Recent advances in the biodegradation of azo dyes

Methyl Red degradation by a subseafloor fungus Schizophyllum commune 15R-5-F01: efficiency, pathway, and product toxicity

Synthetic dyes pose a significant environmental threat due to their complex structures and resistance to microbial degradation. S. commune 15R-5-F01 exhibited over 96% degradation efficiency of Methyl Red in a medium with 100 mg L-1 Methyl Red within 3 h. The fungus demonstrated adaptability to various environmental conditions, including different pH levels, temperatures, oxygen concentrations, salinity, and heavy metals. S. commune 15R-5-F01 is capable of achieving repeated cycles of Methyl Red reduction with sustained degradation duration minimum of 6 cycles. It showed a maximum Methyl Red biodegradation capacity of at least 558 mg g-1 dry mycelia and a bioadsorption capacity of 57 mg g-1. Gas chromatography-mass spectrometry analysis confirmed the azo reduction of Methyl Red into N,N-dimethyl-p-phenylenediamine and 2-aminobenzoic acid. Enzymatic activity assays indicated the involvement of lignin peroxidases, laccases, and manganese peroxidase in the biodegradation process. Phytotoxicity tests on Triticum eastivum, Oryza sativa, and Vigna umbellata seeds revealed reduced toxicity of the degradation products compared to Methyl Red. This study identifies S. commune 15R-5-F01 as a viable candidate for the sustainable degradation of synthetic dyes in industrial wastewater.

A statistical optimization for almost-complete methylene blue biosorption by Gracilaria bursa-pastoris

In this study, the dried biomass of four marine algae, namely Porphyra sp., Gracilaria bursa-pastoris, Undaria pinnatifida and Laminaria sp., were screened for their ability to remove methylene blue (MB) dye from aqueous solutions. Statistical approaches of the Plackett-Burman Design (PBD) and Box-Behnken Design (BBD) were applied to optimize different environmental conditions in order to achieve the maximum MB removal percentage by Gracilaria bursa-pastoris. The biosorbent was characterized before and after adsorption process using FTIR, XRD and SEM analysis. Additionally, isotherms, kinetics and thermodynamics studies were conducted to investigate the adsorption behavior of the adsorbent. The results showed that Gracilaria bursa-pastoris achieved the highest dye removal efficiency (98.5 %) compared to 96.5 %, 93.5 % and 93.9 % for Undaria pinnatifida, Porphyra sp. and Laminaria sp., respectively. PBD analysis revealed that the agitation speed, pH, and biomass dose were found to be the significant parameters affecting MB removal onto Gracilaria dried biomass. According to the BBD results, the maximum dye removal percentage (99.68 %) was obtained at agitation speed of 132 rpm, pH 7 and biomass dose of 7.5 g/L. FTIR, XRD and SEM analysis demonstrated the participation of several functional groups in the adsorption process and changes in the cell surface morphology of the adsorbent following the dye adsorption. The adsorption isotherms showed better fit to Freundlich model (R2 = 0.9891) than the Langmuir, Temkin, and Dubinin-Radushkevich models. The adsorption kinetics were best described by the pseudo-second-order model (R2 = 0.9999), suggesting the chemical interactions between dye ions and the algal biomass. The thermodynamic parameters indicated that the adsorption of MB onto Gracilaria dried biomass was spontaneous, feasible, endothermic and random. These results indicate that dried biomass of Gracilaria bursa-pastoris is an attractive, environmentally friendly, cheap and effective agent for MB dye removal from environmental discharges.

Efficient degradation and detoxification of structurally different dyes and mixed dyes by LAC-4 laccase purified from white-rot fungi Ganoderma lucidum

The purpose of this study is to evaluate the decolorization ability and detoxification effect of LAC-4 laccase on various types of single and mixed dyes, and lay a good foundation for better application of laccase in the efficient treatment of dye pollutants. The reaction system of the LAC-4 decolorizing single dyes (azo, anthraquinone, triphenylmethane, and indigo dyes, 17 dyes in total) were established. To explore the decolorization effect of the dye mixture by LAC-4, two dyes of the same type or different types were mixed at the same concentration (100 mg/L) in the reaction system containing 0.5 U laccase, and time-course decolorization were performed on the dye mixture. The combined dye mixtures consisted of azo + azo, azo + anthraquinone, azo + indigo, azo + triphenylmethane, indigo + triphenylmethane, and triphenylmethane + triphenylmethane. The results obtained in this study were as follows. Under optimal conditions of 30 °C and pH 5.0, LAC-4 (0.5 U) can efficiently decolorize four different types of dyes. The 24-hour decolorization efficiencies of LAC-4 for 800 mg/L Orange G and Acid Orange 7 (azo), Remazol Brilliant Blue R (anthraquinone), Bromophenol Blue and Methyl Green (triphenylmethane), and Indigo Carmine (indigo) were 75.94%, 93.30%, 96.56%, 99.94%, 96.37%, and 37.23%, respectively. LAC-4 could also efficiently decolorize mixed dyes with different structures. LAC-4 can achieve a decolorization efficiency of over 80% for various dye mixtures such as Orange G + Indigo Carmine (100 mg/L+100 mg/L), Reactive Orange 16 + Methyl Green (100 mg/L+100 mg/L), and Remazol Brilliant Blue R + Methyl Green (100 mg/L+100 mg/L). During the decolorization process of the mixed dyes by laccase, four different interaction relationships were observed between the dyes. Decolorization efficiencies and rates of the dyes that were difficult to be degraded by laccase could be greatly improved when mixed with other dyes. Degradable dyes could greatly enhance the ability of LAC-4 to decolorize extremely difficult-to-degrade dyes. It was also found that the decolorization efficiencies of the two dyes significantly increased after mixing. The possible mechanisms underlying the different interaction relationships were further discussed. Free, but not immobilized, LAC-4 showed a strong continuous batch decolorization ability for single dyes, two-dye mixtures, and four-dye mixtures with different structures. LAC-4 exhibited high stability, sustainable degradability, and good reusability in the continuous batch decolorization. The LAC-4-catalyzed decolorization markedly reduced or fully abolished the toxic effects of single dyes (azo, anthraquinone, and indigo dye) and mix dyes (nine dye mixtures containing four structural types of dyes) on plants. Our findings indicated that LAC-4 laccase had significant potential for use in bioremediation due to its efficient degradation and detoxification of single and mixed dyes with different structural types.

Biodegradation of commercial textile reactive dye mixtures by industrial effluent adapted bacterial consortium VITPBC6: a potential technique for treating textile effluents

Textile industries release major fraction of dyestuffs in effluents leading to a major environmental concern. These effluents often contain more than one dyestuff, which complicates dye degradation. In this study ten reactive dyes (Reactive Yellow 145, Reactive Yellow 160, Reactive Orange 16, Reactive Orange 107, Reactive Red 195, Reactive Blue 21, Reactive Blue 198, Reactive Blue 221, Reactive Blue 250, and Reactive Black 5) that are used in textile industries were subjected to biodegradation by a bacterial consortium VITPBC6, formulated in our previous study. Consortium VITPBC6 caused single dye degradation of all the mentioned dyes except for Reactive Yellow 160. Further, VITPBC6 efficiently degraded a five-dye mixture (Reactive Red 195, Reactive Orange 16, Reactive Black 5, Reactive Blue 221, and Reactive Blue 250). Kinetic studies revealed that the five-dye mixture was decolorized by VITPBC6 following zero order reaction kinetic; Vmax and Km values of the enzyme catalyzed five-dye decolorization were 128.88 mg L-1 day-1 and 1003.226 mg L-1 respectively. VITPBC6 degraded the dye mixture into delta-3,4,5,6-Tetrachlorocyclohexene, sulfuric acid, 1,2-dichloroethane, and hydroxyphenoxyethylaminohydroxypropanol. Phytotoxicity, cytogenotoxicity, microtoxicity, and biotoxicity assays conducted with the biodegraded metabolites revealed that VITPBC6 lowered the toxicity of five-dye mixture significantly after biodegradation.

Microorganism-mediated bioremediation of dyes from contaminated soil: Mechanisms, recent advances, and future perspectives

Many methods have been proposed for the remediation of dye-contaminated soils, a widespread form of environment pollution. Bioremediation, it is hoped, can combine ecological benefits with efficiency of dye decontamination. We review the types and sources of dye contaminants; their possible effects on plant, animal, and human health; and emerging strategies for microbial bioremediation. Challenges, limitations, recommendations for future research, and prospects for large-scale commercialization of microbial bioremediation are discussed.

Decolorization, degradation and detoxification of mutagenic dye Methyl orange by novel biofilm producing plant growth-promoting rhizobacteria

Discharge of untreated dyeing wastewater nearby water-bodies is one of major causes of water pollution. Generally, bacterial strains isolated from industrial effluents and/or contaminated soils are used for the bioremediation of Methyl orange (MO), a mutagenic recalcitrant mono-azo dye, used in textiles and biomedical. However, MO degradation by biofilm producing plant growth-promoting rhizobacteria (BPPGPR) was not studied yet. In this study, 19 out of 21 BPPGPR strains decolorized 96.3-99.9% and 89.5-96.3% MO under microaerophilic and aerobic conditions, respectively from Luria-Bertani broth (LBB) followed by yeast-extract peptone and salt-optimized broth plus glycerol media within 120 h of incubation at 28 °C. Only selected BPPGPR including Pseudomonas fluorescens ESR7, P. veronii ESR13, Stenotrophomonas maltophilia ESR20, Staphylococcus saprophyticus ESD8, and P. parafulva ESB18 were examined for process optimization of MO decolorization using a single factor optimization method. This study showed that under optimal conditions (e.g., LBB, 100 mg L-1 MO, pH 7, incubation of 96 h, 28 °C), these strains could remove 99.1-99.8% and 97.6-99.5% MO under microaerophilic and aerobic conditions, respectively. Total azoreductase and laccase activities responsible for biodegradation were also remarkably activated in the biodegraded samples under optimal conditions, while these activities were repressed under unfavorable conditions (e.g., 40 °C and 7.5% NaCl). This study confirmed that MO was degraded and detoxified by these bacterial strains through breakage of azo bond. So far, this is the first report on bioremediation of MO by the BPPGPR strains. These BPPGPR strains are highly promising to be utilized for the bioremediation of dyeing wastewater in future.

Modified alginate materials for wastewater treatment: Application prospects

Sodium alginate is a natural macromolecule widely used because of its abundance, low cost of acquisition, and rich hydroxyl and carboxyl groups in the matrix. The physical modification of sodium alginate can be made by blending it with polymer materials. The so-yielded alginate complex is commonly unstable in an aqueous environment due to alginate backbones' high hydrophilicity. The chemical modification can remove its hydrophilic groups and introduce special functional groups or polymers onto the alginate backbones to provide excess reaction sites for specific reactions and effective complexation sites for accommodating antibiotics, dyes, heavy metal ions, and radioactive elements. Sodium alginate has been used in water treatment engineering under revised modification protocols. This article also reviews the latest modification protocols for sodium alginate and outlines the novel application of the modified materials. The limitations of modified sodium alginate materials are described, and research prospects are put forward.

AIEgen orthopalladated hybrid polymers for efficient inactivation of the total coliforms in urban wastewater

Monitorable AIE polymers with a bioactive pattern are employed in advanced biomedical applications such as functional coatings, theranostic probes, and implants. After the global COVID-19 pandemic, interest in developing surfaces with superior antimicrobial, antiproliferative, and antiviral activities dramatically increased. Many formulations for biocide surfaces are based on hybrid organic/inorganic materials. Palladium (II) complexes display relevant activity against common bacteria, even higher when compared to their uncoordinated ligands. This article reports the design and synthesis of two series of orthopalladated polymers obtained by grafting a cyclopalladated fragment on two different O, N chelating Schiff base polymers. Different grafting percentages were examined and compared for each organic polymer. The fluorescence emission in the solid state was explored on organic matrixes and grafted polymers. DFT analysis provided a rationale for the role of the coordination core. The antibacterial response of the two series of hybrid polymers was tested against the total coliform group of untreated urban wastewater, revealing excellent inactivation ability.

ZnO Hollow Quasi-Spheres Modified Screen-Printed Graphite Electrode for Determination of Carmoisine

Food colorants are important in food selection because they improve the gastronomic appeal of foods by improving their aesthetic appeal. However, after prolonged use, many colorants turn toxic and cause medical problems. A synthetic azo-class dye called carmoisine gives meals a red color. Therefore, the carmoisine determination in food samples is of great importance from the human health control. The current work was developed to synthesis ZnO hollow quasi-spheres (ZnO HQSs) to prepare a new electrochemical carmoisine sensor that is sensitive. Field emission-scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) have been used to analyze the properties of prepared ZnO HQSs. A screen-printed graphite electrode (SPGE) surface was modified with ZnO HQSs to prepare the ZnO HQSs-SPGE sensor. For carmoisine detection, the ZnO HQSs-SPGE demonstrated an appropriate response and notable electrocatalytic activities. The carmoisine electro-oxidation signal was significantly stronger on the ZnO HQSs-SPGE surface compared to the bare SPGE. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CHA), and differential pulse voltammetry (DPV) have been utilized to investigate the suggested protocol. The DPV results revealed an extensive linear association between variable carmoisine concentrations and peak current that ranged from 0.08 to 190.0 µM, with a limit of detection (LOD) as narrow as 0.02 µM. The ZnO HQSs-SPGE's ability to detect carmoisine in real samples proved the sensor's practical application.

Influence of the azo-dye amaranth on the trophic structure of activated sludge in a model experiment

The textile industry generates significant amounts of wastewater containing high concentrations of azo dyes. An important point in the process of purification of azo dyes is their influence on the activated sludge (AS) in wastewater treatment plants. Azo dyes, such as amaranth, play the role of xenobiotics. This article seeks to answer the question of how organisms manage to respond to xenobiotics remains very important and open, i.e., how they will react to toxic conditions. The aim of this research was to study how these changes are expressed in terms of the different trophic levels of AS. In our experiment, it was found that the dominant trophic units are significantly changed due to the xenobiotic entering the system. The data reveal the significant development of the bacterial segment (genus Pseudomonas and azo-degrading bacteria) at times of large amaranth removal. In the most active phase of amaranth biodetoxification (48 h), the culturable bacteria of the genus Pseudomonas change by about 40%, while the azo-degrading bacteria change by about 2%. Fauna organisms have a sharp change in the dominant groups-from attached and crawling ciliates and testate amoebas to the mass development of small and large flagellates. This is of great importance because micro- and metafauna play an important role in the detoxification process by ingesting some of the xenobiotics. This role is expressed in the fact that after dying, macro-organisms release this xenobiotic in small portions so that it can then be effectively degraded by adapting to the amaranth biodegradation bacteria. In this study, it is clear that all these events lead to a decline in the quality of AS. But on the other hand, these allow AS to survive as a microbial community, and the fauna segment does not disappear completely.

Physiological Properties of Three Pelagic Fungi Isolated from the Atlantic Ocean

Oceanic fungi are widely understudied compared to their terrestrial counterparts. However, they have been shown to be important degraders of organic matter in the global pelagic oceans. By examining the physiological characteristics of fungi isolated from the pelagic waters of the ocean it is possible to infer specific functions of each species in the biogeochemical processes that occur in the marine ecosystem. In this study, we isolated three pelagic fungi from different stations and depths across a transect in the Atlantic Ocean. We identified two yeasts [(Scheffersomyces spartinae (Debaryomycetaceae, Saccharomycetes, Ascomycota) and Rhodotorula sphaerocarpa (Sporidiobolaceae, Microbotryomycetes, Basidiomycota)], and the hyphae-morphotype fungus Sarocladium kiliense (Hypocreales, Sordariomycetes, Ascomycota), and conducted physiological experiments to investigate their preferred carbon uptake as well as their growth patterns under different environmental conditions. Despite their taxonomic and morphological differences, all species exhibited a high tolerance towards a wide range of salinities (0–40 g/L) and temperatures (5–35 °C). Furthermore, a shared metabolic preference for oxidizing amino acids was found among all fungal isolates. Collectively, this study provides relevant information on the physiological properties of oceanic pelagic fungi, revealing a high tolerance towards salinity and temperature changes, ultimately contributing to understanding their ecology and distribution in the oceanic water column.

Microwave-assisted sustainable exploration of cocklebur leaves (Xanthium strumarium L.) as a novel source of distinct yellow natural colorant for dyeing cotton fabric

During current times, the use of bio-colorants attained public acceptance as a sustainable alternative to synthetic ones which in turn reduced the environmental contamination. The present study focused on the green, safe, and clean technology for the resurgence of natural colorant from cocklebur (Xanthium strumarium L.) leaves and their application to cotton fabric. Natural colorants were extracted by employing an eco-friendly microwave-assisted extraction process using an aqueous and alkaline medium. Dyeing of cotton fabric was carried out using irradiated and unirradiated cotton fabric with irradiated and unirradiated natural dyes of cocklebur leaves. The results of extraction experiments revealed that 4 min microwave-assisted alkaline extract exhibited significantly outstanding color strength onto microwave-treated cotton fabric compared to aqueous one. Further to investigate the optimum dyeing conditions for cotton fabric, various dyeing variables such as dyeing time, dyeing temperature, dye concentration, and exhausting agent were monitored and found a superior result using a dye concentration of 45 ml, for dyeing cotton fabric at 75 °C for 50 min in the presence of 4 g/100 ml of table salt. For improvement in color strength and color fastness properties, the effects of various bio-mordants, such as eucalyptus bark, acacia bark, turmeric rhizome, and onion shells, and chemical mordants (aluminum and copper) on dyed cotton fabric were also evaluated. It was also observed that cotton fabric dyed with alkaline extract of cocklebur leaves using bio-mordants as pre-mordants (4% acacia, 4% eucalyptus, 2% onion) and post-mordants (3% onion, 3% eucalyptus, 4% acacia) exhibited the highest color strength and various hues with acceptable colorfastness properties against light, washing, and rubbing in comparison to chemical mordants. The ISO standard for fastness also revealed that bio-mordanting has enhanced the rating from good to excellent in comparison to chemical mordants. The results provide ample scope for the extraction of yellow natural dye from the cocklebur leaves for eco-friendly coloration of fabrics using bio-mordants.

Preparation of magnetic Co–Fe layered double hydroxides and its adsorption properties for the removal of methyl orange

In this study, Co–Fe layered double hydroxides are prepared by a hydrothermal method. The Co–Fe layered double hydroxides are used as an adsorbent for the investigation of the thermodynamic parameters and adsorption kinetics of methyl orange from aqueous solution. The results show that adsorption is affected by adsorbent dosage, adsorption time, and temperature. The characteristics of samples are investigated using X-ray powder diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and N2 adsorption–desorption isotherms. The adsorption saturation level of Co–Fe layered double hydroxides on methyl orange is studied, with the results showing that the maximum uptake capacity for methyl orange is 10.21 mg g−1 based on Co–Fe layered double hydroxides. The adsorption kinetics of methyl orange is consistent with the Temkin isotherm equation and quasi-secondary kinetic model. Furthermore, separation is easily accomplished under the action of an applied magnetic field. The prepared Co–Fe layered double hydroxides can be applied as an effective adsorbent for decontamination of anionic dyes in industrial effluents.

Construction of microbial consortia for microbial degradation of complex compounds

Increasingly complex synthetic environmental pollutants are prompting further research into bioremediation, which is one of the most economical and safest means of environmental restoration. From the current research, using microbial consortia to degrade complex compounds is more advantageous compared to using isolated bacteria, as the former is more adaptable and stable within the growth environment and can provide a suitable catalytic environment for each enzyme required by the biodegradation pathway. With the development of synthetic biology and gene-editing tools, artificial microbial consortia systems can be designed to be more efficient, stable, and robust, and they can be used to produce high-value-added products with their strong degradation ability. Furthermore, microbial consortia systems are shown to be promising in the degradation of complex compounds. In this review, the strategies for constructing stable and robust microbial consortia are discussed. The current advances in the degradation of complex compounds by microbial consortia are also classified and detailed, including plastics, petroleum, antibiotics, azo dyes, and some pollutants present in sewage. Thus, this paper aims to support some helps to those who focus on the degradation of complex compounds by microbial consortia.

Biofilm-mediated decolorization, degradation and detoxification of synthetic effluent by novel biofilm-producing bacteria isolated from textile dyeing effluent

Biofilm-mediated bioremediation of xenobiotic pollutants is an environmental friendly biological technique. In this study, 36 out of 55 bacterial isolates developed biofilms in glass test tubes containing salt-optimized broth plus 2% glycerol (SOBG). Scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and Congo red- and Calcofluor binding results showed biofilm matrices contain proteins, curli, nanocellulose-rich polysaccharides, nucleic acids, lipids, and peptidoglycans. Several functional groups including -OH, N-H, C-H, CO, COO^-, -NH_2, PO, C-O, and C-C were also predicted. By sequencing, ten novel biofilm-producing bacteria (BPB) were identified, including Exiguobacterium indicum ES31G, Kurthia gibsonii ES43G, Kluyvera cryocrescens ES45G, Cedecea lapagei ES48G, Enterobacter wuhouensis ES49G, Aeromonas caviae ES50G, Lysinibacillus sphaericus ES51G, Acinetobacter haemolyticus ES52G, Enterobacter soli ES53G, and Comamonas aquatica ES54G. The Direct Red (DR) 28 (a carcinogenic and mutagenic dye used in dyeing and biomedical processes) decolorization process was optimized in selected bacterial isolates. Under optimum conditions (SOBG medium, 75 mg L^-1 dye, pH 7, 28 °C, microaerophilic condition and within 72 h of incubation), five of the bacteria tested could decolorize 97.8% ± 0.56-99.7% ± 0.45 of DR 28 dye. Azoreductase and laccase enzymes responsible for biodegradation were produced under the optimum condition. UV-Vis spectral analysis revealed that the azo (-NN-) bond peak at 476 nm had almost disappeared in all of the decolorized samples. FTIR data revealed that the foremost characteristic peaks had either partly or entirely vanished or were malformed or stretched. The chemical oxygen demand decreased by 83.3-91.3% in the decolorized samples, while plant probiotic bacterial growth was indistinguishable in the biodegraded metabolites and the original dye. Furthermore, seed germination (%) was higher in the biodegraded metabolites than the parent dye. Thus, examined BPB could provide potential solutions for the bioremediation of industrial dyes in wastewater.

Facile synthesis of CoFe2O4@MIL-53(Al) nanocomposite for fast dye removal: Adsorption models, optimization and recyclability

The global occurrence of textile dyes pollution has recently emerged, posing a serious threat to ecological systems. To abate dye contamination, we here developed a novel magnetic porous CoFe₂O₄@MIL-53(Al) nanocomposite by incorporating magnetic CoFe₂O₄ nanoparticles with MIL-53(Al) metal-organic framework. This nanocomposite possessed a surface area of 197.144 m² g^-1 and a pore volume of 0.413 cm³ g^-1. The effect of contact time (5-120 min), concentration (5-50 mg L^-1), dosage (0.1-1.0 g L^-1), and pH (2-10) on Congo red adsorption was clarified. CoFe₂O₄@MIL-53(Al) could remove 95.85% of Cong red dye from water with an accelerated kinetic rate of 0.6544 min^-1 within 10 min. The kinetic and isotherm models showed the predominance of Bangham and Temkin. According to Langmuir, the maximum uptake capacities of CoFe₂O₄@MIL-53(Al), CoFe₂O₄, and MIL-53(Al) adsorbents were 43.768, 17.982, and 15.295 mg g^-1, respectively. CoFe₂O₄@MIL-53(Al) was selected to optimize Cong red treatment using Box-Behnken experimental design. The outcomes showed that CoFe₂O₄@MIL-53(Al) achieved the highest experimental uptake capacity of 35.919 mg g^-1 at concentration (29.966 mg L^-1), time (14.926 min), and dosage (0.486 g L^-1). CoFe₂O₄@MIL-53(Al) could treat dye mixture (methylene blue, methyl orange, Congo red, malachite green, and crystal violet) with an outstanding removal efficiency of 81.24% for 30 min, and could be reused up to five cycles. Therefore, novel recyclable and stable CoFe₂O₄@MIL-53(Al) is recommended to integrate well with real dye treatments systems.

Insights into Two Novel Orthopalladated Chromophores with Antimicrobial Activity against Escherichia coli

Advanced chromophoric tools, besides being biologically active, need to meet the expectations of the technological demands including stability, colour retention, and proper solubility for their target. Many coordination compounds of conjugated ligands are antibacterial dyes, able to combine a strong dyeing performance with a useful biological activity. Specifically, palladium (II) complexes of Schiff base ligands are known for their relevant activity against common bacteria. In this article, we report the synthesis and comprehensive experimental and theoretical characterization of two novel Pd(II) chromophore complexes obtained from a cyclopalladated Schiff base as two different chelating azo dyes. The antibacterial response of these two novel complexes was tested against the ubiquitous Escherichia coli bacterium in an aqueous medium and revealed a noteworthy antimicrobial activity, higher than when compared with their uncoordinated biologically active ligands.

Molecular response of Anoxybacillus sp. PDR2 under azo dye stress: An integrated analysis of proteomics and metabolomics

Treating azo dye wastewater using thermophilic bacteria is considered a more efficient bioremediation strategy. In this study, a thermophilic bacterial strain, Anoxybacillus sp. PDR2, was regarded as the research target. This strain was characterized at different stages of azo dye degradation by using TMT quantitative proteomic and non-targeted metabolome technology. A total of 165 differentially expressed proteins (DEPs) and 439 differentially metabolites (DMs) were detected in comparisons between bacteria with and without azo dye. It was found that Anoxybacillus sp. PDR2 can degrade azo dye Direct Black G (DBG) through extracellular electron transfer with glucose serving as electron donors. Most proteins related to carbohydrate metabolism, including acetoacetate synthase, and malate synthase G, were overexpressed to provide energy. The bacterium can also self-synthesize riboflavin as a redox mediator of in vitro electron transport. These results lay a theoretical basis for industrial bioremediation of azo dye wastewater.

Biodegradation of Azo Dye Methyl Red by Pseudomonas aeruginosa: Optimization of Process Conditions

Water pollution due to textile dyes is a serious threat to every life form. Bacteria can degrade and detoxify toxic dyes present in textile effluents and wastewater. The present study aimed to evaluate the degradation potential of eleven bacterial strains for azo dye methyl red. The optimum degradation efficiency was obtained using P. aeruginosa. It was found from initial screening results that P. aeruginosa is the most potent strain with 81.49% degradation activity and hence it was subsequently used in other degradation experiments. To optimize the degradation conditions, a number of experiments were conducted where only one variable was varied at a time and where maximum degradation was observed at 20 ppm dye concentration, 1666.67 mg/L glucose concentration, 666.66 mg/L sodium chloride concentration, pH 9, temperature 40 °C, 1000 mg/L urea concentration, 3 days incubation period, and 66.66 mg/L hydroquinone (redox mediator). The interactive effect of pH, incubation time, temperature, and dye concentration in a second-order quadratic optimization of process conditions was found to further enhance the biodegradation efficiency of P. aeruginosa by 88.37%. The metabolites of the aliquot mixture of the optimized conditions were analyzed using Fourier transform infrared (FTIR), GC-MS, proton, and carbon 13 Nuclear Magnetic Resonance (NMR) spectroscopic techniques. FTIR results confirmed the reduction of the azo bond of methyl red. The Gas Chromatography-Mass Spectrometry (GC-MS) results revealed that the degraded dye contains benzoic acid and o-xylene as the predominant constituents. Even benzoic acid was isolated from the silica gel column and identified by ¹H and ¹³C NMR spectroscopy. These results indicated that P. aeruginosa can be utilized as an efficient strain for the detoxification and remediation of industrial wastewater containing methyl red and other azo dyes.

Emulsion-Templated Porous Polymers for Efficient Dye Removal

A high internal phase emulsion (HIPE) method was used to produce adsorbents with an interconnected porous structure. HIPE was prepared using vinyl benzyl chloride (VBC), divinylbenzene (DVB), tert-butyl acrylate, and Span80 as the organic phase and water with K₂S₂O₈ and CaCl₂ as the water phase. The polymerization of the organic phase produced highly porous polymers called polyHIPE, carrying two functional groups. As a result of the template method, polyHIPEs have a low surface area. To overcome this drawback, polyHIPE was hyper-cross-linked through VBC to create meso- and micropores, resulting in a higher surface area. Then the polymer surface was tailored with carboxylic acid groups by simple hydrolysis of tert-butyl acrylate. The adsorption performances of the acidic functional hyper-cross-linked polyHIPEs prepared for the various reaction times of 0, 15, and 60 min were compared for methylene blue. The hyper-cross-linked polyHIPEs showed an enhanced adsorption kinetics for methylene blue, and the 15 min hyper-cross-linking reaction increased the rate of methylene blue adsorption significantly. It was proven that the polyHIPE adsorbent can be reused by treating it with an aqueous acidic solution in ethanol.

Advancement in electrochemical strategies for quantification of Brown HT and Carmoisine (Acid Red 14) Drom Azo Dyestuff class

Brown HT and carmoisine, which are the most used dyestuffs in pharmaceuticals, textiles, cosmetics and foods, are important components of the Azo family. Although the Azo group is not toxic or carcinogenic under normal conditions, these dyestuffs require great care due to the reduction of the Azo functional group to amines. In particular, fast, reliable, easy, on-site and precise determinations of these substances are extremely necessary and important. In this review, the properties, applications, and electrochemical determinations of brown HT and carmoisine, which are used as synthetic food colorants, are discussed in detail. Up to now, sensor types, detection limits (LOD and LOQ), and analytical applications in the developed electrochemical strategies for both substances were compared. In addition, the validation parameters such as the variety of the sensors, sensitivity, selectivity and electrochemical technique in these studies were clarified one by one. While the electrochemical techniques recommended for brown HT were mostly used for the removal of dyestuff, for carmoisine they included fully quantitative centered studies. The percentiles of voltammetric techniques, which are the most widely used among these electroanalytical methods, were determined. The benefits of a robust electrochemical strategy for the determination of both food colors are summed up in this review. Finally, the brown HT and carmoisine suggestions for future perspectives in electrochemical strategy are given according to all their applications.