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

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

Decolorization and degradation of crystal violet dye by electron beam radiation: Performance, degradation pathways, and synergetic effect with peroxymonosulfate.

Ionizing radiation (mainly including gamma ray and electron beam) technology provides a more efficient and ecological option for dye-containing wastewater treatment, which is supported by its successful achievements in industrial-scale applications. However, the degradation pathway of triphenylmethane dyes by radiation technology is still unclear. In this study, crystal violet (CV) was selected as representative cationic triphenylmethane dye, the decolorization and degradation performance by electron beam radiation technology was systematically evaluated. The results showed that CV can be efficiently decolorized and mineralized by radiation, and its degradation kinetics followed the first-order kinetic model. The effect of inorganic anions and chelating agents commonly existed in dye-containing wastewater on CV decolorization and total organic carbon (TOC) removal was explored. Quenching experiments, density functional theory (DFT) calculation and high performance liquid chromatography mass spectrometry (HPLC-MS) analysis were employed to reveal CV decolorization and degradation mechanism and pathway, which mainly included N-demethylation, triphenylmethane chromophore cleavage, ring-opening of aromatic products and further oxidation to carboxylic acid, and mineralization to CO2 and H2O. Additionally, electron beam radiation/PMS process was explored to decrease the absorbed dose required for decolorization and degradation, and the synergetic effect of radiation with PMS was elucidated. More importantly, the findings of this study would provide the support for treating actual dyeing wastewater by electron beam radiation technology.

A hybrid electrocoagulation-biocomposite adsorption system for the decolourization of dye wastewater.

Among the various methods for the removal of azo dye, electrocoagulation is recognized to be highly efficient. However, the process is associated with high operation and maintenance cost, which demands the need for reducing the electrolysis time without compromising the performance efficiency. This can be achieved by adopting hybrid electrocoagulation process with a low-cost but effective process, such as adsorption. The study investigated the performance of a hybrid electrocoagulation-biocomposite system (H-EC-BC) for removing methyl orange dye. Firstly, the operating parameters of electrocoagulation process were optimized and a removal efficiency of 99% has been attained using Fe-SS electrodes at a pH of 6 for a reaction time of 30 min. The performance of EC process was found to be decreasing with increase in dye concentration. Secondly, biocomposite was synthesized from Psidium guajava leaves and characterized using SEM, FTIR, EDAX, and XRD analyses. The results suggested that it is having a porous nature and cellulose crystal structure and confirmed the presence of chemical elements such as carbon (65.2%), oxygen (29.1%) as primary with Fe, Cl, Na and Ca as secondary elements. The performance of the biocomposite was evaluated for the dye adsorption using spectrophotometric methods. Various operating parameters were optimized using experimental methods and a maximum removal efficiency of 65% was achieved at a pH of 6, dosage of 5 g/L and an adsorption contact time of 120 min. The maximum efficiency (92.78%) was obtained with Fe-SS electrodes and KCl as a sustaining electrolyte under acidic circumstances (pH 6). The biocomposite was observed to be more efficient for higher dye concentration. Langmuir and Freundlich adsorption isotherms were fitted with the experimental results with R2 values as 0.926 and 0.980 respectively. The adsorption kinetics were described using Pseudo-first and Pseudo-second order models, wherein Pseudo-second order model fits the experimental results with R2 value of 0.999. The energy consumption of electrocoagulation (EC) process in the hybrid H-EC-BC system was compared to that of a standard EC process. The results demonstrated that the hybrid system is approximately 7 times more energy efficient than the conventional process, thereby implicating its adaptability for field application.

New insights on the decolorization of waste flows by Saccharomyces cerevisiae strain - A systematic review.

One of the common causes of water pollution is the presence of toxic dye-based effluents, which can pose a serious threat to the ecosystem and human health. The application of Saccharomyces cerevisiae (S. cerevisiae) for wastewater decolorization has been widely investigated due to their efficient removal and eco-friendly treatments. This review attempts to create an awareness of different forms and methods of using Saccharomyces cerevisiae (S. cerevisiae) for wastewater decolorization through a systematic approach. Overall, some suggestions on classification of dyes and related environmental/health problems, and treatment methods are discussed. Besides, the mechanisms of dye removal by S. cerevisiae including biosorption, bioaccumulation, and biodegradation and cell immobilization methods such as adsorption, covalent binding, encapsulation, entrapment, and self-aggregation are discussed. This review would help to inspire the exploration of more creative methods for applications and modification of S. cerevisiae and its further practical applications.

Physiological and transcriptome profiling of Chlorella sorokiniana: A study on azo dye wastewater decolorization.

Over decades, synthetic dyes have become increasingly dominated by azo dyes posing a significant environmental risk due to their toxicity. Microalgae-based systems may offer an alternative for treatment of azo dye effluents to conventional physical-chemical methods. Here, microalgae were tested to decolorize industrial azo dye wastewater (ADW). Chlorella sorokiniana showed the highest decolorization efficiency in a preliminary screening test. Subsequently, the optimization of the experimental design resulted in 70% decolorization in a photobioreactor. Tolerance of this strain was evidenced using multiple approaches (growth and chlorophyll content assays, scanning electron microscopy (SEM), and antioxidant level measurements). Raman microspectroscopy was employed for the quantification of ADW-specific compounds accumulated by the microalgal biomass. Finally, RNA-seq revealed the transcriptome profile of C. sorokiniana exposed to ADW for 72 h. Activated DNA repair and primary metabolism provided sufficient energy for microalgal growth to overcome the adverse toxic conditions. Furthermore, several transporter genes, oxidoreductases-, and glycosyltransferases-encoding genes were upregulated to effectively sequestrate and detoxify the ADW. This work demonstrates the potential utilization of C. sorokiniana as a tolerant strain for industrial wastewater treatment, emphasizing the regulation of its molecular mechanisms to cope with unfavorable growth conditions.

Preparation of sisal fiber/polyaniline/bio-surfactant rhamnolipid-layered double hydroxide nanocomposite for water decolorization: kinetic, equilibrium, and thermodynamic studies.

Sisal fiber is a potent economical biomaterial for designing composites because of its low density, high specific strength, no toxic effects, and renewability. The present study utilized sisal fiber as a starting material and subjected it to modification to produce a sisal fiber/polyaniline/bio-surfactant rhamnolipid-layered double hydroxide nanocomposite material denoted as SF@PANI@LDH@RL. The composite was evaluated for its efficacy in removing reactive orange 16 (RO16) and methylene blue (MB) from aqueous solutions. The synthesized adsorbent was characterized by FTIR, XRD, and SEM-EDS techniques; these analyses indicated the successful modification of the sisal fiber. The primary factors, including contact time, adsorbent dosage, dye concentration, temperature, and pH, were optimized for achieving the most excellent adsorption efficiency. On the one hand, methylene blue removal is enhanced in the basic solution (pH = 10). On the other hand, reactive orange 16 adsorption was favored in the acidic solution (pH = 3). The highest adsorption capacities for methylene blue and reactive orange 16 were 24.813 and 23.981 mg/g at 318 K, respectively. The Temkin isotherm model, which proves the adsorption procedure of methylene blue and reactive orange 16 could be regarded as a chemisorption procedure, supplies the most suitable explanation for the adsorption of methylene blue (R2 = 0.983) and reactive orange 16 (R2 = 0.996). Furthermore, Elovich is the best-fitting kinetic model for both dyes (R2 = 0.986 for MB and R2 = 0.987 for RO16). The recommended SF@PANI@LDH@RL adsorbent was reused six consecutive times and showed stable adsorption performance. The results demonstrate that SF@PANI@LDH@RL is a perfect adsorbent for eliminating cationic and anionic organic dyes from aqueous media.

Low-cost treated lignocellulosic biomass waste supported with FeCl3/Zn(NO3)2 for water decolorization.

Dye pollution has always been a serious concern globally, threatening the lives of humans and the ecosystem. In the current study, treated lignocellulosic biomass waste supported with FeCl3/Zn(NO3)2 was utilized as an effective composite for removing Reactive Orange 16 (RO16). SEM/EDAX, FTIR, and XRD analyses exhibited that the prepared material was successfully synthesized. The removal efficiency of 99.1% was found at an equilibrium time of 110 min and dye concentration of 5 mg L-1 Adsorbent mass of 30 mg resulted in the maximum dye elimination, and the efficiency of the process decreased by increasing the temperature from 25 to 40 °C. The effect of pH revealed that optimum pH was occurred at acidic media, having the maximum dye removal of greater than 90%. The kinetic and isotherm models revealed that RO16 elimination followed pseudo-second-order (R2 = 0.9982) and Freundlich (R2 = 0.9758) assumptions. Surprisingly, the performance of modified sawdust was 15.5 times better than the raw sawdust for the dye removal. In conclusion, lignocellulosic sawdust-Fe/Zn composite is promising for dye removal.

Regenerated Silk Nanofibers for Robust and Cyclic Adsorption-Desorption on Anionic Dyes.

In recent years, adsorption-based membranes have been widely investigated to remove and separate textile pollutants. However, cyclic adsorption-desorption to reuse a single adsorbent and clear scientific evidence for the adsorption-desorption mechanism remains challenging. Herein, silk nanofibers were used to assess the adsorption potential for the typical anionic dyes from an aqueous medium, and they show great potential toward the removal of acid dyes from the aqueous solution with an adsorption rate of ∼98% in a 1 min interaction. Further, we measured the filtration proficiency of a silk nanofiber membrane in order to propose a continuous mechanism for the removal of acid blue dye, and a complete rejection was observed with a maximum permeability rate of ∼360 ± 5 L·m-2·h-1. The Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy studies demonstrate that this fast adsorption occurs due to multiple interactions between the dye molecule and the adsorbent substrate. The as-prepared material also shows remarkable results in desorption. A 50-time cycle exhibits complete adsorption and desorption ability, which not only facilitates high removal aptitude but also produces less solid waste than other conventional adsorbents. Additionally, fluorescent 2-bromo-2-methyl-propionic acid (abbreviated as EtOxPY)-silk nanofibers can facilitate to illustrate a clear adsorption and desorption mechanism. Therefore, the above-prescribed results make electrospun silk nanofibers a suitable choice for removing anionic dyes in real-time applications.

Annotation of chemotaxis gene clusters and proteins involved in chemotaxis of Bacillus subtilis strain MB378 capable of biodecolorizing different dyes.

This study explores the chemotactic potential of Bacillus subtilis MB378 against industrial dyes. Initial screening with swim plate assay showed significant movement of Bacillus subtilis MB378 towards test compounds. According to quantitative capillary assay, B. subtilis MB378 exhibited high chemotaxis potential towards Acid Orange 52 (CI: 9.52), followed by Direct Red 28 (CI: 8.39) and Basic Green 4 (CI: 5.21) in glucose-supplemented medium. Sequencing and gene annotation results evidently showed presence of chemotaxis genes and flagellar motor proteins in Bacillus subtilis draft genome. Methyl-accepting proteins (involved in chemotaxis regulation) belonged to pfam00672, pfam00072, and pfam00015 protein families. Annotated chemotaxis machinery of MB378 comprised 8 Che genes, 5 chemoreceptor genes, associated flagellar proteins, and rotary motors. Chemotaxis genes of B. subtilis MB378 were compared with genes of closely related Bacillus strains (168, WK1, and HTA426), depicting highly conserved regions showing evolutionary relation between them. Considering results of present study, it can be speculated that test compounds triggered chemotactic genes, which made these compounds bioavailable to the bacterium. Hence, the bacterium recognized and approached these compounds and facilitated biodegradation and detoxification of these compounds.

Factors Influencing Decolourization and Detoxification of Remazol Brilliant Blue R Dye by Aspergillus flavus.

<b>Background and Objectives:</b> Anthraquinone synthetic dyes are widely used in textile, dyeing and paper painting. The discharge of these dyes into the environment causes detriment. The removal of physiochemical dyes is sometimes unsuccessful and expensive. Biological removal is inexpensive, eco-friendly and may break down organic contaminants. In the current work, a fungal technique was applied to decolorize and detoxify dye. <b>Materials and Methods:</b> Dye decolorizing fungi isolation, selection and identification of the most effective isolate and dye decolorization optimization based on carbon and nitrogen sources. In addition, the product's cytotoxicity and metabolites were tested. The enzyme activities were measured to determine dye decolorization. <b>Results:</b> Decolorization of reactive blue 19 dye by the most effective fungal strain isolate (5BF) isolated from industrial effluents were studied. This isolate was identified as <i>Aspergillus flavus</i> based on phenotypic characteristics and confirmed using 18S rRNA gene sequencing. Thin-layer chromatography indicated that this strain is aflatoxins free. Furthermore, metabolites produced from dye treatment with <i>A. flavus</i> were assessed using gas chromatography-mass spectrometry. Toxicity data revealed that <i>A. flavus</i> metabolites were not toxic to plants. Using a one-factor-at-a-time optimization technique, a maximum decolorization percentage (99%) was obtained after 72 hrs in the presence of mannitol and NH₄NO₃ or NH₄Cl as carbon and nitrogen sources. Two enzymes (laccase and manganese peroxidase) were shown to be active during dye decolorization by <i>A. flavus</i>. <b>Conclusion:</b> The <i>A. flavus</i> strain was shown to be safe when it came to removing dye from a synthetic medium with high efficiency and their metabolites had no negative influence on the environment. As a result, this strain will be used in the future for dye wastewater bioremediation.

In Vitro Heme Coordination of a Dye-Decolorizing Peroxidase-The Interplay of Key Amino Acids, pH, Buffer and Glycerol.

Dye-decolorizing peroxidases (DyPs) have gained interest for their ability to oxidize anthraquinone-derived dyes and lignin model compounds. Spectroscopic techniques, such as electron paramagnetic resonance and optical absorption spectroscopy, provide main tools to study how the enzymatic function is linked to the heme-pocket architecture, provided the experimental conditions are carefully chosen. Here, these techniques are used to investigate the effect of active site perturbations on the structure of ferric P-class DyP from Klebsiella pneumoniae (KpDyP) and three variants of the main distal residues (D143A, R232A and D143A/R232A). Arg-232 is found to be important for maintaining the heme distal architecture and essential to facilitate an alkaline transition. The latter is promoted in absence of Asp-143. Furthermore, the non-innocent effect of the buffer choice and addition of the cryoprotectant glycerol is shown. However, while unavoidable or indiscriminate experimental conditions are pitfalls, careful comparison of the effects of different exogenous molecules on the electronic structure and spin state of the heme iron contains information about the inherent flexibility of the heme pocket. The interplay between structural flexibility, key amino acids, pH, temperature, buffer and glycerol during in vitro spectroscopic studies is discussed with respect to the poor peroxidase activity of bacterial P-class DyPs.

A screening method for decoloration of xenobiotic dyes by fungi.

Wood degrading fungi are often screened for their ability to degrade xenobiotics such as dyes. Dye decoloration by these fungi on solid media could until now only be assessed qualitatively. We here describe a fast quantitative method to screen for dye decoloration on such media. Decoloration of crystal violet (CV), malachite green (MG), orange G (OG), rose bengal (RB) and remazol brilliant blue R (RBBR) by 124 isolates of the basidiomycete Schizophyllum commune was quantified with a flatbed scanner and the CIE-L*a*b* model. Colour and intensity changes were calculated with the Euclidean distance formula. More than 10 strains showed high MG decoloration. Isolates 136, 140 and 213 showed superior CV decoloration, while OG was most effectively decolorized by isolates 183, 216 and 227. Six strains showed high RB decoloration with isolate 216 being superior. The latter strain was also highly active on RBBR together with isolates 177 and 227. Together, dye decoloration was highly variable between the 124 isolates but strain 216 showed high activity on 3 out of 5 dyes. The fast screening method described in this paper enables identification of strains effectively decolorizing dyes.

Biotransformation of Reactive Red 141 by Paenibacillus terrigena KKW2-005 and Examination of Product Toxicity.

A total of 37 bacterial isolates were obtained from dye-contaminated soil samples at a textile processing factory in Nakhon Ratchasima Province, Thailand, and the potential of the isolates to decolorize and biotransform azo dye Reactive Red 141 (RR141) was investigated. The most potent bacterium was identified as Paenibacillus terrigena KKW2-005, which showed the ability to decolorize 96.45% of RR141 (50 mg/l) within 20 h under static conditions at pH 8.0 and a broad temperature range of 30-40°C. The biotransformation products were analyzed by using UV-Vis spectrophotometry and Fourier-transform infrared spectroscopy. Gas chromatography-mass spectroscopy analysis revealed four metabolites generated from the reductive biodegradation, namely sodium 3-diazenylnaphthalene-1,5-disulfonate (I), sodium naphthalene-2-sufonate (II), 4-chloro-1,3,5-triazin-2-amine (III) and N1-(1,3,5-triazin-2-yl) benzene-1,4-diamine (IV). Decolorization intermediates reduced phytotoxicity as compared with the untreated dye. However, they had phytotoxicity when compared with control, probably due to naphthalene and triazine derivatives. Moreover, genotoxicity testing by high annealing temperature-random amplified polymorphic DNA technique exhibited different DNA polymorphism bands in seedlings exposed to the metabolites. They compared to the bands found in seedlings subjected to the untreated dye or distilled water. The data from this study provide evidence that the biodegradation of Reactive Red 141 by P. terrigena KKW2-005 was genotoxic to the DNA seedlings.

Increase in lipid productivity and photosynthetic activities during distillery wastewater decolorization by Chlorella vulgaris cultures.

Finding an eco-friendly process for the decolorization of distillery wastewaters is a major concern. This study shows that the Chlorella vulgaris CCAP 211/19 strain can be used for color removal and direct production of oleaginous biomass. A response surface method was used for determining optimal operating conditions, including the dilution factor of industrial wastewater. The highest daily light supply values were the most efficient for color removal. The analysis of the microalgae physiological status confirmed that these colored waters could have a photoprotective action. Moreover, the increase in photosystem 2 activities of C. vulgaris CCAP 211/19 strain after short-term incubations in the presence of a synthetic melanoidin confirmed that this fraction is involved in the enhancement of lipid-enriched biomass production. The results show for the first time the stimulation effect of a melanoidin fraction on the lipid content and productivity by C. vulgaris. These results suggest that this approach may be used to design a closed loop, including water and CO2 recycling for the wastewater dilution and photosynthetic carbon fixation, respectively, while providing biomass for useful renewable algae-based feedstocks of potential interest for a distillery process. KEY POINTS: • Chlorella vulgaris cultures can be used for decolorization of distillery wastewaters. • Diluted distillery wastewaters stimulate biomass and lipid productivities. • Melanoidins, as well as distillery wastewater, stimulate photosynthetic activities.

Dye-decolorization of a newly isolated strain Bacillus amyloliquefaciens W36.

Dye-decolorization is one of the most important steps in dye-polluted wastewater treatment. The dye-decolorization bacteria were isolated from active sludge collected from wastewater treating pond of a dyeing and printing plant using serial dilution method. Among the 44 bacteria isolates from the active sludge, the strain Bacillus amyloliquefaciens W36 was found to have strong ability in dye-decolorization. The effects of carbon source, nitrogen sources, C/N, metal ions, temperature, pH, and rotation speed for dye-decolorization were investigated. The optimum decolorization conditions were that the strain was grown in enriched mineral salt medium (EMSM) using maltose 1 g/L, (NH4)2SO4 1 g/L as carbon and nitrogen source respectively, supplemented with 100 mg/L different dyes (pH 6.0), at 30 °C, 200 rpm from 48 to 96 h. The bacteria could aerobically decolorize dyes, such as Coomassie brilliant blue (95.42%), Bromcresol purple (93.34%), Congo red (72.37%) and Sarranine (61.7%), within 96 h. The dyes decolorization products were analyzed by ultra-violet and visible (UV-vis) spectroscopy before and after decolorization, which indicated that the four dyes were significantly degraded by the strain. The results indicated that the bacteria Bacillus amyloliquefaciens W36 could be used in dye-polluted wastewater treatment.

Development of photochemical integrated submerged membrane bioreactor for textile dyeing wastewater treatment.

A pilot-scale photocatalytic membrane bioreactor (PMBR) was developed for the treatment of textile dyeing wastewater. The PMBR is made of mild steel rectangular reactor of photocatalytic unit and polyethersulphone submerged hollow fibre membrane bioreactor unit with the working volume of about 20 L. For easy recovery, the tungsten oxide (WO3) and WO3/1% graphene oxide (GO)-powdered photocatalyst were made into bead and immersed in photocatalytic reactor. Graphene oxide incorporation has shown better results in decolourisation and degradation when compared with WO3 alginate alone. The incorporation of GO into WO3 minimises the recombination of photogenerated electron-hole pairs. The operating conditions such as 3 h of contact time for photocatalysis reaction (WO3/1% GO), 10 h hydraulic retention time for MBR and 100 kPa of transmembrane pressure were optimised. Chemical oxygen demand removal efficiency of 48% was attained with photocatalysis, and the removal efficiency was further increased up to 76% when integrated with MBR. The colour removal efficiency after photocatalysis was 25% further increased up to 70% with MBR. Complete total suspended solid removal has been achieved with this hybrid system.

Understanding molecular enzymology of porphyrin-binding α + ß barrel proteins - One fold, multiple functions.

There is a high functional diversity within the structural superfamily of porphyrin-binding dimeric α + ß barrel proteins. In this review we aim to analyze structural constraints of chlorite dismutases, dye-decolorizing peroxidases and coproheme decarboxylases in detail. We identify regions of structural variations within the highly conserved fold, which are most likely crucial for functional specificities. The loop linking the two ferredoxin-like domains within one subunit can be of different sequence lengths and can adopt various structural conformations, consequently defining the shape of the substrate channels and the respective active site architectures. The redox cofactor, heme b or coproheme, is oriented differently in either of the analyzed enzymes. By thoroughly dissecting available structures and discussing all available results in the context of the respective functional mechanisms of each of these redox-active enzymes, we highlight unsolved mechanistic questions in order to spark future research in this field.

Screening and identification of newly isolated Pseudomonas sp. for biodegrading the textile azo dye C.I. Procion Red H-3B.

AIM: To test the potential of a newly isolated strain of Pseudomonas sp., and its optimization for carrying out bioremediation of textile azo dye Procion Red H-3B. METHOD: The isolation of the bacterial strain was done from a textile waste dumping site, followed by screening techniques to study the decolourization of an azo dye. The isolated pure culture was selected by its ability to form clear zones. The biochemical tests gave partial confirmation of the isolates, and the phylogenic analysis made the complete confirmation by 16S rRNA sequencing. RESULT: The identified strain belongs to the genus Pseudomonas. The phylogenic analysis confirmed that the strain belongs to Pseudomonas stutzeri. The culture exhibited maximum decolourization at pH between 6 and 8, the optimum at pH 7·5 and 37°C temperature. A maximum of 96% discolouration was observed at 50 mg l-1 of initial dye concentration after 24 h of incubation period. At a dye concentration equally or greater than 600 mg l-1 , the colour removal was drastically decreased to 30%. The use of fructose at 1% (w/v) and peptone 0·5% (w/v) concentration for 24 h of incubation, as carbon and nitrogen source, showed luxuriant decolourization. The results showed that the Pseudomonas sp. holds immense potential in treating textile effluents containing the dye Procion red H-3B. CONCLUSION: Pseudomonas is a known organism in bioremediation of various textile dyes but not much has being reported about the role of P. stutzeri in the bioremediation of azo dyes. This study revealed the immense potential of this strain in degrading the azo dyes. SIGNIFICANCE AND IMPACT OF THE STUDY: The strain shows prospective for industrial application in the field of textile wastewater treatment. Bioremediation is comparatively cheaper and more effective treatment, thus holds promising future for a cleaner environment.

Optimization of spore laccase production by Bacillus amyloliquefaciens isolated from wastewater and its potential in green biodecolorization of synthetic textile dyes.

The spore laccase enzyme production by B. amyloliquefaciens was optimized. It was characterized and tested for its textile dye decolorization potential. LB medium was found to be the most promising growth medium with addition of glucose (1-2%), yeast extract (0.1%), FeCl3 (0.01 mM) and MnCl2 (0.001 mM). The optimum spore laccase production was at pH 8, 30 °C, 1:5 medium to air ratio, 2% inoculum size and 7 days incubation. The characterization study of the enzyme showed the maximum activity at 60 °C and pH 6-7.5. It was induced by Ca+2, Mg+2, Fe+3, Zn+2, Cu+2 and Na+ at 1 mM concentration. Also, it was stable in the presence of methanol, ethanol, acetone and chloroform. In addition, it enhanced about 34% by 5 mM H2O2 and it was nearly stable at 10-20 mM H2O2. Furthermore, mediators such as ABTS, syrengaldazine and 2, 6 dimethyl phenol enhanced the spore laccase activity. The spore laccase enzyme efficiently decolorized direct red 81 and acid black 24 after 24 h. Phytotoxicity of the direct red 81 solution after decolorization by tested spore laccase was lower than that of the untreated dye solution. Finally, this study added a promising spore laccase candidate for ecofriendly and cost-effective dye wastewater bio-decolorization.

Industrial polluted soil borne fungi decolorize the recalcitrant azo dyes Synozol red HF-6BN and Synozol black B.

Today's world needs to control the industrial pollution through smarter ways. Presently, we observed the capacity of soil borne fungi to digest Synozol Red HF-6BN and Synozol Black B. Initially, 86 fungal strains were isolated from soil samples randomly collected from industrial sites. Among these, 31 isolates were capable of dye decolorization on solid media, with SN12f and SN13a isolates showed the highest decolorization capacity. The dye decolorization by both strains was higher (80-95%), when incubated for 120 h under optimized conditions of pH, concentration, nutrient source and temperature. The dye (Synozol red HF-6BN and Synozol black B) decolorization by SN12f isolate was maximum (˃90%) at pH7, whereas the SN13a decolorized 90% of Synozol red HF-6BN and 89% of Synozol black B at pH3. The SN13a and SN12f isolates at 40 mg/L showed de-colorization of 94.71%, 81.4% (for Synozol red HF-6BN) and 90.5%, 84.4% (Synozol black B), respectively. Our isolates also mitigated the toxic effect of azo dyes on the growth of phosphate solubilizing soil bacteria. In fact, the untreated effluent showed toxic effects on the growth of beneficial bacterial by developing zone of inhibition (16.5 mm around Aeromonas spp., 14.5 mm around Sallmonella while 14.25 mm around Citrobacter spp). However, the fungal treated dye was unable to develop zone of inhibition. Laccase activity was positive for both of fungal isolates after incubation on Bassnell Hass Medium (0.0733 U/mL for SN12f and 0.0439 U/mL SN13a). Using molecular approaches (ITS region), SN12f was identified as Aspergillus nidulans, while SN13a as Aspergillus fumigatus. The current study showed that local fungal flora can reclaim the contaminated soils and support the agro-friendly micro-flora.