Decolorization Activity Research Articles

Design of laccase–metal–organic framework hybrid constructs for biocatalytic removal of textile dyes

This study aims to present a simple and effective carrier matrix to immobilize laccase as opposed to complex and tedious immobilization processes and also to use it in the removal of textile dyes. For this purpose, Cobalt (Co) and Copper (Cu) based metal-organic frameworks (MOFs) were prepared and laccase was immobilized on two different MOFs via encapsulation. The characterization outcomes showed that laccase was well immobilized into MOF supports. Optimum pH and temperature were found for Lac/Co-MOF (pH 4.5 at 50 °C) and Lac/Cu-MOF (pH 5.0 at 50 °C). The Km (0.03 mM) and Vmax (97.4 μmol/min) values of Lac/Cu-MOF were lower than those of Lac/Co-MOF (Km = 0.13 mM, Vmax = 230.7 μmol/min). The immobilized laccases showed good reusability as well as improved resistance to temperature denaturation and high storage stability. For instance, the Lac/Co-MOF and Lac/Cu-MOF retained more than 58% activity after 4 weeks of storage at room temperature. Meanwhile, Lac/Co-MOF and Lac/Cu-MOF maintained 56.5% and 55.8% of their initial activity, respectively, after 12 reuse cycles. Moreover, thermal deactivation kinetic studies of immobilized laccases displayed lower k value, higher t1/2, and enhancement of thermodynamic parameters, which means better thermostability. Finally, the decolorization activities for the Lac/Co-MOF were 78% and 61% at the 5th cycle for Reactive Blue 171 and Reactive Blue 198, respectively. In conclusion, it can be inferred that the MOFs are more sustainable and beneficial support for laccase immobilization and they can be efficient for removing textile dyes from industrial wastes.

Improving the decolorization activity of Bacillus pumilus W3 CotA-laccase to Congo Red by rational modification

Congo Red (CR) is a typical azo dye with highly toxic and carcinogenic properties. This study aimed to improve the decolorization activity of Bacillus pumilus W3 CotA-laccase for azo dye CR. This work analyzed the interaction between CotA-laccase and CR based on homology modeling and molecular docking. The three amino acids (Gly323, Thr377, Thr418) in the substrate-binding pocket were rationally modified through saturation mutation. Finally, the obtained multi-site mutants T377I/T418G and G323S/T377I/T418G decolorized 76.59% and 59.37% of CR within 24 h at pH 8.0 without a mediator, which were 3.15- and 2.44-fold higher than the wild-type CotA. The catalytic efficiency of the multi-site mutants T377I/T418G and G323S/T377I/T418G to CR were increased by 2.21- and 2.01-fold compared with the wild-type CotA, respectively. The mechanism of activity enhancement of mutants was proposed by structural analysis. This evidence suggests that the mutants T377I/T418G and G323S/T377I/T418G could be used as novel bioremediation tools.

EVALUATION OF AZO DYE ORANGE G DECOLORIZATION AND DEGRADATION BY BACTERIA ISOLATED FROM TEXTILE EFFLUENT

The bacteria were isolated and identified from textile effluent, and their ability to decolorize the hazardous azo dye Orange G was evaluated. After incubating the isolates for 24 hours in mineral salt medium supplemented with 100 ppm Direct Orange G, their decolorizing activity was measured spectrophotometrically. Lysinibacillus sp. AUBTP7 (AK1), Bacillus muralis strain1Y118 (AK2), and Bacillus thuringiensis strain N3 (AK3) were identified as the bacterial strains. Bacillus thuringiensis strain N3 (AK3) was the most efficient bacteria at decolorizing Orange G (100ppm), removing 93% of the color in 24 hours at 36ºC temperature. Study of HPLC chromatogram of Orange G and degradation products suggests the formation of new compounds. As a result of this research, it has been revealed that some bacteria live in textile effluents and use dyes as a source of energy and nourishment, implying their usefulness in the treatment of industrial effluents.

Laccase-Mediator System Using a Natural Mediator as a Whitening Agent for the Decolorization of Melanin.

In this study, a laccase-mediator system (LMS) using a natural mediator was developed as a whitening agent for melanin decolorization. Seven natural mediators were used to replace synthetic mediators and successfully overcome the low redox potential of laccase and limited access of melanin to the active site of laccase. The melanin decolorization activity of laccases from Trametes versicolor (lacT) and Myceliophthora thermophila (lacM) was significantly enhanced using natural mediators including acetosyringone, syringaldehyde, and acetovanillone, which showed low cytotoxicity. The methoxy and ketone groups of natural mediators play an important role in melanin decolorization. The specificity constants of lacT and lacM for melanin decolorization were enhanced by 247 and 334, respectively, when acetosyringone was used as a mediator. LMS using lacM and acetosyringone could also decolorize the melanin present in the cellulose hydrogel film, which mimics the skin condition. Furthermore, LMS could decolorize not only synthetic eumelanin analogs prepared by the oxidation of tyrosine but also natural melanin produced by melanoma cells.

Biodegradation of Brown 706 Dye by Bacterial Strain Pseudomonas aeruginosa

Dyes are the most challenging pollutants for the aquatic environment that are not only toxic, but also interfering photosynthesis as light penetration into deep water is changed. A number of methods are used for the water reclamation, however, among them biological methods are preferably used due to their compatibility with nature. In the present research, 15 different bacterial strains were used to decolorize Brown 706 dye. Among the bacterial strains, Pseudomonas aeruginosa showed maximum decolorization activity; hence in the subsequent experiments Pseudomonas aeruginosa was used. First the decolorization activities were carried out under different physicochemical conditions to obtain the optimum decolorization benefits of the selected microorganism. The optimum conditions established were 37°C, pH of 7 and operation cycle time 72 h. In the subsequent experiment all optimum conditions were combined in a single experiment where 73.91% of decolorization efficiency was achieved. For the evaluation of metabolites formed after decolorization/degradation the aliquots containing bacteria were homogenized, filtered and then subjected to extraction. The extracted metabolites were then subjected to the silica gel column isolation. UV–Vis, FTIR, and NMR techniques were used to elucidate structures of the metabolites. Out of the collected metabolites only P-xylene was identified, which has been formed by cleavage of azo linkage by azo reductase enzyme of bacteria following the deamination and methylation of nitro substituted benzene ring.

Laccase bound to cryogel functionalized with phenylalanine for the decolorization of textile dyes.

In this study, amino acid functionalized poly(2-hydroxyethyl methacrylate-N-methacrylolyl-l-phenylalanine) [PHEMAPA] cryogel discs were prepared. In this respect, phenylalanine containing N-methacryloyl-(L)-phenylalanine methyl ester (MAPA) was polymerized with 2-hydroxyethyl methacrylate (HEMA) without requirement of any activation step. Laccase bound poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-phenylalanine) [Lac-PHEMAPA] cryogel discs were applied for decolorization of Reactive Blue-247 (RB-247). The ability of Lac-PHEMAPA cryogel discs on dye decolorization was found to be as 90% in 2 h and even more within 4h. The decolorization activities of 86% and 73% were observed at relatively low (4°C) and high (60°C) temperatures, respectively. The effect of dye concentration on dye decolorization and 100% decolorization activity was achieved in dye concentration between 50–300 ppm. Lac-PHEMAPA cryogel discs maintained 80% of its decolorization activity after six cycles. Consequently, the PHEMAPA cryogel discs are promising materials for immobilizing laccase. The Lac-PHEMAPA has a rapid dye decolorization in a broad range of temperature. The preparation is furthermore very stable and activity is preserved during storage.

Comparatively Investigation of Textile Dye Decolorization by a White Rot Fungus and Various Bacterial Strains

The aim of this study is to comparatively investigate the decolorization of Reactive Blue 171 (RB 171) by using three different bacterial strains as Bacillus megaterium A1 (A1), Gordonia sp. MC-D1 (D1) and Bacillus pumilus D3 (D3) and also a white rot fungus (Pleurotus ostreatus). All tested bacteria were incubated with RB 171 dye at 150 mg/L concentration for 24-72 h under static or agitated (150 rpm) conditions while the fungus was incubated with 150 mg/L of the dye under the same conditions for 3-24 h. The highest bacterial decolorization values were obtained after 72 h of incubation under static conditions and the maximum decolorization rates were detected as 84, 83 and 75% for A1, D1 and D3, respectively. However, the color of RB 171 dye was removed at 93% rate by Pleurotus ostreatus under static conditions after 24 h of incubation. Similar results were also obtained from the agitated studies of the tested fungal and bacterial strains except A1. The maximum decolorization values obtained with A1, D1 and D3 at 150 rpm, 72 h were 30, 88 and 89%, respectively. The highest decolorization activities of Pleurotus ostreatus were 93% for both static and agitated (150 rpm) conditions. In addition, zymogram analyzes of the fungal culture fluids obtained from SBM and SBM containing 150 mg/L RB 171 were also performed to detect the presence of laccase.

Brevibacterium limosum sp. nov., Brevibacterium pigmenatum sp. nov., and Brevibacterium atlanticum sp. nov., three novel dye decolorizing actinobacteria isolated from ocean sediments.

During a study of the marine actinobacterial biodiversity, a large number of Brevibacterium strains were isolated. Of these, five that have relatively low 16S rRNA gene similarity (98.5-99.3%) with validly published Brevibacterium species, were chosen to determine taxonomic positions. On the basis of 16S rRNA gene sequence analysis and BOX-PCR fingerprinting, strains o2T, YB235T, and WO024T were selected as representative strains. Genomic analyses, including average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH), clearly differentiated the three strains from each other and from their closest relatives, with values ranging from 82.8% to 91.5% for ANI and from 26.7% to 46.5% for dDDH that below the threshold for species delineation. Strains YB235T, WO024T, and o2T all exhibited strong and efficient decolorization activity in congo red (CR) dyes, moderate decolorization activity in toluidine blue (TB) dyes and poor decolorization in reactive blue (RB) dyes. Genes coding for peroxidases and laccases were identified and accounted for these strains' ability to effectively oxidize a variety of dyes with different chemical structures. Mining of the whole genome for secondary metabolite biosynthesis gene clusters revealed the presence of gene clusters encoding for bacteriocin, ectoine, NRPS, siderophore, T3PKS, terpene, and thiopeptide. Based on the phylogenetic, genotypic and phenotypic data, strains o2T, YB235T and WO024T clearly represent three novel taxa within the genus Brevibacterium, for which the names Brevibacterium limosum sp. nov. (type strain o2T = JCM 33844T = MCCC 1A09961T), Brevibacterium pigmenatum sp. nov. (type strain YB235T = JCM 33843T = MCCC 1A09842T) and Brevibacterium atlanticum sp. nov. (type strain WO024T = JCM 33846T = MCCC 1A16743T) are proposed.

Production and characterization of crude laccase from Irpex sp. JS7 that decolorizes synthetic and natural melanin.

The JS7 strain, isolated from an old forest tree, produces extracellular enzymes that decolorize synthetic and natural melanin from human hair. Phylogenetic analysis based on the internal transcribed spacer (ITS) sequence indicated that JS7 belongs to the genus Irpex. The JS7 strain has laccase activity while it lacks manganese and lignin peroxidase activity, which suggests that the JS7 strain melanin decolorization activity originated from laccase. Laccase production from the Irpex sp. JS7 improved three-fold in the presence of veratryl alcohol, compared to without an inducer. The optimum pH and temperature for melanin decolorization were 7.5 and 40 °C, respectively. The crude enzyme half-life at 25 °C was about 100days, and it had high storage stability. The melanin decolorization reaction rate by the crude enzyme conformed to typical enzyme kinetic principles. In the presence of syringaldehyde as a redox mediator, the melanin decolorization rate was 75% within 5days, similar to the decolorization percentage obtained using the enzyme alone. Based on these results, the Irpex sp. JS7 enzyme is suitable for use in melanin decolorization by whitening agents in the cosmetics industry.

Charge transfer complexation between some transition metal ions with azo Schiff base donor as a smart precursor for synthesis of nano oxides: An adsorption efficiency for treatment of Congo red dye in wastewater

This mentioned article aimed to synthesized of nanostructured CuO, Co3O4 and NiO oxides based on the thermal decomposition of precursors associated from the complexation between azo Schiff base chelate (2,2′-((1E,1′E)-hydrazine-1,2-diylidenebis(methaneylylidene))bis(4-((E)-phenyldiazenyl)phenol) (NNOO)) and metal chloride salts with 1:1 M ratio. The NNOO azo Schiff base chelate, and its Cu(II), Co(II) and Ni(II) complexes were synthesized and discussed using microanalytical, molar conductance, magnetic properties, FT-IR, UV–Vis, 1H NMR, mass, and TGA (thermogravimetric analysis) techniques. According to the microanalysis and spectroscopic results, the coordination mode between azo Schiff base ligand and the central metal ion was occurs through NNOO donating atoms of azo Schiff base ligand. The electronic spectra and magnetic susceptibility analyses concluded that all synthesized metal complexes have an octahedral geometrical structural. The metal oxides (CuO, Co3O4, and NiO) nanoparticles were synthesized after the calcination of azo Schiff base complexes at 800 °C in a static air. The assignments of CuO, Co3O4 and NiO nanostructured oxides were discussed based on the FTIR, XRD, and TEM analysis technique. The ability of CuO, Co3O4 and NiO was compared by catalytic degradation of Congo red azo dye. The decolorization behavioral of Congo red dye was examined using spectroscopic UV–Vis techniques. Furthermore, the rate of catalytic decolorization activity of Congo red dye using prepared metal oxides was successfully performed. The dye has been successfully decolorized by ~57% in the presence of Co3O4 NPs at room temperature.

BIODEGRADATION OF AZO DYE (REACTIVE GREEN 19) BY Pseudomonas aeruginosa ISOLATED FROM TEXTILE EFFLUENT


 Azo dyes are widely used in the textile industry. The release of these undesirable dye effluents to the environment can be toxic and carcinogenic towards humans and other organisms. The removal of these dyestuff wastes using the biodegradation method is to consider eco-friendlier compared to physical and chemical methods. Thus, this study was conducted to identify and analyze the biodegradation activity of the azo dye by the potential bacteria isolated from textile dye effluent. For decolorization analysis, the isolated bacteria were inoculated into flasks containing mineral salt medium added with Reactive Green 19 dye (50 mg/L) and was incubated for 9 days at 37°C. Spectrophotometry analysis was carried out at 635 nm to analyze the level of azo dye degradation. From the analysis, we found that the optimum pH, temperature, and dye concentration for the decolorization were detected at pH 7, 37°C, and 50 mg/L, respectively. The identified bacteria Pseudomonas aeruginosa showed 94% decolorization of Reactive Green 19 dye after 9 days of incubation. The result of decolorization activity by this bacterial strain can be used in the biological treatment of textile effluent.

Decolorization of lignin-mimicking dyes by Stenotrophomonas sp. CFB-09: Enzyme activity, transformation dynamics and process optimization

Increased discharge of dyes into the environment and consequent contamination of water bodies have been issues of public health concern due to the toxicity of dyes. In this study, the ability of Stenotrophomonas sp. CFB-09 to decolorize lignin-mimicking dyes [Congo red (CR), toluidine blue (TB), methyl blue (MB), remazol brilliant blue R (RBBR) and indigo carmine (IC)] and produce ligninolytic enzymes were investigated. Dye decolorization activity was carried out qualitatively on plates and quantitatively by UV–Vis spectrophotometric analysis of broths. Influence of process parameters (initial pH, incubation temperature and media composition) on dye decolorization were also determined. Identification of biodegradation products was done by GC-MS. Results revealed that Stenotrophomonas sp. CFB-09 decolorized dyes by concomitantly producing ligninolytic enzymes and achieved ≥90% decolorization of 25 mg/L CR, MB, RBBR, and IC and 75.0–86.5% decolorization of 100 mg/L of IC, CR and MB at 120 h. Lignin peroxidase exhibited the highest activity among ligninolytic enzymes studied on all dyes. Optimum decolorization for all dyes was achieved at pH 8.0 and 35 °C in the presence of oil palm empty fruit bunch (OPEFB). Findings show that the ligninolytic bacterium, Stenotrophomonas sp. CFB-09 has potentials for application in bioremediation of dye containing effluents.

Iron Species-Supporting Hydrophobic and Nonswellable Polytetrafluoroethylene/Poly(acrylic acid-co-hydroxyethyl methacrylate) Composite Fiber and Its Stable Catalytic Activity for Methylene Blue Oxidative Decolorization.

Polytetrafluoroethylene emulsion was ultrasonically mixed with an extremely spinnable poly(acrylic acid-co-hydroxyethyl methacrylate) solution to get a dispersion with good spinnability, and the obtained dispersion was then wet-spun into water-swellable fiber. Crosslinking agents and iron species were simultaneously introduced into the water-swellable fiber through simple impregnation and water swelling. A composite fiber with Fenton reaction-catalyzing function was then fabricated by sequentially conducting crosslinking and sintering treatment. Due to crosslinking-induced good resistance to water swelling and PTFE component-induced hydrophobicity, the composite fiber showed a highly stable activity to catalyze H2O2 to oxidatively decolorize methylene blue (MB). Within nine cycles, the composite fiber could decolorize more than 90% of MB within one minute in the presence of H2O2 and did not show any attenuation in MB decolorization efficiency. The composite fiber still could reduce the total organic carbon of MB aqueous solution from 18.3 to 10.3 mg/L when used for the ninth time. Therefore, it is believable that the prepared fiber has good and broad application prospects in the field of dye wastewater treatment.

Dispersion of Graphene Using cetyltrimethylammonium bromide (CTAB): Dye Removal and Characterization Studies

The aim of this study to determine the usability of CTAB-RGO composites in the removal of MB from aqueous solutions and to investigate the stability of composites in the aqueous dispersions. And also, we compared the effects of three different CTAB concentrations on the decolorization of MB. The CTAB-RGO composites performed increasing decolorization activity, decreasing average particle size and resulting individual graphene layers with the increasing CTAB concentration. CTAB-RG0 with 40 and 80 mg/L composites were unstable, RGO and CTAB-RGO with 120 mg/L had good stability in the aqueous solutions. Effective repulsive forces of CTAB-RGO-120 composite prevented to forming graphene aggregates. The highest decolorization rate of CTAB-RGO-120 composite at neutral pH can result from both the electrostatic interaction and π-π interaction.

Assessment of anammox, microalgae and white-rot fungi-based processes for the treatment of textile wastewater.

The treatability of seven wastewater samples generated by a textile digital printing industry was evaluated by employing 1) anammox-based processes for nitrogen removal 2) microalgae (Chlorella vulgaris) for nutrient uptake and biomass production 3) white-rot fungi (Pleurotus ostreatus and Phanerochaete chrysosporium) for decolorization and laccase activity. The biodegradative potential of each type of organism was determined in batch tests and correlated with the main characteristics of the textile wastewaters through statistical analyses. The maximum specific anammox activity ranged between 0.1 and 0.2 g N g VSS-1 d-1 depending on the sample of wastewater; the photosynthetic efficiency of the microalgae decreased up to 50% during the first 24 hours of contact with the textile wastewaters, but it improved from then on; Pleurotus ostreatus synthetized laccases and removed between 20–62% of the colour after 14 days, while the enzymatic activity of Phanerochaete chrysosporium was inhibited. Overall, the findings suggest that all microbes have great potential for the treatment and valorisation of textile wastewater after tailored adaptation phases. Yet, the depurative efficiency can be probably enhanced by combining the different processes in sequence.

Fabrication of mesoporous WO3-SBA-15 catalysts and enhanced photocatalytic degradation of harmful dyes

Mesoporous SBA-15 and x% WO3-SBA-15 (X = 2.7 %, 5.5 %, 8.3 % and 11.1 %) catalysts were synthesized by hydrothermal in-situ method. All the synthesized catalysts were subjected to different analytical techniques such as XRD, FT-IR, BET, XPS, FE-SEM, EDX, HR-TEM, DRS-UV and PL. The HR-TEM images showed that WO3 species were highly dispersed in the uniform pore channels of SBA-15. Photo decolorization activity of the bare and composite catalysts measured in the degradation of harmful dyes such as rhodamine B (RhB), methylene blue (MB) and crystal violet (CV) under UV, visible and solar light irradiations. Among the catalysts, 5.5 % WO3-SBA-15 exhibited the highest photocatalytic activity (81 %, 90 %, and 77 %) towards the degradation of RhB, MB and CV dyes under visible light irradiation. TOC and COD studies indicated that the three dyes chosen for the present study were all degraded to large extent. The trapping experiment confirmed that the major species responsible for the photocatalytic degradation of different dyes over 5.5 % WO3-SBA-15 catalysts were found to be h+ and O2−. The stability of the most active catalysts 5.5 % WO3-SBA-15, was determined by the recyclability test. A suitable mechanism was proposed based on experimental evidence.

Identification and optimization of triphenylmethane dyes removal by Streptomyces sp. from forest soil

This study identified a common Streptomyces sp. (MN262194) from forest soil as an efficient decolorizer of triphenylmethane (TPM) dyes. Partial 16S rRNA sequencing identified the isolate as possibly Streptomyces bacillaris (similarity 99.32%). Live and dead cells of Streptomyces sp. were applied to decolorize Malachite Green (MG), Methyl Violet (MV), Crystal Violet (CV), and Cotton Blue (CB). The decolorization efficacy for both cell types was further optimized based on One-Factor-At-A-Time (OFAT) method to determine the influence of pH, agitation speed (rpm), biomass (g), initial dye concentration (mg L− 1), and oxygen. Removal of TPM dyes was repeated for both live and dead cells using combined optimal conditions determined for each biomass type. Results revealed that optimum conditions for live cells were pH 7, 100 rpm agitation, 0.5 g cell biomass, initial dye concentration of 100 mg L− 1 (50 mg L− 1 for CB), and with the presence of oxygen. In contrast, pH 9 (MG, MV, CV) and pH 3 (CB), with 100 rpm agitation, 0.75 g cell biomass, and initial dye concentrations of 100 mg L− 1 (50 mg L− 1 for CB), were the optimum conditions for dead cells. At optimal conditions, live cells showed significantly higher decolorization activities for all dyes (MG 95%, MV 92%, CV 87%, CB 68%). Removal of TPM dyes was via biosorption and biodegradation, detected with changes of ultraviolet-visible spectra between the untreated dye and treated dye. Sorption by Streptomyces sp. conforms to the Langmuir isotherm model. Streptomyces sp. was established as an effective decolorizer for most TPM dyes with > 85% decolorization (with the exception for CB).

Identification and Evaluation of Azo Dye Decolorizing Fungal Species from Industry Effluent for the Development of Consortia Bio Inoculants

Azo dyes are the largest class dye used in textile and other industries. Beside of its large benefits it is also toxic, carcinogenic, mutagenic and teratogenic, that constitutes a significant burden to the environment, human as well as animal health. Physicochemical treatment was employed to degrade and detoxify these azo dyes. However this method has limitation in releasing toxic degradant and not economical. It is timely important to search alternative biological ecofriendly treatment methods. The aim of this study was to screen, identify and evaluate potential fungal species having the ability to decolorize and degrade the Azo dyes for the development of consortia bio inoculants.150 industry effluent waste water was collected and fungal species were isolated & identified using Biolog Microstaton identification technology. The fungal azodye decolorization activities were qualitatively evaluated on Remazol yellow, Navey blue, Procion red MX-5B dyes using solid agar plate and broth assay. The result revealed that the percentage of frequency of fungi in waste water was 63.88 % were filamentous fungi and 38.22% non-filamentous fungi. Aspergillus species were dominant (32%). Thirteen fungal species was identified using Biolog MicroStaion reading machine. These are Trichosporon begilli, Rodotrula auranticaA, Candida palmioleophila, Cryptococus terrus, Yarrowia lipolytica, Cryptococus albidus, Aspergillus ochraceus, Aspergillus restrictus, Aspergillus carneus, Penicillium brevicompactum, Penicillium roqueforti, Penicillium digitatum, Fusarium javanicum. Among the fungal isolates tested, only 6 fungi species showed 72-92% decolorization potential measured by Biolog turbidimeter, these are T. begilli, R. aurantica A, P. roqueforti, P. digitatum, A. ochraceus F. javanicum four species, C. palmioleophila, C. terrus, Y. lipolytica, C. albidus, 34-71% decolorizing ability of Navy blue. 3 species, P. brevicompactum, A. carneus, A. restrictus showed 16-29% decolorizing ability. Trichosporon begilli was superior in clear zone formation on solid agar plate test (5.4mm). Through supporting this preliminary study by HPLC, &spectrophotometer analysis for enzymes and secondary metabolite study, it is possible to formulate and develop fungal bioinnoculant consortia for mycoremediation service.

Azo dye decolorization by using four different psychrotolerant Bacillus species

Since the early ages, human beings have used colored materials to leave marks on their environment and the following generations. In time, paints, which gained great importance with painting the objects and the items they used, brought environmental problems with them. Synthetic paints/dyes used to meet the increasing need over time had to be eliminated from the environment. Nowadays, using bacteria is considered as a good solution for eliminating dyes that contain azo groups. These dyes are used in large quantities and difficult to decompose. The main goal of this study was to decolor six different (amido black 10B, evans blue, janus green, methyl orange, methyl red, and orange G) azo dyes by use of four different psychrotolerant Bacillus (Bacillus sp, B. cereus, B. mycoides, and B. subtilis) isolates. According to the obtained results, it was determined that the psychrotolerant Bacillus isolates could remove colors of the six azo dyes by presenting high decolorization activity (up to 98%).

A green approach for the synthesis of silver nanoparticles by Chlorella vulgaris and its application in photocatalytic dye degradation activity

Biosynthesis of the silver nanoparticle (AgNPs) is gaining significant importance since it is eco-friendly and can withstand variable environmental conditions. In this present study, AgNPs have been synthesized by using a freshwater green alga, Chlorella vulgaris . For the improved production, experiments on the standardization of AgNPs synthesis were investigated at different parameters. The results affirmed that the synthesize of AgNPs was at 8:2 v/v in extract ratio, pH 12 in the solution of AgNO 3 , 3 mM in molarity of AgNO 3 , shaking process in the incubation of reactants and 24 h time in synthesis period. Further, synthesized AgNPs were characterized by using spectroscopic and microscopic techniques. The synthesized AgNPs showed the Surface Plasmon Resonance (SPR) peak between the 410–450 nm. Fourier Transform Infrared Spectroscopy (FTIR) revealed that the algal extract has stabilized with the nanoparticles by capping. The Field Emission Scanning Electron Microscopy (FESEM) analysis confirms the spherical shape of the AgNPs with an average size of 55.06 ± 9.67 nm. The X-ray diffraction (XRD) analysis showed a crystalline nature of the particle with an average size of 61.89 ± 12.13 nm. The photocatalytic decolorization of the methylene blue by using synthesized AgNPs was evaluated under the sunlight irradiation method. The synthesized AgNPs have shown 96.51% of photocatalytic decolorization activity by using methylene blue dye (100 ppm) within 3 h incubation time. • Green synthesis of AgNPs by using cell free extract of Chlorella vulgaris . • Synthesized AgNPs were characterized by FTIR, FESEM, XRD and DLS analysis. • AgNPs were spherical in shape and the average size of the particle is 55.06 ± 9.67 nm. • AgNPs were showed good photocatalytic activity against methylene blue dye.