Red HE-3B Research Articles

Biomineralization induced synthesis and self-assembly of photocatalyst-enzyme hybrid system for highly efficient environmental remediation

The photocatalyst-enzyme hybrid systems (PEHSs) provided a promising method for environmental remediation by simultaneously harnessing the power of solar-energy conversion and biocatalysis. However, the use of PEHSs for environmental remediation was restricted by a complicated synthesis and assembly process. This work explored a simple one-pot biomineralization approach to fabricate PEHS. It was found that the cytochrome enzyme could be directly self-assembled onto the biosynthesized CdS during biomineralization by Shewanella oneidensis MR-1. More strikingly, those attached cytochrome enzymes could efficiently receive the photoelectrons from the CdS and serve as the photoreduction center which formed a typical PEHS. Impressively, this bio-CdS-cytochrome PEHS exhibited an extremely high photocatalytic decolorization rate of 69.4 mg/g/min, which was the highest record ever reported for procion red H-E3B. This work provided a simple and facile approach for PEHSs fabrication, which would be promising for practical application in environmental remediation.

Saccharomyces pastorianus Residual Biomass Immobilized in a Polymer Matrix as a Biosorbent for Reactive Dye Removal: Investigations in a Dynamic System.

The use of residual microbial biomass from various industries in emerging pollutant removal strategies represents a new area of research in the field. In this case, we examined how to remove reactive dyes from an aqueous solution utilizing a biosorbent made of residual biomass from immobilized Saccharomyces pastorianus (S. pastorianus) in a polymer matrix using a dynamic system. Fluidized bed column biosorption investigations were carried out on a laboratory scale. Brilliant Red HE-3B was chosen as the target molecule. The main parameters considered for this purpose were the flow rate (4.0 mL/min; 6.1 mL/min), initial pollutant concentration (51.2 mg/L; 77.84 mg/L), and biosorbent mass (16 g; 20 g). The experimental data of the fluidized bed study were evaluated by mathematical modeling. The Yoon-Nelson, Bohart-Adams, Clark, and Yan models were investigated for an appropriate correlation with the experimental data. An acceptable fit was obtained for a flow rate of 4 mL/min, an initial pollutant concentration of 51.2 mg/L, and a biosorbent amount of 20 g. The obtained results indicate that the biosorbent can be used efficiently in a dynamic system both for the removal of the studied dye and in extended operations with a continuous flow of wastewater. As a conclusion, the investigated biocomposite material can be considered a viable biosorbent for testing in the removal of reactive dyes from aqueous environments and creates the necessary conditions for the extension of studies toward the application of these types of biosorbents in the treatment of industrial effluents loaded with organic dyes.

Statistical Analysis and Optimization of the Brilliant Red HE-3B Dye Biosorption onto a Biosorbent Based on Residual Biomass.

Using various techniques, natural polymers can be successfully used as a matrix to immobilize a residual microbial biomass in a form that is easy to handle, namely biosorbents, and which is capable of retaining chemical species from polluted aqueous media. The biosorption process of reactive Brilliant Red HE-3B dye on a new type of biosorbent, based on a residual microbial biomass of Saccharomyces pastorianus immobilized in sodium alginate, was studied using mathematical modeling of experimental data obtained under certain conditions. Different methods, such as computer-assisted statistical analysis, were applied, considering all independent and dependent variables involved in the reactive dye biosorption process. The optimal values achieved were compared, and the experimental data supported the possibility of using the immobilized residual biomass as a biosorbent for the studied reference dye. The results were sufficient to perform dye removals higher than 70–85% in an aqueous solution containing around 45–50 mg/L of reactive dye, and working with more than 20–22 g/L of prepared immobilized microbial biosorbent for more than 9.5–10 h. Furthermore, the proposed models agreed with the experimental data and permitted the prediction of the dye biosorption behavior in the experimental variation field of each independent variable.

Empirical Modeling and Optimization by Active Central Composite Rotatable Design: Brilliant Red HE-3B Dye Biosorption onto Residual Yeast Biomass-Based Biosorbents

(1) Introduction: Natural polymers can be successfully used as a matrix to immobilize residual yeast-based biomass in a form that is easy to handle and can be used as biosorbent capable of removing persistent polluting species from different aqueous systems such as reactive azo dyes. (2) Experimental: Two types of new biosorbents were prepared based on residual Saccharomyces pastorianus yeast biomass immobilized in sodium alginate (using two different practice techniques) and studied in the biosorption process of reactive Brilliant Red HE-3B dye using certain experimental planning matrices according to the active central composite rotatable design of 23 order. The experimental data obtained under certain selected working conditions were processed considering the influence of three independent variables (biosorbent concentration—X1, initial dye concentration—X2 and biosorption time—X3) onto the dependent variable (Y = f(X1,X2,X3)) expressing the performance of reactive dye biosorption onto the new prepared biosorbents (i.e., dye removal degree, %). (3) Results: Two mathematical models were proposed for each prepared biosorbent. The maximum dye removal was 52.878% (Y1) when 18 g/L biosorbent 1 (micro-encapsulated form) was applied in 70 mg/L dye-containing solution for at least 8 h, and 75.338% (Y2) for 22.109 g/L biosorbent 2 (immobilized form) in 48.49 mg/L dye-containing solution for at least 8.799 h. (4) Discussion: The optimal values achieved for the two tested biosorbents were compared, and we investigated the possibility of using this residual biomass as a biosorbent for the reactive dye removal, supported by the experimental results with the recommended variation domains of each influencing variable. The results are sufficient to permit performing dye removal higher than 50% (biosorbent 1) or 70% (biosorbent 2), working with more than 18–22 g/L biosorbent after at least 8 h (as an exchange at work). (5) Conclusions: The proposed models are in good agreement with the experimental data and permit the prediction of dye biosorption behavior onto the experimental variation domain of each independent variable.

Polysaccharides Used in Biosorbents Preparation for Organic Dyes Retaining from Aqueous Media.

Natural polymers can themselves be efficient as materials with biosorptive properties but can also be used to transform microbial biomass into an easy-to-handle form, respectively, into biosorbents, through immobilization. The article aims to study biosorbents based on residual microbial biomass (Saccharomyces pastorianus yeast, separated after the brewing process by centrifugation and dried at 80 °C) immobilized in sodium alginate. The biosorptive properties of this type of biosorbent (spherical particles 2 and 4 mm in diameter) were studied for removal of reactive dye Brilliant Red HE-3B (with concentration in range of 16.88–174.08 mg/L) from aqueous media. The paper aims at three aspects: (i) the physico-chemical characterization of the biosorbent (Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared (FTIR) spectra); (ii) the modeling of biosorption data in order to calculate the quantitative characteristic parameters using three equilibrium isotherms (Langmuir, Freundlich, and Dubinin–Radushkevich—DR); and (iii) the evaluation of thermal effect and the possible mechanism of action. The results of the study showed that biosorption capacity evaluated by Langmuir (I) model is 222.22 mg/g (ϕ = 2 mm) and 151.51 mg/g (ϕ = 4 mm) at 30 °C, and the free energy of biosorption (E) is in the range of 8.45–13.608 KJ/mol (from the DR equation). The values of thermodynamic parameters suggested an exothermic process due the negative value of free Gibbs energy (ΔG0 = −9.031 kJ/mol till −3.776 kJ/mol) and enthalpy (about ΔH0 = −87.795 KJ/mol). The obtained results underline our finding that the immobilization in sodium alginate of the residual microbial biomass of Saccharomyces pastorianus led to an efficient biosorbent useful in static operating system in the case of effluents with moderate concentrations of organic dyes.

Biodegradation of Carcinogenic Reactive Azo Dyes by Indigenous Bacterial Consortium X5RC5

Reactive azo dyes are considered as a major source of water and soil contamination. Carcinogenicity and the recalcitrant nature of these dyes is a worldwide problem. Exclusion of these dyes from the effluent is necessary for a clean and green environment. A bacterial consortium X5RC5 was developed for the effective removal of two of the primary reactive azo dyes utilized widely in textile industries (reactive orange 3R and reactive red HE7B). The consortium includes two indigenous bacterial isolates, Lysinibacillus macroides and Stenotrophomonas acidaminiphila, from textile effluent. The X5RC5 completely degraded the reactive orange 3R in 4 days and reactive red HE7B in 5 days of incubation periods. In two days, more than 50% degradation was observed for both dyes. Biodegradation of these dyes was affirmed through the UV-Vis spectra and Fourier-transform infrared spectroscopy (FTIR) analysis. This investigation advances the utilization of consortium X5RC5 as a biological tool for the bio-handling of effluent containing dyes.

Composites Based on Natural Polymers and Microbial Biomass for Biosorption of Brilliant Red HE-3B Reactive Dye from Aqueous Solutions.

Natural polymers have proven to be extremely interesting matrices for the immobilization of microbial biomasses, via various mechanisms, in order to bring them into a form easier to handle—the form of composites. This article aimed to study composites based on a residual microbial biomass immobilized in sodium alginate via an encapsulation technique as materials with adsorbent properties. Thus, this study focused on the residual biomass resulting from beer production (Saccharomyces pastorianus yeast, separated after the biosynthesis process by centrifugation and dried at 80 °C)—an important source of valuable compounds, used either as a raw material or for transformation into final products with added value. Thus, the biosorptive potential of this type of composite was tested—presenting in the form of spherical microcapsules 900 and 1500 μm in diameter—in a biosorption process applied to aqueous solutions containing the reactive dye Brilliant Red HE-3B (16.88–174.08 mg/L), studied in a batch system. The preparation and characterization of the obtained polymeric composites (pHPZC, SEM, EDS and FTIR spectra) and an analysis of different equilibrium isotherms (Langmuir, Freundlich and Dubinin-Radushkevich—D–R) were investigated in order to estimate the quantitative characteristic parameters of the biosorption process, its thermal effects, and its possible mechanisms of action. The modelling of the experimental data led to the conclusion that the studied biosorption process took place after reaching the Langmuir isotherm (LI), and that the main mechanism was possibly physical, being spontaneous and probably exothermic according to the values obtained for the free energy of biosorption (E = 8.45–13.608 kJ/mol, from the DR equation), as well as the negative values for the Gibbs free energy and the enthalpy of biosorption (ΔH0 = −87.795 kJ/mol). The results obtained lead to the conclusion that encapsulation of this residual microbial biomass in sodium alginate leads to an easier-to-handle form of biomass, thus being an efficient biosorbent for static or dynamic operating systems for effluents containing moderate concentrations of reactive organic dyes.

UTILIZATION OF WATER HYACINTH FOR DYE EFFLUENT PURIFICATION

Water hyacinth (Eichhornia crassipes) (WH) is an invasive plant floating freely on the water, which is widely spread in tropical and subtropical regions. The plant is characterized by high porosity and a high number of functional groups, such as hydroxyl (-OH), carboxyl (–COOH), and amino groups (–NH2). Activated carbon, which is widely accepted on an industrial level for the adsorption of dyes from wastewaters, is a highly expensive material. Thus, in this research, a bioadsorbent material was prepared based on WH biomass and investigated as an alternative tool for water quality remediation, in the case of dye pollutants (RR HE3B). The WH plants were collected from the nearby Lake Tana and used as an adsorbent material without chemical treatment. The batch adsorption test was performed by varying the pH of the solution, adsorbent dosage and initial dye concentration. The powdered WH and RR HE3B dye loaded WH were characterized using FTIR, revealing the emergence of new stretching vibration peaks in the range from 2800 to 3000 cm-1 on the spectrum of Reactive Red HE3B (RR HE3B) dye loaded WH, confirming that -CH and -CH2 were responsible for the adsorption. The analysis of the adsorption isotherm and of the suitability of different models for describing it has led to the following order: Freundlich > Langmuir > Temkin > Dubinin-Radushkevich, based on their correlation coefficient value. This implies that the WH adsorbent surface is heterogeneous and the adsorption of the dye onto it depends not only on the specific reaction sites, as the n-value of the Freundlich constant confirms that the physical adsorption process might be favored. Therefore, WH could be a potential alternative adsorbent to remove the RR HE3B dye from dye polluted wastewaters.

Mycoremediation of reactive red HE7B dye by Aspergillus salinarus isolated from textile effluents.

Reactive dyes are widely utilized in the textile industry due to their advantageous properties of vivid color, water-fastness, and simple application procedures with minimal energy usage. The toxicity of most azo dyes is a significant environmental concern, as effluents from dye processing and manufacturing sectors are known to be carcinogenic and mutagenic to numerous species. These issues are more grievous in Bangladesh, one of the largest exporters of apparel. This study aimed to isolate and identify potential fungal strains from textile effluent that are capable of degrading Reactive Red HE7B dye (a sulphonated reactive azo dye), a widely used dye in local thread dyeing industries. Dye degradation assay was performed in potato dextrose broth supplemented with 50 mg/l Reactive Red HE7B and the degradation rate was measured by a UV spectrophotometer. DNA extraction, quantification, PCR, internal transcribed spacer (ITS) sequencing, and phylogenetic analysis were performed to identify the selected fungi. Among the isolates, the three best performing strains TEF -3, TEF -4, and TEF -5 showed 97.41%, 93.12%, and 82.89% dye degrading efficacy after 96 h of incubation, respectively. All three strains, TEF-3, TEF-4, and TEF-5 showed similarity with Aspergillus salinarus (accession no. NR_157473.1) and the similarity percentages were 97.02, 96.95, and 95.28 respectively. Interestingly, this study probably the very first indication of textile dye degradation by Aspergillus salinarus strains. Thus, these fungal strains possess the prospectiveness to be utilized in the textile wastewater treatment plants, since the isolates demonstrated the substantial capacity (>80%) to degrade Reactive Red dye after 96 h of incubation.

Brilliant Red HE-3B Dye Biosorption by Immobilized Residual Consortium Bacillus sp. Biomass: Fixed-Bed Column Studies

Residual biomass from various industries represents an important source of valuable compounds, used as raw materials for the production of a wide range of new products and also in various treatment and valorization processes or/and sanitation services, thus responding to the principles of sustainable development, waste recovery, and a green and circular economy. The aim of this work is to make use of residual Bacillus sp. biomass (resulting from a process of removing fatty acids from municipal wastewater) immobilized in alginate that, although it results in large quantities from biotechnological processes, is not reported to be valorized in dye biosorption processes, except in few specific applications. The biosorption potential of residual Bacillus sp. biomass in the reactive Brilliant Red HE-3B textile dye removal from aqueous systems was studied in a fixed-bed column. The effects of various experimental operating parameters, such as bed depth (h), flow rate (Fv), were investigated, and the modeling of experimental data based on Thomas and Yoon–Nelson kinetic models was satisfactorily achieved. The obtained results reconfirm that the studied residual biomass can be also considered as a good biosorbent in dynamic operating system, and can be beneficially used in the treatment of wastewater containing small quantities of organic dyes.

Salt free dyeing properties of cotton fabrics grafted with ε-polylysine(ε-PL)

ABSTRACT Cotton fabric was chemically modified with ε-Poly-L-lysine (ε-PL), which contains abundant imino groups and primary amino groups. ε-PL was grafted onto cotton fabric by a reaction between aldehyde groups of oxidized cellulose and amino groups of ε-PL. FT-IR of grafted cotton fabrics was researched and it demonstrated the covalent bonds combination between ε-PL and cellulose fibers. Zeta potential of cotton fabrics grafted with ε-PL was positive when pH was lower than 7.5. Dyeing properties of modified cotton fabrics were investigated. Exhaustion rate and fixation rate of reactive dyes on modified cotton fabrics with a salt-free dyeing process were higher than those of unmodified cotton fabrics with a conventional dyeing process. Compared with that of the unmodified cotton fabrics, the washing fastness, rubbing fastness, and leveling properties of the modified cotton fabrics were also good. The dyeing behavior of Procion Red H-E3B on modified cotton fabric was examined and found to follow a Langmuir-type adsorption curve. It is concluded that ε-PL could be used as a salt-free auxiliary in reactive dyeing on cotton fabrics.

Sustainable pilot scale reactive dyeing based on silicone oil for improving dye fixation and reducing discharges

The textile dyeing industry has been under the increasing pressure from liberalized economic regime and environmental protection. To alleviate the pressure, nonaqueous dyeing technology has been extensively investigated for improving dye fixation and reducing effluent discharge. In this investigation, a pilot scale dyeing of cotton with high temperature reactive dye Procion Red in silicone oil nonaqueous dyeing system was studied. When the amount of dye is the same, the color depth of dyed cotton fiber and the fixation of dye in the silicone non-aqueous dyeing system are higher than that of the traditional water based dyeing system. When the K/S value of dyed sample is same, silicone and water based dyeing system required initial dye is 2.0% and 4.9% on weight of fiber, respectively. Compared with the traditional water based dyeing, the water consumption and wastewater treatment are only 20% of the traditional water based dyeing system. The higher fixation of reactive dyes not only saves water consumption, but also reduces the consumption of dyes, alkalis and other chemicals by 41%. Moreover, the loss of the silicone nonaqueous medium is controlled within 2%. The hydrolytic reaction energy gap of reactive dye with density functional theory was investigated in silicone nonaqueous medium and traditional water based dyeing system. It was found that the hydrolytic reaction energy of the Procion Red H-E3B in an alkaline environment is much lower than that in a pure aqueous environment. The higher hydrolytic reaction energy of reactive dye in the silicone nonaqueous medium dyeing system proves that why reactive dye can keep a long reactivity during the dyeing. The success of the pilot-scale silicone nonaqueous medium dyeing system shows that this dyeing technology will change the current conventional water dyeing in terms of the huge amount of water consumption and the serious issue of wastewater pollution.

Valorizing lignin-like dyes and textile dyeing wastewater by a newly constructed lipid-producing and lignin modifying oleaginous yeast consortium valued for biodiesel and bioremediation

Construction of a multipurpose yeast consortium suitable for lipid production, textile dye/effluent removal and lignin valorization is critical for both biorefinery and bioremediation. Therefore, a novel oleaginous consortium, designated as OYC-Y.BC.SH has been developed using three yeast cultures viz. Yarrowia sp. SSA1642, Barnettozyma californica SSA1518 and Sterigmatomyces halophilus SSA1511. The OYC-Y.BC.SH was able to grow on different carbon sources and accumulate lipids, with its highest lipid productivity (1.56 g/L/day) and lipase activity (170.3 U/mL) exhibited in xylose. The total saturated fatty acid content was 36.09 %, while the mono-unsaturated and poly-unsaturated fatty acids were 45.44 and 18.30 %, respectively, making OYC-Y.BC.SH valuable for biodiesel production. The OYC-Y.BC.SH showed its highest decolorization efficiency of Red HE3B dye (above 82 %) in presence of sorghum husk as agricultural co-substrate, suggesting its feasibility for simultaneous lignin valorization. The significant higher performance of OYC-Y.BC.SH on decolorizing the real dyeing effluent sample at pH 8.0 suggests its potential and suitability for degrading most of the wastewater textile effluents. Clearly, toxicological studies underline the additional advantage of using OYC-Y.BC.SH for bioremediation of industrial dyeing effluents in terms of decolorization and detoxification. A possible mechanism of Red HE3B biodegradation and ATP synthesis was also proposed.

Electrochemical preparation of Nb2O5 nanochannel photoelectrodes for enhanced photoelectrocatalytic performance in removal of RR120 dye

The present work describes the synthesis of niobium oxide nanochannels (Nb2O5NCs) with high surface area, porosity, photocurrent density, and photoelectrochemical stability as photocatalyst. The Nb2O5NCs were prepared by electrochemical anodization of niobium foil in different electrolytes: 1 M H2SO4 containing 0.4 wt% HF (S1); glycerol containing 0.4 M NH4F (S2); 0.25 g NH4F with 4 vol% water in glycol at 50 °C (S3); and glycerol containing 10 wt% K2HPO4, at 130 °C (S4, annealed in air; S5, annealed in N2). All the Nb2O5NCs showed well-organized arrays of nanochannels grown on the Nb foil, with tube diameters in the order S4<S2<S1<S3 and film thicknesses in the order S1<S2<S3<S4, as determined using FEG-SEM analyses. The samples were also characterized using XRD, EDX, DRS, XPS, EIS, Mott-Schottky analysis, and LSV curves. But, best results were obtained only when phosphorus (about 1% doping) was incorporated into the electrodes samples prepared in glycerol containing 10 wt% K2HPO4 at 130 °C (i.e. S4 and S5). This procedure enhances the absorption intensity in the UV–Vis regions, the conductivity, the charge carrier density, and the photocurrent density. The Nb2O5NC sample S5 was tested for the degradation of Procion Red HE-3B (RR120) dye, as a model pollutant, achieving efficient photoelectrodegradation with nearly 2 times higher mineralization efficiency compared to photolysis (PT) and photocatalysis (PC). Thus, the results indicate that the modification of Nb2O5NC thin film photoelectrodes by phosphorous doping can be a powerful and efficient alternative to usual approaches applied to the treatment of complex reactive dyes.

Molecular identification of dye degrading bacterial isolates and FT-IR analysis of degraded products

In the present study, dye decolorizing bacteria were isolated from water and soil samples, collected from textile industries in Jodhpur province, India. Two bacterial species namely, &lt;i&gt;Bacillus pumilis&lt;/i&gt; and &lt;i&gt;Paenibacillus thiaminolyticus&lt;/i&gt; were screened and identified based on biochemical characterization. The degradation efficiency of these two microorganisms was compared through optimization of pH, incubation time, initial dye concentration and inoculum size. &lt;i&gt;B. pumilis&lt;/i&gt; and &lt;i&gt;P. thiominolyticus&lt;/i&gt; were able to degrade 61% and 67% Red HE3B, 81% and 75% Orange F2R, 49.7% and 44.2% Yellow ME4GL and 61.6% and 59.5% Blue RC CT dyes of 800mg/l concentration respectively. The optimum pH and time were found to be 8 within 24 hours. The FT-IR analysis confirmed that microorganisms were able to degrade toxic azo dyes into a non-toxic product as proved through structural modifications to analyze chemical functions in materials by detecting the vibrations that characterize chemical bonds. It is based on the absorption of infrared radiation by the microbial product. Therefore, &lt;i&gt;Bacillus pumilis&lt;/i&gt; and &lt;i&gt;Paenibacillus thiaminolyticus&lt;/i&gt; are a promising tool for decolorization of dyes due to its potential to effectively decolorize higher azo dye concentrations (10-800 mg/L) and can be exploited for bioremediation.

Development of activated carbon from Nerium oleander flower and their rapid adsorption of direct and reactive dyes

ABSTRACTThe present study investigates the thermally activated carbon derived from Nerium oleander flower which was used an adsorbent. Physicochemical properties of Nerium oleander flower carbon (NOFC) were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared for the removal of DTB (Direct Turquoise Blue) and RR-HE7B (Reactive red–HE7B) dyes from aqueous solution. Adsorption studies were carried out with different pH, adsorbent dose, contact time, and initial concentration dye solution. Optimum conditions for maximum removal of DTB and RR-HE7B was achieved to be pH 2 for both dyes, adsorbent dose of 100 mg and equilibrium time of 35 and 60 min, respectively, for NOFC. The maximum adsorption capacity of NOFC was found to be 33.33 and 19.60 mg g−1, respectively, for the removal of dye solution. The mechanism of adsorption was studied by using different kinetic models and isotherms. The results clearly showed that the NOFC adsorption was fitted to pseudo–first-order for DTB and pseudo–second-order for RR-HE7B. Equilibrium data were well fitted with both isotherm models. According to the results, NOFC can effectively remove DTB and RR-HE7B from aqueous solutions.

The Dyeing Properties of Woody Fiber Regenerated from Waste MDF by Reactive Dyes

This study aims to review the relations between the dyeing conditions (i.e., dye concentration, addition amounts of salt and alkali, and dyeing temperature) and dyeing properties and color fastness to light for identifying the optimal dyeing conditions when dyed regenerated woody fibers were obtained through the defibration of waste medium density fiberboard (MDF) using reactive Red H-E3B (Bis-monochlorotriazine (MCT)/MCT type) and reactive Red RB133% (Bis-MCT/Vinyl sulphone type). The dyeing yield (K/S) obtained using two types of reactive dyes increased as the dye concentration increased by 1–10% (on the weight of fiber (OWF)). In addition, the K/S of H-E3B was higher than that of RB133% irrespective of the dye concentration. The color difference of H-E3B after ultraviolet (UV) radiation was lower than that of RB133%, denoting good resistance to discoloration by UV. As the amount of sodium sulfate increased, the color difference and K/S also increased, and the adequate salt content was determined to be 50–70 g/L. Further, the color difference and K/S significantly increased only the addition of 2 g/L of sodium carbonate; however, almost no difference was observed when more than 2 g/L of sodium carbonate was added. The addition amount of sodium carbonate was adequate 5–10 g/L to dyeing the fiber and the pH at this addition level was 10. The dyeing yield of H-E3B increased when the dyeing temperature increased; however, it subsequently decreased after the dyeing temperature became 80°C. The dyeing yield of RB133% was almost the same up to 60–70°C but declined subsequently. Thus, the adequate temperatures were 80°C and 60°C for H-E3B and RB133%, respectively. If the waste MDF woody fiber was dyed under the aforementioned optimal conditions, dyed regenerated woody fiber can be obtained having the following colors: 1.5 to 2.0R with the H-E3B dye and 9.6 to 10.0 PR with RB133%.

Enzymatic analysis, structural study and molecular docking of laccase and catalase from B. subtilis SK1 after textile dye exposure

The textile dye decolorizing efficiency of Bacillus subtilis SK1 against 70 mg/L each of Malachite Green, Methyl Orange, Rubine GFL and Red HE3B was observed as 71.7, 73.6, 74.4 and 82.6%, respectively within 3 h. UV–Vis spectroscopy, GC–MS and HPTLC analysis confirmed mineralization of model dyes into its metabolites. Physico-chemical characterization confirmed acidic and hydrophilic nature of both laccase and catalase enzymes. Both enzymes contain dominant random coiled secondary structure (SOPMA tool) and intracellular location (CELLO_v.2.5), however, laccase alone contains two disulfide bridges (CYS_REC tool). The validation of constructed 3D structure (Modeller 9.19) of laccase and catalase enzymes revealed, RAMPAGE- 96.3 and 95.8% residues in favoured region, ProSA- Z score −8.2 and −9.6, respectively and ERRAT-Overall quality factor > 68. Potential energies −1.328 × 106 kJ/mol and −2.685 × 106 kJ/mol remained constant after 1395 and 1545 steps for laccase and catalase, respectively in energy minimization. Molecular docking results showed interaction of Methyl Orange with laccase (Thr260) and catalase (Lys 48), Rubine GFL with laccase (Thr 262) and catalase (His 176) and Red HE3B with laccase (Asn 264, Thr 418, Gly 321, Thr 262 and Gly 378) and catalase (Gln 258). This study provides dye degrading potential of Bacillus subtilis strain SK1 with structurally different textile dyes and vital role of the polar amino acids of laccase and catalase in these interactions.

Optimization of Factors Affecting Decolourization of Sulphonated Azo Dye Red HE7b in vitro by bacillus Sp. Azo1

A zo dyes are widely used organic molecules that are generally recalcitrant to biodegradation, thus causing environmental pollution. In this study, the effect of various growth conditions like temperature, pH, dye concentration, aeration and presence/absence of co-substrate on decolourization of azo dye Red HE7B by Bacillus sp. Azo1 has been determined. Decolourization of the dye was achieved under static condition. Optimum decolourization of Red HE7B was observed at 30°C and 50 mg/l dye concentration, where more than 90% decolourization was achieved within three days of inoculation. Bacillus sp. Azo1 could decolourize the dye through a range of pH values from 6 to 9. Presence of co-substrate limited the decolourization with glucose being the most potential inhibitor. Identification of factors influencing decolourization will help in rapid removal of these pollutants from contaminated habitat.

Alkaline textile wastewater biotreatment: A sulfate-reducing granular sludge based lab-scale study

In this study the feasibility of treating dyeing wastewater with sulfate reducing granular sludge was explored, focusing on decolorization/degradation of azo dye (Procion Red HE-7B) and the performance of microbial consortia under alkaline conditions (pH=11). Efficiency of HE-7B degradation was influenced strongly by the chemical oxygen demand (COD) concentration which was examined in the range of 500–3000mg/L. COD removal efficiency was reduced at high COD concentration, while specific removal rate was enhanced to 17.5 mg-COD/gVSSh−1. HE-7B removal was also improved at higher organic strength with more than 90% removal efficiency and a first-rate removal constant of 5.57h−1 for dye degradation. Three dye-degradation metabolites were identified by HPLC–MS. The granular structure provided enhanced removal performance for HE-7B and COD in comparison to a near-identical floc SRB system and the key functional organisms were identified by high throughput sequencing. This study demonstrates an example of a niche application where SRB granules can be applied for high efficient and cost-effective treatment of a wastewater under adverse environmental conditions.