacteria (Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis, and Staphylococcus aureus). The Fe2O3-NPs were clearly more effective on gram-positive bacteria (S. aureus and B. subtilis) than gram-negative bacteria (E. coli and P. aeruginosa). Thus, the mycosynthesized Fe2O3-NPs exhibited an ecofriendly, sustainable, and effective route for decolorization of navy blue and safranin dyes and antibacterial activity.

Decolorization of various dyes by microorganisms and green-synthesized nanoparticles: current and future perspective.

Various types of colored pigments have been recovered naturally from biological sources including shells, flowers, insects, and so on in the past. At present, such natural colored substances (dyes) are replaced by manmade dyes. On the other hand, due to their continuous usage in various purpose, these artificial dyes or colored substances persist in the environmental surroundings. For example, industrial wastewater contains diverse pollutant substances including dyes. Several of these (artificial dyes) were found to be toxic to living organisms. In recent times, microbial-based removal of dye(s) has gained more attention. These methods were relatively inexpensive for eliminating such contaminants in the environmental system. Hence, various researchers were isolated microbes from environmental samples having the capability of decolorizing synthetic dyes from industrial wastewater. Furthermore, the microorganisms which are genetically engineered found higher degradative/decolorize capacity to target compounds in the natural environs. Very few reviews are available on specific dye treatment either by chemical treatments or by bacteria and/or fungal treatments. Here, we have enlightened literature reports on the removal of different dyes in microbes like bacteria (including anaerobic and aerobic), fungi, GEM, and microbial enzymes and also green-synthesized nanoparticles. This up-to-date literature survey will help environmental managements to co-up such contaminates in nature and will help in the decolorization of dyes.

Biochemical and Structural Properties of a High-Temperature-Active Laccase from Bacillus pumilus and Its Application in the Decolorization of Food Dyes.

A novel laccase gene isolated from Bacillus pumilus TCCC 11568 was expressed, and the recombinant laccase (rLAC) displayed maximal activity at 80 °C and at pH 6.0 against ABTS. rLAC maintained its structural integrity at a high temperature (355 K) compared to its tertiary structure at a low temperature (325 K), except for some minor adjustments of certain loops. However, those adjustments were presumed to be responsible for the formation of a more open access aisle that facilitated the binding of ABTS in the active site, resulting in a shorter distance between the catalytic residue and the elevated binding energy. Additionally, rLAC showed good thermostability (≤70 °C) and pH stability over a wide range (3.0-10.0), and displayed high efficiency in decolorizing azo dyes that are applicable to the food industry. This work will improve our knowledge on the relationship of structure-function for thermophilic laccase, and provide a candidate for dye effluent treatment in the food industry.