Recalcitrant Synthetic Dyes Research Articles

Microbial biodegradation of recalcitrant synthetic dyes from textile-enriched wastewater by Fusarium oxysporum

The present study reported the improvement of biological treatment for the removal of recalcitrant dyes including aniline blue, reactive black 5, orange II, and crystal violet in contaminated water. The biodegradation efficiency of Fusarium oxysporum was significantly enhanced by the addition of mediators and by adjusting the biomass density and nutrient composition. A supplementation of 1% glucose in culture medium improved the biodegradation efficiency of aniline blue, reactive black 5, orange II, and crystal violet by 2.24, 1.51, 4.46, and 2.1 folds, respectively. Meanwhile, the addition of mediators to culture medium significantly increased the percentages of total removal for aniline blue, reactive black 5, orange II, and crystal violet, reaching 86.07%, 68.29%, 76.35%, and 95.3%, respectively. Interestingly, the fungal culture supplemented with 1% remazol brilliant blue R boosted the biodegradation up to 97.06%, 89.86%, 91.38%, and 86.67% for aniline blue, reactive black 5, orange II, and crystal violet, respectively. Under optimal culture conditions, the fungal culture could degrade these synthetic dyes concentration up to 104 mg/L. The present study demonstrated that different recalcitrant dye types can be efficiently degraded using microorganism such as F. oxysporum.

Microbial remediation of triphenylmethane dyes contaminated wastewater: A review

Extensive dependence of textile and other industries on the synthetic dyes have made these chemicals a necessary evil nowadays. Among all classes of dyes, triphenylmethane dyes (TPMs) are most common and unfortunately most hazardous. The wastewater originated from various industries is usually found to contain a major portion of TPMs along-with other synthetic dyes, inorganic and organic contaminant which lead to serious environmental consequences. In this regard, microbial remediation of such synthetic chemicals seems to be a very robust, cost effective and environment friendly strategy. Microbial remediation exploits the enzymatic capabilities of microorganisms (bacteria, fungi or microalgae) to cope with recalcitrant synthetic dyes and other chemicals. The remediation of TPMs can occur either by the phenomenon of adsorption onto the microbial systems or through the degradation by the enzymatic or metabolic mechanisms of the microbe under optimized conditions. Both of the two ways convert the toxic chemicals to harmless and friendly products. Biodegradation or bioremediation of pollutants can be achieved through various living organisms such as plants and algae. But the current review only focuses on the remediation of TPMs by microbes such as bacteria, yeast and fungi. The factors such as pH, temperature, inoculum size, dye concentration etc. which have profound effect on optimization of degradation of TPMs, can never be neglected and hence they are discussed in detail in the present study. In this way we claim that the present article will provide deep insights into the current consequences of TPMs and related toxicants being added to our environment. Further, an emphasis on the implementation of bioremediation to get rid of such chemicals from our waters would be helpful to enhance the interest of researchers and scientists already working on the same theme.

A novel and highly active recombinant spore-coat bacterial laccase, able to rapidly biodecolorize azo, triarylmethane and anthraquinonic dyestuffs

Laccases are enzymes able to catalyze the oxidation of a wide array of phenolic and non-phenolic compounds using oxygen as co-substrate and releasing water as by-product. They are well known to have wide substrate specificity and in recent years, have gained great biotechnological importance.To date, most well studied laccases are from fungal and mesophilic origin, however, enzymes from extremophiles possess an even greater potential to withstand the extreme conditions present in many industrial processes.This research work presents the heterologous production and characterization of a novel laccase from a thermoalkaliphilic bacterium isolated from a hot spring in a geothermal site. This recombinant enzyme exhibits remarkably high specific activity (>450,000 U/mg) at 70 °C, pH 6.0, using syringaldazine substrate, it is active in a wide range of temperature (20–90 °C) and maintains over 60% of its activity after 2 h at 60 °C. Furthermore, this novel spore-coat laccase is able to biodecolorize eight structurally different recalcitrant synthetic dyes (Congo red, methyl orange, methyl red, Coomassie brilliant blue R250, bromophenol blue, malachite green, crystal violet and Remazol brilliant blue R), in just 30 min at 40 °C in the presence of the natural redox mediator acetosyringone.

Combination of thermal and biological treatments for bio-removal and detoxification of some recalcitrant synthetic dyes by betaine-induced thermostabilized laccase

The presence of recalcitrant synthetic dyes in environment is a major concern due to their possible threat on living organisms and aquatic ecosystems. To investigate the potential of combined thermal and enzymatic decolorization, betaine was applied to protect the secondary and tertiary structures as well as the enzymatic activity of laccase under thermal stress. At 60 °C, betaine 1 M significantly enhanced the stability of laccase in addition to keeping its catalytic efficiency ( p < 0.05). Differential scanning calorimetry showed a 20 °C increase in T m of laccase in the presence of betaine. Once incubated at 60 °C, betaine exhibited superior protein-stabilizing properties than at 25 °C. Furthermore, fluorescence spectroscopy supported this concept that the overall folded structure of laccase became more rigid in the presence of betaine at 60 °C. Betaine-stabilized laccase was used for combined thermal and enzymatic decolorization of some recalcitrant organic dyes. This osmolyte could improve the enzymatic removal of most dyes at 60 °C. A detoxification study with respect to the inhibition of bacterial growth showed a decrease in microtoxicity of the laccase-treated dye solution in the presence of betaine at 60 °C. • Betaine protects secondary and tertiary structures of laccase under thermal stress. • Betaine enhances the thermal stability and catalytic efficiency of laccase. • Laccase shows a dramatic increase in α -helix content in the presence of betaine. • Betaine improved the enzymatic removal of some recalcitrant synthetic dyes at 60 °C. • Microtoxicity of treated dyes was remarkably decreased compared to nontreated dyes

Sequential electrochemical oxidation and bio-treatment of the azo dye congo red and textile effluent

Textile effluent is often difficult to manage as it contains a high concentration of toxic and recalcitrant synthetic dyes. In this study, congo Red and textile effluent were treated by electrochemical oxidation using RuO2-IrO2 coated titanium electrode as an anode followed by biodecolorization using Pseudomonas stutzeri MN1 and Acinetobacter baumannii MN3. Effluent pre-treatment is often necessary to minimize the inhibitory effects of textile dyes on dye degrading bacterial during bio-treatment. The pre-treatment of Congo Red by electrochemical oxidation for 10 min resulted in a decolorization rate of 98% at a pH, NaCl concentration, and current density of 7, 2 g L−1, and 20 mA cm−2. Subsequent bio-treatment of the pretreated Congo Red enhanced the biodegradation to 93%. The COD removal efficiency in real textile effluent following electrochemical pretreatment and biological treatment using bacterial consortium were 3.8% and 93%, respectively. Therefore, integrating electrochemical oxidation and microbial consortia offers an effective and environmentally friendly approach for treating complex industrial effluents.

Enhancing laccase production by a newly-isolated strain of Pycnoporus sanguineus with high potential for dye decolouration

Response surface methodology (RSM) was applied to optimise laccase production by a new strain of Pycnoporus sanguineus, isolated from the Uruguayan forests, grown on bark shavings under semi-solid-state fermentation conditions. Enhancement of laccase production was studied, with a full 24 factorial design with two replicates and four central points. Operating under the optimal conditions obtained (pH 3.0, yeast extract 10 g L−1, glucose 5 g L−1 and bark shavings 3 g), a laccase activity of nearly 3000 U L−1 was achieved. Subsequently, the effect of different potential inducers on laccase production (Cu+2, Mn+2 and lignin) was tested using the one-factor-at-a-time approach. It was found that the addition of 0.5 mM Cu+2 into the cultures considerably increased laccase production and, thus, maximum activity values of about 16000 U L−1 were achieved. Further, the optimised culture broth (containing mainly laccase) showed high capacity to decolourise different recalcitrant synthetic dyes such as Acid Red 88 (AR88), Reactive Black 5 (RB5) and Lanaset Grey G (LG). After selecting enzyme concentration and time of reaction, almost 70% of AR88 could be decolourised in the absence of redox mediators. However, mediators were necessary to bleach RB5 and LG. Methyl syringate was the most effective mediator for AR88 (reaching a decolouration degree over 90%) and RB5 (nearly 70%). Around 80% of LG could be decolourised in the presence of violuric acid. These promising results make this enzyme a very useful tool for developing wastewater treatments.

Heterologous expression and characterization of a novel laccase isoenzyme with dyes decolorization potential from Coprinus comatus

Two new laccase genes, named lac1 and lac2, were cloned from the edible basidiomycete Coprinus comatus. Comparison of the deduced amino acid sequences revealed two laccases showed 66.12% identity and clustered with lac2 and lac3 from Coprinopsis cinerea in same phylogenetic group. Lac1 and lac2 encode proteins of 517 and 523 amino acids preceded by 18 and 21-residue signal peptides, respectively. Lac1 was functionally expressed in Pichia pastoris. The optimum pHs of recombinant Lac1 were 3.0, 6.0, 5.5 and 6.0 and the optimum temperatures were 65, 55, 70 and 50°C for ABTS, guaiacol, 2,6-dimethylphenol and syringaldazine, respectively. The Km values of Lac1 were 34, 4,317, 7,611 and 14μM, and the corresponding kcat values were 465.79, 7.67, 1.15 and 0.60 (s(-1)mM), for ABTS, guaiacol, 2,6-dimethylphenol and syringaldazine, respectively. The enzyme activity was completely inhibited by sodium azide (NaN(3)) and 1,4-dithiothreitol (DTT) at the concentration of 5mM. Laccase activity was also inhibited by several metal ions, especially Fe(2+), while K(+) and NH(4) (+) slightly enhanced laccase activity. Twelve synthetic dyes belonging to anthraquinone, azo and triphenylmethane dyes were decolorized by the recombinant Lac1 at different extents. The recombinant Lac1 decolorized azo dye Reactive Dark Blue KR up to 90% without any mediator and increasing to 96% with mediator, indicating its potential in the treatment of industrial effluent containing some recalcitrant synthetic dyes.

Catalytic potential of cauliflower (Brassica oleracea) bud peroxidase in decolorization of synthetic recalcitrant dyes using redox mediator

We investigated the effect of cauliflower (Brassica oleracea) bud peroxidase along with redox mediators on decolorization of dyes (Reactive Red 2, Reactive Black 5, Reactive Blue 4, Disperse Orange 25 and Disperse Black 9). Results indicated that among the chosen mediators, 1-hydroxybenzotriazole (HOBT) followed by riboflavin were most effective for dye decolorization. At 0.36 EU/ml and with 0.8 mM HOBT in conjunction with 0.75 mM H2O2 the soluble cauliflower bud peroxidase proteins could decolorize the dyes. The enzyme worked in a broader range of pH and temperature and was adequately effective in batch processes when used with organic contaminants (dioxane and dimethylformide), detergents (Triton X-100 and sodium dodecyl sulfate), sodium chloride and heavy metals including zinc and cadmium chloride. Thus peroxidase from cauliflower bud is a better choice than other vegetable peroxidases as it is sufficiently thermostable, operates in a wide range of pH, economic and effective with low concentration of redox mediators in decolorizing recalcitrant synthetic dyes. Such peroxidases with better catalytic activity have potential of being used on a large scale.

Potential of peroxidase enzyme from Trichosanthes diocia to mediate disperse dye decolorization in conjunction with redox mediators

Abstract Disperse dyes are frequently used worldwide for dyeing polyester, nylon, cellulose acetate and acrylic fibers. The highly variable and complex chemical structure of the dyes makes them difficult to remove using conventional wastewater treatment systems. Redox mediated enzymatic catalysis has wide applications including degradation of polycyclic compounds, phenols, aromatic amines, biphenyls, pesticides, insecticides etc. We investigated the effect of Trichosanthes diocia peroxidase along with redox mediators on decolorization of water insoluble disperse dyes; Disperse Red 19 and Disperse Black 9. Nine different redox mediators; bromophenol, 2,4-dichlorophenol, guaiacol, 1-hydroxybenzotriazole, m-cresol, quinol, syringaldehyde, vanillin and violuric acid were evaluated. Results indicated that among the chosen mediators, 1-hydroxybenzotriazole (HOBT) was most effective for decolorization. At a concentration of 0.45 U mL−1 the peroxidase could decolorize Disperse Red 19 to a maximum of 79% with O.2 mM 1-hydroxybenzotriazole whereas Disperse Black 9 decolorized upto 60% with 0.5 mM 1-hydroxybenzotriazole. The time, pH and temperature at which maximum decolorization were recorded was 60 min, 4 and 42 °C. Data were analyzed by one-way ANOVA and Mann Whitney test. The study suggests that peroxidase from T. diocia could be a cheap, easy, effective source and along with redox mediators be used to treat recalcitrant synthetic dyes.

Effect of cosubstrates on primary biodegradation of triphenylmethane dyes by &lt;i&gt; Pseudomonas&lt;/i&gt; sp.

The effect of substrates (glucose, starch, lactose and sucrose) on primary biodegradation (decolourisation) of recalcitrant triphenylmethane dyes Brilliant green and Crystal violet) by Pseudomonas sp was investigated. Biodegradation was enhanced in cultures with substrate supplementation. Glucose and starch were the best among the substrates tested. The percentage decolourisation increased with increasing concentration up to maximum of 0.2mgL-1 for glucose and 0.3mgL-1 for starch. The percentage with glucose was 93.30 ± 1.40% for Brilliant green and 90.20± 0.75% for Crystal violet. With 0.30 mgL-1 of starch the percentage decolourisation was 85.30± 0.180% for Brilliant green and 88.50± 0.90% for Crystal violet. Enhanced biodegradation was attributed to generation of redox equivalent (electron donors) as a result of metabolism of glucose and starch as cosubstrates. Decrease in percentage decolorisation at concentration above the maximum for glucose and starch was attributed to saturation of the binding; sites for redox equivalents to the chromophoric group (of quinone) of the dyes and/or metabolite repression of the peroxidase enzyme that catalyses the reductive cleavage of the chromophoric group. Cassava peeling (an agricultural waste) gave values of percentage decolourisation of 63± 0.8% for Brilliant green and 67.70± 0.60% for Crystal violet. The potential of agricultural wastes to enhance primary biodegradation of recalcitrant synthetic dyes is also revealed in this work. Keywords: Pseudomonas sp., Triphenylmethane dyes, primary biodegradation, cosubstrates AJAZEB Vol. 7 2005: pp. 38-44