Decolorization Of Crystal Violet Research Articles

Biodegradation of crystal violet mediated by CotA from Bacillus amyloliquefaciens

Triphenylmethane dyes are commonly used in dyeing and printing, but such dyes are recalcitrant to degradation and thus biodegradation of dye compounds has received increasing attention. Here, a recombinant bacterial laccase, CotA, from Bacillus amyloliquefaciens MN-13 was expressed in Escherichia coli BL21(DE3) and used as a biocatalyst to degrade crystal violet (CV). The recombinant CotA remained stable at temperatures in the range 30-40°C and retained 44-100% enzyme activity at pH 4.5-8.0. The CotA exhibited high activities for decolorization of CV and, after 72h of incubation, CotA decolorized 70.98% of CV at pH 5.0 and 30°C. In the UV-visible spectra of CV solution treated by CotA, the full wavelength scan indicated that the chromophore of the triphenylmethane structure of CV was destroyed and CV was degraded into small-molecule aromatic compounds. The main degradation compounds of CV were identified as bis[4-(dimethylamino) phenyl] methanone and its N-demethylation derivative by HPLC/MS/MS. Based on these data, a hypothetical degradation pathway of CV by CotA, including N-demethylation and cleavage of the chromophore structure initiated by radicals, is proposed.

Visible-light-responsive Al2O3 powder: Photocatalytic study

A visible-light-responsive hybrid material was prepared by surface-modification of γ-Al2O3, an insulator with a bandgap of about 8.7 eV, with 5-aminosalicylic acid (5-ASA), leading to the formation of an interfacial charge transfer (ICT) complex. The microstructural characterization of pristine γ-Al2O3 includes X-ray diffraction analysis, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. The pristine γ-Al2O3 powder consists of agglomerated rod-like nanoparticles ((2-3) × (15-20) nm, diameter × length) with the large specific surface area (~420 m2/g). An enormous absorption red-shift is observed upon the formation of the ICT complex. The absorption onset of the inorganic-organic hybrid was found to be at 730 nm by diffuse reflection spectroscopy. The photocatalytic performance of prepared samples was thoroughly tested using the decolorization of the organic dye crystal violet (CV) under illumination in different spectral regions and different light intensities. Excitation with UV light leads to complete decolorization of CV, while the degradation kinetics are impeded when a visible light source is used. Also, the increase of UV light intensity induced significantly faster degradation kinetics of CV, while the degradation rates of CV are quite insensitive to the increase of visible light intensity.

Biochars and their magnetic derivatives as enzyme-like catalysts mimicking peroxidases

Various materials have been extensively investigated to mimic the structures and functions of natural enzymes. We describe the discovery of a new catalytic property in the group of biochar-based carbonaceous materials, which are usually produced during biowaste thermal processing under specific conditions. The tested biochars exhibited peroxidase-like catalytic activity. Biomaterial feedstock, pyrolysis temperature, size of resulting biochar particles or biochar modification (e.g., magnetic particles deposition) influenced the peroxidase-like activity. Catalytic activity was measured with the chromogenic organic substrates N,N-diethyl-p-phenylenediamine (DPD) or 3,3′,5,5′-tetramethylbenzidine (TMB), in the presence of hydrogen peroxide. Magnetic biochar composite was studied as a complementary material, in which the presence of iron oxide particles enhances catalytic activity and enables smart magnetic separation of catalyst even from complex mixtures. The activity of the selected biochar had an optimum at pH 4 and temperature 32 °C; biochar catalyst can be reused ten times without the loss of activity. Using DPD as a substrate, Km values for native wood chip biochar and its magnetic derivative were 220 ± 5 μmol L−1 and 690 ± 80 μmol L−1, respectively, while Vmax values were 10.1 ± 0.3 μmol L−1 min−1 and 16.1 ± 0.4 μmol L−1 min−1, respectively. Biochar catalytic activity enabled the decolorization of crystal violet both in the model solution and the fish pond water containing suspended solids and dissolved organic matter. The observed biochar enzyme mimetic activity can thus find interesting applications in environmental technology for the degradation of selected xenobiotics. In general, this property predestines the low-cost biochar to be a perspective supplement or even substitution of common peroxidases in practical applications.

Sorption of crystal violet from aqueous solution using live roots of Eichhornia crassipes: Kinetic, isotherm, phyto and cyto-genotoxicity studies

In the present study, Water hyacinth (Eichhornia crassipes), a worst obtrusive aquatic weed has utilized for biosorption of cationic dye, crystal violet from aqueous solution. To evaluate the biosorption capacity, the effect of solution pH, initial dye concentration, and contact time were investigated. The highest qe was observed at pH 7 and biosorption capacity was experiential up to dye concentration 1 gL−1. Kinetic data was fitted well to the pseudo-second order kinetics with R2=0.993 and qe=19.84 mg g−1 at concentration 100 mgL−1. Other adsorption models like pseudo-first order with R2=0.947 and intraparticle diffusion R2=0.785 were also operated for the mathematical description of the sorption kinetics. The Freundlich isotherm model fitted well to the adsorption data with R2=0.999, kf= 5.039 mg g−1 and 1/n = 0.535. The other equilibrium data were also mathematically described using Langmuir (R2=0.941), Dubinin–Radushkevitch (D–R)​ (R2=0.936) and Temkin (R2=0.978) isotherm models. UV–Vis and FT-IR analyses were executed to accomplish the decolorization of crystal violet from aqueous solution. In addition, phytotoxicity and cyto-genotoxicity analyses were prosecuted. The results indicated that the solution spawned were far less toxic than the crystal violet solution. These results consigned that E. crassipes is effective in decolorizing crystal violet dye and could be auspicious in phytoremediation of dye contaminated wastewater.

Colorimetric methods for rapid determination of pyrazinamide resistance.

Because pyrazinamide (PZA) is only effective for Mycobacterium tuberculosis at an acidic pH, susceptibility tests are more difficult to perform than those for other anti-tuberculosis (TB) drugs. The purpose of our work was to investigate the effectiveness of colorimetric methods to detect PZA susceptibility and to detect pncA gene mutations in resistant isolates by sequence analysis. In this study, 30 clinical isolates and 2 reference isolates were used, 15 of which were resistant to PZA. The PZA susceptibility of all the isolates was determined by the BACTEC MGIT 960 reference method. As colorimetric methods, Resazurin Microtiter Assay (REMA), Nitrate Reductase Assay (NRA), Malachite Green Decolorization Assay (MGDA), and Crystal Violet Decolorization Assay (CVDA) methods were included in the study. In addition, mutations in the pncA gene were investigated using sequence analysis in PZA-resistant isolates. As a result of the comparison of the colorimetric methods with the reference method, agreement was determined as 93.3% in REMA and NRA, 90% in MGDA, and 93.3% in CVDA. In 13 of 15 resistant isolates, the pncA gene mutation was detected by sequence analysis. As a result of the work, the results from the colorimetric methods were found to be at a high level of concordance with the reference method. They are also inexpensive and easily applicable methods.

Evaluation of crystal violet decolorization assay and resazurin microplate assay for antimycobacterial screening

The main obstacle in antimycobacterial discovery is the extremely slow growth rates of pathogenic mycobacteria that lead to the long incubation times needed in antimycobacterial screening. Some in vitro testings has been developed and are currently available for antimycobacterial screening. The aim of the study was to compare Resazurin Microplate Assay (REMA) and Crystal Violet Decolorization Assay (CVDA) for testing mycobacteria susceptibility to isoniazid and rifampicin as well as for antimycobacterial screening of natural products (NP). Mycobacterium tuberculosis strain H37Rv and Mycobacterium smegmatis strain mc2 155 were used as tested mycobacteria. Serial two-fold dilutions from 0.0625 to 1.0 μg/mL for the isoniazid and rifampicin and from 6.25 to 100.0 μg/mL for the NP A and B were prepared. Tested mycobacteria were then incubated with tested drugs or NPs in each growth medium at 37 °C for 7 days for M. tuberculosis and 3 days for M. smegmatis. MIC values against M. tuberculosis were interpreted 24–48 h after adding resazurin or at least 72 h after adding crystal violet, whereas MIC values against M. smegmatis were interpreted 1 h after adding resazurin or 24 h after adding crystal violet. The MIC values against M. tuberculosis interpreted by REMA were 0.0625, 0.0625, 6.25, and >100 μg/mL for rifampicin, isoniazid, NP A, and NP B, respectively, and those interpreted by CVDA were 0.0625, 0.0625, 6.25, and >100 μg/mL for rifampicin, isoniazid, NP A, and NP B, respectively. Moreover, the MIC values against M. smegmatis interpreted by REMA were 0.0625, >1, 6.25, and 100 μg/mL for rifampicin, isoniazid, NP A, and NP B, respectively, and those interpreted by CVDA were 0.125, >1, 6.25, and >100 μg/mL for rifampicin, isoniazid, NP A, NP B respectively. In conclusion, REMA is faster and easier than CVDA to interpret MIC values, however CVDA produces higher MIC values than REMA for rifampicin and NP B in M. smegmatis susceptibility testing. Therefore, REMA and CVDA can be used for antimycobacterial screening.

Oxidation of Crystal Violet in Aqueous Solutions Using the Fenton Process

: Advanced oxidation processes (AOPs) are always accompanied by producing highly-reactive hydroxyl radicals (OH) with great potential for the decolorization and mineralization of organic compounds. Todays, dyestuff and pigments are considered a notorious concern for the pollution of aqueous environments. Proposing new methods to dispose of this problem is therefore essential. The present study was conducted to investigate the use of the Fenton process for removing crystal violet (CV) from aqueous solutions. The effectiveness of this method was influenced by several factors, including pH, initial concentration of the dye, different interfering ions and reaction duration. The residual concentration of the dye was determined using spectrophotometry at a maximum wavelength of about 586 nm. The data were analyzed and interpreted in Excel. The optimal pH was obtained as 3, and the optimal initial concentration and Fe/H2O2 ratio as 50 mg/L and 1:10 respectively. Given the effect of the contact duration, the minimum Fenton reaction duration was considered 30 minutes. In next step the effect of interference in the progression of the Fenton process were investigated for KCl, NaCl and NaHCO3. Moreover, the efficiency of CV decolorization was 96% under optimal conditions. Fenton can be therefore considered an appropriate process for removing CV from colored wastewater in textile industries.

Sono-sorption efficiencies and equilibrium removal of triphenylmethane (crystal violet) dye from aqueous solution by activated charcoal

In this present work, the sorption of crystal violet (CV) pigment from laden aqueous solution carried out via ultrasound-assisted. The sorption of CV on activated charcoal was performed in the existence and absence of ultrasound. Using of combined ultrasound/activated charcoal process gave high CV decolorization than using sorption or sonolysis alone because of the synergistic process achieved in this combined system. Experiments were performed at different initial pigment concentration and temperature. The sorption isotherms were achieved by the Freundlich, Langmuir, D–R and Temkin isotherm model. The sorption of CV onto activated charcoal demonstrated more suitable for Langmuir than the Freundlich isotherm model. The maximum monolayer sorption capacity was 50.1 mg/g. The thermodynamic parameters, namely the entropy, Gibbs free energy and enthalpy of the CV sorption process were determined. The enthalpy and free energy indicate an exothermic, feasible and spontaneous process. It has been shown that the proposed combined ultrasound/activated charcoal process may be useable in the treatment of pigment solution from textile wastewater.

Characteristics of White-rot Fungus Phlebia brevispora TMIC33929 and Its Growth-Promoting Bacterium Enterobacter sp. TN3W-14 in the Decolorization of Dye-Contaminated Water.

The dye decolorization potential of the white-rot fungus Phlebia brevispora TMIC33929 when grown alone or in coculture with its growth-promoting bacterium Enterobacter sp. TN3W-14 was evaluated in low nitrogen liquid medium at different pHs. Axenic fungus removed a similar amount of Congo red and crystal violet at pH 4.5 and 7.0, respectively. The bacterium alone achieved only slightly better decolorization of crystal violet than the fungus at pH 9.0. Compared with axenic fungus, cocultures provided no increased crystal violet removal but achieved higher removal of crystal violet in mixed dye at all pHs, and the best-mixed dye decolorization at pH 9.0. Unlike bacterial growth on dyes, growth of fungal mycelia was not inhibited by the dyes at all pH but the cocultures gave comparably higher mycelial growth.

Post-discharge DBD plasma treatment for degradation of organic dye in water: A comparison with different plasma operation methods

Dielectric barrier discharge (DBD) plasma reactor is an innovative advanced oxidation technology for degradation of organic dye in water. In this study, the crystal violet (CV) solution was exposed to a post-discharge DBD plasma in which O2 was used as the feed gas. In this mode, the liquid target is isolated from the plasma medium and the plasma effluent gas is bubbled across the liquid target to increase mass transfer between reactive species and the solution. The influence of operating parameters including applied power and gas flow rate was studied. It was shown that increasing reactor temperature resulted in the reduction of CV removal. Dilution of the plasma forming gas (pure O2) with Ar enhanced the CV removal up to 44%. The kinetic model of CV bleaching was shown to follow a first-order reaction. In the most suitable experimental condition after one minute treatment, the CV decolorization of 100% was achieved, and the total organic carbon (TOC) dropped to zero. Preliminary investigation into the byproducts through UV-VIS, TOC and GC-MS were done which showed the disappearance of the aromatic rings. This work also outlines current operation methods for plasma treatment of organic dyes in water and compares their performance in terms of energy efficiency, degradation rate constant and formation of main reactive species. The interesting results of post discharge treatment which can be compared quite favorably with those achieved by other operation methods, are the degradation rate constant of 4.37 (1/min) and energy efficiency of 12.2 (g/kWh).

Decomposition of Crystal Violet by an Atmospheric Pressure RF Plasma Jet: The Role of Radicals, Ozone, Near-Interfacial Reactions and Convective Transport

Cold atmospheric pressure plasma (CAP) oxidizes organic compounds in water through the generation of a variety of reactive species including O3 and OH radicals. While the energy efficiency and rate of decomposition of the chemical compound in water is already extensively studied, only few studies focused on the reactive species responsible for the decomposition. We report on an investigation of the chemical reactive species involved in the decomposition of crystal violet (CV), a model organic compound, by an RF driven plasma jet in different gas mixtures. Different gas mixtures lead to different concentrations of reactive species responsible for the decolorization of CV. Moreover, the effect of transport limitations on the efficiency of the plasma treatment is reported. A study of positive control measurements, the effect of scavengers of relevant reactive species and particle imaging velocimetry reveal the dominant role of short-lived species at the plasma–liquid interface in which OH most likely plays an important role. Moreover, the decolorization rate is limited by transport of CV to the near boundary region. The results suggest that for the optimization of water treatment by the short-lived species generated by a plasma, an optimum transport of the to-be-treated compounds to the interface might be more critical than effective reactive species production in the plasma.

Decolorization of crystal violet from aqueous solutions by a novel adsorbent chitosan/nanodiopside using response surface methodology and artificial neural network-genetic algorithm

A novel adsorbent of chitosan/nanodiopside nanocomposite (CS-NDIO) was synthesized as a green composite for the removal of crystal violet (CV) and characterized by techniques like XRD, FT-IR, BET, and FESEM analysis. The influence of parameters like molar ratios of CS to NDIO, initial pH of the solution, dosage of adsorbent, initial concentration of CV and contact time was investigated and evaluated by central composite design (CCD; 5 levels and 4 factors). Also, Hybrid model of (ANN) model with genetic algorithm (GA) optimization was applied to the experimental data get through CCD. The optimized molar ratio of CS-NDIO was found: 20/80. Optimal parameter choice for maximum CV adsorption process using CCD and ANN-GA were as follows: pH = 7.50 and 7.499, adsorbent mass: 0.0077 and 0.0077 g, CV concentration: 20.000 and 20.002 mg/L, and contact time: 25.00 and 25.00 min, respectively. The evaluation adsorption equilibrium and kinetic data were fitted with the Langmuir monolayer isotherm model (qmax: 104.66 mg g−1 and R2: 0.9937) and pseudo-second order kinetics mechanism (R2: 0.9978). Thermodynamic parameters (R2: 0.9180, ΔH°: −74.93 kJ mol−1, ΔG°: −12.89 kJ mol−1, and ΔS°: 0.93 kJ mol−1 K−1) were calculated and indicating adsorption to be an exothermic and spontaneous process.

Biodegradation of triphenylmethane dye crystal violet by Cedecea davisae.

The present study focuses on the biodegradation of triphenylmethane dye crystal violet (CV) by Cedecea davisae. The degradation of CV was evaluated via ultraviolet absorbance at 254 nm (UV254) and chemical oxygen demand (COD) removal, and the kinetics was used to evaluate the degradation efficiency. Intermediate products were analyzed via UV-vis spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), and high-performance liquid chromatography (HPLC). Results showed that C. davisae was able to decolorize the CV, and the maximum decolorization ratio reached 97%. COD reduction was observed after decolorization, with average removal rates of >90% after 48 h. Moreover, 50% of UV254 can be removed after 14 h. The removal efficiency of CV by C. davisae followed first- and second-order reaction kinetics at temperature ranged from 20 °C to 40 °C and pH 4.0 to 6.0, respectively. By using UV, the peak representing the CV disappeared 14 h after CV decolorization, and the degradation of aromatic and naphthalene rings was attributed to the formation of a new metabolite. The FTIR spectra of metabolites showed that a new functional group of OH, CH, CH2, CH3, NH, CN, CN, or CO was produced. The chromatograms of HPLC recorded at 589 nm at retention time decreased and were not detected following incubation for 8 h by C. davisae.

Use of lactic acid modified MoS2 nanopetals to improve photocatalytic degradation of organic pollutants

Transition metal dichalcogenide-based molybdenum disulfide (MoS2) are currently gaining considerable attention due to their prospective technological applications. Herein, we report a facile and simple one-step preparation of self-assembled two-dimensional MoS2 nanopetals modified with lactic acid (LA@MoS2). An investigation of the properties of the synthesized LA@MoS2 nanopetals under different conditions reveals that the weight percentage of lactic acid (LA) significantly influences the structural purity, crystalline quality, and morphology of the products, and the appropriate concentration of LA is the determining factor in the synthesis. Photocatalytic activity of LA@MoS2 nanopetals for organic dye decolorization is examined using crystal violet (CV) and methyl orange (MO). The results showed that LA molecules cover the MoS2 with C–S bonds, which significantly enhance photocatalytic decolorization of CV and MO pollutants under simulated solar light irradiation. The LA@MoS2 demonstrated excellent photocatalytic performance compared to bulk MoS2. Furthermore, electrochemical studies reveal fast electron and hole pathways for the reduction of pollutant molecules in aqueous solution. These results indicate that LA@MoS2 is a good photocatalyst because of the desirable active species in the modified catalyst.

Direct Detection of Multidrug Resistant Tuberculosis on Smear Positive Pulmonary Specimens by Using Crystal Violet Decolorization Assay

Background: Emergence of multidrug resistant (MDR) and extensively drug resistant (XDR) tuberculosis (TB) highlights the need for rapid, cost effective and reliable test for drug susceptibility testing. Crystal violet has antibacterial activity however; mycobacteria reduce crystal violet by its sequestration into lipid contents of cell wall. Therefore, this study was conducted to evaluate the utility of a crystal violet decolorization assay (CVDA) for the detection of isoniazid (INH) and rifampicin (RIF) resistance in smear positive pulmonary specimens. Methods & Materials: The study was carried out at department of microbiology, Armed Forces Institute of Pathology, Rawalpindi Pakistan from June 2017 through Sept 2017. 50 smear positive pulmonary specimens were simultaneously tested for INH and rifampicin RIF resistance by CVDA and MGIT 960 system (taken as gold standard). In CVDA, three tubes were used; one growth control (GC) without drug and other two were drug labeled having INH and RIF. The samples were incubated for 14 days and then on 14th day, 100 μL of CV (25 mg/L stock solution) was then added to all tubes. The tubes were then again left for incubation for an additional 48-72 hrs. Specimens sensitive to INH and RIF failed to decolorize CV where as viable isolates in specimens resistant to the respective drug decolorized CV resulting in change of color from blue/purple to colorless. Results: Out of total 50 specimens, one specimen in GC tube did not decolorize CV at the end of protocol (30 days) and therefore was excluded from the final data analysis. The sensitivity, specificity, positive predictive value, negative predictive value and agreement for INH were 82%, 100%, 100%, 100% and 100%, respectively, and 85.7%, 100%, 100%, 91.6% and 94.7%, respectively for RIF. Mean time to obtain results was 18.5 days with a range of 17–21 days. Overall agreement of CVDA was 95% when compared with MGIT 960 system. Conclusion: CVDA is rapid, cost effective, reliable as well as easy to perform drug susceptibility method for detection of MDR-TB on smear positive pulmonary specimens especially in resource starved countries. However, further studies on large scale are needed to know its usefulness in our setup.

Expression and characterization of novel laccase gene from Pandoraea sp. ISTKB and its application

In the present study, a non-blue laccase gene from previously reported lignin degrading bacterium, Pandoraea sp. ISTKB, was isolated, cloned and expressed in E. coli. Bioinformatics analysis of sequence discovered twin-arginine translocation signal sequence, copper binding motifs and presence of more random coil compare to helices and sheets in structure. The enzyme was found to be active on wide pH range and the pH optima was observed at pH 4 and 8 on substrate 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) and 2,6-Dimethoxyphenol respectively. This is a thermophilic enzyme with maximum activity around 50–70 °C. The enzyme was further characterized by spectroscopy, reaction kinetics and effect of metal ions and inhibitors were studied. Compared to laccase alone; the treatment of dyes with laccase plus mediator resulted in enhanced decolorization of crystal violet, methylene blue, azure B, carmine and Congo red but the effect of mediator was not observed on trypan blue. Laccase treatment triggered polymerization on vanillic acid (VA) and kraft lignin (KL). Laccase plus mediator treatment reversed the polymerization and resulted in transformation or degradation of VA and KL. This thermophilic and alkalophilic non-blue laccase from Pandoraea sp. ISTKB is promising with prospective biotechnological application.

Multilayer petal-like enzymatic-inorganic hybrid micro-spheres [CPO-(Cu/Co/Cd)3(PO4)2] with high bio-catalytic activity

CPO, a versatile enzyme, has limitations in industrial applications due to its poor stability and the difficulty of reuse. The preparation of stable immobilized enzymes with high catalytic activity is therefore desirable, but remains a challenge. A facile preparation of a series of enzyme-inorganic hybrid micro-spheres [chloroperoxidase (CPO)-(Cu/Co/Cd)3(PO4)2] and its application in the decolorization of crystal violet is reported in this work. All the hybrid micro-spheres show a multilayer petal-like structure. The formation of hybrid micro-spheres were proposed via four stages: crystallization, in-situ coordination, self-assembly and size growth. The process was entropy-driven, and there was a competition between precipitation of phosphate and coordination of M2+ with amide groups of CPO. The introduction of excess of chloride ions retarded the phosphate from precipitating by forming [MCl4]2− complexes, while simultaneously promoting the coordination of M2+ with amide groups. These hybrid materials showed high bio-catalytic activity in the decolorization of crystal violet. The decolorization efficiency reached 99.66%, 98.44% and 98.05% just within 3min using CPO-Cu3(PO4)2, CPO-Cd3(PO4)2 and CPO-Co3(PO4)2 respectively. They also have good thermal stability, and can keep 52.89% catalytic activity after 8 cycles of use.CPO-inorganic hybrid micro-spheres [chloroperoxidase (CPO)-(Cu/Co/Cd)3(PO4)2] is promising in the treatment of waste water containing crystal violet. It also has potential application for treatment of other soluble organic dyes in industrial wastewater.

Preparation of perovskites PbBiO2I/PbO exhibiting visible-light photocatalytic activity

The first synthetic study on PbBiO2I/PbO nanocomposite preparation using a controlled hydrothermal method is reported. The morphologies and composition of the samples are controlled by adjusting some parameters, including reaction pH, Pb/Bi molar ratio, and temperature. All the samples are characterized by XRD, TEM, XPS, SEM-EDS, PL, BET, EPR, and UV–vis-DRS. The photodegradation activities are evaluated against the de-colorization of crystal violet (CV) and 2-hydroxybenzoic acid (2-HBA) in aqueous solution under visible light illumination. In particular, the catalytic performance illustrates the best reaction rate constant 1.159 × 10−1 h−1 once PbBiO2I/PbO is used as the photocatalyst for the degradation of CV; which is 3 and 20 times higher than the reaction rate constants of PbBiO2I and PbO being the photocatalysts, respectively. This study reveals that PbBiO2I/PbO can be used for repressing the recombination of photo-generated electron-hole pairs and contribute to the enhanced photocatalytic activity of semiconductors in the visible-light-driven catalysis. The possible photocatalytic degradation mechanism is studied by using different active species through EPR and adding suitable scavengers. When being irradiated, two major active species, O2− and 1O2, and a minor active species, h+, can be produced for the CV degradation.

One-step hydrothermally synthesized ferrite@polymeric nanoparticles for decolorization of crystal violet

One-step hydrothermally synthesized ferrite@polymeric nanoparticles for decolorization of crystal violet

Crystal violet decolorization assay for rapid detection of multidrug-resistant Mycobacterium tuberculosis isolates: A multicenter study.

Effective control of tuberculosis is achieved by early diagnosis and drug susceptibility testing for initiation of appropriate treatment. The performance of crystal violet decolorization assay (CVDA) for susceptibility testing of Mycobacterium tuberculosis to isoniazid (INH) and rifampicin (RIF) was compared in a multicenter study. Seventy-two M. tuberculosis isolates were tested in two phases by CVDA. In Phase I, the specificity, sensitivity, positive predictive value (PPV), negative predictive value (NPV), and agreement for INH were 100%, respectively. Specificity, sensitivity, PPV, NPV, and agreement for RIF were 98.2%, 100%, 94.1%, 100%, and 98.6%, respectively. In Phase II, specificity, sensitivity, PPV, NPV, and agreement were 98%, 100%, 95.4%, 100%, and 98.6% for INH, respectively. Specificity, sensitivity, PPV, NPV, and agreement for RIF were 96.3%, 88.2%, 88.2%, 96.3%, and 94.4%, respectively. Results in the study were obtained on average 10.9 ± 3.1 days in Phase I and 9.8 ± 2.2 days in Phase II. CVDA can be performed for drug susceptibility testing in developed and developing countries. In addition, further studies with larger sample size are needed for evaluation of this method.