Untreated release of toxic synthetic and colorful dyes is a serious threat to the environment. Every year, several thousand gallons of dyes are being disposed into the water resources without any sustainable detoxification. The accumulation of hazardous dyes in the environment poses a severe threat to the human health, flora, fauna, and microflora. Therefore, in the present study, a lignin peroxidase enzyme from Pseudomonas fluorescence LiP-RL5 has been employed for the maximal detoxification of selected commercially used dyes. The enzyme production from the microorganism was enhanced ~ 20 folds using statistical optimization tool, response surface methodology. Four different combinations (pH, production time, seed age, and inoculum size) were found to be crucial for the higher production of LiP. The crude enzyme showed decolorization action on commonly used commercial dyes such as Crystal violet, Congo red, Malachite green, and Coomassie brilliant blue. Successful toxicity mitigation of these dyes culminated in the improved seed germination in three plant species, Vigna radiate (20-60%), Cicer arietinum (20-40%), and Phaseolus vulgaris (10-25%). The LiP treated dyes also exhibit reduced bactericidal effects against four common resident microbial species, Escherichia coli (2-10 mm), Bacillus sp. (4-8 mm), Pseudomonas sp. (2-8 mm), and Lactobacillus sp. (2-10 mm). Therefore, apart from the tremendous industrial applications, the LiP from Pseudomonas fluorescence LiP-RL5 could be a potential biocatalyst for the detoxification of synthetic dyes.

This research was performed to assess the physicochemical properties of textile effluents collected from different sampling points (industrial park, Hosur, Tamil Nadu, India) and also evaluate the multiple metal tolerance efficiency of pre-isolated Aspergillus flavus. Moreover, their textile effluent decolourization potential was investigated and quantity and temperature required for effective bioremediation was optimized. About 5 textile effluent samples (S0, S1, S2, S3, and S4) were collected from various sampling points and noted that certain physicochemical properties (pH: 9.64 ± 0.38, Turbidity: 18.39 ± 1.4 NTU, Cl^-: 3185.38 ± 15.8 mg L^-1, BOD: 82.52 ± 6.9 mg L^-1, COD: 342.28 ± 8.9 mg L^-1, Ni: 74.21 ± 4.31 mg L^-1, Cr: 48.52 ± 18.34 mg L^-1, Cd: 34.85 ± 1.2 mg L^-1, Zn: 25.52 ± 2.4 mg L^-1, Pb: 11.25 ± 1.5 mg L^-1, Hg: 1.8 ± 0.05 mg L^-1, and As: 7.1 ± 0.41 mg L^-1) were beyond the permissible limits. The A. flavus, showed remarkable metal tolerance to Pb, As, Cr, Ni, Cu, Cd, Hg, and Zn on PDA plates with elevated dosage up to 1000 μg mL^-1. The optimal dosage required for effective decolourization was found as 3 g (48.2%) and compare to dead biomass (42.1%) of A. flavus, the viable biomass showed remarkable decolourization activity on textile effluents in a short duration of treatment process. The optimal temperature for effective decolourization by viable biomass was found at 32 ᵒC. The toxic effects of S4 samples treated at 32 ᵒC on O. sativa as well as brine shrimp larvae were significantly reduced. These findings show that pre-isolated A. flavus viable biomass can be used to decolorize metal-enriched textile effluent. Furthermore, the effectiveness of their metals remediation should be investigated using ex-situ and ex-vivo approaches.

The physicochemical attributes of textile effluents collected from secondary treatment stage was investigated in this study and also assess the biosorption potential of membrane immobilized Bacillus cereus and free form of Bacillus cereus on textile effluent through bioreactor model study to find a sustainable solution to manage the textile effluent as vital need. Furthermore, the phytotoxicity and cytotoxicity nature of treated and untreated textile effluents on Vigna mungo and Artemia franciscana larvae under laboratory conditions as a novel approach. The textile effluent physicochemical parameter analysis results showed that the properties such as colour (Hazen unit), pH, turbidity, As, Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Cd, Cl, Cr, Cu, Hg, Ni, Pb, SO₄^2-, and Zn were beyond the acceptable limits. Bacillus cereus immobilized on a polyethylene membrane eliminated greater amounts of dye (25.0 ± 1.3, 56.5 ± 1.8, 57.18 ± 1.5, and 54.34 ± 1.7 Hazen unit from An1, Ae2, Ve3, and So4 respectively) and pollutants (As: 0.9-2.0, Cd: 6-8, Cr: 300-450, Cu: 5-7, Hg: 0.1-0.7, Ni: 8-14, Pb: 4-5, and Zn: 4-8 mg L^-1) from textile effluent in a week of biosorption investigation using a bioreactor model (batch type) compared to a free form of B. cereus on textile effluent. The phytotoxicity and cytotoxicity study results revealed that the membrane immobilized B. cereus treated textile effluent exposure showed reduced phytotoxicity and minimal cytotoxicity (including mortality) percentage compared with free form B. cereus treated and untreated textile effluents. These entire results conclude that the membrane immobilized B. cereus may considerably minimize/detoxify the harmful pollutants from the textile effluents. A large scale level biosorption approach need to be performed to validate the maximum pollutants removing potential of this membrane immobilized bacteria species and optimal conditions for effective remediation.

Effluents of textile industries caused serious environmental problem throughout the world. In this study, a total of 23 bacterial strains from five bacterial species were isolated from the dye effluent. Of these strains, a unique and novel Enterobacter aerogenes ES014 was utilized for dye decolourization and toxicity analysis. The selected strain could effectively decolourize three selected azo dyes. It showed the capability for decolourizing acid orange (82.3 ± 3.6%), methyl orange (78.2 ± 3.3%), and congo red (81.5 ± 3.2%). The selected bacterial strain significantly decolourized 100 mg/L acid orange at 35 °C, pH 7.5 with 6% sodium chloride concentration. Most of the tested nitrogen and carbon sources effectively enhanced decolourization process. It showed the ability to decolourize acid orange in the culture medium containing 1.5% glucose (100 ± 2.8%) and 0.8% beef extract (100 ± 3.1%). A laboratory-scale batch bioreactor was used to decolourize azo dye at optimized culture conditions. The decolourizing ability improved with 100 mL/h hydraulic retention time. The treated wastewater quality was improved due to sharp depletion of Total Dissolved Solids (TDS), pH, Chemical Oxygen Demand (COD), alkalinity and sulphate concentration. The selected bacteria has the potential to produce dye degrading laccase. Laccase was detected during fermentation process in batch bioreactor as a key enzyme for decolourization produced by E. aerogenes ES014. Phytotoxicity and acute toxicity analysis were performed using Arachis hypogaea (pea nut) seed and first instar larvae of Artemia parthenogenetica (brine shrimp). The seed germination rate of treated wastewater was improved (94.3 ± 1.8%) and enhanced survival rate (91.7 ± 2.9%) in the first instar Artemia larvae treated with wastewater after 24 h. Overall, E. aerogenes ES014, might be a promising bacterial strain for the treatment of textile effluents with high azo dye concentrations.

The color effluent discharged by alcohol distilleries comprises very high pollution loads due to the plethora of refractory chemicals even after anaerobic treatment and causing adverse effects to the environment. The present study aimed to examine the phytotoxic, cytotoxic, and genotoxic potential of the identified refractory organic and inorganic pollutants discharged in bio-methanated distillery effluent (BMDE). Physico-chemical analyses revealed that BMDE retains high BOD, COD, TDS along with heavy metals like Fe (572.64 mg L^-1), Mn (4.269 mg L^-1), Cd (1.631 mg L^-1), Zn (2.547 mg L^-1), Pb (1.262 mg L^-1), (Cr 1.257 mg L^-1), and Ni (0.781 mg L^-1) beyond the permissible limits for effluent discharge. GC-MS analysis revelaed the presence of hexadecanoic acid, TMS ester; octadecanoic acid, TMS ester; 2,3 bis[(TMS)oxy]propyl ester; stigmasterol TMS ether; β-sitosterol TMS ester; hexacosanoic acid; and tetradecanoic acid, TMS ester as major refractory organic pollutants, which are listed as potential endocrine disruptor chemicals (EDCs) as per USEPA. Furthermore, phytotoxicity assessment with Phaseolus aureus L. showed the toxic nature of BMDE as it inhibited various seedling growth parameters, seed germination, and suppression of α-amylase activity in seed germination experiment. Moreover, genotoxicity and cytotoxicity evaluation of the discharged BMDE evidenced in root-tip meristematic cells of Allium cepa L. where chromosomal aberration such as disturbed metaphase, c-mitosis, laggard chromosomes, sticky chromosomes, prolonged prophase, polyploid cells, and apoptotic bodies etc. were observed. Thus, this study's results suggested that BMDE discharged without adequate treatment poses potential risk to environment and may cause a variety of serious health threats in living beings upon exposure.

Twenty-one fungal strains were isolated from dye-contaminated soil; out of them, two fungal strains A2 and G2-1 showed the highest decolorization capacity for real textile effluent and were, hence, identified as Aspergillus flavus and Fusarium oxysporium based on morphological and molecular methods. The highest decolorization percentage of 78.12 ± 2.1% was attained in the biotreatment with fungal consortium followed by A. flavus and F. oxysporium separately with removal percentages of 54.68 ± 1.2% and 52.41 ± 1.0%, respectively. Additionally, ultraviolet-visible spectroscopy of the treated effluent showed that a maximum peak (λ_max) of 415 nm was reduced as compared with the control. The indicators of wastewater treatment efficacy, namely total dissolved solids, total suspended solids, conductivity, biological oxygen demand, and chemical oxygen demand with removal percentages of 78.2, 78.4, 58.2, 78.1, and 77.6%, respectively, demonstrated a considerable decrease in values due to fungal consortium treatment. The reduction in peak and mass area along with the appearance of new peaks in GC-MS confirms a successful biodegradation process. The toxicity of treated textile effluents on the seed germination of Vicia faba was decreased as compared with the control. The shoot length after irrigation with effluents treated by the fungal consortium was 15.12 ± 1.01 cm as compared with that treated by tap-water, which was 17.8 ± 0.7 cm. Finally, we recommended the decrease of excessive uses of synthetic dyes and utilized biological approaches for the treatment of real textile effluents to reuse in irrigation of uneaten plants especially with water scarcity worldwide.

The newly isolated Trametes polyzona PBURU 12 demonstrated a high tolerance and potential for the degradation of phenanthrene. The fungal isolate was able to tolerate 100 ppm of phenanthrene with 45% relative growth. The crude laccase produced by Trametes polyzona PBURU 12 was able to degrade phenanthrene by up to 98% within 24 h. The degradation metabolites showed the absence of toxic compounds. Microbial viability tests using E. coli and B. subtilis revealed that the treated phenanthrene was less toxic than untreated phenanthrene. Phytotoxicity and genotoxicity tests, using Vigna radiata and Allium cepa, indicated that the treated phenanthrene was less toxic to the plants. No mutagenic activity was found in the Ames test. The crude laccase from Trametes polyzona PBURU 12 was demonstrated as a potential tool for the biodegradation of PAHs (phenanthrene), with low toxic effects after the degradation.

An effective strategy for enhancement of catalytic activity and stability of immobilized laccase via metal affinity adsorption on Fe₃O₄@C-Cu²⁺ nanoparticles was developed, which involved the fabrication of hydroxyl and carboxyl functionalized Fe₃O₄@C nanoparticles via a simple hydrothermal process and the subsequent chelation with Cu²⁺ for the immobilization of laccase under a mild condition. Our results revealed that the Fe₃O₄@C-Cu²⁺ nanoparticles possess a high loading amount of bovine serum albumin (BSA, 436 mg/g support) and laccase activity recovery of 82.3 % after immobilization. Laccase activity assays indicated that thermal and pH stabilities, and resistances to organic solvents and metal ions of the immobilized laccase were relatively higher than those of the free enzyme. The immobilized laccase maintained more than 61 % of its original activity after 10 consecutive reuses. Most importantly, the immobilized laccase possessed excellent degradation of diverse synthetic dyes. The degradation rates of malachite green (MG), brilliant green (BG), crystal violet (CV), azophloxine, Procion red MX-5B, and reactive blue 19 (RB19) was approximately 99, 93, 79, 88, 75 and 81 (%) in the first cycle. Even after 10 consecutive reuses, the removal efficiencies of the six dyes were found to be 94, 80, 71, 78, 60, and 65 (%), respectively.

Aquatic ecosystem contaminated with hazardous pollutants has become a high priority global concern leading to serious economic and environmental damage. Among various treatment approaches, carbon nanostructured materials have received particular interest as a novel platform for emerging pollutants removal owing to their unique chemical and electrical properties, biocompatibility, high scalability, and infinite functionalization possibility with an array of inorganic nanomaterials and bio-molecules. Within this framework, carbon nanotubes (CNTs) are widely used due to their hollow and layered structure and availability of large specific surface area for the incoming contaminants. Carbon nanotubes can be used either as single-walled, multi-walled, or functionalized nanoconstructs. TiO₂/SiO₂-functionalized CNTs are among the most promising heterogeneous photocatalytic candidates for the degradation of a range of organic compounds, heavy metals reduction, and selective oxidative reactions. Herein, we reviewed recent development in the application of TiO₂ and SiO₂ functionalized nanostructured carbon materials as potential environmental candidates. After a brief overview of synthesis and properties of CNTs, we explicitly discussed the potential applications of TiO₂/SiO₂ functionalized CNTs for the remediation of a variety of environmentally-related pollutants of high concern, including synthetic dyes or dye-based hazardous waste effluents, as polycyclic aromatic hydrocarbons (PAHs), pharmaceutically active compounds, pesticides, toxic heavy elements, remediation of metal-contaminated soil, and miscellaneous organic contaminants. The work is wrapped up by giving information on current challenges and recommended guidelines about future research in the field bearing in mind the conclusions of the current review.

Aquatic ecosystem contaminated with toxic pollutants and heavy metals due to the rapid growth of industrialization has become a top-priority global concern exhibiting highly adverse effects on human health and the environment. Many treatment techniques have been envisioned for the removal of these toxic contaminants from the aqueous environment. Among these techniques, magnetic separation has attracted burgeoning research attention owing to its simplicity, eco-friendly nature, large surface area, electron mobility, and excellent performance for removing water contaminants. In particular, interfacial active nanoparticles and nanocomposites with unique structures and magnetic properties are considered as ideal provides candidates in material science for next-generation water treatment. This review gives an insight into current research activities associated with the synthesis strategies and applications of interfacially active and magnetically responsive nanomaterials and nanocomposites for sustainable purification processes. In the first half, various synthesis routes for magnetic iron oxide nanoparticles development and the corresponding formation mechanism are summarized. In the second half, we reviewed the magnetic and wettability properties of interfacially active and magnetically responsive nanocomposites and their environmental applications including oil-water separation, removal of hazardous dye-based pollutants and potentially toxic heavy metals. Finally, the review is wrapped up with major concluding remarks and future perspectives of these magnetic nanoscale composite materials for sustainable wastewater remediation.

Industries are the paramount driving force for the economic and technological development of society. However, the flourishing industrialization and unimpeded growth of current production unit's result in widespread environmental pollution due to increased discharge of wastes loaded with baleful, hazardous, and carcinogenic contaminants. Physicochemical-based remediation means are costly, create a secondary disposal problem and remain inadequate for pollution mitigating because of the continuous emergence of new recalcitrant pollutants. Due to eco-friendly, social acceptance, and lesser health hazards, microbial bioremediation has received considerable global attention for pollution abatement. Moreover, with the recent advancement in biotechnology and microbiology, genetically engineered bacteria with high ability to remove environmental pollutants are widely used in the fields of environmental restoration, resulting in the bioremediation in a more viable and eco-friendly way. This review summarized the advantages of genetically engineered bacteria and their application in the treatment of a wide variety of environmental contaminants such as synthetic dyestuff, heavy metal, petroleum hydrocarbons, polychlorinated biphenyls, phenazines and agricultural chemicals which will include herbicides, pesticides, and fertilizers. Considering the risk of genetic material exchange by using genetically engineered bacteria, the challenges and limitations associated with the application of recombinant bacteria on contaminated sites are also discussed. An integrated microbiological, biological and ecological acquaintance accompanied by field engineering designs are the desired features for effective in situ bioremediation of hazardous waste polluted sites by recombinant bacteria.

The textile industry, as recognized conformist and stake industry in the world's economy, is facing serious environmental challenges. In numerous industries, in practice, various chemical-based processes from initial sizing to final washing are fascinating harsh environment concerns. Some of these chemicals are corrosive to equipment and cause serious damage itself. Therefore, in the twenty-first century, chemical and allied industries quest a paradigm transition from traditional chemical-based concepts to a greener, sustainable, and environmentally friendlier catalytic alternative, both at the laboratory and industrial scales. Bio-based catalysis offers numerous benefits in the context of biotechnological industry and environmental applications. In recent years, bio-based processing has received particular interest among the scientist for inter- and multi-disciplinary investigations in the areas of natural and engineering sciences for the application in biotechnology sector at large and textile industries in particular. Different enzymatic processes such as chemical substitution have been developed or in the process of development for various textile wet processes. In this context, the present review article summarizes current developments and highlights those areas where environment-friendly enzymatic textile processing might play an increasingly important role in the textile industry. In the first part of the review, a special focus has been given to a comparative discussion of the chemical-based "classical/conventional" treatments and the modern enzyme-based treatment processes. Some relevant information is also reported to identify the major research gaps to be worked out in future.

In the twenty-first century, chemical and associated industries quest a transition prototype from traditional chemical-based concepts to a greener, sustainable and environmentally-friendlier catalytic alternative, both at the laboratory and industrial scale. In this context, bio-based catalysis offers numerous benefits along with potential biotechnological and environmental applications. The bio-based catalytic processes are energy efficient than conventional methodologies under moderate processing, generating no and negligible secondary waste pollution. Thanks to key scientific advances, now, solid-phase biocatalysts can be economically tailored on a large scale. Nevertheless, it is mandatory to recover and reprocess the enzyme for their commercial feasibility, and immobilization engineering can efficiently accomplish this challenge. The first part of the present review work briefly outlines the immobilization of lignin-modifying enzymes (LMEs) including lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase of white-rot fungi (WRF). Whereas, in the second part, a particular emphasis has been given on the recent achievements of carrier-immobilized LMEs for the degradation, decolorization, or detoxification of industrial dyes and dye-based industrial wastewater effluents.

An indigenous and industrially important manganese peroxidase (MnP) was isolated from solid-state bio-processing of wheat bran by white-rot fungal strain Ganoderma lucidum IBL-05 under pre-optimized growth conditions. Crude MnP extract was partially purified (2.34-fold) to apparent homogeneity by ammonium sulphate precipitation and dialysis. The homogeneous enzyme preparation was encapsulated on gelatin matrix using glutaraldehyde as a cross-linking agent. Optimal conditions for highest immobilization (82.5%) were: gelatin 20% (w/v), glutaraldehyde 0.25% (v/v) and 2 h activation time using 0.6 mg/mL of protein concentration. Gelatin-encapsulated MnP presented its maximum activity at pH 6.0 and 60 °C. Thermo-stability was considerably improved after immobilization. The optimally active MnP fraction was tested against MnSO₄ as a substrate to calculate kinetic parameters. More than 90% decolorization of Sandal-fix Red C₄BLN (Reactive Red 195A) dye was achieved with immobilized MnP in 5 h. It also preserved more than 50% of its original activity after the sixth reusability cycle. The water quality parameters (pH, chemical oxygen demand, total organic carbon) and cytotoxicity (brine shrimp and Daphnia magna) studies revealed the non-toxic nature of the bio-treated dye sample. A lower K_m, higher V_max, greater acidic and thermal-resistant up to 60 °C were the improved catalytic features of immobilized MnP suggesting its suitability for a variety of biotechnological applications.

Microbial biotechnologies for the decolorization of textile wastewaters have attracted worldwide attention because of their economic suitability and easiness in handling. However, the presence of high amounts of salts and metal ions in textile wastewaters adversely affects the decolorization efficiency of the microbial bioresources. In this regard, the present study was conducted to isolate salt tolerant bacterial strains which might have the potential to decolorize azo dyes even in the presence of multi-metal ion mixtures. Out of the tested 48 bacteria that were isolated from an effluent drain, the strain NA6 was found relatively more efficient in decolorizing the reactive yellow-2 (RY2) dye in the presence of 50 g L(-1) NaCl. Based on the similarity of its 16S rRNA gene sequence and its position in a phylogenetic tree, this strain was designated as Proteus sp. NA6. The strain NA6 showed efficient decolorization (>90 %) of RY2 at pH 7.5 in the presence of 50 g L(-1) NaCl under static incubation at 30 °C. This strain also had the potential to efficiently decolorize other structurally related azo dyes in the presence of 50 g L(-1) NaCl. Moreover, Proteus sp. NA6 was found to resist the presence of different metal ions (Co(+2), Cr(+6), Zn(+2), Pb(+2), Cu(+2), Cd(+2)) and was capable of decolorizing reactive dyes in the presence of different levels of the mixtures of these metal ions along with 50 g L(-1) NaCl. Based on the findings of this study, it can be suggested that Proteus sp. NA6 might serve as a potential bioresource for the biotechnologies involving bioremediation of textile wastewaters containing the metal ions and salts.