Valorization of sugarcane bagasse for high-yield production of laccase through Aspergillus terreus for effective azo dye decolourization.

Synthetic dyes such as azo dyes are significant pollutants in the wastewater released from various textile industries. The low biodegradability and production from synthetic sources with high shelf life make azo dyes a challenging material for degradation. This study used chemically mutated Aspergillus terrus in the laccase production under solid-state fermentation using sugarcane bagasse. Initially, the wild-type strain produced a laccase activity of 4.12 U/mL. Later, the alkaline pretreatment of sugarcane bagasse showed a significant increase in laccase activity by 38.9%. Further, random mutagenesis treatment with 100 mM EMS generated a hyper laccase-producing strain with a 2.3-fold increment in laccase activity compared to the wild-type strain. The enzyme displayed optimal activity at pH 6.5 and 35 °C. The metal ions such as Fe3+ (29.4 U/mL), Fe2+ (20.8 U/mL) and Cu2+ (18.05 U/mL) showed positive effects on laccase activity. The crude laccase was used to bioremediate Congo red, a prominent azo dye used in textile and pharmaceutical industries. The preliminary studies with a crude enzyme displayed 68.86% dye decolourization after 24 h of incubation. Additionally, with Taguchi orthogonal array optimization experiments, the maximal dye decolorization of 78.24% was achieved by maintaining crude enzyme concentration (20 U), dye concentration (25 mg/L) and pH 4.5.

An efficient biosorbent material for green remediation of contaminated water medium.

The discharge of large amounts of wastewater carrying various contaminants from many anthropogenic activities into the receiving water environment is a multidimensional issue negatively affecting the ecological system and natural balance in many ways. The removal of pollutants by the biologically-originated materials is an emerging area of interest due to profoundly their environmental friendliness, renewability, sustainability, readily availability, biodegradability, multiplicity, low (or no) economic cost, high affinity, capacity, and stability. In the present study, a popular ornamental plant, Pyracantha coccinea M. J. Roemer, was converted into a green sorbent material with the goal to effectively remove a widespread contaminant (synthetic dye, C. I. Basic Red 46) from synthetic wastewater. The physicochemical characteristics of the prepared biosorbent were determined by the instrumental analyses of FTIR and SEM. The batch experiments of various operational influence parameters were conducted to maximize the system efficiency. The wastewater remediation behavior by the material was investigated by the kinetics, thermodynamics, and isotherm experiments. The biosorbent had a non-uniform and rough surface architecture with a diversity of functional groups. The maximum remediation yield was achieved with the contact duration of 360 min, the pollutant load of 30 mg L-1, the pH of 8, and the biosorbent quantity of 10 mg (0.1 g L-1). The kinetics of the contaminant removal showed good agreement with the pseudo-second-order model. Thermodynamics study indicated that the treatment process was spontaneous and occurred by physisorption. Langmuir model fitted the isotherm data of the biosorption operation well and the maximum pollutant cleanup capacity of the material was determined to be 169.354 mg g-1. These outcomes showed that P. coccinea M. J. Roemer could be used as a promising material for low-cost and green treatment of wastewater.

In the current study, Pyracantha coccinea M. J. Roemer was converted into a novel alternative sorbent material that is low-cost and green with the goal to effectively remove C. I. Basic Red 46, a widespread synthetic dye contaminant, from wastewater. The results indicated that P. coccinea M. J. Roemer could be used as an efficient biosorbent material for the green remediation of contaminated water medium.

Multi-pollutant biosorption of organic and inorganic pollutants by brown algae waste from alginate production: batch and fixed-bed investigation.

The reuse of biomass waste has been gaining attention in adsorption processes to remove pollutants of emerging concern from water and wastewater. In this work, the potential of alginate-extracted macro-algae waste to uptake synthetic dyes and metal cations was evaluated in comparison with raw algae. In affinity assays, both materials were able to remove metal cations and cationic dyes up to maximum rates, and no significant removal was observed for an anionic dye in an acidic medium. Competition was observed in multi-component systems of metal cations and dyes. For binary samples containing organic and inorganic contaminants, kinetic modeling evidenced the distinct nature of both types of adsorbates. Pb(II) biosorption was best described as a first-order process, while second-order and Elovich models better fitted methyl blue (MB) uptake data. For equimolar binary samples, the Sips isothermal model fitted the experimental data more satisfactorily at room temperature. Isotherms for 20, 30, 40, and 60 °C exhibited favorable adsorption profiles with spontaneous ΔG values for both raw macro-algae and waste from alginate extraction. Maximum adsorption capacities were competitive with previous reports in the literature for a wide range of biomaterials, pointing to the slightly higher efficiency with algae waste in batch experiments. In elution tests, HNO3 (0.5 M) showed the best recovery rates of metal cations. Continuous biosorption operation revealed the performance of the brown algae waste was considerably more efficient than raw algae with breakthrough biosorption capacities up to 3.96 and 0.97 mmol.g-1 for the removal of Pb(II) and MB, respectively. A total of 3.0 g of algae and algae waste were able to deliver 1.20 and 1.62 L of contaminant-free water, respectively. XPS analyses corroborate previous assays that pointed to the prevalence of physisorption with evidence of complexation, ionic exchange, and hydrogen displacement mechanisms.

Degradation of Diazo Dye and its Kinetic and Equilibrium Studies Using the Potential of Bryophyllum fedtschenkoiin Aqueous System.

Phytoremediation is emerging as an eco-friendly, innovative, and cost-effective approach for the removal of textile dyes from wastewater from the previous decade. The current research work aims to explore the potential of a terrestrial ornamental plant, Bryophyllum fedtschenkoi (Raym.-Hamet & H. Perrier) Lauz.-March. for remediating the diazo dye as Congo red (CR) in aqueous form. B. fedtschenkoi was grown hydroponically before treatment with 100 mL of a different concentration of CR dye solution. A maximum decolorization potential of 90% was obtained for 10 mg L- 1 after 40 h of equilibrium. The kinetic studies have revealed that the experimental results for the removal of CR dye using the B .fedtschenkoi plant are suitable for Pseudo-first order with R2 ≥ 0.92, while the equilibrium studies agreed with the Freundlich adsorption isotherm with R2 ≥ 0.909. The dye removal by the plant was confirmed with the help of analytical techniques Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). Gas Chromatography-Mass Spectrometry (GC-MS) and High-Performance Liquid Chromatography (HPLC) were also performed on dye-degraded metabolites to explore the mechanism of dye degradation.

Application of biorefinery by-product of Nigella sativa L. herb for green treatment of synthetic dye impurity in aquatic environment: a circular economy based approach to water purification.

In this work, the performance of residual biomass of Nigella sativa L. plant from the process of bio-oil production toward the green removal of synthetic dye pollution from aquatic medium was systematically studied for the first time based on the circular economy strategy. The characterization of material was performed using Electron Microscope of Scanning and Infrared Spectrometer of Fourier Transform. The main process variables like pH, biosorbent amount, synthetic dye loading, and contact duration were optimized by the batch biosorption experiments to achieve the maximum remediation yield. The analyses of kinetics, equilibrium, and thermodynamics were conducted to understand the possible mechanism of purification. The experimental dynamics and equilibrium data were in better agreement with the pseudo-second-order and Langmuir models. For the targeted model synthetic dye compound (C. I. Basic Red 46), the biosorption capacity was obtained as 136.2 mg g-1 at the optimized conditions of pH of 8, biosorbent amount of 10 mg (100 mg L-1), synthetic dye loading of 30 mg L-1, and duration of 360 min. The treatment process was favorable, spontaneous, and physical. The characterization operation showed that the dye molecules were restrained on the rough surface of biosorbent. This study reveals that the reuse of herbal oil refinery residue as a biosorbent can present an economic, efficient, and eco-friendly option for the remediation of synthetic dye pollution in aqueous medium.

Here, by adopting the circular economy based approach, an exemplary study was conducted using the waste biomass of Nigella sativa L. left over from the bio-oil production process for the removal of synthetic dye pollution from water environment. N. sativa L. (Black seed, Ranunculaceae plant family) is an annual herb containing many different bioactive molecules. Mostly, the seed part of plant is widely used for domestic and industrial purposes (such as food, medicine, cosmetic, and biofuel) almost all over the world. Most of the bioactive compounds of plant are concentrated in the oil content of seed (30­38%). A huge amount of waste seed biomass remains after the extraction process to obtain this rich oil ingredient. The reuse of this vegetal oil refinery by-product as a biosorbent material for the remediation of synthetic dye pollution in aqueous environment has not been investigated so far. A cationic azo dye (C. I. Basic Red 46) extensively employed in the textile industry was selected as the model synthetic dye compound to test the treatment efficiency of novel biosorbent. The optimization, dynamics, equilibrium, thermodynamics, characterization, and comparison analyses were performed to evaluate the performance of synthetic dye removal of biosorbent from water medium. This work showed that the application of N. sativa L. oil refinery residue as a novel biosorbent could offer a promising option for the treatment of synthetic dye impurity in water medium.

Sensing of azo toxic dyes using nanomaterials and its health effects - A review.

Development of science has taken over our lives and made it mandatory to live with science. Synthetic technology takes more than it has given for our welfare. In the process of meeting the demand of the consumers, industries supported synthetic products to meet the same. One such sector that employs synthetic azo dyes for food coloring is the food industry. The result of the process is the production of a variety of colored foods which looks more appealing and palatable. The process not only meets the consumer's demand it also has an impact on customers' health because the consumption of azo-toxic dye-treated foods regularly or in direct contact with synthetic azo dyes can also cause severe human health consequences. Nanotechnology is a rapidly evolving branch of research in which nanosensors are being developed for a variety of applications, including sensing various azo-toxic dyes in food products, which provides a wider scope in the future, with the innovation in designing different nanosensors. The current review focuses on the different types of nanosensors, their key role in sensing, and the sensing of azo toxic dyes using nanosensors, their advantages over other sensors, applications of nanomaterials, and the health impacts of azo dyes on humans, appropriate parameters for maximum permissible limits, and an Acceptable Daily Intake (ADI) of azo toxic dye to be followed. The regulations followed on the application of colorants to the food are also elaborated. The review also focuses on the application of enzyme-based biosensors in detecting azo dyes in food products.

Identification of Tartrazine adulteration and evaluating exposure to synthetic dyes of sunset yellow and Quinoline yellow through consumption of food products among children.

Excessive consumption of synthetic food dyes by children may raise concerns about their health. These dyes may aggravate the hyperactivity symptoms and exacerbate asthma in sensitive children. The purpose of this study was to determine the presence of sunset yellow and quinoline yellow dyes, as well as tartrazine in dairy-free fruit ice cream, freeze pop, jelly, and candy. Additionally, we evaluated the amount of two food dyes consumed by children. To do so, a total of 150 food samples, including 20 dairy-free fruit ice creams, 25 freeze pops, 57 jelly products, and 48 types of candy were randomly selected from stores in Shiraz, Iran. Then, using the high-performance liquid chromatography (HPLC) method and an ultraviolet (UV) detector, we measured the amounts of sunset yellow and quinoline yellow dyes and identified the use of tartrazine. Also, the per capita consumption (grams per day) of the mentioned foods was calculated using a checklist in two groups of male and female primary schoolchildren aged 6-9 years and 10-13 years in Shiraz, Iran. According to the results, 11 (7.33%) samples contained only tartrazine and 107 (71.33%) samples contained quinoline yellow and sunset yellow synthetic dyes. In addition, of 107 samples that used quinoline yellow and sunset yellow, 102 (95.33%) contained unauthorized tartrazine. Only seven (6.54%) samples contained exceedingly high concentrations of authorized quinoline yellow and sunset yellow synthetic dyes. However, the exposure assessment showed that the intake of quinoline yellow and sunset yellow was at average levels and the 95th percentile in both age groups was less than the associated acceptable daily intake (ADI). For synthetic dyes, the target hazard quotient (THQ) and hazard index (HI) were less than one, indicating that ingestion of these two dyes via food products does not pose a risk to children's overall health.

One-pot alkanolamines-assisted synthesis of magnetic mesoporous silica for synthetic dye adsorption.

Magnetic mesoporous silica (MMS) was synthesized in a one-pot system using various alkanolamines (triethanolamine, diethanolamine, tris (hydroxymethyl)aminomethane) as a basic catalyst. The characterization of the composites was conducted using scanning electron microscope, transmission electron microscope, X-ray diffractometer, surface area analyzer, and X-ray photoelectros spectroscopy. The MMS synthesized with tris(hydroxymethyl)aminomethane (MMSTRIS) showed the highest specific surface area, pore volume, and average pore diameter. However, when the composites were applied as adsorbents for brilliant green (BG) dye, MMS synthesized with diethanolamine (MMSDEA) showed the highest maximum adsorption capacity of 339.7 mg g-1. The fastest adsorption rate constant of 1.57 × 10-2 g mg-1 min-1 was obtained for MMSTRIS, which has the largest average pore size among all composites. The adsorption kinetic study suggested that the adsorption of BG onto the prepared MMS composites was mainly chemisorption process, which most likely involves electrostatic interaction and hydrogen bonding between BG molecule and the surface of the composites.

Ultrasensitive Electrochemical Detection and Plasmon-Enhanced Photocatalytic Degradation of Rhodamine B Based on Dual-Functional, 3D, Hierarchical Ag/ZnO Nanoflowers.

The sensitive detection and degradation of synthetic dyes are pivotal to maintain safety owing to the adverse side effects they impart on living beings. In this work, we developed a sensitive electrochemical sensor for the nanomolar-level detection of rhodamine B (RhB) using a dual-functional, silver-decorated zinc oxide (Ag/ZnO) composite-modified, screen-printed carbon electrode. The plasmon-enhanced photocatalytic degradation of organic pollutant RhB was also performed using this nanocomposite prepared by embedding different weight percentages (1, 3, and 5 wt%) of Ag nanoparticles on the surface of a three-dimensional (3D), hierarchical ZnO nanostructure based on the photoreduction approach. The structure and morphology of an Ag/ZnO nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental mapping, ultraviolet-visible (UV-vis) spectroscopy, and X-ray diffraction (XRD). The electrochemical sensor exhibited a very high sensitivity of 151.44 µAµM-1cm-2 and low detection limit of 0.8 nM towards RhB detection. The selectivity, stability, repeatability, reproducibility, and practical feasibility were also analyzed to prove their reliability. Furthermore, the photocatalysis results revealed that 3 wt% of the Ag/ZnO hybrid nanostructure acquired immense photostability, reusability, and 90.5% degradation efficiency under visible light. Additionally, the pseudo-first-order rate constant of Ag-3/ZnO is 2.186 min-1 suggested promising activity in visible light photocatalysis.

Exploring a safer alternative to eosin in soft tissue staining.

Context: Hematoxylin-eosin (H&E) stain has stood the test of time as the standard stain for histologic examination of human tissues. Haematoxylin is a natural dye, on the contrary, its counterstain eosin is a synthetic dye which belongs to the xanthene group. Synthetic dyes are hazardous to human and animal health. With the increasing awareness of a green earth, it is advisable to use environment-friendly and biodegradable materials. Therefore, an attempt was made to develop as biofriendly substitute in the form of food colour as a counterstain for haematoxylin. Aim: To assess the staining ability of food colouring agents in routine staining and to compare its staining efficacy with Eosin. Settings and Design: Two food colours were obtained and stain was prepared by using 70% ethyl alcohol as counterstain for haematoxylin. Different tissue structures such as epithelium, keratin, collagen fibers, muscles, salivary glands, adipocytes, blood vessels, RBCs were observed and evaluated. Methods and Material: Group A -10 slides stained with green food colour, Group B - 10 slides stained with tomato red food colour and Group C - 10 slides stained with conventional H and E. The stained sections were assessed and graded for nuclear staining, cytoplasmic staining, clarity, uniformity and crispness of staining. Statistical Analysis Used: The non-parametric Kruskal-Wallis and Mann-Whitney U tests were performed for statistical analysis. Results: There was no statistically significant difference between the three study groups with respect to all the parameters except crispness of staining. The crispness of Tomato Red and H and E was better compared to green food colour. Conclusions: Food colouring agents can be used as a safe, biofriendly and inexpensive substitute to eosin in conventional soft tissue staining.

Chemically induced oxidative stress improved bacterial laccase-mediated degradation and detoxification of the synthetic dyes.

To alleviate the risk of textile effluent, the development of highly effective bioremediation strategies for synthetic dye removal is needed. Herein, we aimed to assess whether intensified bioactivity of Bacillus pumilus ZB1 by oxidative stress could improve the removal of textile dyes. Methyl methanesulfonate (MMS) induced oxidative stress significantly promoted laccase expression of B. pumilus ZB1. Both the level of hydrogen dioxide and superoxide anion showed a significant positive correlation with laccase activity (RSQ = 0.963 and 0.916, respectively) along with the change of MMS concentration. The regulation of laccase expression was closely related to oxidative stress. The overexpressed laccase in the supernatant improved the decolorization of synthetic dyes (16.43% for Congo Red, 54.05% for Crystal Violet, and 41.61% for Reactive Blue 4). Laccase was subsequently expressed in E. coli. Investigation of the potential of bacterial laccase in dye remediation using Congo Red showed that an effective degradation of azo dye could be achieved with laccase treatment. Laccase remediation alleviated the cytotoxicity of Congo Red to human hepatocytes. In silico study identified eight amino acid residues of laccase involved in binding with Congo Red. Overall, regulation of oxidative stress towards bacterium can be used as a promising approach for the improvement of bacterial bioactivity in synthetic dye remediation.

Decolorization kinetics and mass transfer mechanisms of Remazol Brilliant Blue R dye mediated by different fungi.

The release of synthetic dye into the environment causing abnormal growth of phytoplankton may lead to a decline in the photosynthetic performance of aquatic ecosystem. Scientific knowledge of Remazol Brilliant Blue R (RBBR) decolorization is essential for designing the engineered bioremediation systems of employing fungal mycelium. The biodegradation of RBBR dye mediated by an appropriate fungus was analyzed using the modified mass transfer factor models to get better understanding on the decolorization kinetics and mechanisms of external and internal mass transfer. The results showed that the limited capacities of the kinetic and isotherm models are still not able to comprehensively explain many important phenomena of RBBR decolorization mediated by the T. citrinoviride, T. koningiopsis and Pestalotiopsis sp. strains. The rate-limiting step of RBBR decolorization depends on the EMT resistance and the vegetative growth rates of T. citrinoviride, T. koningiopsis and Pestalotiopsis sp. strains can be described by second-order polynomial equation. The analysis of decolorization performance may provide a new insight on the role of fungus in the degradation of RBBR dye.

Co-immobilized spore laccase/TiO2 nanoparticles in the alginate beads enhance dye removal by two-step decolorization.

Combinatorial application of different dye removal methods with specific features can lead to a novel and robust decolorizing system. In this study the bacterial spore laccase and TiO2 nanoparticles were co-entrapped to enhance dye degradation. The optimum entrapment conditions were achieved in the presence of alginate 2% (w/v) and Ca2+ (0.2M), Cu2+ (0.05M) and Zn2+ (0.25M) as matric polymer and counterions, respectively. Immobilized laccase showed a wide range of pH and temperature stability in comparison to the free spores. The entrapped degradation systems include single laccase, single TiO2, laccase + TiO2 (one-step remediation), TiO2/laccase (two-step remediation), and laccase/TiO2 (two-step remediation) that result to the 22%, 26% 45.6%, 47.6%, and 69.3% indigo carmine decolorization in 60 min. In the kinetic studies, the half-life of indigo carmine (25 mg/l) in the remediation processes containing laccase, TiO2, laccase + TiO2, TiO2/laccase, and laccase/TiO2 was calculated as 173, 138, 161, 115, and 57 min, respectively. The degradation products by co-entrapped system were not toxic against Sorghum vulgare. The results showed two-step decolorization by co-entrapped spore laccase and TiO2 nanoparticles, including the pretreatment of dye by laccase, and then, treatment by TiO2 has potential for degradation of indigo carmine.

An economical and effective alternative to commercial activated carbon for treatment of synthetic dye pollution in aquatic environment: surfactant modified waste product of Zostera marina.

In this study, a novel biosorbent material was created from the waste product of Zostera marina with the surfactant modification (Hexadecyltrimethylammonium bromide) and tried as a potential alternative to commercial (powdered) activated carbon for the treatment of synthetic dye (Fast green FCF, triarylmethane (anionic) type) pollution in aquatic environment. The treatment capability of biosorbent material was evaluated by the parameter optimization, kinetic, thermodynamic, equilibrium and characterization experiments. The optimum treatment conditions were found to be pH of 3, biosorbent amount of 10 mg, synthetic dye concentration of 15 mg L-1, temperature of 45 °C and operation time of 360 min. It was determined that Elovich model was the most suitable model among the models used to define the biosorption kinetic data. The synthetic dye treatment process was endothermic and spontaneous. Freundlich model best explained the biosorption isotherm data. The biosorbent has very heterogeneous surface with the different functional groups. The treatment capabilities of prepared biosorbent and activated carbon under the same operating conditions were calculated to be 163.075 and 110.635 mg g-1, respectively. Hereby, these experimental findings show that the synthesized eco-friendly and low-cost biosorbent can be a powerful alternative to commercial activated carbon for the purification of synthetic dye pollution in water environment.

Synthetic dyes biodegradation by fungal ligninolytic enzymes: Process optimization, metabolites evaluation and toxicity assessment.

This work aimed to provide information that contributes to establishing environmental-friendly methods for synthetic dyes' degradation. The potential decolorization capacity of the crude enzymatic extract produced by Phanerochaete chrysosporium CDBB 686 using corncob as a substrate was evaluated on seven different dyes. Critical variables affecting the in-vitro decolorization process were further evaluated and results were compared with an in-vivo decolorization system. Decolorization with enzymatic extracts presented advantages over the in-vivo system (higher or similar decolorization within a shorter period). Under improved in-vitro process conditions, the dyes with higher decolorization were: Congo red (41.84 %), Poly R-478 (56.86 %), Methyl green (69.79 %). Attempts were made to confirm the transformation of the dyes after the in-vitro process as well as to establish a molecular basis for interpreting changes in toxicity along with the degradation process. In-vitro degradation products of Methyl green presented a toxicity reduction compared with the original dye; however, increased toxicity was found for Congo red degradation products when compared with the original dyes. Thus, for future applications, it is crucial to evaluate the mechanisms of biodegradation of each target synthetic dye as well as the toxicity of the products obtained after enzymatic oxidation.

A low-cost and eco-friendly biosorbent material for effective synthetic dye removal from aquatic environment: characterization, optimization, kinetic, isotherm and thermodynamic studies.

A novel biosorbent was prepared by the surface modification of Zostera marina L. bioresidues and used for the removal of model synthetic dye, methylene blue from aqueous medium in this study. Taguchi design of experiment (DoE) methodology was employed to investigate the influence of significant operational parameters (reaction time, pH of medium and dye concentration) on the biosorption process and to develop a mathematical model for the estimation of biosorption potential of biosorbent. The percentage contribution of each of these process variables on the dye biosorption was found to be 9.03%, 1.95% and 88.84%, respectively. The dye biosorption capacity under the obtained optimum environmental conditions (reaction time of 120 min, pH of 8 and dye concentration of 15 mg L-1) was estimated to be 140.154 mg g-1 (R2: 99.83). This value was very close to the experimentally obtained dye removal performance value (140.299 mg g-1). These findings indicated the high ability of Taguchi DoE technique in the optimization and simulation of dye biosorption system. The kinetic and equilibrium modeling studies showed that the pseudo-second-order and Langmuir models were the best models for the elucidation of dye removal behavior of biosorbent. Besides, the performance of dye decontamination system was evaluated using the pseudo-second-order kinetic parameters. The thermodynamic analyses displayed that the dye biosorption was a feasible, spontaneous and exothermic process. For large scale dye purification applications, a single-stage batch biosorption system was also designed using the mathematical modeling data. All these results revealed that Z. marina L. bioresidues could be used as a promising alternative biosorbent material for the effective and eco-friendly dye biosorption systems.

Evaluation of several white-rot fungi for the decolorization of a binary mixture of anionic dyes and characterization of the residual biomass as potential organic soil amendment.

Industrial pollution is a great concern for modern society and developing cyclic processes is one of the major challenges. As far as we know, this work is the first to report the use of multiple white-rot fungi species for degrading a binary mixture of anionic dyes under solid state fermentation (SSF) conditions and a further physicochemical characterization of the residual biomass. First, eight white-rot fungi decolorized the dye mixture of brilliant blue FCF and allura red AC adsorbed onto corncob, reaching decolorizations between 11.47% and 87.64%. Then, I. lacteus, B. adusta and T. versicolor, based on the decolorization yield, were selected to evaluate the effect of carbon:nitrogen ratio, moisture content and inoculum quantity on the decolorization percentage. The factorial designs showed that C:N ratio had a negative effect while moisture and inoculum quantity a positive effect. In terms of the kinetics, the three white-rot fungi achieved their maximum decolorization level, around 80.11-86.04%, after 10-12 days. I. lacteus exhibited the highest decolorization percentage, even though only the enzyme manganese peroxidase was detected, with a maximum activity of 6.62 U gds-1 at day 14. Besides, T. versicolor was the only species with laccase activity, with a maximum of 15.94 U gds-1 at day 6 of fermentation. The physicochemical characterization of the biomass allowed to conclude that these aggregates represent a potential organic amendment, as for their significant oxidizable organic carbon (more than 9.5% on wet basis) and essential nutrients content, as well as for their low ash content (less than 1% on wet basis). Finally, for outlining an efficient bioremediation cycle, a cheap and effective methodology for drying the biomass at the end of the SSF process is required.

Decolorization of Acid Green 25 by Surface Display of CotA laccase on Bacillus subtilis spores.

In this study, we expressed cotA laccase from Bacillus subtilis on the surface of B. subtilis spores for efficient decolorization of synthetic dyes. The cotE, cotG, and cotY genes were used as anchoring motifs for efficient spore surface display of cotA laccase. Moreover, a His6 tag was inserted at the C-terminal end of cotA for the immunological detection of the expressed fusion protein. Appropriate expression of the CotE-CotA (74 kDa), CotG-CotA (76 kDa), and CotY-CotA (73 kDa) fusion proteins was confirmed by western blot. We verified the surface expression of each fusion protein on B. subtilis spore by flow cytometry. The decoloration rates of Acid Green 25 (anthraquinone dye) for the recombinant DB104 (pSDJH-EA), DB104 (pSDJH-GA), DB104 (pSDJH-YA), and the control DB104 spores were 48.75%, 16.12%, 21.10%, and 9.96%, respectively. DB104 (pSDJH-EA) showed the highest decolorization of Acid Green 25 and was subsequently tested on other synthetic dyes with different structures. The decolorization rates of the DB104 (pSDJH-EA) spore for Acid Red 18 (azo dye) and indigo carmine (indigo dye) were 18.58% and 43.20%, respectively. The optimum temperature for the decolorization of Acid Green 25 by the DB104 (pSDJH-EA) spore was found to be 50°C. Upon treatment with known laccase inhibitors, including EDTA, SDS, and NaN3, the decolorization rate of Acid Green 25 by the DB104 (pSDJH-EA) spore decreased by 23%, 80%, and 36%, respectively.

Taguchi DoE methodology for modeling of synthetic dye biosorption from aqueous effluents: parametric and phenomenological studies.

Biosorption technology has been acknowledged as one of the most successful treatment approaches for colored industrial effluents. The problems such as its high manufacturing cost and poor regeneration capability in the use of activated carbon as a biosorbent have prompted the environmental scientists to develop alternative biosorbent materials. In this context, as a sustainable green generation alternative biosorbent source, the discarded seed biomass from pepper (Capsicum annuum L.) processing industry was explored for the biotreatment of colored aqueous effluents in this study. To test the wastewater cleaning ability of biosorbent, Basic red 46 was selected as a typical model synthetic dye. Taguchi DoE methodology was employed to study the effect of important operational parameters, contact time, pH and synthetic dye concentration, on the biosorption process and to develop a mathematical model for the estimation of biosorption potential of biosorbent. The percentage contribution of each of these process variables on the dye biosorption was found to be 19.31%, 41.39%, and 38.74%, respectively. The biosorption capacity under the optimum environmental conditions, contact time of 360 min, pH of 8 and dye concentration of 30 mg L-1, was estimated to be 92.878 mg g-1 (R2: 99.45). This value was very close to the experimentally obtained dye removal performance value (92.095 mg g-1). These findings indicated the high ability of Taguchi DoE technique in the optimization and simulation of dye biosorption system. The kinetic and equilibrium modeling studies showed that the pseudo-second-order and Langmuir models were the best models for the elucidation of dye removal behavior of biosorbent. The thermodynamic studies displayed that the dye biosorption was a feasible, spontaneous and exothermic process. This parametric and phenomenological survey revealed that the discarded pepper seed biomass can be introduced as a potential and efficient biosorbent for the bioremediation of colored industrial effluents.

Decolourization and detoxification of monoazo dyes by laccase from the white-rot fungus Trametes versicolor.

The decolourization and detoxification of azo dyes (Orange 2, Acid Orange 6) by fungal laccase from Trametes versicolor were evaluated. For laccase catalysed reaction, the azonaphthol Orange 2, with 72.8% decolourization, was degraded more rapidly than the azobenzene Acid Orange 6, with 45.3%. The presence of hydroxyl group at o-position to azo bond in the structure of Orange 2 was more preferable than the presence of two hydroxyl groups at o- and p-positions to azo bond in Acid Orange 6. Although the laccase treatment was more effective for the Orange 2 decolourization, the toxicity of both monoazo dye solutions became less toxic for the prokaryote growth. The phytotoxicity of Orange 2 and Acid Orange 6 solutions after laccase treatment was decreased in the range of 41.2-64.3 %. Also, the photoxicity, as measured by the production of chlorophylls a and b by Chlorella vulgaris and Microcystis aeruginosa, was decreased by laccase treatment of selected monoazo dyes. Our results show that different dyes can be decolorized and detoxified by laccase from T. versicolor in a single step.