Effect of malachite green toxicity on non target soil organisms

A sustainable, eco-friendly Tb/Eu-modified HOFs for ultrasensitive detection and efficient adsorption of carcinogens in complex water environments

Developing a multifunctional material that can detect and remove carcinogens in water environments, simultaneously monitor their toxic metabolites in living organisms is significant for environmental remediation and human health. However, most research only focused on detection or adsorption carcinogens due to the difficulty of integrating multiple functions into one material, let alone monitoring their toxic metabolites. Here, a multifunctional Tb/Eu@TATB-HOF (1) is first developed to monitor two carcinogens, malachite green (MG) and its metabolites leucomalachite green (LMG), and simultaneously remove MG from the contaminated water. 1, as the dual-emission fluorescence sensor, can achieve ultrasensitive and highly visualized sensing for MG and LMG with different response modes. Even in actual samples, 1 still exhibits satisfactory sensing performances. As the adsorbent, 1 displays good recyclability and high adsorption capacity for MG. The sensing and adsorption mechanisms are explored through experiments and theoretical calculations. This work not only provides a novel insight for environmental remediation and human health through detection and removal of carcinogens, simultaneously monitoring their toxic metabolites, but first reveals the enormous potential of HOFs as multifunctional materials simultaneously for fluorescence sensing and adsorption.

Decolorization and detoxication of malachite green by engineered Saccharomyces cerevisiae expressing novel thermostable laccase from Trametes trogii

Malachite Green (MG) is a widely used industrial dye that is hazardous to health. Herein, the decolourisation and detoxification of MG were achieved using the engineered Saccharomyces cerevisiae expressing novel thermostable laccase lcc1 from Trametes trogii. The engineered strain RCL produced a high laccase activity of 121.83 U L-1. Lcc1 was stable at temperatures ranging from 20 ℃ to 60 ℃ and showed a high tolerance to organic solvents. Moreover, Lcc1 could decolorize different kinds of dyes (azo, anthraquinone and triphenylmethane), among which, the decolorization ability of MG is the highest, reaching 95.10 %, and the decolorization rate of other triphenylmethane dyes also over 50 %. The RCL decolorized about 95 % of 50 mg L-1 of MG dye in 10 h at 30 ℃. The MG degradation products were analyzed. The industrial application potential of the RCL was evaluated by treating industrial wastewater and the decolourisation rates were over 90 %.

Novel small multidrug resistance protein Tmt endows the Escherichia coli with triphenylmethane dyes bioremediation capability

Dye contamination in printing and dyeing wastewater has long been a major concern due to its serious impact on both the environment and human health. In the quest for bioremediation of these hazardous dyes, biological resources such as biodegradation bacteria and enzymes have been investigated in severely polluted environments. In this context, the triphenylmethane transporter gene (tmt) was identified in six distinct clones from a metagenomic library of the printing and dyeing wastewater treatment system. Escherichia coli expressing tmt revealed 98.1% decolorization efficiency of triphenylmethane dye malachite green within 24 h under shaking culture condition. The tolerance to malachite green was improved over eightfold in the Tmt strain compared of the none-Tmt expressed strain. Similarly, the tolerance of Tmt strain to other triphenylmethane dyes like crystal violet and brilliant green, was improved by at least fourfold. Site-directed mutations, including A75G, A75S and V100G, were found to reinforce the tolerance of malachite green, and double mutations of these even further improve the tolerance. Therefore, the tmt has been demonstrated to be a specific efflux pump for triphenylmethane dyes, particularly the malachite green. By actively pumping out toxic triphenylmethane dyes, it significantly extends the cells tolerance in a triphenylmethane dye-rich environment, which may provide a promising strategy for bioremediation of triphenylmethane dye pollutants in the environments.

Aramid nanofiber membrane decorated with monodispersed silver nanoparticles as robust and flexible SERS chips for trace detection of multiple toxic substances

Aramid nanofibers (ANFs) as an innovative nanoscale building block exhibit great potential for novel high-performance multifunctional membranes attributed to their extraordinary performance. However, the application of aramid nanofibers in the field of surface enhanced Raman scattering (SERS) sensing has been rarely reported. In this work, aramid nanofibers derived from commercial Kevlar fibers were synthesized by a facile dimethyl sulfoxide/potassium hydroxide (DMSO/KOH) solution treatment. The monodispersed silver nanoparticle-decorated aramid nanofiber (m-Ag@ANF) membranes were constructed by an efficient vacuum filtration technique. Taking advantages of unique intrinsic properties of ANF, the m-Ag@ANF substrates exhibit good flexibility, excellent mechanical properties and prominent thermal stability. Besides, due to the abundance of positively charged amino-group on the ANF substrates, the negatively charged m-AgNPs were uniformly and firmly deposited on the surface of ANF substrate through electrostatic interactions. As a result, the optimal flexible m-Ag-9@ANF SERS substrate exhibits high sensitivity of 10-9 M for methylene blue (MB) and excellent signal reproducibility (RSD = 6.37 %), as well as outstanding signal stability (up to 15 days). Besides, the 2D Raman mapping and FDTD simulations further reveal prominent signal homogeneity and strong electric field distribution for flexible m-Ag-9@ANF SERS substrate. Finally, it is demonstrated that the flexible m-Ag-9@ANF SERS substrate can also be used for detection of toxic molecules on irregular surfaces by a feasible paste-and-read process. The m-Ag@ANF paper exhibits potential applications as a flexible, low-cost, robust and stable SERS sensing platform for trace detection of toxic materials.

Biodegradation of malachite green by Pleurotus eryngii: a study on decolorization, mechanism, toxicity, and enzyme

The purpose of this study was to investigate the biodegradation of malachite green (MG) by Pleurotus eryngii via decolorization. This study also explored the possible mechanisms and toxicity. The results indicated that this fungus exhibited strong decolorizing potential. MG degradation based on UPLC-TOF-Triple-MS analysis revealed the formation of intermediates such as 4-(dimethylamino)benzophenone, 4-(methylamino)benzophenone, and 4-(dimethylamino)phenol. Furthermore, a significant reduction in the toxicity of the degradation products was observed using the zebrafish animal model. A newly discovered dye-decolorizing peroxidase (DyP-PE) from P. eryngii was amplified, cloned, and expressed. The purified 56.4 kDa DyP-PE strongly decolorized MG, suggesting potentially application in the bioremediation of MG pollution. Thus, the DyP-PE derived from P. eryngii may contribute to the degradation of MG.

A recyclable Eu3+-functionalized dual-emissive metal-organic framework for portable, rapid detection and efficient removal of malachite green

A europium-functionalized, dual-emissive, metal-organic framework-based fluorescence sensor (EuUCNDA) was constructed via post-synthetic modification of an UiO-66-type precursor through coordination interactions. EuUCNDA exhibited extremely high selectivity and sensitivity for malachite green (MG) with a low detection limit of 13.01 nM, a wide linear concentration range (0.05-50 μM), excellent anti-interference properties, a rapid response (<1 min), and the possibility of recycling. The good sensing performance of EuUCNDA enables the practical detection of MG in fish pond water and grass carp with good recoveries. Moreover, EuUCNDA can be reused for sensing MG and over 90% of fluorescence intensity can be restored after 7 cycles. Furthermore, EuUCNDA-embedded paper-based sensors combined with smartphone imaging afford portable and visual monitoring of MG in real samples. Notably, besides good sensing performance, EuUCNDA could efficiently remove MG from water. Hence, this work provides a recyclable and sensitive fluorescence sensor for portable, visual, rapid detection and efficient removal of MG.

Toxicological approaches as tool to assess the effects of a mixture of photocatalytic degradation products originated from the unregulated neonicotinoid acetamiprid employing a terrestrial organism (Eisenia andrei)

Acetamiprid (ACT) has been detected in several water sources in Latin America. The presence of its degradation products in the environment is not negligible and transformation products (TPs) significantly contribute to environmental health risks. Although advanced oxidative processes are promising for the treatment of this neocotinoid, effects of these are still unknown. In this context, the effects of a mixture of photocatalytic degradation products resulting from an ACT treatment for 90 min employing TiO2/UV on cytotoxicity and oxidative stress parameters in Eisenia andrei earthworms in acute and chronic experiments using typical Latin American soil were assessed. Acute contact tests were performed (72 h) using a filter paper moistened with an ACT solution and a chronic test was performed using Oxisoil (200 g) moistened with an ACT solution for 45 days. Catalase (CAT) and glutathione-S-transferase (GST) activities, reduced glutathione (GSH) levels and cytotoxicity (cellular eleocyte and amoebocyte assessments) were investigated. Over 75 % of ACT was degraded within the first 15 min of treatment, with levels below the limit of detection after 60 min. The acute test revealed greater cytotoxic effects associated with the effluents treated for T0 and T15 min, with decreased cell density noted after 48 h of exposure, in addition to CAT induction (in all treatments) and GST induction following T0, T15 and T90 min exposures. Concerning the chronic assay, decreases in cell density (T0, T15, T60 and T90 min) and viability (T0, T60 and T90 min) were observed after 45 days, in addition to induced CAT activity following T0, T15 and T60 exposures and GST induction following the T60 min exposure. Reduced glutathione levels were unaltered, comprising the least sensitive biomarker among the investigated parameters to the treated effluent exposures. The mixture of ACT degradation products can cause toxic effects to non-target organisms, despite parent compound degradation, alerting for the need for ecotoxicological tests to prove decreased effluent toxicity, in addition to the improvement of degradation techniques.

Magnetic hydrochar grafted-chitosan for enhanced efficient adsorption of malachite green dye from aqueous solutions: Modeling, adsorption behavior, and mechanism analysis

Water pollution by organic dyes is one of the most serious environmental problems worldwide. Malachite green (MG) is considered as one the serious organic dyes which is discharged in wastewater by leather and textile manufacturing plants. MG dye can cause severe hazards to the environment and human health. Therefore, the removal of MG dye from wastewater is very important and essential. This study aims to synthesize a new magnetic hydrochar grafted to chitosan (MWSHC@CS) for the removal of MG dye from the aqueous solutions. Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, and Zeta potential analysis were used to characterize the synthesized MWSHC@CS. Batch experiments were conducted to optimize MG dye adsorption conditions, including adsorbent mass, pH, temperature, initial concentration, and contact time. The results revealed that MWSHC@CS had an excellent removal efficiency (96.47 %) for MG dye at the optimum condition (at m: 20 mg, pH: 7.5, t: 420 min, and T: 298 K). Adsorption isotherms outcomes revealed the MG adsorption data were best fit by the Langmuir model with a maximum adsorption capacity (420.02 mg/g). Adsorption kinetics outcomes exhibited that the adsorption process of MG dye fitted well to the Elovich model. The thermodynamic results revealed that the adsorption process was physical, exothermic, and spontaneous. The adsorption mechanisms of MG onto MWSHC@CS were hydrogen bonding, electrostatic interaction, and π-π interactions. Furthermore, MWSHC@CS showed excellent reusability for the removal of MG over five cycles of adsorption-desorption (83.76 %). In conclusion, the study provides a new, low-cost, and effective magnetic nanocomposite based on chitosan as a promising adsorbent for the high-performance removal of MG dye from aqueous solutions.

Preparation of room-temperature phosphorescence-ratiometric fluorescence magnetic mesoporous imprinted microspheres and its application in detection of malachite green and tartrazine in multimatrix

The photoluminescent properties of Mn-doped ZnS quantum dots were fully exploited, and room-temperature phosphorescence (RTP)-ratiometric fluorescence (RF) magnetic mesoporous molecularly imprinted polymers (PFMM-MIPs) were prepared by integrating molecular imprinting technology. RTP was used to detect malachite green (MG). The fluorescence at 420 nm and the peak at 590 nm in the fluorescence mode were used as the response reference signals respectively to detect tartrazine (TZ). The linear responsive range and detection limit of MG were 0.01-150 μM and 4.3 nM, and these of TZ were 0.05-80 μM and 23.7 nM. RTP, which can avoid the interference of background fluorescence, and RF with self-calibration ability can both largely weaken the matrix effect. This work enables single-probe-type MIPs to achieve dual-target analysis via RTP and RF. This method provides excellent sensitivity, specificity, recovery and recyclability, and is expected to be prospectively applied in the fields of food, environment and biological analyses.

Graphitic carbon nitride-adorned PDMS self-cleaning floating photocatalyst for simultaneous removal of Rhodamine B, Crystal Violet and Malachite Green from a ternary dye mixture

Graphitic carbon nitride-adorned polydimethylsiloxane (PDMS) floating catalyst was prepared by a simple procedure. The prepared catalyst was utilized for the simultaneous mitigation of recalcitrant organic pollutants such as Rhodamine B, Crystal Violet and Malachite Green from their ternary mixture for the first time. Derivative spectroscopic method was used to calculate the degradation efficiencies of individual dyes in the mixture. The prepared catalyst showed a consistent degradation performance up to 4 cycles inducing a degradation of 94.02%, 92.1% and 97.13% of Rhodamine B, Crystal Violet and Malachite Green, respectively, in a dye(s) solution with a catalytic loading of 0.5 g L-1. A kinetic analysis of the dye(s) degradation under visible light was carried out during the course of this work up to 120 min. A detailed characterization of the surface of this novel catalyst was carried out in this study by SEM, EDX, XRD, DRS, DTG, FTIR, Raman spectroscopy and UV-Vis spectroscopy and provided the experimental proof for the catalyst presenting high hydrophobicity, self-cleaning ability, good recyclability and high chemical stability.

Fabrication and characterisation of novel chitosan-based polymer inclusion membranes and their application in environmental remediation

Several water and wastewater technologies have been implored for the removal of dyes during wastewater treatments; however; different types have been reportedly found in surface and groundwater systems. Hence, there is a need to investigate other water treatment technologies for the complete remediation of dyes in aquatic environments. In this study, novel chitosan-based polymer inclusion membranes (PIMs) were synthesized for the removal of malachite green dye (MG) which is a recalcitrant of great concern in water. Two types of PIMs were synthesized in this study, the first PIM (PIMs-A) was composed of chitosan, bis-(2-ethylhexyl) phosphate (B2EHP), and dioctyl phthalate (DOP). While, the second PIMs (PIMs-B) were composed of chitosan, Aliquat 336, and DOP. The physico-thermal stability of the PIMs was investigated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), both PIMs demonstrated good stability with a weak intermolecular force of attraction amongst the various components of the membranes. The effects of the initial concentration of MG, pH of the MG solution, stripping solution, and time were investigated. At optimum conditions, both membranes (PIM-A and B) recorded the highest efficiencies of 96 % and 98 % at pH 4 and initial contaminants concentration of 50 mg/L, respectively. Finally, both PIMs were used for the removal of MG in different environmental samples (river water, seawater, and tap water) with an average removal efficiency of 90 %. Thus, the investigated PIMs can be considered a potential suitable technique for the removal of dyes and other contaminants from aquatic matrices.

Dye degradation by early colonizing marine bacteria from the Arabian Sea, India

Malachite green dye belongs to the triphenylmethane group and is a common environmental pollutant that threatens non-target organisms. We report the potential of the early colonizing marine bacterium Pseudomonas sp. ESPS40 isolated from the Arabian Sea, India, to decolorize malachite green (MG). The bacterium ESPS40 exhibited a higher ability for MG degradation (86-88%) at varying NaCl concentrations (1-3%). The highest MG degradation (~ 88%) was observed at 1% NaCl. The bacterial strain ESPS40 showed degradation up to 800 mg L^-1 MG. Further, enzyme activities such as tyrosinase (63.48-526.52 U L^-1) and laccase (3.62-28.20 U L^-1) were also analyzed with varying concentrations (100 mg L^-1-1000 mg L^-1) of MG during the degradation process. The dye degradation was confirmed by Fourier transform infrared spectroscopy (FTIR) and high-performance liquid chromatography (HPLC). The outcome of the present study demonstrated Pseudomonas sp. ESPS40 as a potential strain for the efficient degradation of MG at higher concentrations. Thus, Pseudomonas sp. ESPS40 can be utilized as a potential candidate for the biodegradation of MG in wastewater treatment.

Malachite green and leucomalachite green in fish: a global systematic review and meta-analysis

Malachite green (MG), an antibiotic with antifungal activity, is illegally used in aquaculture. Given that this chemical is teratogenic and mutagenic, abstinence from intake seems to be a need for public safety. The goal of this systematic review and meta-analysis was to determine the global contamination of fishes by MG and its reduced metabolite, leucomalachite green (LMG), in a number of marine and farmed fish species. For literature published prior to January 2022, several databases (Web of Science, PubMed, and Scopus) were investigated. In total, 20 publications (10 countries, 724 samples) achieved the criteria for inclusion. The overall average MG and LMG concentrations were 0.48 (95% CI: 0.47, 0.49 µg kg^-1) and 0.59 (95% CI: 0.39, 0.79 µg/kg^-1), respectively. Eel (M. albus) 15.50 (95% CI: (14.39, 45.39 µg kg^-1) and eel (A. anguilla) 4.46 (95% CI: 1.23, 7.69 µg kg^-1) had the greatest contamination of MG and LMG, according to the effect size, respectively. Warm-water fish had a concentration of 2.591 (95% CI: 2.25, 2.93 µg kg^-1) while cold-water fish had a concentration of 1.55 (95% CI: 0.25, 2.84 µg kg^-1). Fish containing medium-fat level of 1.86 (95% CI: 1.27, 2.44 µg kg^-1) and high-fat content of 1.10 (95% CI: 0.93, 1.26 µg kg^-1) had accumulate MG and LMG in their tissues, respectively. As a result, total MG observed in countries including China, Iran, and the Netherlands was higher than authorized (2 µg kg^-1). The toxicity of MG and LMG demands more monitoring, especially in countries where these chemicals' residues are significant.

Co-Carbonized Waste Polythene/Sugarcane Bagasse Nanocomposite for Aqueous Environmental Remediation Applications

The conversion of worthless municipal solid wastes to valuables is a major step towards environmental conservation and sustainability. This work successfully proposed a technique to utilize the two most commonly available municipal solid wastes viz polythene (PE) and sugarcane bagasse (SB) for water decolorization application. An SBPE composite material was developed and co-pyrolyzed under an inert atmosphere to develop the activated SBPEAC composite. Both SBPE and SBPEAC composites were characterized to analyze their morphological characteristics, specific surface area, chemical functional groups, and elemental composition. The adsorption efficacies of the composites were comparatively tested in the removal of malachite green (MG) from water. The SBPEAC composite had a specific surface area of 284.5 m²/g and a pore size of ~1.33 nm. Batch-scale experiments revealed that the SBPEAC composite performed better toward MG adsorption compared to the SBPE composite. The maximum MG uptakes at 318 K on SBPEAC and SBPE were 926.6 and 375.6 mg/g, respectively. The adsorption of MG on both composites was endothermic. The isotherm and kinetic modeling data for MG adsorption on SBPEAC was fitted to pseudo-second-order kinetic and Langmuir isotherm models, while Elovich kinetic and D-R isotherm models were better fitted for MG adsorption on SBPE. Mechanistically, the MG adsorption on both SBPE and SBPEAC composites involved electrostatic interaction, H-bonding, and π-π/n-π interactions.

Dynamics of the role of LacMeta laccase in the complete degradation and detoxification of malachite green

Laccases highlight for xenobiotic bioremediation, as well as application in the fine chemical, textile, biofuel and food industries. In a previous work, we described the preliminary characterization of laccase LacMeta, a promising enzyme for the bioremediation of dyes, able to decolorization malachite green (MG), trypan blue, methylene blue. Here we demonstrate that LacMeta is indeed suitable for the complete degradation and detoxification of MG dye, not just for its discoloration, since some works show false positives due to the formation of colorless intermediates such as leucomalachite. The optimal pH and temperature parameters of LacMeta were 5.0 and 50 °C, respectively (MG as substrate). LacMeta was tolerant of up to 10 mmol L^- 1 EDTA (82%) and up to 5% (V/V) acetone (91%) and methanol (71%), while SDS promoted severe inhibition. For ions, a high tolerance to cobalt, zinc, manganese, and calcium (10 mmol L^- 1) was also observed (> 90%). Even under high-salinity conditions (1 mol L^- 1 NaCl), the residual bleaching activity of the dye remained at 61%. Furthermore, the bleaching product of MG did not inhibit the germination of sorghum and tomato seeds and was inert to the vegetative structures of the germinated seedlings. Additionally, this treatment effectively reduced the cytotoxic effect of the dye on microorganisms (Escherichia coli and Azospirillum brasilense), which can be explained by H-NMR spectral analysis results since LacMeta completely degraded the peak signals corresponding to the aromatic rings in the dye, demonstrating extreme efficiency in the bioremediation of the xenobiotic at high concentrations (50 mg L^- 1).

Sequestration of Anionic and Cationic Dyes through Thermally Activated Slate and Their Kinetics and Thermodynamic Characteristics

Adsorption is one of the most common and most robust techniques for the decontamination approach of effluents, owing to its design flexibility, simplicity, cost effectiveness, and high efficiency. However, its application is limited on a large scale due to its cost. The current study investigates the use of low-cost, ecofriendly, and ubiquitous thermally activated clay material. Thermally treated clay was used for the adsorption of crystal violet (CV), Congo red (CR), and malachite green (MG) organic dyes from aqueous solutions. Characterization of slate was carried out with Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy, X-ray diffraction, N₂ physisorption, and XRF spectrometry. The adsorption process was studied as a function of concentration, time, pH, and temperature. Using the batch adsorption technique, the experimentally obtained adsorption data were fitted to both Langmuir and Freundlich isotherms. The adsorption data followed the pseudo-second-order kinetics, and the adsorption capacity was recorded as 360.12 mg/g for CV, 409.23 mg/g for CR, and 390.14 mg/g for MG. The good uptake is the outcome of a greater surface area (24.751 m²/g) for the slate activated at 873 K. The thermodynamic studies showed that the adsorption process remained endothermic and spontaneous. Thermally activated slate proved itself to be an efficient adsorbent and can effectively be used for the removal of textile dyes from the contaminated water, and it is evident from the good uptake of the adsorbate by the adsorbent.

Enhanced Removal of Malachite Green Using Calcium-Functionalized Magnetic Biochar

To efficiently remove malachite green (MG), a novel calcium-functionalized magnetic biochar (Ca/MBC) was fabricated via a two-step pyrolysis method. Iron-containing oxides endowed the target complexes with magnetic properties, especially the chemotactic binding ability with MG, and the addition of calcium significantly changed the morphology of the material and improved its adsorption performance, especially the chemotactic binding ability with MG, which could be confirmed through FTIR, XPS, and adsorption experiments. Electrostatic adsorption, ligand exchange, and hydrogen bonding acted as essential drivers for an enhanced adsorption process, and the maximum theoretical adsorption capacity was up to 12,187.57 mg/g. Ca/MBC maintained a higher adsorption capacity at pH = 4–12, and after five adsorption–desorption cycles, the adsorption capacity and adsorption rate of MG remained at 1424.2 mg/g and 71.21%, highlighting the advantages of Ca/MBC on adsorbing MG. This study suggests that biochar can be modified by a green synthesis approach to produce calcium-functionalized magnetic biochar with excellent MG removal capacity. The synthetic material can not only remove pollutants from water but also provide an efficient way for soil remediation.

Enhanced malachite green photolysis at the colloidal-aqueous interface

Colloids, such as natural particulate matter and microplastics, can play a significant role in the fate and transport of organic contaminants. Specifically, these small nano-to micron-sized particles provide large surface area; thus, particle-aqueous interfacial chemistry becomes significant. In this work, we present an experimental investigation of interfacial photokinetics of malachite green cation (MG+) adsorbed at the surface of polystyrene carboxyl (PSC) microspheres suspended in aqueous solution. Second harmonic generation (SHG), an interfacial selective laser spectroscopic tool, has been used to probe the buried interface. It is revealed that relative to the bulk, photoinduced degradation of MG+ is accelerated by approximately 10-fold at this noncatalytic particle surface. By measuring the SHG-based surface electronic spectra, we have also demonstrated that N-demethylated intermediates of MG+ remain at the interface until they are further decomposed. MG+ exhibits a bathochromic shift at the interface. Together with strong binding affinity and faster initial rate of photodegradation of MG+ at the interface, this work highlights that adsorption and surface photolysis are important pathways by which organic compounds can be transformed within the aquatic environment. Moreover, this research also stimulates further questions on the enrichment of reactive species at the colloidal-aqueous interface and their influence on facilitating decompositions of organic pollutants.

Autonomous magnetic microbots for environmental remediation developed by organic waste derived carbon dots

Biodegradable precursors for micro/nanobots development are key requirements for several sustainable applications. In this regard, we propose an innovative solution for water purification at minimum cost and efforts where organic waste is used for the treatment of organic pollutants. Herein, catalytic magnetic microbots were developed by functionalizing iron oxide nanoparticles with carbon dots (C-Dots), which were synthesized by using household waste such as potato peels as precursors. The speed of these autonomously propelling bots indeed is found very promising for large distance swimming even in viscous medium by using hydrogen peroxide as fuel. These microbots catalytically propel and degrade toxic polar as well as sparingly water-soluble industrial dyes without any external agitation. The degradation of dyes was confirmed by mass-spectra analysis. Furthermore, these microbots can efficiently degrade a mixture of dyes and reused without compromising its performance significantly. Additionally, rate constant (K) and activation energy (E_a) were also determined to establish the catalytic nature of the bots. The present microbots acted as nanozyme owing to its synergistic catalytic activity of Fe₃O₄ and C-Dots for degradation of mixture of toxic dyes, essential for large scale water treatment.

Heterologous expression of bacterial CotA-laccase, characterization and its application for biodegradation of malachite green

Malachite green (MG) is used as fungicide/parasiticide in aquaculture, its persistence is detrimental as it exhibits carcinogenic effects to aquatic organisms. Bacterial laccase evaluated as the best enzyme at extreme condition for aquatic MG removal. Study aims to increase laccase concentration, CotA-laccase from Bacillus subtilis was cloned and overexpressed in Escherichia coli. Optimal catalysis for purified CotA-laccase were at pH 5.0, 60 °C, and 1 mM of (2,2-azino-di-[3-ethylbenzothiazoline-sulphonate-(6)]) with Km and Kcat 0.087 mM and 37.64 S^-1 respectively. MG biodegradation by CotA-laccase in clam and tilapia pond wastewaters and cytotoxic effect of biodegraded products in grouper fin-1 cells were determined. MG degradation by CotA-laccase was equally efficient, exhibiting upto 90-94% decolorization at freshwater and saline conditions and treated solution was non-toxic to GF-1 cells. Thus, recombinant-CotA-laccase could be an environmentally-friendly enzyme for aquaculture to remove MG, thereby effective to reduce its accumulation in aquatic organisms and ensuring safe aquaculture products.

Combination of the endophytic manganese-oxidizing bacterium Pantoea eucrina SS01 and biogenic Mn oxides: An efficient and sustainable complex in degradation and detoxification of malachite green

Recently, Mn oxides (MnOxs) have been attracting considerable interest in the oxidation of organic pollutants. However, the reduction of MnOx in these reactions leads to the deactivation of the catalyst, which must be frequently regenerated. We evaluated the application of a manganese-oxidizing bacterium (MOB) and MnOx in removing toxic dyes. We studied the co-function of a plant-endophytic MOB, Pantoea eucrina SS01, with its bio-generated MnOx and evaluated the detoxification activity and chemical transformation mechanisms of the complex in malachite green (MG) degradation. We found a synergistic effect between MnOx and the strain. Particularly, strain SS01 could adsorb MG but could not degrade it, whereas the addition of Mn(II) promoted MG degradation by the formation of a complex containing the bacterium and MnOx aggregates (SS01-bio-MnOx), with distinct morphology characteristics. The complex showed a marked sustainability in the degradation of MG into less toxic or non-toxic metabolites. In this process, strain SS01 might have enhanced the regeneration of MnOx, accelerating MG degradation. Our data not only contribute to understanding the mechanism of MG removal by the SS01-bio-MnOx complex, but also provide a scientific basis for the future application of MOB and MnOx.

Effective Removal of Malachite Green from Aqueous Solutions Using Magnetic Nanocomposite: Synthesis, Characterization, and Equilibrium Study

In this work, magnetized activated Juniperus procera leaves (Fe3O4@AJPL) were successfully prepared via chemical activation of JPL and in situ coprecipitation with Fe3O4. A Fe3O4@AJPL nanocomposite was successfully applied for the elimination of malachite green (MG) dye from aqueous media. The prepared Fe3O4@AJPL adsorbent was characterized by SEM, EDX, TEM, XRD, FTIR, TGA, and BET surface area analyses. The BET surface area and pore size of the Fe3O4@AJPL nanocomposite were found to be 38.44 m2/g and 10.6 nm, respectively. The XRD and FTIR results indicated the formation of a Fe3O4@AJPL nanocomposite. Different parameters, such as pH of the solution (3–8), adsorbent dosage (10–100 mg), temperature (25–45°C), contact time (5-240 min), and initial MG concentrations (20–350 mg/L), for the elimination of the MG dye using Fe3O4@AJPL were optimized and found to be 7, 50 mg, 45°C, 120 min, and 150 mg/L, respectively. The nonlinear isotherm and kinetic studies exhibited a better fitting to second-order kinetic and Langmuir isotherm models, with a maximum monolayer adsorption capacity of 318.3 mg/g at 45°C, which was highly superior to the previously reported magnetic nanocomposite adsorbents. EDX analyses confirmed the presence of nitrogen on the Fe3O4@AJPL surface after MG adsorption. The calculated thermodynamic factors indicated endothermic and spontaneous processes. The desorption of MG dye from Fe3O4@AJPL was performed using a solution of 90% ethanol. Finally, it could be concluded that the designed Fe3O4@AJPL magnetic nanocomposite will be a cost-effective and promising adsorbent for the elimination of MG from aqueous media.

A Simple Microextraction Method for Toxic Industrial Dyes Using a Fatty-Acid Solvent Mixture

A mixture of dodecanoic and hexanoic fatty acids was used to perform a simple and efficient microextraction method for industrial dyes such as methylene blue (MB), methyl violet (MV), and malachite green (MG) in aqueous solution. The fatty-acid microextractants were simply mixed and heated until the mixture became homogeneous before adding it to the dye solutions. The fatty-acid solvent and its components were characterized with Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) measurements, while the dye concentrations were measured using UV-Vis spectroscopy. The performance of the extracting mixture was observed to vary across different dye contaminants, dosages of the extractant, concentrations of the dyes, and contact times. High extraction efficiencies of up to ~99% were obtained for MG as well as MV, and ~73% efficiency was achieved for MB. The study shows how a mixture of fatty acids can be used as a simple, efficient, green, and sustainable low-volume method for the removal of toxic industrial dyes in aqueous solutions.

Recent progress in green and biopolymer based photocatalysts for the abatement of aquatic pollutants

Enormous research studies on the abatement of anthropogenic aquatic pollutants including organic dyes, pesticides, cosmetics, antibiotics and inorganic species by using varieties of semiconductor photocatalysts have been reported in recent decades. Besides, many of these photocatalysts suffer in real applications owing to their high production cost and low stability. In many cases, the photocatalysts themselves are being considered as secondary pollutants. To eliminate these drawbacks, the green synthesized photocatalysts and the use of biopolymers as photocatalyst supports are considered in recent years. In this context, recent developments in green synthesized metals, metal oxides, other metal compounds, and carbon based photocatalysts in water purification are critically reviewed. Furthermore, the pivotal role of biopolymers including chitin, chitosan, cellulose, natural gum, hydroxyapatite, alginate in photocatalytic removal of aquatic pollutants is comprehensively reviewed. The presence of functional groups, electron trapping ability, biocompatibility, natural occurrence, and low production cost are the major reasons for using biopolymers in photocatalysis. Finally, the summary and conclusion are presented along with existing challenges in this research area.

iTRAQ-facilitated proteomic analysis of Bacillus cereus via degradation of malachite green

The wide use of malachite green (MG) as a dye has caused substantial concern owing to its toxicity. Bacillus cereus can against the toxic effect of MG and efficiently decolourise it. However, detailed information regarding its underlying adaptation and degradation mechanisms based on proteomic data is scarce. In this study, the isobaric tags for relative and absolute quantitation (iTRAQ)-facilitated quantitative method was applied to analyse the molecular mechanisms by which B. cereus degrades MG. Based on this analysis, 209 upregulated proteins and 198 downregulated proteins were identified with a false discovery rate of 1% or less during MG biodegradation. Gene ontology and KEGG analysis determined that the differentially expressed proteins were enriched in metabolic processes, catalytic activity, antioxidant activity, and responses to stimuli. Furthermore, real-time qPCR was utilised to further confirm the regulated proteins involved in benzoate degradation. The proteins BCE_4076 (Acetyl-CoA acetyltransferase), BCE_5143 (Acetyl-CoA acetyltransferase), BCE_5144 (3-hydroxyacyl-CoA dehydrogenase), BCE_4651 (Enoyl-CoA hydratase), and BCE_5474 (3-hydroxyacyl-CoA dehydrogenase) involved in the benzoate degradation pathway may play an important role in the biodegradation of MG by B. cereus. The results of this study not only provide a comprehensive view of proteomic changes in B. cereus upon MG loading but also shed light on the mechanism underlying MG biodegradation by B. cereus.

Sandalwood-derived carbon quantum dots as bioimaging tools to investigate the toxicological effects of malachite green in model organisms

Malachite green is an N-methylated diaminophenylmethane dye that has generated much concern over its suggestive carcinogenic nature. After its excessive use in aquaculture industry as an effective ectoparasitide, much debate was raised over its toxicological effects leading to scientific studies conducted on animal models. Even after several bans, malachite green is still easily available in many parts of the world and unscrupulously even used to give green vegetables a fresher look. This study aims to address this concern by systematically studying the toxicological effects of malachite green through bioimaging in plant and animal cell and tissue. Sandalwood-derived carbon quantum dots have been used as a bioimaging tool since they are non-cytotoxic and show excellent fluorescence properties. Onion tissues demonstrate the translocation of the dye inside cells having high affinity for the nuclei and cell walls. Toxicological effects on the growth of Vigna radiata (mung beans) have been studied methodically. Bioimaging of the transverse cross-section of the dye-treated plant root shows a significant difference from the control. In animal cells, dose-dependent decrease in cell viability of MG-63 cells was observed with MG. CQD showed good fluorescence in both cytoplasm and nucleus of MG63 cells. In addition, CQDs were employed as a great tool for bioimaging of the histopathologically adverse effects of MG in Golden hamster animal model. This study showed CQDs could be used as an alternative non-site specific fluorescent probe for cell and tissue imaging for better visualization of cell and tissue architectural changes.

Electro-activated persulfate oxidation of malachite green by boron-doped diamond (BDD) anode: effect of degradation process parameters

In this paper, boron-doped diamond (BDD) electro-activated persulfate was studied to decompose malachite green (MG). The degradation results indicate that the decolorization performance of MG for the BDD electro-activated persulfate (BDD-EAP) system is 3.37 times that of BDD electrochemical oxidation (BDD-EO) system, and BDD-EAP system also exhibited an enhanced total organic content (TOC) removal (2.2 times) compared with BDD-EO system. Besides, the degradation parameters such as persulfate concentration, current density, and pH were studied in detail. In a wider range of pH (2-10), the MG can be efficiently removed (>95%) in 0.02 M persulfate solution with a low current density of 1.7 mA/cm² after 30 min. The BDD-EAP technology decomposes organic compounds without the diffusion limitation and avoids pH adjustment, which makes the EO treatment of organic wastewater more efficient and more economical.

Electrospun reduced graphene oxide/TiO2/poly(acrylonitrile-co-maleic acid) composite nanofibers for efficient adsorption and photocatalytic removal of malachite green and leucomalachite green

Electrospun reduced graphene oxide/TiO₂/poly(acrylonitrile-co-maleic acid) composite nanofibers (E-spun RGO/TiO₂/PANCMA NFs) were fabricated using electrospinning of the dispersive solution of PANCMA, GO and TiO₂ followed by post-chemical reduction. The obtained composite nanofibers were compressed in a dialyzer and then used to absorb and degrade malachite green (MG) and leucomalachite green (LMG) from aqueous solution. Compared to the E-spun TiO₂/PANCMA and GO/TiO₂/PANCMA NFs, the E-spun RGO/TiO₂/PANCMA NFs exhibited higher adsorption capacity and photocatalytic degradation ability. Under optimized conditions, 90.6% of MG and 93.7% of LMG from 50 mL aqueous sample solution were adsorbed on the RGO/TiO₂/PANMA NFs (3.0 mg fibers) in 2.0 min, and subsequent the 91.4% and 95.2% of MG and LMG adsorbed on the NFs were degradated in 60 min under UV irradiation, respectively. In addition, the E-spun RGO/TiO₂/PANMA NFs exhibited good reusability and could be reused in multiple cycles of operations for adsorption and photocatalytic degradation of MG and LMG. This work demonstrated that the electrospun composite nanofibers are promising materials for removal of pollutants from environmental water samples.

A novel hierarchical stiff carbon foam with graphene-like nanosheet surface as the desired adsorbent for malachite green removal from wastewater

A novel hierarchical stiff carbon foam (HSCF) was successfully prepared via a carbothermal reduction between the carbon foam with two-level pore structure and the Al₂O₃ from aluminum sulfate, and used as a bulk adsorbent for removing malachite green (MG) dye. The structures of the HSCF were characterized using SEM, XRD, FTIR, BET, and XPS, and the effects of adsorption condition on the MG removal were studied through batch adsorption experiments. Results show that large-sized and complex-shaped HSCF can be easily fabricated with a high compression strength of 1.58 MPa at a low bulk density (0.10 g cm^-3). The HSCF possesses a fluffy graphene-like nanosheet surface with a mesoporous structure and meanwhile exhibits good hydrophilicity loaded with aluminum hydroxide. The experimental maximum adsorption capacity for MG reaches 425.2 mg g^-1 with a relatively high partition coefficient of 9.38 mg g^-1 μM^-1 at the optimal condition. The experimental data are in good agreement with Langmuir isotherm and pseudo-second-order kinetic model, and meanwhile, the adsorption of MG onto the HSCF is a spontaneous and endothermic process. Also, the HSCF still exhibits good adsorption ability and stability after seven regeneration cycles.

Metagenomics-Based Discovery of Malachite Green-Degradation Gene Families and Enzymes From Mangrove Sediment

Malachite green (MG) is an organic contaminant and the effluents with MG negatively influence the health and balance of the coastal and marine ecosystem. The diverse and abundant microbial communities inhabiting in mangroves participate actively in various ecological processes. Metagenomic sequencing from mangrove sediments was applied to excavate the resources MG-degradation genes (MDGs) and to assess the potential of their corresponding enzymes. A data set of 10 GB was assembled into 33,756 contigs and 44,743 ORFs were predicted. In the data set, 666 bacterial genera and 13 pollutant degradation pathways were found. Proteobacteria and Actinobacteria were the most dominate phyla in taxonomic assignment. A total of 44 putative MDGs were revealed and possibly derived from 30 bacterial genera, most of which belonged to the phyla of Proteobacteria and Bacteroidetes. The MDGs belonged to three gene families, including peroxidase genes (up to 93.54% of total MDGs), laccase (3.40%), and p450 (3.06%). Of the three gene families, three representatives (Mgv-rLACC, Mgv-rPOD, and Mgv-rCYP) which had lower similarities to the closest sequences in GenBank were prokaryotic expressed and their enzymes were characterized. Three recombinant proteins showed different MG-degrading activities. Mgv-rPOD had the strongest activity which decolorized 97.3% of MG (300 mg/L) within 40 min. In addition, Mgv-rPOD showed a more complete process of MG degradation compared with other two recombinant proteins according to the intermediates detected by LC-MS. Furthermore, the high MG-degrading activity was maintained at low temperature (20°C), wider pH range, and the existence of metal ions and chelating agent. Mgv-rLACC and Mgv-rCYP also removed 63.7% and 54.1% of MG (20 mg/L) within 24 h, respectively. The results could provide a broad insight into discovering abundant genetic resources and an effective strategy to access the eco-friendly way for preventing coastal pollution.

Decolourization and detoxification of monoazo dyes by laccase from the white-rot fungus Trametes versicolor

The decolourization and detoxification of azo dyes (Orange 2, Acid Orange 6) by fungal laccase from Trametes versicolor were evaluated. For laccase catalysed reaction, the azonaphthol Orange 2, with 72.8% decolourization, was degraded more rapidly than the azobenzene Acid Orange 6, with 45.3%. The presence of hydroxyl group at o-position to azo bond in the structure of Orange 2 was more preferable than the presence of two hydroxyl groups at o- and p-positions to azo bond in Acid Orange 6. Although the laccase treatment was more effective for the Orange 2 decolourization, the toxicity of both monoazo dye solutions became less toxic for the prokaryote growth. The phytotoxicity of Orange 2 and Acid Orange 6 solutions after laccase treatment was decreased in the range of 41.2-64.3 %. Also, the photoxicity, as measured by the production of chlorophylls a and b by Chlorella vulgaris and Microcystis aeruginosa, was decreased by laccase treatment of selected monoazo dyes. Our results show that different dyes can be decolorized and detoxified by laccase from T. versicolor in a single step.

A test battery for assessing the ecotoxic effects of textile dyes

The textile dyeing industry is one of the main sectors contributing to environmental pollution, due to the generation of large amounts of wastewater loaded with dyes (ca. 2-50% of the initial amount of dyes used in the dye baths is lost), causing severe impacts on human health and the environment. In this context, an ecotoxicity testing battery was used to assess the acute toxicity and genotoxicity of the textile dyes Direct Black 38 (DB38; azo dye) and Reactive Blue 15 (RB15; copper phthalocyanine dye) on different trophic levels. Thus these dyes were tested using the following assays: Filter paper contact test with earthworms (Eisenia foetida); seed germination and root elongation toxicity test (Cucumis sativus, Lactuca sativa and Lycopersicon esculentum); acute immobilization test (Daphnia magna and Artemia salina); and the Comet assay with the rainbow trout gonad-2 cell fish line (RTG-2) and D. magna. Neither phytotoxicity nor significant effects on the survival of E. foetida were observed after exposure to DB38 and RB15. Both dyes were classified as relatively non-toxic to D. magna (LC₅₀ > 100 mg/L), but DB38 was moderately toxic to A. salina with a LC₅₀ of 20.7 mg/L. DB38 and RB15 induced significant effects on the DNA of D. magna but only DB38 caused direct (alkaline comet assay) and oxidative (hOGG1-modified alkaline comet assay) damage to RTG-2 cells in hormetic responses. Therefore, the present results emphasize that a test battery approach of bioassays representing multiple trophic levels is fundamental in predicting the toxicity of textile dyes, aside from providing the information required to define their safe levels for living organisms in the environment.

Target and non-target response of Swietenia Mahagoni Jacq. chemical constituents against tobacco cutworm Spodoptera litura Fab. and earthworm, Eudrilus eugeniae Kinb

Toxicological screening of Swietenia mahagoni Jacq. (Meliaceae, West Indies Mahogany) against the lepidopteran pest Spodoptera litura was examined. Phytochemical screening through GC-MS analysis revealed nine peaks with prominent peak area % in Bis (2-ethylhexyl) phthalate (31.5%) was observed. The larvae exposed to discriminating dosage of 100 ppm deliver significant mortality rate compare to other treatment concentrations. The lethal concentrations (LC₅₀ and LC₉₀) was observed at the dosage of 31.04 and 86.82 ppm respectively. Sub-lethal concentrations (30 ppm) showed higher larval and pupal durations. However, pupal weight and mean fecundity rate reduced significantly. Similarly, the adult longevity reduced significantly in dose dependent manner. Midgut histology studies showed that the methanolic extracts significantly disturbs the gut epithelial layer, lumen and brush border membrane compare to the control. The soil assay on a non-target beneficial organism, the soil indicator earthworm Eudrilus eugeniae, with extracts from S. mahagoni (200 mg/kg) showed no toxicity compared to Monocrotophos at the dosage of 10 ppm/kg. Current results suggest that this bio-rational plant product from S. mahagoni displays a significant effect to reduce lepidopteran pests with low toxicity to other beneficial species.

Fabrication and characterization of β-cypermethrin-loaded PLA microcapsules prepared by emulsion-solvent evaporation: loading and release properties

Microcapsulses can be designed to effectively encapsulate, protect, and control the release of pesticides. In this study, emulsion-solvent evaporation method was used to fabricate microcapsules using dichloromethane as the solvent, polylactic acid (PLA) as the carrier materials, poly(vinyl alcohol) as the emulsifier, and β-cypermethrin as the entrapped pesticide. The effects of process parameters on the microcapsules characteristics (size, loading content, and encapsulation efficiency) were investigated. Also, the release behavior of the β-cypermethrin was measured experimentally and modeled mathematically. Kinetic analysis indicated that release mechanism of β-cypermethrin was compatible to Fickian diffusion. By optimizing the process parameters, β-cypermethrin-loaded microcapsules were successfully produced with spherical shape, smooth surface, high encapsulation efficiency (> 80%), and a range of pesticide contents. These parameters could be adjusted to achieve delivery systems with desirable release profiles. The results are beneficial to develop delivery systems for rational and effective usage of pesticides.

Lethal and sub-lethal evaluation of Indigo Carmine dye and byproducts after TiO2 photocatalysis in the immune system of Eisenia andrei earthworms

The Indigo carmine (IC) dye has been widely used in textile industries, even though it has been considered toxic for rats, pigs and humans. Owing to its toxicity, wastes containing this compound should be treated to minimize or eliminate their toxic effects on the biota. As an alternative to wastewater treatment, advanced oxidative processes (AOPs) have been highlighted due to their high capacity to destruct organic molecules. In this context, this study aimed to evaluate Indigo Carmine toxicity to soil organisms using the earthworm Eisenia andrei as a model-organism and also verify the efficiency of AOP in reducing its toxicity to these organisms. To this end, lethal (mortality) and sub-lethal (loss or gain of biomass, reproduction, behavior, morphological changes and immune system cells) effects caused by this substance and its degradation products in these annelids were evaluated. Morphological changes were observed even in organisms exposed to low concentrations, while mortality was the major effect observed in individuals exposed to high levels of indigo carmine dye. The organisms exposed to the IC during the contact test showed mortality after 72h of exposure (LC₅₀ = 75.79mgcm^-2), while those exposed to photoproducts showed mortality after 48h (LC₅₀ = 243min). In the chronic study, the organisms displayed a mortality rate of 14%, while those exposed to the photoproduct reached up to 32.7%. A negative influence of the dye on the reproduction rate was observed, while by-products affected juvenile survival. A loss of viability and alterations in the cellular proportion was verified during the chronic test. However, the compounds did not alter the behavior of the annelids in the leak test (RL ranged from 20% to 30%). Although photocatalysis has been presented as an alternative technology for the treatment of waste containing the indigo carmine dye, this process produced byproducts even more toxic than the original compounds to E. andrei.

Target and non-target toxicity of botanical insecticide derived from Couroupita guianensis L. flower against generalist herbivore, Spodoptera litura Fab. and an earthworm, Eisenia foetida Savigny

Botanical insecticides may provide alternatives to synthetic insecticides for controlling Spodoptera litura (F.) and they are target specific, biodegradable, and harmless to mammals. Eight natural chemical compounds with larvicidal activity were identified from fraction F6 of C. guianensis flower extract. Probit analysis of 95% confidence level exposed an LC50 of 223ppm against S. litura third instar larvae. The growth and development of S. litura was affected in sub-lethal concentrations of fraction F6 (50, 100, 150 and 200ppm) compared to controls. Similarly nutritional indices values decreased significantly compared to controls. Fraction F6 also damaged the gut epithelial layer and brush border membrane (BBM). This study also resolved the effects of toxicity to non-target earthworm treated with fraction F6 and chemical pesticides (monotrophos and cypermethrin) and the results showed that fraction F6 had no harmful effect on E. fetida. Further, fraction F6 was eluted and sub fractions F6c (50ppm) showed high mortality against S. litura third instar larvae. Octacosane from fraction F6c was established and confirmed using IR spectrum and HPLC. The time of retention of fraction F6c was confirmed with the octacosane standard. Fraction F6 of C. guianensis extract caused dose-dependent mortality towards S. litura. Octacosane in fraction F6c was establish to be the prominent chemical compound associated with causing mortality but other compounds present in the fraction F6 were shown to be associated with changes in development of S. litura at low dosages. S. litura at low dosage. Therefore, these findings suggest that octacosane may be one of the major insecticidal compounds affecting S. litura survival.

Malachite green adsorption onto Fe3O4@SiO2-NH2: isotherms, kinetic and process optimization

A novel magnetic adsorbent with an amino-modified SiO₂-coated Fe₃O₄ magnetite was prepared. Under the optimal conditions, the removal efficiency of malachite green is over 90% by Fe₃O₄@SiO₂-NH₂.