Dye Decolorization Research Articles

Innovative optimization for maximum magnetic nanoparticles production by Trichoderma asperellum with evaluation of their antibacterial activity, and application in sustainable dye decolorization

A pioneer microbial-based synthesis of various nanoparticles is gaining more attention due to their potent applications in various industries. The magnetic nanoparticles (M-nps) were fabricated for the first-time using the cell free extract of Trichoderma asperellum. The M-nps bioprocess optimization was performed using Response Surface Methodology and Artificial Neural Network.The bioprocess was significantly (P < 0.05) affected by pH, stirring speed, and incubation period. The M-nps displayed a strong antibacterial efficiency against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus in a dose-dependent manner. The minimum inhibitory concentration (MIC) for E. coli, P. aeruginosa, and S. aureus were respectively found to be 25.0, 6.25, and 3.125 µg/ml. While the minimum bactericidal concentration (MBC) was 25.0, 12.5, and 6.25 µg/ml. The highest inhibition zone of 22 mm was recorded for B. subtilis at 80 µg/ml with MIC and MBC of 3.125 µg/ml. The sodium alginate/M-nps microbeads was successfully prepared without any crosslinkers. The microbeads exhibited the highest adsorptive efficiency (84.32%) for malachite green at pH 8.0, dose 0.1 g, and time 60 min. The experimental data were superlative fitted to Langmuir’s isotherm, hinting monolayer adsorption of MG molecules with 117.65 mg g‐−1 adsorptive capacity. The regenerated beads continued up-to six consecutive cycles and maintained more than 90%, indicating the multiple time use of the prepared material. Hence, the green magnetic nanoparticles display promising application in combating bacterial pathogens. The magnetic microbeads can be employed as an alternative eco-friendly, highly efficient, sustainable, and low-cost biosorbent in removing contaminants from wastewater.

Antibacterial potential and dye decolorization with graphitic carbon nitride and eudragit doped CdTe nanostructures evidential molecular docking analysis

Co-precipitation procedure was employed to prepare efficient ternary system-based catalysts composed of various concentrations (2 and 4 wt.%) of graphitic carbon nitride (g-C3N4) and fixed amount (3 wt.%) of eudragit (Eud)-doped cadmium telluride (CdTe) nanostructures (NSs). The main objective of this study was to explore and enhance the dye degradation potential by changing the recombination rate of CdTe with doping and improving their multifunctional efficacy as catalysts and antibacterial agents. The dopants have altered the particle size, dispersal and optical properties of CdTe. The different concentrations of g-C3N4 and fixed amount of Eud, reaction temperature, and duration influence these characteristic properties of CdTe. g-C3N4 /Eud-doped CdTe with porous structure showed excellent methyl orange (MO) dye degradation efficiency (98.0 %) in neutral medium. Furthermore, 4 wt.% of g-C3N4 doped NSs exhibited significant inhibition zone as 9.35 ± 0.08 mm against MDR S. aureus bacteria. The molecular docking studies were conducted to elucidate the mechanistic interactions between g-C3N4/Eud-doped CdTe nanostructures and the target enzymes DNA gyrase S. aureus and D alanine-D-alanine ligase (ddlB)S. aureus, in order to justify their microbicidal efficacy.

Strategic decolorization of rose bengal in an aqueous environment using a zinc oxide-loaded reduced graphene oxide photocatalyst

The environmental and health hazards posed by synthetic organic dyes, such as Rose Bengal, have spurred significant concern in recent years. Herein, a novel zinc oxide/reduced graphene oxide (ZnO/rGO)-based photocatalyst is developed and used for the efficient decolorization of RB dye in aqueous solutions. The as-synthesized nanostructured material is characterized using advanced techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) mapping to elucidate its crystalline structure, morphology, and elemental composition. The XRD pattern confirmed the wurtzite crystalline phase structure with an average size of 67.8 nm, while SEM imaging verified the successful incorporation of ZnO nanoparticles into the rGO matrix. Further, the as-prepared material was used as a photocatalyst, which demonstrated remarkable performance in RB dye decolorization, achieving ≥96.1 % degradation within just 5 min at a minimal catalyst dosage of 8.0 mg. Moreover, kinetic studies revealed that the decolorization process followed a pseudo-second-order reaction mechanism, further enhancing the understanding of the catalytic behavior. It is more interesting that the catalyst exhibited exceptional reusability for up to seven cycles with only a decrease in catalyst efficiency from 96.1 % to 77.5 %, underscoring its practical viability and sustainability. The significance of this work lies in its contribution to addressing the environmental challenges associated with synthetic dyes, particularly rose bengal, by offering an efficient and reliable photocatalytic solution. The demonstrated efficacy of the ZnO/rGO photocatalyst not only showcases its potential for large-scale rose bengal dye degradation but also suggests broader applicability for the treatment of other synthetic dye pollutants.

Decolorization of anthraquinone dye by Brevibacillus laterosporus R81 via polysaccharides excreted

AbstractThe aim of this research was to assess the efficacy of different microbial strains in the decolorization of anthraquinone dyes. Strain R81 was obtained from a textile company's wastewater discharge for its remarkable ability to decolorize reactive blue 19 (RB19). By employing physiological and biochemical analyses, along with 16S rRNA gene sequencing, strain R81 was determined to be Brevibacillus laterosporus. After optimization, the decolorization rate achieved a peak of 86.24% over a 48‐h timeframe, utilizing an initial dye concentration of 100 mg L–1. The decolorization capacity of strain R81 was observed to be impeded by heightened levels of salt and temperature in culture solutions, yet remained unaltered when R81 cells were directly introduced into dye solutions. Furthermore, cells that were induced through prior cultivation in a medium containing RB19 demonstrated enhanced efficacy in decolorization compared to noninduced cells. Subsequent analysis indicated that the development of biofilms and the synthesis of polysaccharides by strain R81 were augmented in a concentration‐dependent fashion by RB19. Nevertheless, the decolorization efficacy of R81 was impeded by the existence of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), both of which possess the capacity to eliminate polysaccharides. The decolorization capabilities were reinstated by the SDS or CTAB eluent containing polysaccharides, suggesting a reliance on the presence of polysaccharides. The employment of stepwise diethylaminoethyl (DEAE)‐cellulose chromatography and decolorization experiments elucidated the importance of a specific polysaccharide in the decolorization process. This study proposes a bacteria‐derived polysaccharide as a promising remedy for treating dyeing wastewater contaminated with anthraquinones.

Green biocatalyst for decolorization of azo dyes from industrial wastewater: Coriolopsis trogii 2SMKN laccase immobilized on recycled brewer's spent grain.

This study presents an innovative approach for the reuse and recycling of waste material, brewer's spent grain (BSG) for creating a novel green biocatalyst. The same BSG was utilized in several consecutive steps: initially, it served as a substrate for the cultivation and production of laccase by a novel isolated fungal strain, Coriolopsis trogii 2SMKN, then, it was reused as a carrier for laccase immobilization, aiding in the process of azo dye decolorization and finally, reused as recycled BSG for the second successful laccase immobilization for six guaiacol oxidation, contributing to a zero-waste strategy. The novel fungal strain produced laccase with a maximum activity of 171.4 U/g after 6 days of solid-state fermentation using BSG as a substrate. The obtained laccase exhibited excellent performance in the decolorization of azo dyes, both as a free and immobilized, at high temperatures, without addition of harmful mediators, achieving maximum decolorization efficiencies of 99.0%, 71.2%, and 61.0% for Orange G (OG), Congo Red, and Eriochrome Black T (EBT), respectively. The immobilized laccase on BSG was successfully reused across five cycles of azo dye decolorization process. Notably, new green biocatalyst outperformed commercial laccase from Aspergillus spp. in the decolorization of OG and EBT. GC-MS and LC-MS revealed azo-dye degradation products and decomposition pathway. This analysis was complemented by antimicrobial and phytotoxicity tests, which confirmed the non-toxic nature of the degradation products, indicating the potential for safe environmental disposal.

Structural Properties and Photocatalytic Activity of TiO2/Au Nanocomposites Synthesized with Glucose

AbstractA one‐pot synthesis of plasmonic gold‐modified TiO2 nanocomposites is reported by using glucose reduction of HAuCl4 in presence of titanium tetraisopropoxide. The resulting nanocomposites are characterized by thermal‐gravimetric analyses, X‐ray diffraction combined with X‐ray fluorescence and photoelectron spectroscopies. A binary system of β‐TiO2 and anatase phases is obtained for low Au content while only anatase form is favored when the initial Au rate rises. This investigation also suggests the inclusion of gold in the TiO2 structure. Although the optical bandgap of the different nanocomposites remains around 3 eV, the increase of Au content induces a shift of both valence and conduction edge bands to lower energy levels. The photocatalytic activity of TiO2/Au nanocomposites is assessed through the decolorization of different cationic and anionic dyes as model compounds. Regarding rhodamine and methylene blue dyes, the sample TiO2 modified with 3.5 wt% of Au presents the best performance. The relation between the structure of the nanocomposites and their capacity to degrade pollutants is discussed.

Histidine–cysteine–copper hybrid nanoflowers as active site-inspired laccase mimics for the colorimetric detection of phenolic compounds in PDMS microfluidic devices

Although laccases are essential multicopper oxidases in biosensing and bioremediation, their widespread use is hindered by issues such as instability and high cost. In this study, drawing inspiration from the active site structure of laccase, we developed hybrid nanoflowers through the coordination of copper ions with histidine-cysteine dipeptides (HC–Cu NFs) as highly robust laccase-mimicking nanozymes. The HC–Cu NFs possessed higher laccase-like activity compared to free laccase, yielding an approximately five-fold higher Vmax with a similar Km at the same mass concentration. Additionally, HC–Cu NFs exhibited exceptional stability across diverse environments, including a broad range of pH, temperature, salinity, and extended storage periods. Notably, HC-Cu NFs catalyzed the decolorization of phenolic dyes more rapidly than natural laccase. Utilizing these beneficial features, HC–Cu NFs were incorporated in a polydimethylsiloxane-based microfluidic device, enabling the on-site colorimetric determination of phenolic compounds, such as p-aminophenol, catechol, and hydroquinone, with outstanding sensitivity. By injecting only 20 μL of the sample solution through the inlet of the device, the sample solution rapidly moves to the detection zones where the HC-Cu NFs are retained, followed by catalytic oxidation to further react with 4-aminoantipyrine to produce a colored adduct. Using the microfluidic device, the target phenolic compounds were successfully determined within 20 min at ambient conditions using an image acquired with a smartphone with the ImageJ software. This study unequivocally demonstrates that active site-mimicking dipeptide-incorporated hybrid nanoflowers have the potential to serve as nanozymes, to replace natural laccase. This lays the groundwork for the further advancement of hybrid nanoflower-type nanozymes and their applications, particularly in point-of-care testing environments.

Brilliant green decolorization by dye decolorizing peroxidase producing bacterium, Achromobacter insolitus isolated from Forest soils of Similipal Biosphere Reserve, Odisha

Dye-decolorizing peroxidases (DyPs) are recently identified superfamily of heme-containing peroxidases which has received much attention for its potential application in dye decolourization. In the current research, six bacterial colonies (SDB1-6) showing lignolytic activity were isolated from forest soils of SBR using a minimal salt medium supplemented with alkali lignin and screened for DyP activity using brilliant green dye supplemented luria bertani agar medium. The highest DyP activity showing bacterium was identified using biochemical and 16SrRNA sequencing and was identified as Achromobacter insolitus. A. insolitus was found to be an efficient strain showing the highest DyP activity of 2.7 U/mL/ml at un-optimized condition. The RSM optimization was conducted to increase the DyP enzyme activity. A. insolitus demonstrated DyP activity of 6.20 U/mL/min with an increase of 2.29 times of enzyme activity in optimal condition of pH 7.0, temperature 25 °C, H2O2 concentration 0.1 mM, and time 24 h. The bacterium was further screened for dye decolorization taking crystal violet, methyl orange, methylene blue, brilliant green and methyl red dyes supplemented in LB medium. The bacterium showed maximum brilliant green degradation ability was analyzed using UV-Vis and FTIR analyses to characterize the degraded product. The highest brilliant green degradation activity of the A. insolitus in the present study could be exploited for bioremediation of brilliant green contaminated industrial effluents in a ecofriendly and cost effective way.

Trametes versicolor Laccase-Based Magnetic Inorganic-Protein Hybrid Nanobiocatalyst for Efficient Decolorization of Dyes in the Presence of Inhibitors.

In the present investigation, an ecofriendly magnetic inorganic-protein hybrid system-based enzyme immobilization was developed using partially purified laccase from Trametes versicolor (TvLac), Fe3O4 nanoparticles, and manganese (Mn), and was successfully applied for synthetic dye decolorization in the presence of enzyme inhibitors. After the partial purification of crude TvLac, the specific enzyme activity reached 212 U∙mg total protein-1. The synthesized Fe3O4/Mn3(PO4)2-laccase (Fe3O4/Mn-TvLac) and Mn3(PO4)2-laccase (Mn-TvLac) nanoflowers (NFs) exhibited encapsulation yields of 85.5% and 90.3%, respectively, with relative activities of 245% and 260%, respectively, compared with those of free TvLac. One-pot synthesized Fe3O4/Mn-TvLac exhibited significant improvements in catalytic properties and stability compared to those of the free enzyme. Fe3O4/Mn-TvLac retained a significantly higher residual activity of 96.8% over that of Mn-TvLac (47.1%) after 10 reuse cycles. The NFs showed potential for the efficient decolorization of synthetic dyes in the presence of enzyme inhibitors. For up to five reuse cycles, Fe3O4/Mn-TvLac retained a decolorization potential of 81.1% and 86.3% for Coomassie Brilliant Blue R-250 and xylene cyanol, respectively. The synthesized Fe3O4/Mn-TvLac showed a lower acute toxicity towards Vibrio fischeri than pure Fe3O4 nanoparticles did. This is the first report of the one-pot synthesis of biofriendly magnetic protein-inorganic hybrids using partially purified TvLac and Mn.

Potential of White Rot Fungi from Berbak-Sembilang National Park, Indonesia for Decolorization and Detoxification Commercial Direct Dyes

Commercial direct dyes are frequently employed in the dyeing of Jumputan, a traditional craft originating from South Sumatra, Indonesia. The introduction of synthetic dyes into the environment can have a detrimental impact on ecosystem stability, necessitating the implementation of remedial measures. There has been a growing interest in the utilization of White Rot Fungi (WRF) as a viable biological agent for the purpose of decolorizing and detoxifying synthetic colors. However, it is imperative to investigate the isolated WRF from Berbak-Sembilang National Park (TNBS) due to the varying capacities of decolorization and detoxification exhibited by each WRF. The study involved 5 WRF from TNBS screened in solid media, and grown in a liquid medium containing commercial direct dyes (direct turquoise, direct orange and direct yellow). WRF grown on liquid medium contains a single dye, mixture dyes and temperature characterization. It measured decolorization, biomass and enzyme activities. Toxicity is measured by the BSLT method. The findings indicated that 3 specific fungi, namely Phellinus noxius (BRB 11), Lentinus sajor-caju (BRB 12) and Leotrametes menziesii (BRB 73), exhibited a significant capacity to remove the color from both individual and mixture of direct dyes through the production of laccase and MnP enzymes. The optimal temperature for decolorization of the mixture of direct dyes was 35 °C for BRB 11 (61.4 %) and BRB 73 (60.7 %), whereas BRB 12 (47.4 %) exhibited optimal temperature at 30 °C. The toxicity assay conducted using A. salina showed a progressive rise in the LC50 value, from 15.37 mgL−1 in the control group to a range of 21.63 - 35.84 mgL−1 in the treated group, indicating a detoxification process. However, the most toxic isolate was BRB 12. This study proposes the potential of 2 isolates, Phellinus noxius (BRB 11) and Leotrametes menziesii BRB 73, from TNBS for degradation of single and mixture dye wastewater in the environment. HIGHLIGHTS The discovery of 3 White Rot Fungi from TNBS (Indonesia) has the ability to remove color and reduce the level of toxicity of commercial direct dyes, both individual and mixture of commercial direct dyes. Uncovering one of White Rot Fungi has not been widely published for decolorization and detoxification commercial direct dyes, namely Leotrametes menziesii (BRB 73). The optimal temperature was 35 °C for decolorization of commercial direct dyes by Phellinus noxius (BRB 11) and Leotrametes menziesii (BRB 73) GRAPHICAL ABSTRACT

Microalgal and activated sludge processing for biodegradation of textile dyes

The textile industry contributes substantially to water pollution. To investigate bioremediation of dye-containing wastewater, the decolorization and biotransformation of three textile azo dyes, Red HE8B, Reactive Green 27, and Acid Blue 29, were considered using an integrated remediation approach involving the microalga Chlamydomonas mexicana and activated sludge (ACS). At a 5 mg L−1 dye concentration, using C. mexicana and ACS alone, decolorization percentages of 39%–64% and 52%–54%, respectively, were obtained. In comparison, decolorization percentages of 75%–79% were obtained using a consortium of C. mexicana and ACS. The same trend was observed for the decolorization of dyes at higher concentrations, but the potential for decolorization was low. The toxic azo dyes adversely affect the growth of microalgae and at high concentration 50 mg L−1 the growth rate inhibited to 50–60% as compared to the control. The natural textile wastewater was also treated with the same pattern and got promising results of decolorization (90%). Moreover, the removal of BOD (82%), COD (72%), TN (64%), and TP (63%) was observed with the consortium. The HPLC and GC-MS confirm dye biotransformation, revealing the emergence of new peaks and the generation of multiple metabolites with more superficial structures, such as N-hydroxy-aniline, naphthalene-1-ol, and sodium hydroxy naphthalene. This analysis demonstrates the potential of the C. mexicana and ACS consortium for efficient, eco-friendly bioremediation of textile azo dyes.

Multigene phylogeny, bioactive properties, enzymatic and dye decolorization potential of selected marine fungi from brown algae and sponges of Mauritius

Marine fungi represent an important proportion of the microbial diversity in the oceans. They are attractive candidates for biotechnological purposes and industrial applications. Despite an increasing interest in mycology, marine fungi associated with sponges and algae have been poorly studied in Mauritius. The objectives of this study were to: 1) use multigene phylogenetic analyses to identify isolated marine fungi; 2) determine the differences in the antimicrobial and antioxidant properties of the fungal extracts; and 3) assess their enzyme activities and dye decolorization potential. Five fungal isolates viz Aspergillus chevalieri, Aspergillus iizukae, Aspergillus ochraceus, Exserohilum rostratum and Biatriospora sp. Were identified based on phylogenetic analyses. There was no significant difference in the antimicrobial properties of the liquid and solid media extracts unlike the antioxidant properties (p < 0.05). The solid media extract of Aspergillus chevalieri (F2-SF) had a minimum inhibitory concentration of 0.156 mg/ml against Staphylococcus aureus while Aspergillus ochraceus (F25-SF) had a minimum inhibitory concentration of 0.313 and 2.5 mg/ml against Enterococcus faecalis and Salmonella typhi. The solid media extract of Biatriospora sp. (F34-SF) had a minimum inhibitory concentration of 0.195 and 1.563 mg/ml against Bacillus cereus, Escherichia coli and Enterobacter cloacae. An IC50 of 78.92 ± 4.71 μg/ml in the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging assay, ferric reducing antioxidant power (FRAP) value of 11.17 ± 0.20 mM Fe2+/g dry weight extract (DWE) and total phenolic content 360.35 ± 10.31 mg GAE/g DWE was obtained with the solid media extract of Aspergillus chevalieri (F2-SF). Aspergillus ochraceus (F25-SF) and Biatriospora sp. (F34-SF) solid media extracts showed lower IC50 values in the DPPH assay and higher total phenolic content as compared to the liquid media extracts. Aspergillus chevalieri was a good producer of the enzymes DNAse and lipase and had maximum percentage dye decolorization of 79.40 ± 17.72% on Congo red. An enzymatic index ≥2 was found for the DNAse and lipase and the maximum percentage dye decolorization of 87.18 ± 3.80 % was observed with Aspergillus ochraceus on Methylene blue. Regarding Biatriospora sp., it was a moderate producer of the three enzymes amylase, DNAse and protease and had a maximum dye decolorization potential of 56.29 ± 6.51% on Crystal violet. This study demonstrates that Mauritian marine fungi possess good bioactive properties, enzymatic and dye decolorization potentials, that can potentially be considered for use in pharmaceutical and industrial applications.

Expression of Concern: Efficient decolorization and detoxification of triarylmethane and azo dyes by porous-cross-linked enzyme aggregates of Pleurotus ostreatus laccase

Expression of Concern: Efficient decolorization and detoxification of triarylmethane and azo dyes by porous-cross-linked enzyme aggregates of Pleurotus ostreatus laccase

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.

The adsorption behaviour of biochar derived from Prosopis juliflora with surface modified by KOH against Allura red dye

This study examined the efficacy of ProsopisJuliflora with surface changes as a bioadsorbent for the removal of Allura Red dye. The effects of adsorptive dosage, pH, and contact period with starting dye attentiveness on adsorption were examined in the batch adsorption study. The study demonstrated that the Allura Red dye may be absorbed by surfaces that had been treated with KOH compound.The percentages of Allura Red dye eliminated were 67.18 %, 75.88 %, and 94.37 %, respectively. UV–visible adsorption spectroscopy is used to quantify the extent of dye decolorization. The modified surface characteristics of the adsorbent produced by ProsopisJuliflora were reported using XRD, FTIR, and SEM. The Adams-Bohart mathematical models are employed in the computation and assessment of adsorption efficiency. The adsorption-derived R2 values for the equilibrium isotherm data model were 94.63, 86.67, and 96.35. Diffusion and intraparticle regeneration were investigated to bolster the adsorption investigation.

Enhanced visible-light-active MOF-based PbO photocatalyst for binary dye decolorization: A comprehensive study

Developing efficient and sustainable wastewater treatment technologies like photocatalysis is essential to combating global water pollution. Despite lead oxide's photocatalytic potential, its high recombination rate and low active sites restrict its application. In the current study, the first MOF-based PbO nanostructure has been successfully synthesized in a facile way. The as-synthesized sample, PbO/Aluminum fumarate metal–organic framework (PbO/AlFu), was characterized in multiple manners and applied to degrade mixtures of methyl green (MeG) and crystal violet (CV) dyes under visible light irradiation. The incorporation of AlFu metal–organic framework as a support for PbO significantly enhanced photo-degradation performance. This enhancement can be attributed to the increased visible light harvesting, adsorption capabilities facilitated by AlFu, and separation of photo-generated electron-hole pairs due to the formation of the step-scheme (S-scheme) heterojunction. Photocatalytic efficiencies and operational parameters were modeled and optimized respectively using the Box-Behnken design (BBD). Under optimized conditions, MeG and CV dyes were removed at 95.6 and 86.1 percent, respectively. •O2– and •OH radicals were identified as key contributors to the photo-degradation of both dyes. Kinetic studies revealed that photo-degradation of both dyes followed the Langmuir-Hinshelwood model, suggesting a surface-mediated reaction mechanism. PbO/AlFu demonstrated outstanding stability and reusability in five sequential photo-degradation cycles. The present findings highlight the potential of PbO/AlFu as a promising photocatalyst for wastewater treatment.

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.

Immobilization of fungal mycelial and laccase from Trametes hirsuta EDN082 in alginate-cellulose beads and its use in Remazol Brilliant Blue R dye decolorization

In this study, laccase from Trametes hirsuta EDN 082 was immobilized onto alginate-cellulose beads (CAC-L) and employed for the decolorization of Remazol Brilliant Blue R (RBBR) dye. The characterization and decolorization efficiency of the CAC-L beads were compared to immobilized laccase without cellulose (CA-L), immobilized fungal mycelia (CAC-FM), alginate-cellulose (CAC), and alginate beads (CA), and examined using light microscopy, FTIR, and SEM. The results showed that laccase was successfully immobilized onto alginate-cellulose beads with an enzyme loading of 1.9 U/mL and an immobilization efficiency of 97.7 %. The optimal decolorization (89.2 %) was achieved with 2 g CAC-L beads and 1.9 U/mL laccase activity at 40 °C and pH 5 for 6 h of incubation. Furthermore, the decolorization extent was >70–80 % after five cycles. The phytotoxicity test using Vigna radiata and Artemia salina revealed biodetoxification, indicating that CAC-L beads could be used as a biocatalyst for dye removal.

Heterogeneous photo-Fenton using sustainable catalysts for the decolorization of red dye 6

Heterogeneous photo-Fenton using sustainable catalysts for the decolorization of red dye 6

Decolorization and detoxification of Brilliant Crocein GR by a newly enriched thermophilic consortium

The environmental pollution caused by azo dyes at high temperatures has become an urgent problem. However, little attention has been paid to decolorizing azo dyes by thermophilic consortiums. In this study, a thermophilic bacterial consortium (BCGR-T) mainly composed of two genera, namely, Caldibacillus (70.90%) and Aeribacillus (17.63%) was first enriched, which can decolorize Brilliant Crocein GR (BCGR) at high temperatures (50–75 °C), pH values of 6∼8, dye concentrations (100–400 mg/L) and salinities (1–5%, w/v). The enzyme activity results showed that the azoreductase activity was nearly 8.8 times that of the control (p < 0.01), and the intracellular lignin peroxidase was also highly expressed with enzyme activity of 5.64 U (min−1 mg−1 protein) (p < 0.05), indicated that both azoreductase and intracellular lignin peroxidase played an important part in the decolorization process. Furthermore, seven new intermediate metabolic products, including aniline, phthalic acid, 2-carboxy benzaldehyde, phenylacetic acid, benzoic acid, toluene, and 4-methyl-hexanoic acid, were identified. In addition, functional genes related with the azo dye decolorization, such as those encoding the azoreductase, laccase, FMN reductase, NADPH-/NADH-quinone oxidoreductases and NADPH-/NADH dehydrogenases, catechol dioxygenase, homogentisate 1,2-dioxygenase, protocatechuate 3,4-dioxygenase, gentisate 1,2-dioxygenase, azobenzene reductase, naphthalene 1,2-dioxygenase, benzoate/toluate 1,2-dioxygenase, and anthranilate 1,2-dioxygenase and so on were found in the metagenome of the consortium BCGR-T. Finally, a new decolorization pathway of the thermophilic consortium BCGR-T was proposed. In addition, the phototoxicity of BCGR decreased after decolorization. Overall, the thermophilic consortium BCGR-T could be a promising candidate in the treatment of high concentration azo dye wastewater at high temperatures.