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

Harnessing bromide ions to boost peroxymonosulfate for reactive yellow 145 dye degradation

Bromide (Br-) was found in the fresh waters at concentrations from 0.1 to 1 mg/L and can be used to activate peroxymonosulfate (PMS) as a widely used chemical oxidation agent. In the present study, the reaction between PMS and Br- ions (PMS/Br- process) for the effective degradation of reactive yellow 145 (RY-145) dye was investigated by changing operational parameters vis solution pH, dosage of Br- ions and PMS, RY-145 concentration, and reaction time. Based on the results, the simultaneous presence of PMS and Br- ions in the solution led to efficient degradation of RY-145 with a synergistic index of 11.89. The degradation efficiency of RY-145 was decreased in severe basic pH and the presence of CO32- ions as a coexisting anion. Likewise, 4 mg/L of humic acid (HA), used as a classic scavenger, led to a 26.53% decrease in the RY-145 degradation efficiency. The free bromine (HOBr/OBr-), superoxide radical (●O2-), and singlet oxygen (1O2) was the dominant oxidation agents in RY-145 degradation, which confirmed the nonradical degradation pathway. In addition, PMS/Br- process showed excellent ability in mineralizing RY-145 in different aqueous solutions (total organic carbon (TOC) decreased 86.39% in deionized water and 78.23% in tap water). Although pollutants such as azo dyes can be effectively removed in the PMS/Br- process, the formation of byproducts should be strategically controlled and special attention should be paid when the PMS-based advance oxidation process is applied to treat Br- containing solutions.

Biodecolorization and biodegradation of Reactive Green 12 textile industry dye and their post-degradation phytotoxicity-genotoxicity assessments

The employment of versatile bacterial strains for the efficient degradation of carcinogenic textile dyes is a sustainable technology of bioremediation for a neat, clean, and evergreen globe. The present study has explored the eco-friendly degradation of complex Reactive Green 12 azo dye to its non-toxic metabolites for safe disposal in an open environment. The bacterial degradation was performed with the variable concentrations (50, 100, 200, 400, and 500 mg/L) of Reactive Green 12 dye. The degradation and toxicity of the dye were validated by high-performance liquid chromatography, Fourier infrared spectroscopy analysis, and phytotoxicity and genotoxicity assay, respectively. The highest 97.8% decolorization was achieved within 12 h. Alternations in the peaks and retentions, thus, along with modifications in the functional groups and chemical bonds, confirmed the degradation of Reactive Green 12. The disappearance of a major peak at 1450 cm-1 corresponding to the -N=N- azo link validated the breaking of azo bonds and degradation of the parent dye. The 100% germination of Triticum aestivum seed and healthy growth of plants verified the lost toxicity of degraded dye. Moreover, the chromosomal aberration of Allium cepa root cell treatment also validated the removal of toxicity through bacterial degradation. Thereafter, for efficient degradation of textile dye, the bacterium is recommended for adaptation to the sustainable degradation of dye and wastewater for further application of degraded metabolites in crop irrigation for sustainable agriculture.

Treatment of industrial wastewaters by algae-bacterial consortium with Bio-H2 production: Recent updates, challenges and future prospects

Currently, scarcity/security of clean water and energy resources are the most serious problems worldwide. Industries use large volume of ground water and a variety of chemicals to manufacture the products and discharge large volume of wastewater into environment, which causes severe impacts on environment and public health. Fossil fuels are considered as major energy resources for electricity and transportation sectors, which release large amount of CO2 and micro/macro pollutants, leading to cause the global warming and public health hazards. Therefore, algae-bacterial consortium (A-BC) may be eco-friendly, cost-effective and sustainable alternative way to treat the industrial wastewaters (IWWs) with Bio-H2 production. A-BC has potential to reduce the global warming and eutrophication. It also protects environment and public health as it converts toxic IWWs into non or less toxic (biomass). It also reduces 94%, 90% and 50% input costs of nutrients, freshwater and energy, respectively during IWWs treatment and Bio-H2 production. Most importantly, it produce sustainable alternative (Bio-H2) to replace use of fossil fuels and fill the world's energy demand in eco-friendly manner. Thus, this review paper provides a detailed knowledge on industrial wastewaters, their pollutants and toxic effects on water/soil/plant/humans and animals. It also provides an overview on A-BC, IWWs treatment, Bio-H2 production, fermentation process and its enhancement methods. Further, various molecular and analytical techniques are also discussed to characterize the A-BC structure, interactions, metabolites and Bio-H2 yield. The significance of A-BC, recent update, challenges and future prospects are also discussed.

Reviving the Potential of Vermiculite-Based Adsorbents: Exceptional Ibuprofen Removal on Novel Amide-Containing Gemini Surfactants

In this study, we introduce a novel series of gemini surfactants with amide groups (HDAB, HDAHD, and HDAPX) and use these surfactants to decorate sodium vermiculite (Na-Vt) for the adsorption of Ibuprofen (IBP) from wastewater. Exceptional IBP uptake on organo-vermiculites (organo-Vts) is obtained, with maximum adsorption capacities reaching 249.87, 342.21, and 460.15 mg/g for HDAB-Vt, HDAHD-Vt, and HDAPX-Vt (C0 = 500 mg/L, modifier dosage = 0.2 CEC), respectively. The adsorption of IBP is well fitted by pseudo-second-order, intraparticle diffusion, and Freundlich isotherm models, verifying chemical adsorption processes with multilayer arrangement of IBP in organo-Vts. Thermodynamically, the removal of IBP on HDAHD-Vt is exothermic, while the endothermic nature aptly describes the adsorption process of HDAB-Vt and HDAPX-Vt. Moreover, organo-Vts can be stably regenerated in three cycles. Outstanding adsorption performance of organo-Vts is attributed to synergistic effects of the partition process and functional interaction, which are influenced by the steric hindrance and chain configuration of the modifier. A combined evaluation of adsorption tests and fitting calculations is employed to reveal the adsorption mechanism: (i) the incorporation of amides into the alkyl chain significantly enhances the utilization of the interlayer space in organo-Vts. (ii) Smaller steric hindrance and higher rigidity of the modifier spacer contribute to improved adsorption performance. The findings in this study rekindle interest in Vt-based adsorbents, which demonstrate comparable potential to other emerging adsorbents that are yet to be fully explored.

Advances from conventional to biochar enhanced biotreatment of dyeing wastewater: A critical review

DW (Dyeing wastewater) contains a large amount of dye organic compounds. A considerable proportion of dye itself or its intermediate products generated during wastewater treatment process exhibits CMR (Carcinogenic/Mutagenic/Toxic to Reproduction) toxicity. Compared with physicochemical methods, biological treatment is advantageous in terms of operating costs and greenhouse gas emissions, and has become the indispensable mainstream technology for DW treatment. This article reviews the adsorption and degradation mechanisms of dye organic compounds in wastewater and analyzed different biological processes, ranging from traditional methods to processes enhanced by biochar (BC). For traditional biological processes, microbial characteristics and communities were discussed, as well as the removal efficiency of different bioreactors. BC has adsorption and redox electron mediated effects, and coupling with biological treatment can further enhance the process of biosorption and degradation. Although BC coupled biological treatment shows promising dye removal, further research is still needed to optimize the treatment process, especially in terms of technical and economic competitiveness.

In Vitro Biofilm-Mediated Biodegradation of Pesticides and Dye-Contaminated Effluents Using Bacterial Biofilms

Overuse of pesticides in agricultural soil and dye-polluted effluents severely contaminates the environment and is toxic to animals and humans making their removal from the environment essential. The present study aimed to assess the biodegradation of pesticides (cypermethrin (CYP) and imidacloprid (IMI)), and dyes (malachite green (MG) and Congo red (CR)) using biofilms of bacteria isolated from pesticide-contaminated soil and dye effluents. Biofilms of indigenous bacteria, i.e., Bacillus thuringiensis 2A (OP554568), Enterobacter hormaechei 4A (OP723332), Bacillus sp. 5A (OP586601), and Bacillus cereus 6B (OP586602) individually and in mixed culture were tested against CYP and IMI. Biofilms of indigenous bacteria i.e., Lysinibacillus sphaericus AF1 (OP589134), Bacillus sp. CF3 (OP589135) and Bacillus sp. DF4 (OP589136) individually and in mixed culture were tested for their ability to degrade dyes. The biofilm of a mixed culture of B. thuringiensis + Bacillus sp. (P7) showed 46.2% degradation of CYP compared to the biofilm of a mixed culture of B. thuringiensis + E. hormaechei + Bacillus sp. + B. cereus (P11), which showed significantly high degradation (70.0%) of IMI. Regarding dye biodegradation, a mixed culture biofilm of Bacillus sp. + Bacillus sp. (D6) showed 86.76% degradation of MG, which was significantly high compared to a mixed culture biofilm of L. sphaericus + Bacillus sp. (D4) that degraded only 30.78% of CR. UV-VIS spectroscopy revealed major peaks at 224 nm, 263 nm, 581 nm and 436 nm for CYP, IMI, MG and CR, respectively, which completely disappeared after treatment with bacterial biofilms. Fourier transform infrared (FTIR) analysis showed the appearance of new peaks in degraded metabolites and disappearance of a peak in the control spectrum after biofilm treatment. Thin layer chromatography (TLC) analysis also confirmed the degradation of CYP, IMI, MG and CR into several metabolites compared to the control. The present study demonstrates the biodegradation potential of biofilm-forming bacteria isolated from pesticide-polluted soil and dye effluents against pesticides and dyes. This is the first report demonstrating biofilm-mediated bio-degradation of CYP, IMI, MG and CR utilizing soil and effluent bacterial flora from Multan and Sheikhupura, Punjab, Pakistan.

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 36 h 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 1 g/L of glucose and 2 g/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.

Systematic computational toxicity analysis of the ozonolytic degraded compounds of azo dyes: Quantitative structure-activity relationship (QSAR) and adverse outcome pathway (AOP) based approach

The present study identifies and analyses the degraded products of three azo dyes (Reactive Orange 16, Reactive Red 120, and Direct Red 80) and proffers their in silico toxicity predictions. In our previously published work, the synthetic dye effluents were degraded using an ozonolysis-based Advanced Oxidation Process. In the present study, the degraded products of the three dyes were analysed using GC-MS at endpoint strategy and further subjected to in silico toxicity analysis using Toxicity Estimation Software Tool (TEST), Prediction Of TOXicity of chemicals (ProTox-II), and Estimation Programs Interface Suite (EPI Suite). Several physiological toxicity endpoints, such as hepatotoxicity, carcinogenicity, mutagenicity, cellular and molecular interactions, were considered to assess the Quantitative Structure-Activity Relationships (QSAR) and adverse outcome pathways. The environmental fate of the by-products in terms of their biodegradability and possible bioaccumulation was also assessed. Results of ProTox-II suggested that the azo dye degradation products are carcinogenic, immunotoxic, and cytotoxic and displayed toxicity towards Androgen Receptor and Mitochondrial Membrane Potential. TEST results predicted LC50 and IGC50 values for three organisms Tetrahymena pyriformis, Daphnia magna, and Pimephales promelas. EPISUITE software via the BCFBAF module surmises that the degradation products' bioaccumulation (BAF) and bioconcentration factors (BCF) are high. The cumulative inference of the results suggests that most degradation by-products are toxic and need further remediation strategies. The study aims to complement existing tests to predict toxicity and prioritise the elimination/reduction of harmful degradation products of primary treatment procedures. The novelty of this study is that it streamlines in silico approaches to predict the nature of toxicity of degradation by-products of toxic industrial affluents like azo dyes. These approaches can assist the first phase of toxicology assessments for any pollutant for regulatory decision-making bodies to chalk out appropriate action plans for their remediation.

Eco-friendly detoxification of hazardous Congo red dye using novel fungal strain Trametes flavida WTFP2: Deduced enzymatic biomineralization process through combinatorial in-silico and in-vitro studies

Growing textile industry is a major global concern, owing to the presence of recalcitrant hazardous pollutants, like synthetic dyes in discharged effluents. To explore new bioresources for mycoremediation, a high laccase-producing novel white-rot fungus (WRF), Trametes flavida WTFP2, was employed. T. flavida is an underexplored member of Polyporales. Using bioinformatic tools, 8 different cis-acting RNA elements were identified in the 5.8 S ITS gene sequence, where CRISPR (CRISPR-DR15), sRNA (RUF1), and snoRNA (ceN111) are uniquely present. Molecular docking was adopted to predict the catalytic interaction of chosen toxic diazo colorant, Congo red (CR), with four dye-degrading enzymes (laccase, lignin peroxidase, azoreductase, and aryl alcohol oxidase). With 376.41 × 10³ U/L laccase production, novel WRF exhibited dye-decolorization potential. WTFP2 effectively removed 99.48 ± 0.04% CR (100 mg/L) and demonstrated remarkable recyclability and persistence in consecutive remediation trials. Mycelial dye adsorption was not only substantial driver of colorant elimination; decolorization using active T. flavida was regulated by enzymatic catalysis, as outlined by in-vitro growth, induction of extracellular enzymes, and FESEM. Fifteen metabolites were identified using HRLCMS-QTOF, and novel CR degradation pathway was proposed. Furthermore, microbial and phyto-toxicity tests of metabolites suggested complete detoxification of toxic dye, making the process clean, green, and economically sustainable.

Lighting Up Agricultural Sustainability in the New Era through Nanozymology: An Overview of Classifications and Their Agricultural Applications

With the concept of sustainable agriculture receiving increasing attention from humankind, nanozymes, nanomaterials with enzyme-like activity but higher environmental endurance and longer-term stability than natural enzymes, have enabled agricultural technologies to be reformative, economic, and portable. Benefiting from their multiple catalytic activities and renewable nanocharacteristics, nanozymes can shine in agricultural scenarios using enzyme engineering and nanoscience, acting as sustainable toolboxes to improve agricultural production and reduce the risk to agricultural systems. Herein, we comprehensively discuss the classifications of nanozymes applied in current agriculture, including peroxidase-like, oxidase-like, catalase-like, superoxide dismutase-like, and laccase-like nanozymes, as well as their biocatalytic mechanisms. Especially, different applications of nanozymes in agriculture are deeply reviewed, covering crop protection and nutrition, agroenvironmental remediation and monitoring, and agroproduct quality monitoring. Finally, the challenges faced by nanozymes in agricultural applications are proposed, and we expect that our review can further enhance agricultural sustainability through nanozymology.

Biodegradation of Congo Red Using Co-Culture Anode Inoculum in a Microbial Fuel Cell

Congo red is an azo dye widely used as a colouring agent in textile industries. It is a serious threat due to its carcinogenic effects. Its degradation has been challenging due to its complex yet stable structure. The present study was aimed to investigate the effective degradation of Congo red by bioremediating bacteria isolated from different environments. To investigate predominant microorganisms that degrade Congo red and its functions in microbial fuel cells (MFCs), strains isolated from cow dung (Enterococcus faecalis SUCR1) and soil (Pseudomonas aeruginosa PA1_NCHU) were used as a co-culture inocula. The remarkable results establish that E. faecalis as an excellent microbial source for the biological degradation of dye-contaminated wastewater treatment alongside bioactive treating wastewater with varied concentrations of congo red dye. The highest efficiency percentage of dye degradation was 98% after 3 days of incubation at pH 7 and 37 °C, whereas findings have shown that the decolorization at pH 5 and 6 was lower at 66% and 83.3%, respectively, under the same incubation conditions. Furthermore, the co-culture of E. faecalis SUCR1 and P. aeruginosa at a 1:1 ratio demonstrated improved power generation in MFCs. The maximum power density of 7.4 W/m3 was recorded at a 150 mg L−1 concentration of Congo red, indicating that the symbiotic relation between these bacterium resulted in improved MFCs performance simultaneous to dye degradation.

Adaptive Response of Thermophiles to Redox Stress and Their Role in the Process of dye Degradation From Textile Industry Wastewater

Release of dye-containing textile wastewater into the environment causes severe pollution with serious consequences on aquatic life. Bioremediation of dyes using thermophilic microorganisms has recently attracted attention over conventional treatment techniques. Thermophiles have the natural ability to survive under extreme environmental conditions, including high dye concentration, because they possess stress response adaptation and regulation mechanisms. Therefore, dye detoxification by thermophiles could offer enormous opportunities for bioremediation at elevated temperatures. In addition, the processes of degradation generate reactive oxygen species (ROS) and subject cells to oxidative stress. However, thermophiles exhibit better adaptation to resist the effects of oxidative stress. Some of the major adaptation mechanisms of thermophiles include macromolecule repair system; enzymes such as superoxide dismutase, catalase, and glutathione peroxidase; and non-enzymatic antioxidants like extracellular polymeric substance (EPSs), polyhydroxyalkanoates (PHAs), etc. In addition, different bacteria also possess enzymes that are directly involved in dye degradation such as azoreductase, laccase, and peroxidase. Therefore, through these processes, dyes are first degraded into smaller intermediate products finally releasing products that are non-toxic or of low toxicity. In this review, we discuss the sources of oxidative stress in thermophiles, the adaptive response of thermophiles to redox stress and their roles in dye removal, and the regulation and crosstalk between responses to oxidative stress.

Treatment of synthetic dye containing textile raw wastewater effluent using UV/Chlorine/Br photolysis process followed by activated carbon adsorption

This study investigated the efficiency and feasibility of ultraviolet (UV)-assisted photolysis of synthetic dye containing textile raw wastewater effluent. For a said purpose, in-house developed UV/Chlorine/Br process was followed in the presence of activated carbon (AC) which additionally facilitate the dye adsorption. In UV/Chlorine process Cl^•, Cl₂^•-, and HO^• are generated in the solution and destroyed compounds that cannot be oxidized by the conventional oxidant. In this process, free bromine is formed and photolyzed by UV radiation and generate Br^• and Br₂^•- that can enhance the rate of pollutant degradation. In the present study, the dye removal efficiency was contributed by dark bromide (7.18%), UV irradiation (26.8%), dark chlorination (78.67%), and UV/Chlorine/Br (87.01%), respectively. With increasing pH from 3.0 to 8.30, the dye removal efficiency was enhanced but decreased by further increasing pH values. In addition, magnetized activated carbon from pomegranate husk using dual-stage chemical activation was used for post-adsorption of the residual dye and its degradation byproducts. The adsorption of the dye residues by AC followed the second-order kinetics with the rate constant of 1.7 × 10^-3. The phytotoxicity of the treated textile wastewater by UV irradiation, dark chlorination, and UV/Chlorine/Br was assessed by seed germination of Lepidium sativum seeds. The highest inhibition effect on seed germination was related to treated wastewater by UV irradiation (more than 90% inhibition) that alleviated to less than 10% when this effluent diluted to 5% v/v. The highest germination was observed when the seeds were irrigated by the effluent of the UV/Chlorine/Br process. The significant reduction in the toxicity of the treated wastewater revealed that the UV/Chlorine/Br process has a considerable potential to effectively detoxify textile wastewater. Graphical abstract.

Comparison of reactive azo dye removal with UV/H2O2, UV/S2O82- and UV/HSO5- processes in aqueous solutions

Advanced oxidation processes (AOPs) are an effective choice for removal of reactive azo dyes used in the textile industry due to high solubility and low degradability. Within the scope of this study, reactive orange 122 (RO122) azo dye was removed using the UV-based AOPs of ultraviolet (UV) radiation, UV/hydrogen peroxide (UV/H₂O₂), UV/persulfate (UV/S₂O₈^2-), and UV/peroxymonosulfate (UV/HSO₅^-). Oxidant concentration, initial solution pH, initial RO122 concentration, different anions (Cl^-, NO₃^- and SO₄^2-), and solution temperature effects were compared. With only UV radiation (254 nm), 19.5% RO122 removal occurred at the end of 120 min. The RO122 removal reduced with the UV/oxidant processes at pH 9. Experimental results revealed RO122 removal followed pseudo-first-order (PFO) kinetics. There was a linear correlation identified between initial oxidant concentration and the PFO kinetic rate constant (k₁). Among the three UV-based processes, with oxidant concentration 50 mg/L, temperature 20 °C, and pH 5, RO122 removal efficiency was in the order UV/H₂O₂ > UV/HSO₅^- > UV/S₂O₈^2-. RO122 removal rate increased as initial oxidant concentration and temperature increased and reduced as initial RO122 concentration increased. Energy requirements and oxidant costs were assessed. The UV/H₂O₂ process was concluded to be the most efficient and economic process for RO122 removal.

Chemically induced oxidative stress improved bacterial laccase-mediated degradation and detoxification of the synthetic dyes

To alleviate the risk of textile effluent, the development of highly effective bioremediation strategies for synthetic dye removal is needed. Herein, we aimed to assess whether intensified bioactivity of Bacillus pumilus ZB1 by oxidative stress could improve the removal of textile dyes. Methyl methanesulfonate (MMS) induced oxidative stress significantly promoted laccase expression of B. pumilus ZB1. Both the level of hydrogen dioxide and superoxide anion showed a significant positive correlation with laccase activity (RSQ = 0.963 and 0.916, respectively) along with the change of MMS concentration. The regulation of laccase expression was closely related to oxidative stress. The overexpressed laccase in the supernatant improved the decolorization of synthetic dyes (16.43% for Congo Red, 54.05% for Crystal Violet, and 41.61% for Reactive Blue 4). Laccase was subsequently expressed in E. coli. Investigation of the potential of bacterial laccase in dye remediation using Congo Red showed that an effective degradation of azo dye could be achieved with laccase treatment. Laccase remediation alleviated the cytotoxicity of Congo Red to human hepatocytes. In silico study identified eight amino acid residues of laccase involved in binding with Congo Red. Overall, regulation of oxidative stress towards bacterium can be used as a promising approach for the improvement of bacterial bioactivity in synthetic dye remediation.

Synergistic role of bacterial consortium to biodegrade toxic dyes containing wastewater and its simultaneous reuse as an added value

The current environmental research has fascinated the sustainable exploitation of mix bacterial consortium to biodegrade the environmentally-related toxic compounds, including hazardous synthetic dyes. Based on the existing literature evidence, textile and other industrial waste effluents pollute the natural water bodies. Textile effluent contains synthetic dyes which are liberated in the environment without proper treatment. The presence of toxic dyes added to the textile effluents undoubtedly affects the flora and fauna as that untreated water is used for irrigation by local farmers. Many conventional and biological methods are in action for the treatment of wastewater. Physical and chemical processes are expensive as compared to microbial treatments. The use of microbial consortia generates efficient results. Wastewater is a valuable resource, however, up to 80% of wastewater is released to different water matrices. This discernment needs to change for a better tomorrow. In this context, herein, we present a robust microbial-assisted treatment and simultaneously reuse of the treated wastewater as an added value to induce plant growth. Thus, the microbial approach for textile waste treatment release by-product after degradation should be non-toxic for the environment. In the present study, the toxicity of synthetic textile dye named Reactive Red 120, Reactive Orange 122, Reactive Yellow 160, and Reactive Blue 19 was investigated using a bioassay method with plant species namely Sorghum bicolor. Plate and Pot experiment was conducted with respect to untreated Azo dyes, degraded metabolites obtained from single bacteria, and consortium. Efficient Seed germination (89%), shoot length (12.4 cm), root length (15.6 cm) of the plants were observed for bacterial consortium degraded metabolites exposed seeds after comparing with the control. The degraded metabolite also increases protein (45.56 mg/g) and sugar (3.15 mg/g) contents. Bioremediation of various textile industrial effluents saves the ecosystem from the harmful effects of hazardous dyes. The biological decolorization of the textile azo dyes was investigated under co-metabolic conditions. The degraded metabolites can be used to enhance crop productivity and for commercial application. This mandates the current and future research to develop economically feasible and environmentally sustainable wastewater treatment practices.

Decolourisation and Biodegradation of Textile Di-azo Dye Congo Red by Chryseobacterium geocarposphaerae DD3

In the present study, Chryseobacterium geocarposphaerae DD3 isolated from textile industry dye effluent in West Bengal, India, displayed significant tolerance to sulfonated di-azo dye Congo red (CR), up to 500 ppm. The optimum decolourisation revealed that C. geocarposphaerae DD3 was capable of 96.52% decolourisation of 0.2 g L−1 CR within 12 h of treatment in the presence of 5 g L−1 glucose as supplementary carbon source. Biodegradation analysis of decolourised CR containing water was investigated by FTIR, MS and 1H NMR, which confirmed the absence of azo bond as well as the toxic aromatic amines. Further, phytotoxicity analysis was performed to assess the toxicity of CR before and after bacterial treatment. Growth indexes of Vigna radiata L. seed confirmed that the biodegraded water was non-phytotoxic in comparison to the control CR solution. Multivariate analyses confirmed the same, showing significant differences between measured plant health indicators for CR solutions, whereas no significant differences were found between distilled and treated water. This study is novel as it is the first report of dye degradation by C. geocarposphaerae and may lead to a sustainable way of treating dye-contaminated water in the near future.

The Biocatalytic Degradation of Organic Dyes Using Laccase Immobilized Magnetic Nanoparticles

Free laccase has limitations for its use in industrial applications that require laccase immobilization on proper support, to improve its catalytic activity. Herein, the nanoparticles of magnetic iron oxide (Fe3O4) and copper ferrite (CuFe2O4) were successfully used as support for the immobilization of free laccase, using glutaraldehyde as a cross-linker. The immobilization conditions of laccase on the surface of nanoparticles were optimized to reach the maximum activity of the immobilized enzyme. The synthesized free nanoparticles and the nanoparticle-immobilized laccase were characterized using different techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), vibrating sample magnetometer (VSM), and thermogravimetric analysis (TGA). CuFe2O4 nanoparticles, as support, enhanced laccase activity compared to free laccase and Fe3O4 nanoparticle-immobilized laccase that appeared during the study of pH, temperature, and storage stability on free and immobilized laccase. The CuFe2O4 and Fe3O4 nanoparticle-immobilized laccase showed superior activity in a wide pH range, temperature range, and storage period, up to 20 days at 4.0 °C, when compared to free laccase. Additionally, the synthesized nanobiocatalysts were examined and optimized for the biodegradation of the anionic dye Direct Red 23 (DR23). HPLC analysis was used to confirm the dye degradation. The reusability of immobilized laccases for the biodegradation of DR23 dye was investigated for up to six successive cycles, with a decolorization efficiency over 70.0%, which indicated good reusability and excellent stability.

Metal and metal(loids) removal efficiency using genetically engineered microbes: Applications and challenges

The environment is being polluted in different many with metal and metalloid pollution, mostly due to anthropogenic activity, which is directly affecting human and environmental health. Metals and metalloids are highly toxic at low concentrations and contribute primarily to the survival equilibrium of activities in the environment. However, because of non-degradable, they persist in nature and these metal and metalloids bioaccumulate in the food chain. Genetically engineered microorganisms (GEMs) mediated techniques for the removal of metals and metalloids are considered an environmentally safe and economically feasible strategy. Various forms of GEMs, including fungi, algae, and bacteria have been produced by recombinant DNA and RNA technologies, which have been used to eliminate metal and metalloids compounds from the polluted areas. Besides, GEMs have the potentiality to produce enzymes and other metabolites that are capable of tolerating metals stress and detoxify the pollutants. Thus, the aim of this review is to discuss the use of GEMs as advanced tools to produce metabolites, signaling molecules, proteins through genetic expression during metal and metalloids interaction, which help in the breakdown of persistent pollutants in the environment.

Mitigation of environmentally hazardous pollutants by magnetically responsive composite materials

At present, environmental contamination has become an emerging issue among researchers. These facts are due to the adverse impacts of an alarming number of recalcitrant contaminants that can affect both humans and animals. There is an urgent need to develop eco-friendly approaches to mitigate the effects of toxic pollutants from the environment. Magnetically responsive composite-based sorbents are very interesting and popular materials for pollutant abatement owing to the high specific surface area, superior adsorption capacity, and magnetic properties, which make their easy separation from sample solution/media. In this review article, we discuss various synthesis approaches, key physicochemical properties, and applications of magnetic composites for pollutant removal. Current gaps for coping with contamination are identified, and a comprehensive outlook in pollutant treatment using magnetic composites is outlined. This study unveils new horizons to researches for better understanding the properties of magnetically-composite-based sorbents and their application in environmental remediation.

Textile Dye Biodecolorization by Manganese Peroxidase: A Review

Wastewater emissions from textile factories cause serious environmental problems. Manganese peroxidase (MnP) is an oxidoreductase with ligninolytic activity and is a promising biocatalyst for the biodegradation of hazardous environmental contaminants, and especially for dye wastewater decolorization. This article first summarizes the origin, crystal structure, and catalytic cycle of MnP, and then reviews the recent literature on its application to dye wastewater decolorization. In addition, the application of new technologies such as enzyme immobilization and genetic engineering that could improve the stability, durability, adaptability, and operating costs of the enzyme are highlighted. Finally, we discuss and propose future strategies to improve the performance of MnP-assisted dye decolorization in industrial applications.

Diversity of Synthetic Dyes from Textile Industries, Discharge Impacts and Treatment Methods

Natural dyes have been used from ancient times for multiple purposes, most importantly in the field of textile dying. The increasing demand and excessive costs of natural dye extraction engendered the discovery of synthetic dyes from petrochemical compounds. Nowadays, they are dominating the textile market, with nearly 8 × 105 tons produced per year due to their wide range of color pigments and consistent coloration. Textile industries consume huge amounts of water in the dyeing processes, making it hard to treat the enormous quantities of this hazardous wastewater. Thus, they have harmful impacts when discharged in non-treated or partially treated forms in the environment (air, soil, plants and water), causing several human diseases. In the present work we focused on synthetic dyes. We started by studying their classification which depended on the nature of the manufactured fiber (cellulose, protein and synthetic fiber dyes). Then, we mentioned the characteristics of synthetic dyes, however, we focused more on their negative impacts on the ecosystem (soil, plants, water and air) and on humans. Lastly, we discussed the applied physical, chemical and biological strategies solely or in combination for textile dye wastewater treatments. Additionally, we described the newly established nanotechnology which achieves complete discharge decontamination.