Enzymatic degradation and detoxification of azo dye Congo red by a new laccase from Oudemansiella canarii

Identification of Novel Laccase from Ganoderma lucidum and Application in Biotransformation to Bio-based Fragrances Using Alkaline Lignin as Raw Material

A novel laccase, Lac3, was purified from Ganoderma lucidum fermentation broth by salting out, gel filtration chromatography, and Native-PAGE protein recovery. The molecular mass of Lac3 was 58.4 kDa as estimated by SDS-PAGE and exhibited catalytic properties with 2,2'-Biazobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) as substrate. The specific enzyme activity of Lac3 was determined to be 313.69 U/mg. The laccase was stable at temperatures < 65 °C and at pH of 2.5-4.5. The pH, temperature optima, Km and Vmax of the enzyme for ABTS oxidation were 3.0, 55 °C, 0.077 mM, and 2.98 mM/min, respectively. The metal ions and anions showed inhibitory effects on Lac3 activity except Cu2+ (1 mM). GC-MS analysis showed that various aroma products were generated by Lac3 treatment of alkaline lignin. The Lac3 and lignin model compounds had negative binding energy and hydrogen bonding. The analysis of docking suggested that Asp207, Asn256, and His459 play a key role in substrate binding and catalysis.

Production optimization, characterization, and application of a novel thermo- and pH-stable laccase from Bacillus drentensis 2E for bioremediation of industrial dyes

Environmental pollution driven by rapid industrialization and urbanization, has become serious concern due to adverse health effects. Among various bioremediation strategies, laccase, an oxidoreductase enzyme with wide substrate range and high redox-potential (0.4-0.8 V) has garnered significant attention due to its ability to oxidize various organic pollutants into non-toxic products. However, its practical application is often limited due to susceptibility to extreme pH and inhibitory compounds present in wastewater. To overcome this challenge, bacterial laccase, also known as versatile laccases, offer superior stability under harsh environmental conditions making them ideal for bioremediation. Furthermore, isolating native bacterium from contaminated sites enhances their potential, as these organisms are naturally adapted to pollutant-rich environments with intrinsic degradation ability. In this study, Bacillus drentensis 2E was isolated from dye-effluent release site. Laccase production was systematically optimized by One-Factor-at-a-Time, Plackett-Burman Design, and Central Composite Design, yielding a 2.45-fold increase in activity compared to unoptimized condition. Optimized media composition is as follows (g/L): KNO3-5.034,Glucose-3, KH2PO4-0.3,MgSO4-0.3, NaCl-0.55, CaCl2-0.55, CuSO4-0.178 mM, inoculum volume-3.54 %. The enzyme was further characterized for kinetic properties against ABTS, guaiacol and syringaldazine. It demonstrated exceptional stability across a wide temperature (20 ± 1 °C-70 ± 1 °C) and pH range (3.0 ± 0.01-8.0 ± 0.01) with heavy metal tolerance to Ca2+, Mn2+, Mg2+,Zn2+,Cu2+,Co2+,Ni2+. Also, BDLaccase effectively degraded Acid Red-27 (99.76 ± 2.27 %) and Direct Blue-6 (67.43 ± 2.31 %) within 5 h, as confirmed using UV-Vis spectroscopy, FT-IR, and LC-MS. These findings suggests that, BDLaccase is a robust biocatalyst for bioremediation especially in treatment of dyes due to its broad stability and efficiency.

Advancing bioremediation: biosurfactants as catalysts for sustainable remediation

Emerging contaminants such as persistent organic pollutants, perfluorinated compounds, and microplastics pose unparallel challenges to environmental health and current remediation techniques. Microbial biosurfactants, biodegradable compounds produced by microorganisms, have gained attention as eco-friendly alternatives for degrading recalcitrant pollutants. Unlike traditional chemical surfactants, biosurfactants offer the dual benefit of being derived from renewable resources while enhancing the solubility and bioavailability of hydrophobic contaminants. This review is novel in its comprehensive exploration of microbial biosurfactants as a one-step solution for tackling the most persistent environmental pollutants. It introduces recent advancements in metabolic engineering and alternative fermentation strategies that have significantly improved biosurfactant production. Furthermore, the review critically examines the current limitations, including high production costs and complex downstream processing, and proposes cutting-edge approaches to overcome these barriers, such as the use of low-cost feedstocks and integrated bioprocessing techniques. Beyond their established uses, this review also sheds light on their untapped potential in heavy metal removal and microplastic degradation areas that have received little attention. By emphasizing these novel applications and outlining pathways for large-scale production, this review offers valuable insights into how biosurfactants could play a transformative role in sustainable environmental remediation.

Experimental design for assessing the degradation of tannery azo dyes and real-time effluent

Tannery wastewater (TWW) is highly complex and is characterised by high contents of organic, inorganic, and nitrogenous compounds, sulphides, chromium, dissolved solids, and suspended solids. Therefore, our novelty lies in identifying the microbes which are used to degrade harmful azo dyes present in tannery effluent. Based upon the rising problems in tannery industries, the untreated effluent is discharged; to achieve zero effluent, the organisms are isolated from tannery effluent identified as Aeromonas hydrophila (OQ690635) and screened against the degradation potential against the azo dyes and further processed the azo dye-degrading organism for 16S rRNA sequencing. The optimisation was done in various parameters, which resulted in the highest 94% degradation at 37 °C of 7 pH at the 60th hour in 10% of inoculum concentration, which influenced azo dye degradation and confirmed the degradation profile by FT-IR secondary alcohol, alkyne group, alcohol and nitro compounds, isothiocyanate, amine salt, alkyne had been removed and confirmed, also the treated Real-time effluent by novel bacteria which has shown 93% of degradation and also degradation profile by FT-IR and proven toxic free confirmed by GC-MS analysis. Thus, the bacteria isolated in this study can be used as eco-friendly biological expedients for the remediation and detoxification of azo dyes. This could be considered an efficient treatment method for various industrial effluents, as it provides zero sludge disposal during the treatment of industrial effluents.

Environmental Impact of Textile Materials: Challenges in Fiber-Dye Chemistry and Implication of Microbial Biodegradation

Synthetic and natural fibers are widely used in the textile industry. Natural fibers include cellulose-based materials like cotton, and regenerated fibers like viscose as well as protein-based fibers such as silk and wool. Synthetic fibers, on the other hand, include PET and polyamides (like nylon). Due to significant differences in their chemistry, distinct dyeing processes are required, each generating specific waste. For example, cellulose fibers exhibit chemical inertness toward dyes, necessitating chemical auxiliaries that contribute to wastewater contamination, whereas synthetic fibers are a major source of non-biodegradable microplastic emissions. Addressing the environmental impact of fiber processing requires a deep molecular-level understanding to enable informed decision-making. This manuscript emphasizes potential solutions, particularly through the biodegradation of textile materials and related chemical waste, aligning with the United Nations Sustainable Development Goal 6, which promotes clean water and sanitation. For instance, cost-effective methods using enzymes or microbes can aid in processing the fibers and their associated dyeing solutions while also addressing textile wastewater, which contains high concentrations of unreacted dyes, salts, and other highly water-soluble pollutants. This paper covers different aspects of fiber chemistry, dyeing, degradation mechanisms, and the chemical waste produced by the textile industry, while highlighting microbial-based strategies for waste mitigation. The integration of microbes not only offers a solution for managing large volumes of textile waste but also paves the way for sustainable technologies.

Eco-friendly decolorization of synthetic dyes using radiation-induced whole cell biocatalyst with enhanced copper resistance

Toxic and carcinogenic compounds, such as synthetic dyes and polyphenols, were widely employed and released as pollutants in a variety of industries, including textiles, food, and cosmetics. Biological oxidation process that used oxidizing enzymes to breakdown pollutant compounds were environmentally favorable. However, due to the cell toxicity of metal ions supplements used for the biosynthesis of oxidizing enzymes like laccase, their efficient application for biological degradation is limited. In this study, we aimed to boost laccase activity by introducing high copper resistance into whole-cell biocatalysts through irradiation-based accelerated evolution. Bacillus velezensis MBLB0692, a laccase producing bacterium, was employed as model strain that exhibited severe sensitivity under 10 mM copper. The selected Cu-resistant mutants not only overcame growth inhibition, but also increased laccase activity by 2.6-fold. The qRT-PCR analysis confirmed that mutants showed significant change in gene expressions related to laccase generation and copper-related functions. Furthermore, dye decolorization assays showed that mutants degrade synthetic dyes more efficiently under high copper conditions. The varying decolorization efficiencies across dyes were attributed to differences in dye structure and the potential influence of copper on enzyme activity. Collectively, these findings emphasize the interaction between copper concentration and laccase activity, and present implications for environmental bioremediation.

Microwave-induced degradation of Congo red dye in the presence of 2D Ti3C2Tx MXene as a catalyst

In this research, the degradation of Congo red (CR) dye, as an organic pollutant in water, was investigated using microwave-induced reaction technology. This technology requires a microwave-absorbing catalyst and the 2D Ti3C2Tx MXene was synthesized for that purpose. The synthesized catalyst was characterized using XRD, SEM, TEM, EDX, BET, and XPS techniques. Results showed that the prepared 2D Ti3C2Tx MXene with a dosage of 50 mg degraded CR dye with an initial concentration of 25 ppm in an aqueous solution with a degradation percentage of approximately 99% in only 6 min. The parameters studied were catalyst dosage and initial CR dye concentration, which were found to have significant impacts on the degradation rate. When the catalyst dosage was increased significantly, the degradation rate increased significantly. On the other hand, when increasing the initial CR dye concentration, the degradation rate decreased. The degradation kinetics were studied, and the reaction followed the pseudo-first-order model. The rate constants obtained ranged from 0.04 to 0.83 min-1, varying according to the used catalyst dosage and initial CR dye concentration. The catalyst was stable and could be reused for up to five catalytic cycles without losing its degradation efficiency. The active species participating in the degradation process were determined using scavengers such as benzoquinone, Na-EDTA, and isopropyl alcohol. Optimization of the degradation parameters using a response surface methodology study concluded that a maximum degradation percentage could be reached when employing 35.30 mg of 2D Ti3C2Tx MXene and 29.07 ppm of CR dye solution.

Bioremediation of azo dye: A review on strategies, toxicity assessment, mechanisms, bottlenecks and prospects

The synthetic azo dyes are widely used in the textile industries for their excellent dyeing properties. They may be classified into many classes based on their structure and application, including direct, reactive, dispersive, acidic, basic, and others. The continuous discharge of wastewater from a large number of textile industries without prior treatment poses detrimental effects on the environment and human health. Azo dyes and their degradation products are extremely poisonous for their carcinogenic, teratogenic and mutagenic nature. Moreover, exposure to synthetic azo dyes can cause genetic changes, skin inflammation, hypersensitivity responses, and skin irritations in persons, which may ultimately result in other profound issues including the deterioration of water quality. This review discusses these dyes in details along with their detrimental effects on aquatic and terrestrial flora and fauna including human beings. Azo dyes degrade the water bodies by increasing biochemical and chemical oxygen demand. Therefore, dye-containing wastewater should be effectively treated using eco-friendly and cost-effective technologies to avoid negative impact on the environment. This article extensively reviews on physical, chemical and biological treatment with their benefits and challenges. Biological-based treatment with higher hydraulic retention time (HRT) is economical, consumes less energy, produces less sludge and environmentally friendly. Whereas the physical and chemical methods with less hydraulic retention time is costly, produces large sludge, requires high dissolved oxygen and ecologically inefficient. Since, biological treatment is more advantageous over physical and chemical methods, researchers are concentrating on bioremediation for eliminating harmful azo dye pollutants from nature. This article provides a thorough analysis of the state-of-the-art biological treatment technologies with their developments and effectiveness in the removal of azo dyes. The mechanism by which genes encoding azoreductase enzymes (azoG, and azoK) enable the natural degradation of azo dyes by bacteria and convert them into less harmful compounds is also extensively examined. Therefore, this review also focuses on the use of genetically modified microorganisms and nano-technological approaches for bioremediation of azo dyes.

Colorimetric and Smartphone-Based Dual-Mode Rapid Detection of Congo Red Using Iron Oxide Quantum Dots

Congo red is toxic to humans and the environment and persists in the environment for long periods. Therefore, developing a rapid detection method for Congo red is crucial. In this study, iron oxide quantum dots (IOQDs) were synthesized and employed for dual-mode detection (colorimetric and smartphone-based) of Congo red in real samples. Upon mixing with Congo red, the IOQDs induce a color change in the solution due to the strong intermolecular interactions between Congo red and the IOQDs, making them practical as colorimetric sensors. To further increase the on-site detection capabilities of IOQDs, images of the sensor platform were captured using a smartphone, and the color data were analyzed with a dedicated APP. As a colorimetric sensor, the ultraviolet-visible (UV-vis) absorbance response exhibited good linearity for Congo red concentrations between 2 and 50 μM, with a detection limit of 0.89 μM. The smartphone-based sensor also provided highly quantitative results, showing a linear relationship between Congo red concentrations and the blue-to-red (B/R) channel ratio, with a detection limit of 0.58 μM. Moreover, this dual-mode method demonstrated better selectivity for Congo red than other colorimetric sensors, even in the presence of other red dyes. The proposed method is convenient, fast, low-cost, and suitable for real-sample applications.

Properties and kinetic behavior of free and immobilized laccase from Oudemansiella canarii: Emphasis on the effects of NaCl and Na2SO4 on catalytic activities

Studies have highlighted the great potential of Oudemansiella canarii laccase in degrading synthetic dyes for reducing their toxicity. Immobilization of enzymes improves usability in degradation processes and the present work succeeded in immobilizing this laccase onto MANAE-agarose. Immobilization improved pH, thermal, and storage stabilities. Both, free and immobilized enzymes presented Michaelis-Menten kinetics with the substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with Km values of 0.056 ± 0.003 and 0.195 ± 0.022 mM, respectively. Immobilization increased Vmax 1.27-fold. NaCl caused incomplete (hyperbolic) inhibition, which was satisfactorily described by the one-substrate one-modifier mechanism. Immobilization reduced the maximal inhibition by NaCl from 80.2 to 55.7 %. The effect of Na2SO4 was predominantly stimulation, but inhibition of the free enzyme occurred at high substrate concentrations. Stimulation of the immobilized enzyme by Na2SO4 was much more pronounced. It strongly depended on the substrate concentration and was much stronger (up to 300 %) at low substrate concentrations. The combined effects of substrate and sulfate on the immobilized laccase could be satisfactorily described by the one-substrate one-modifier mechanism. The modified response of the immobilized O. canarii laccase to NaCl and Na2SO4 considerably favors its use as a tool in bioremediation processes because environmental contamination by salts frequently represents a strong operational challenge.

Systematic characterisation, and effect of nutritional and physical parameters on culturability, laccase production and dye decolorisation potential by P. pistillaris from Pakistan

Podaxis pistillaris is neutraceutically, cosmoceutically and medicinally recognised macrofungus. During this research work, this edible mushroom was systematically characterised. Its culturability, laccase production, and dye decolorisation potential were evaluated and optimised. Among the different media tested, PDA proved as most efficient medium for culturability of P. pistillaris. Conditions for laccase production were optimised in submerged state fermentation. Maximum laccase secretion was noted after 14th day of Incubation at 35 °C with 130 rpm and 5 pH of medium. Fructose and ammonium-phosphate was found as best carbon and nitrogen source, while wheat straw revealed as good ligno-cellulosic source for strengthening laccase production. Congo-red dye decolorisation capability by crude laccase enzyme was evaluated and found maximum decolorisation potential (92.2%) after 288h of incubation. From this pilot study, it was confirmed that this edible macrofungus has culturability, laccase production and dye decolorisation attributes that will further contribute in delignification, biosorption and bioremediation.

Green reduction of ZnO nanoparticles using cationic dialdehyde cellulose (cDAC) for efficient Congo red dye removal

More sustainable materials have been becoming an important concern of worldwide scientists, and cellulosic materials are one alternative in water decontamination. An efficient strategy to improve removal capacity is functionalizing or incorporating nanomaterials in cellulose-based materials. The new hybrid cDAC/ZnONPs was produced by green synthesis of zinc oxide nanoparticles (ZnONPs), promoting the in situ reduction and immobilization on the cationic dialdehyde cellulose microfibers (cDAC) surface to remove Congo red dye from water. cDAC/ZnONPs was characterized by scanning electron microscopy (SEM-EDS) and infrared spectroscopy (FTIR), which showed efficient nanoparticles reduction. Adsorption efficiency on cationic cellulose surface was investigated by pH, contact time, initial concentration, and dye selectivity tests. The material followed the H isotherm model, which resulted in a maximum adsorption capacity of 1091.16 mg/g. Herein, was developed an efficient and ecologically correct new adsorbent, highly effective in Congo red dye adsorption even at high concentrations, suitable for the remediation of contaminated industrial effluents.

Laccase: Sustainable production strategies, heterologous expression and potential biotechnological applications

Laccase is a multicopper oxidase enzyme that target different types of phenols and aromatic amines. The enzyme can be isolated and characterized from microbes, plants and insects. Its ubiquitous nature and delignification ability makes it a valuable tool for research and development. Sustainable production methods are being employed to develop low cost biomanufacturing of the enzyme while achieving high titers. Laccase have significant industrial application ranging from food industry where it can be used for wine stabilization, texture improvement and detection of phenolic compounds in food products, to cosmetics offering benefits such as skin brightening and hair colouring. Dye decolourization/degradation, removal of pharmaceutical products/emerging pollutants and hydrocarbons from wastewater, biobleaching of textile fabrics, biofuel production and delignification of biomass making laccase a promising green biocatalyst. Innovative methods such as using inducers, microbial co-culturing, recombinant DNA technology, protein engineering have pivotal role in developing laccase with tailored properties. Enzyme immobilization using new age compounds including nanoparticles, carbonaceous components, agro-industrial residues enhance activity, stability and reusability. Commercial formulations of laccase have been prepared and readily available for a variety of applications. Certain challenges including production cost, metabolic stress in response to heterologous expression, difficulty in purification needs to be addressed.

A systematic study on the characteristics and applications of laccases produced by fungi: insights on their potential for biotechnologies

Laccases are polyphenol oxidase enzymes and form the enzyme complex known for their role in wood decomposition and lignin degradation. The present study aimed to systematically review the state-of-the-art trends in scientific publications on laccase enzymes of the last 10 years. The main aspects checked included the laccase-producing fungal genera, the conditions of fungal growth and laccase production, the methods of immobilization, and potential applications of laccase. After applying the systematic search method 177 articles were selected to compound the final database. Although various fungi produce laccase, most studies were Trametes and Pleurotus genera. The submerged fermentation (SmF) has been the most used, however, the use of solid-state fermentation (SSF) appeared as a promising technique to produce laccase when using agro-industrial residues as substrates. Studies on laccase immobilization showed the covalent bonding and entrapment methods were the most used, showing greater efficiency of immobilization and a high number of enzyme reuses. The main use of the laccase was in bioremediation, especially in the discoloration of dyes from the textile industry and the degradation of pharmaceutical waste. Implications and consequences of all these findings in biotechnology and environment, as well as the trends and gaps of laccase research were discussed.

Construction of Metal-Organic Framework-Based Heterogeneous Pepsin and Its Degradation Performance and Mechanism for Phthalic Acid Esters

Biological enzyme-driven degradation of environmental pollutants has attracted widespread attention because it is ecofriendly and highly efficient. Immobilized enzyme technology has emerged as a promising technique in enzymology that addresses the limitations associated with free enzymes. Traditional solid-loaded enzyme substrates are often affected by blockages and restricted substrate accessibility. In this study, we synthesized an efficient heterogeneous pepsin catalyst, named PEP@M-MIL100(Fe), by covalently combining carboxylated ferrite structural expanded metal-organic frameworks with pepsin. This catalyst demonstrated excellent environmental adaptability and remarkable catalytic degradation capabilities. Notably, it rapidly degraded the persistent microplastic pollutant diisononyl phthalate (DINP) within just 150 min, with a removal efficiency of up to 95.88%. Impressively, even after 10 consecutive uses, the catalyst maintained its high performance. We proposed an innovative steady-state heterogeneous enzyme-catalyzed degradation mechanism, i.e., diffusion (D)-absorption (A)-binding (B)-reaction (R)-degradation (D)-link mechanism, which emphasizes the influence of substrate diffusion rates in this process. This work presents the first successful application of pepsin to DINP degradation and offers a sustainable and effective approach for addressing contemporary pollution challenges.

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

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

Kinetic studies on optimized extracellular laccase from Trichoderma harzianum PP389612 and its capabilities for azo dye removal

BACKGROUND

Azo dyes represent a common textile dye preferred for its high stability on fabrics in various harsh conditions. Although these dyes pose high-risk levels for all biological forms, fungal laccase is known as a green catalyst for its ability to oxidize numerous dyes.

METHODS

Trichoderma isolates were identified and tested for laccase production. Laccase production was optimized using Plackett-Burman Design. Laccase molecular weight and the kinetic properties of the enzyme, including Km and Vmax, pH, temperature, and ionic strength, were detected. Azo dye removal efficiency by laccase enzyme was detected for Congo red, methylene blue, and methyl orange.

RESULTS

Eight out of nine Trichoderma isolates were laccase producers. Laccase production efficiency was optimized by the superior strain T. harzianum PP389612, increasing production from 1.6 to 2.89 U/ml. In SDS-PAGE, purified laccases appear as a single protein band with a molecular weight of 41.00 kDa. Km and Vmax values were 146.12 μmol guaiacol and 3.82 μmol guaiacol/min. Its activity was stable in the pH range of 5-7, with an optimum temperature range of 40 to 50 °C, optimum ionic strength of 50 mM NaCl, and thermostability properties up to 90 °C. The decolorization efficiency of laccase was increased by increasing the time and reached its maximum after 72 h. The highest efficiency was achieved in Congo red decolorization, which reached 99% after 72 h, followed by methylene blue at 72%, while methyl orange decolorization efficiency was 68.5%.

CONCLUSION

Trichoderma laccase can be used as an effective natural bio-agent for dye removal because it is stable and removes colors very well.

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.

Detoxification of tetracycline and synthetic dyes by a newly characterized Lentinula edodes laccase, and safety assessment using proteomic analysis

Fungal laccase has strong ability in detoxification of many environmental contaminants. A putative laccase gene, LeLac12, from Lentinula edodes was screened by secretome approach. LeLac12 was heterogeneously expressed and purified to characterize its enzymatic properties to evaluate its potential use in bioremediation. This study showed that the extracellular fungal laccase from L. edodes could effectively degrade tetracycline (TET) and the synthetic dye Acid Green 25 (AG). The growth inhibition of Escherichia coli and Bacillus subtilis by TET revealed that the antimicrobial activity was significantly reduced after treatment with the laccase-HBT system. 16 transformation products of TET were identified by UPLC-MS-TOF during the laccase-HBT oxidation process. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that LeLac12 could completely mineralize ring-cleavage products. LeLac12 completely catalyzed 50 mg/L TET within 4 h by adding AG (200 mg/L), while the degradation of AG was above 96% even in the co-contamination system. Proteomic analysis revealed that central carbon metabolism, energy metabolism, and DNA replication/repair were affected by TET treatment and the latter system could contribute to the formation of multidrug-resistant strains. The results demonstrate that LeLac12 is an efficient and environmentally method for the removal of antibiotics and dyes in the complex polluted wastewater.

In silico and in vitro assays suggests Congo red dye degradation by a Lentinus sp. laccase enzyme

Laccase is a superfamily of ligninolytic enzymes known to degrade a wide variety of xenobiotics, including synthetic dyes. Congo Red (CR) has a diazo dye function, carcinogenic and mutagenic potential, and is currently applied in clinical analysis. The objective of this work was to produce and characterize the crude extract of Lentinus sp. in semi-solid fermentation (FSS) and perform in vitro and in silico studies to assess the potential of the crude extract to discolor the CR dye. Laccase activity was determined using ABTS as substrate and characterized. The in vitro discoloration was carried out using experimental design 22 at room temperature and monitored at 340 nm for 24h. Molecular docking and molecular dynamics simulations were performed between laccase and CR. The maximum laccase activity production was 29.63 U L-1 with six days of FSS. The optimal temperature and pH were 50 °C and 3.0, respectively. Discoloration of the CR dye was obtained only in tests containing CuSO4. Laccase formed stable complexes with the dye, presenting negative binding energy values ranging from -70.94 to -63.16 kcal mol-1 and the occurrence of seven hydrogen bonds. Molecular dynamics results showed the stability of the system (RMSD ranging from 1.0 to 2.5 Ä) and protein-ligand interaction along simulation. RMSF values pointed residues at the end of chains A (residues 300 to 305, 480 to 500) and B (residues 650 to 655 and 950 to 1000) as the most flexible regions of the laccase. This study highlighted the enzymatic action in the bioremediation of CR in vitro in agreement with the in silico simulations that demonstrate the enzyme potential.Communicated by Ramaswamy H. Sarma.

Biodegradation of commercial textile reactive dye mixtures by industrial effluent adapted bacterial consortium VITPBC6: a potential technique for treating textile effluents

Textile industries release major fraction of dyestuffs in effluents leading to a major environmental concern. These effluents often contain more than one dyestuff, which complicates dye degradation. In this study ten reactive dyes (Reactive Yellow 145, Reactive Yellow 160, Reactive Orange 16, Reactive Orange 107, Reactive Red 195, Reactive Blue 21, Reactive Blue 198, Reactive Blue 221, Reactive Blue 250, and Reactive Black 5) that are used in textile industries were subjected to biodegradation by a bacterial consortium VITPBC6, formulated in our previous study. Consortium VITPBC6 caused single dye degradation of all the mentioned dyes except for Reactive Yellow 160. Further, VITPBC6 efficiently degraded a five-dye mixture (Reactive Red 195, Reactive Orange 16, Reactive Black 5, Reactive Blue 221, and Reactive Blue 250). Kinetic studies revealed that the five-dye mixture was decolorized by VITPBC6 following zero order reaction kinetic; Vmax and Km values of the enzyme catalyzed five-dye decolorization were 128.88 mg L-1 day-1 and 1003.226 mg L-1 respectively. VITPBC6 degraded the dye mixture into delta-3,4,5,6-Tetrachlorocyclohexene, sulfuric acid, 1,2-dichloroethane, and hydroxyphenoxyethylaminohydroxypropanol. Phytotoxicity, cytogenotoxicity, microtoxicity, and biotoxicity assays conducted with the biodegraded metabolites revealed that VITPBC6 lowered the toxicity of five-dye mixture significantly after biodegradation.

Harnessing the power of bacterial laccases for xenobiotic degradation in water: A 10-year overview

Industrialization and population growth are leading to the production of significant amounts of sewage containing hazardous xenobiotic compounds. These compounds pose a threat to human and animal health, as well as the overall ecosystem. To combat this issue, chemical, physical, and biological techniques have been used to remove these contaminants from water bodies affected by human activity. Biotechnological methods have proven effective in utilizing microorganisms and enzymes, particularly laccases, to address this problem. Laccases possess versatile enzymatic characteristics and have shown promise in degrading different xenobiotic compounds found in municipal, industrial, and medical wastewater. Both free enzymes and crude enzyme extracts have demonstrated success in the biotransformation of these compounds. Despite these advancements, the widespread use of laccases for bioremediation and wastewater treatment faces challenges due to the complex composition, high salt concentration, and extreme pH often present in contaminated media. These factors negatively impact protein stability, recovery, and recycling processes, hindering their large-scale application. These issues can be addressed by focusing on large-scale production, resolving operation problems, and utilizing cutting-edge genetic and protein engineering techniques. Additionally, finding novel sources of laccases, understanding their biochemical properties, enhancing their catalytic activity and thermostability, and improving their production processes are crucial steps towards overcoming these limitations. By doing so, enzyme-based biological degradation processes can be improved, resulting in more efficient removal of xenobiotics from water systems. This review summarizes the latest research on bacterial laccases over the past decade. It covers the advancements in identifying their structures, characterizing their biochemical properties, exploring their modes of action, and discovering their potential applications in the biotransformation and bioremediation of xenobiotic pollutants commonly present in water sources.

Purification, characterization of laccase from Pleurotus ostreatus HK35, and optimization for congo red biodecolorization using Box-Behnken design

This study is the first report on purification, characterization, and application of laccase derived from the white-rot fungus, Pleurotus ostreatus HK35 (Hungary strain), in Congo Red decolorization. The purification process involved ammonium sulfate precipitation, dialysis, anion exchange chromatography, and ultrafiltration, yielding a specific laccase activity of 15.26 U/mg and a 30.21% recovery rate. The purified enzyme, with a molecular weight of approximately 34 kilodaltons, displayed optimal activity at a temperature of 60 °C and pH 4.0 when using 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) as a substrate. The enzyme maintained over 82.02 ± 1.01% of its activity at temperatures up to 50 °C after 180 min but displayed less than 5% of its activity at 60 and 70 °C. Notably, the enzyme's activity was significantly enhanced by Pb(NO3)2, whereas β-mercaptoethanol completely inhibited the activity. Utilizing the Box-Behnken design, we optimized Congo Red decolorization efficiency to 91.05 ± 0.82% at 100 mg/L Congo Red, 1.5 mM mediator concentration, and 1.6 U/mL laccase activity. Analysis of Variance (ANOVA) suggested the model was significant, and all variables significantly influenced decolorization efficiency.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03926-7.

Biodegradation and Decolorization of Crystal Violet Dye by Cocultivation with Fungi and Bacteria

Microbial degradation of dyes is vital to understanding the fate of dyes in the environment. In this study, a fungal strain A-3 and a bacterial strain L-6, which were identified as Aspergillus fumigatus and Pseudomonas fluorescens, respectively, had been proven to efficiently degrade crystal violet (CV) dye. The decolorization of CV dye by fungal and bacterial cocultivation was investigated. The results showed that the decolorization rate of cocultures was better than monoculture (P. fluorescens in L-6 (PF), and that of A. fumigatus A-3 (AF)). Furthermore, enzymatic analysis further revealed that Lac, MnP, Lip, and NADH-DCIP reductases were involved in the biodegradation of CV dyes. UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and gas chromatography-mass spectrometry (GC-MS) were used to examine the degradation products. GC-MS analysis showed the presence of 4-(dimethylamino) benzophenone, 3-dimethylaminophenol, benzyl alcohol, and benzaldehyde, indicating that CV was degraded into simpler compounds. The phytotoxicity tests revealed that CV degradation products were less toxic than the parent compounds, indicating that the cocultures detoxified CV dyes. As a result, the cocultures are likely to have a wide range of applications in the bioremediation of CV dyes.

Enzyme-triggered approach to reduce water bodies' contamination using peroxidase-immobilized ZnO/SnO2/alginate nanocomposite

Enzyme immobilization on solid support offers advantages over free enzymes by overcoming characteristic limitations. To synthesize new stable and hyperactive nano-biocatalysts (co-precipitation method), ginger peroxidase (GP) was surface immobilized (adsorption) on ZnO/SnO2 and ZnO/SnO2/SA nanocomposite with immobilization efficacy of 94 % and 99 %, respectively. Thereafter, catalytic and biochemical characteristics of free and immobilized GP were investigated by deploying various techniques, i.e., FTIR, PXRD, SEM, and PL. Diffraction peaks emerged at 2θ values of 26°, 33°, 37°, 51°, 31°, 34°, 36°, 56°, indicating the formation of SnO2 and ZnO. The OH stretching of the H2O molecules was attributed to broad peaks between 3200 and 3500 cm-1, whereas ZnO/SnO2 spikes occurred in the 1626-1637 cm-1 range. SnO stretching mode and ZnO terminal vibrational patterns have been verified at corresponding wavelengths of 625 cm-1 and 560 cm-1. Enzyme entrapment onto substrate was verified via interactions between GP and ZnO/SnO2/SA as corroborated by signals beneath 1100 cm-1. GP-immobilized fractions were optimally active at pH 5, 50 °C, and retained maximum activity after storage of 4 weeks at -4 °C. Kinetic parameters were determined by using a Lineweaver-Burk plot and Vmax for free GP, ZnO/SnO2/GP and ZnO/SnO2/SA/GP with guaiacol as a substrate, were found to be 322.58, 49.01 and 11.45 (μM/min) respectively. A decrease in values of Vmax and KM indicates strong adsorption of peroxidase on support and maximum affinity between nano support and enzyme, respectively. For environmental remediation, free ginger peroxidase (GP), ZnO/SnO2/GP and ZnO/SnO2/SA/GP fractions effectively eradicated highly intricate dye. Multiple scavengers had a significant impact on the depletion of the dye. In conclusion, ZnO/SnO2 and ZnO/SnO2/SA nanostructures comprise an ecologically acceptable and intriguing carrier for enzyme immobilization.

Agroindustrial and food processing residues valorization for solid-state fermentation processes: A case for optimizing the co-production of hydrolytic enzymes

In the pursuit of sustainability, managing agro-industrial and food processing residues (AFR) efficiently is crucial. This study proposes a systematic approach to convert AFR into valuable products via solid-state fermentation (SSF). Using fungal enzyme production as a case study, this adaptable methodology suits any SSF bioprocess. Initially, AFR's physicochemical properties were evaluated to assess their feasible use as carbon sources and solid matrices for SSF. Then, five strains were screened for their capability to produce enzymes (Xylanase, X; pectinase, P; cellulase, C). Apple pomace (AP) and brewery spent grain (BSG) with Aspergillus sp. (strain G5) were selected. Subsequent steps involved a two-phase statistical approach, identifying critical factors and optimizing them. Process conditions were screened using a Plackett-Burman design, narrowing critical variables to three (BSG/AP, pH, humidity). Response Surface Methodology (Central Composite Design) further optimized these factors for co-synthesis of X, P, and C. The humidity had the most significant effect on the three responses. The optimum conditions depended on each enzyme and were further validated to maximize either X, P or C. The obtained extracts were used for pectin extraction from orange peels. The extract containing primarily xylanase (X = 582.39, P = 22.86, C = 26.10 U mL-1) showed major pectin yield recovery (12.33 ± 0.53%) and it was obtained using the optimal settings of BSG/AP (81/19), humidity (50.40%), and pH (4.58). The findings will enable adjusting process conditions to obtain enzymatic cocktails with a tailored composition for specific applications.

In-situ encapsulation and construction of Lac@HOFs/hydrogel composite for enhancing laccase stability and azo dyes decolorization efficiency

Enzymes with high catalytic activity and stability have been used for the sustainable development of green chemical applications, such as water remediation. Immobilized laccase can be used to construct a synergistic system for adsorption and degradation, which has great potential for water remediation. Herein, a hydrogen-bonded organic framework was installed onto laccase in-situ to form a net-carboxylate-arranged defective cage, which enhanced its catalytic stability. Thereafter, the CMC/PVA/Lac@HOF-101 hydrogel was fabricated by freeze-thaw cycles using sodium carboxymethylcellulose and polyvinyl alcohol as carriers and copper (II) as a cross-linker. Notably, the MOFs/hydrogel as a protective carrier of laccase maintain long-term recyclability and catalytic stability. After the fifth catalytic cycle, approximately 66.7 % activity of the CP-Lac@HOF-101 was retained. When both free laccase and CP-Lac@HOF-101 were used for decolorization of Acid Orange 7 (AO), the removal rates were 10.9 % and 82.5 % after 5 h, respectively. Furthermore, even in the presence of metal cations, almost 60.0 % of the AO removal efficiency was achieved. The relationship between the structure of the azo dyes and decolorization efficiency of the synergistic system was further investigated. This study offers a method for constructing enzyme@HOF-based composite hydrogels and provides a promising water remediation strategy.

Optimization of laccase from Stenotrophomonas maltophilia E1 by submerge fermentation using coconut husk with its detoxification and biodecolorization ability of synthetic dyes

Enzymatic degradation of synthetic dyes holds an immense promise for addressing the environmental concerns associated with the textile and dye industries. This study aimed to isolate bacteria capable of producing laccase enzymes from an anthropogenic environment. Subsequently, viability of utilizing cost-effective agricultural residues as substrates for laccase production was assessed. Response Surface Methodology (RSM) and the One Variable at a Time (OVAT) approach was pursued for the optimization of laccase production, followed by pH and temperature stability, dye degradation and decolorization experiments, toxicological studies on the degraded dye metabolites. In results, laccase-producing bacterial strain was identified as Stenotrophomonas maltophilia strain E1 (S. maltophilia). Among variety of substrates, coconut husk exhibited optimal efficacy. In a statistical optimization study, it was found that S. maltophilia was capable of producing laccase 51.38 IU/mL, i.e., three times higher than the amount of laccase produced by unoptimized medium (16.7 IU/mL), and the enzyme activity was found to be steady at an acidic pH, and a mesophilic temperature range. The laccase obtained from S. maltophilia E1 demonstrated proficient dye decolorization capabilities, achieving a notable 92.1% reduction in Malachite green dye coloration at a concentration of 500 ppm. Gas chromatography-mass spectrometry (GC-MS) analysis of the decolorized derivatives of Malachite green revealed a conversion into a distinct compounds. Moreover, after undergoing laccase treatment, Malachite green exhibited decreased phytotoxic effects on Oryza sativa, pointing to enzymatic detoxification. Collectively, insights gained from the present study will contribute to the development of efficient enzymatic approaches for addressing the environmental pollution caused by synthetic dyes.

Structural insights, biocatalytic characteristics, and application prospects of lignin-modifying enzymes for sustainable biotechnology

Lignin modifying enzymes (LMEs) have gained widespread recognition in depolymerization of lignin polymers by oxidative cleavage. LMEs are a robust class of biocatalysts that include lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), laccase (LAC), and dye-decolorizing peroxidase (DyP). Members of the LMEs family act on phenolic, non-phenolic substrates and have been widely researched for valorization of lignin, oxidative cleavage of xenobiotics and phenolics. LMEs implementation in the biotechnological and industrial sectors has sparked significant attention, although its potential future applications remain underexploited. To understand the mechanism of LMEs in sustainable pollution mitigation, several studies have been undertaken to assess the feasibility of LMEs in correlating to diverse pollutants for binding and intermolecular interactions at the molecular level. However, further investigation is required to fully comprehend the underlying mechanism. In this review we presented the key structural and functional features of LMEs, including the computational aspects, as well as the advanced applications in biotechnology and industrial research. Furthermore, concluding remarks and a look ahead, the use of LMEs coupled with computational framework, built upon artificial intelligence (AI) and machine learning (ML), has been emphasized as a recent milestone in environmental research.

Enzymatic degradation of azo dyes methylene blue and congo red with peroxidase purified from cauliflower using affinity chromatography technique: Kinetic study, optimization and metal binding activity

The effective results of the enzymatic decolorization of industrial azo dyes found in wastewater, which cause serious health and environmental problems, with peroxidases have recently increased the interest in these enzyme sources. Redox-mediated decolorization of Methylene Blue and Congo Red azo dyes with cauliflower (Brassica oleracea var.botrytis L.) peroxidase (CPOD) purified in one step using 4-amino 3-bromo 2-methyl benzohydrazide molecule was investigated for the first time. The inhibition effect of this molecule, which is used as a ligand in affinity chromatography, on the CPOD enzyme was investigated. The K_i and IC₅₀ values for this enzyme were calculated as 0.113 ± 0.012 mM and 0.196 ± 0.011 mM, respectively. With the affinity gel obtained by binding to the Sepharose-4B-l-tyrosine matrix of this molecule, which shows a reversible inhibition effect, the purification values of CPOD enzyme were determined as 562-fold with a specific activity of 50,250 U mg^-1. The purity of the enzyme was checked by the SDS-PAGE technique and its molecular weight was determined. A single band at 44 kDa was observed for the CPOD enzyme. In dye decolorization studies, the effects of dye, enzyme, and hydrogen peroxide concentrations as well as time, pH, and temperature were investigated. The profiles of the optimum conditions for both dyes were similar, and the percentages of decolorization of Methylene Blue and Congo Red under these conditions were 89% and 83%, respectively, at the end of the 40 min reaction time. Again, when examining the effect of metal ions on enzyme activity, it was found that there was no significant negative change in CPOD.

Heterogeneous biocatalytic system for effective decolorization of textile dye effluent

The current physicochemical methods for decolorizing toxic synthetic dyes are not sustainable to halt the environmental damage as they are expensive and often produce concentrated sludge, which may lead to secondary disposal problems. Biocatalysis (microbes and/or their enzymes) is a cost-effective, versatile, energy-saving and clean alternative. The most common enzymes involved in dye degradation are laccases, azoreductases and peroxidases. Toxic dyes could be converted into less harmful byproducts through the combined action of many enzymes or the utilization of whole cells. The action of whole cells to treat dye effluents is either by biosorption or degradation (aerobic or anaerobic). Using immobilized cells or enzymes will offer advantages such as superior stability, persistence against harsh environmental conditions, reusability and longer half-lives. This review envisages the recent strategies of immobilization and bioreactor considerations with the immobilized system as the effective treatment of textile dye effluents. Packed bed reactors are the most popular heterogeneous biocatalytic reactors for dye decolorization due to their efficiency and cost-effectiveness.

A review on simultaneous heavy metal removal and organo-contaminants degradation by potential microbes: Current findings and future outlook

Industrial processes result in the production of heavy metals, dyes, pesticides, polyaromatic hydrocarbons (PAHs), pharmaceuticals, micropollutants, and PFAS (per- and polyfluorinated substances). Heavy metals are currently a significant problem in drinking water and other natural water bodies, including soil, which has an adverse impact on the environment as a whole. The heavy metal is highly poisonous, carcinogenic, mutagenic, and teratogenic to humans as well as other animals. Multiple polluted sites, including terrestrial and aquatic ecosystems, have been observed to co-occur with heavy metals and organo-pollutants. Pesticides and heavy metals can be degraded and removed concurrently from various metals and pesticide-contaminated matrixes due to microbial processes that include a variety of bacteria, both aerobic and anaerobic, as well as fungi. Numerous studies have examined the removal of heavy metals and organic-pollutants from different types of systems, but none of them have addressed the removal of these co-occurring heavy metals and organic pollutants and the use of microbes to do so. Therefore, the main focus of this review is on the recent developments in the concurrent microbial degradation of organo-pollutants and heavy metal removal. The limitations related to the simultaneous removal and degradation of heavy metals and organo-pollutant pollutants have also been taken into account.

3D printed polylactide scaffolding for laccase immobilization to improve enzyme stability and estrogen removal from wastewater

This study reports a biocatalytic system of immobilized laccase and 3D printed open-structure biopolymer scaffoldings. The scaffoldings were computer-designed and 3D printed using polylactide (PLA) filament. The immobilization of laccase onto the 3D printed PLA scaffolds were optimized with regard to pH, enzyme concentration, and immobilization time. Laccase immobilization resulted in a small reduction in reactivity (in terms of Michaelis constant and maximum reaction rate) but led to significant improvement in chemical and thermal stability. After 20 days of storage, the immobilized and free laccase showed 80% and 35% retention of the initial enzymatic activity, respectively. The immobilized laccase on 3D printed PLA scaffolds achieved 10% improvement in the removal of estrogens from real wastewater as compared to free laccase and showed the significant reusability potential. Results here are promising but also highlight the need for further study to improve enzymatic activity and reusability.

Eco-friendly detoxification of hazardous Congo red dye using novel fungal strain Trametes flavida WTFP2: Deduced enzymatic biomineralization process through combinatorial in-silico and in-vitro studies

Growing textile industry is a major global concern, owing to the presence of recalcitrant hazardous pollutants, like synthetic dyes in discharged effluents. To explore new bioresources for mycoremediation, a high laccase-producing novel white-rot fungus (WRF), Trametes flavida WTFP2, was employed. T. flavida is an underexplored member of Polyporales. Using bioinformatic tools, 8 different cis-acting RNA elements were identified in the 5.8 S ITS gene sequence, where CRISPR (CRISPR-DR15), sRNA (RUF1), and snoRNA (ceN111) are uniquely present. Molecular docking was adopted to predict the catalytic interaction of chosen toxic diazo colorant, Congo red (CR), with four dye-degrading enzymes (laccase, lignin peroxidase, azoreductase, and aryl alcohol oxidase). With 376.41 × 10³ U/L laccase production, novel WRF exhibited dye-decolorization potential. WTFP2 effectively removed 99.48 ± 0.04% CR (100 mg/L) and demonstrated remarkable recyclability and persistence in consecutive remediation trials. Mycelial dye adsorption was not only substantial driver of colorant elimination; decolorization using active T. flavida was regulated by enzymatic catalysis, as outlined by in-vitro growth, induction of extracellular enzymes, and FESEM. Fifteen metabolites were identified using HRLCMS-QTOF, and novel CR degradation pathway was proposed. Furthermore, microbial and phyto-toxicity tests of metabolites suggested complete detoxification of toxic dye, making the process clean, green, and economically sustainable.

Hierarchically-structured laccase@Ni3(PO4)2 hybrid nanoflowers for antibiotic degradation: Application in real wastewater effluent and toxicity evaluation

Laccase@Ni₃(PO₄)₂ hybrid nanoflowers (HNFs) were prepared by the anisotropic growth of biomineralized nickel phosphate. The immobilization yield was 77.5 ± 3.6 %, and the immobilized enzyme retained 50 % of its initial activity after 18 reusability cycles. The immobilized and free enzymes lost 80 % of their activity after 18 and 6 h incubation in municipal wastewater effluent (MWWE), respectively. The increase in α-helix content (8 %) following immobilization led to a more rigid enzyme structure, potentially contributing to its improved stability. The removal of ciprofloxacin from MWWE by laccase@Ni₃(PO₄)₂·HNFs/p-coumaric acid oxidation system was optimized using a Box-Behnken design. Under the optimized conditions [initial laccase activity (0.05 U mL^-1), the concentration of p-coumaric acid (2.9 mM), and treatment time (4.9 h)], the biocatalyst removed 90 % of ciprofloxacin (10 mg L^-1) from MWWE. The toxicity of ciprofloxacin against some G⁺ and G^- bacteria was reduced by 35-70 %, depending on their strain. The EC₅₀ of ciprofloxacin for the alga Raphidocelis subcapitata reduced from 3.08 to 1.07 mg L^-1 (p-value <0.05) after the bioremoval. Also, the acute and chronic toxicity of identified biodegradation products was lower than ciprofloxacin at three trophic levels, as predicted by ECOSAR software.

Textile azo dyes discolouration using spent mushroom substrate: enzymatic degradation and adsorption mechanisms

This study evaluated the adsorption and enzymatic degradation of azo dyes when using SMS. The laccase present in the SMS was characterised, and the maximum activity was obtained at pH 2, a temperature of 45°C, a Michaelis-Menten constant (Km) of 0.264 mM, and a maximum reaction rate (Vmax) of 117.95 µmol L-1 min-1. The presence of NaCl at 5 mM inhibited enzyme activity while no inhibition was observed by Na2SO4, typically found in textile wastewater. The maximum dye adsorption (57.22%) was achieved at pH 8.0, 25°C, and 100 g L-1 of SMS while the maximum enzymatic degradation (14.18%) was obtained under the same conditions, except at pH 4.0. The enzymes laccase, lignin peroxidase, and manganese peroxidase trapped in the SMS resulted in higher dye discolouration when compared to that extracted with aqueous solution, meaning that SMS has strong adsorption capacity and is a natural immobilisation matrix, which improves the enzymatic degradation of the dyes. Thus, SMS can be used in the treatment of textile effluents for dye removal by simultaneous mechanisms of adsorption and enzymatic degradation, with reduction of environmental impacts for SMS disposal and reduction of the costs associated with commercial enzymes and adsorbents.

Photocatalytic degradation of dyes by novel electrospun nanofibers: A review

Textile industry is a significant contributor of wastewater, which contains pollutants including dye and other chemical substances. The release of thousands of tons of dye used in textile processing and finishing into natural streams and aquatic bodies present dire harm to the environment. In response to environmental concerns, a number of research have been done using low-cost technology to produce absorbents that can remove dyes from water bodies. Distinct techniques such as adsorption, enzymatic and photocatalytic degradation, etc. have been employed to remove dyes. In the last few decades, photocatalysis, a simple and green strategy, has emerged as the most valuable and recent principle that deals with wastewater treatment, using uniquely fabricated nanomaterials. Among them, rapid and versatile electrospinning methods have been used for the construction of a large surface area, hierarchical and reusable nanofibers for environmental remediation. As a flexible and fast fabrication method, reviewing the use of electrospun photocatalytic nanofibers, influential parameters in electrospinning and their effectiveness in the generation of oxidizing agents are a promising platform for the fabrication of novel nanomaterials in photocatalytic degradation of dyes. This review discusses techniques for dye removal, electrospun nanofibers, their fabrication and application in photocatalysis; mechanism of photocatalytic degradation, and challenges and suggested remedies for electrospun nanofibers in photocatalysis.

UVB light influence on the laccase enzyme catalytic activity in reverse micelles and in homogeneous aqueous medium

Laccase is a versatile enzyme widely used for the oxidation of environmental contaminants and exhibits great potential in many others applications; however, it undergoes photo-degradation when irradiated with UVB light. The photo-stability of this biomolecule can be improved by immobilization in different encapsulation media and reverse micelles have been employed with this purpose. The laccase activity using syringaldazine as substrate has been studied in the absence and in the presence of reverse micelles of 0.15 M of sodium 1,4-bis (2-ethylhexyl) sulfosuccinate (AOT) in isooctane at W₀ ([H₂O]/[AOT]) = 30, before and after irradiation of the enzyme with UVB light. The kinetic parameters, i.e., Michaelis-Menten constant (K_M), catalytic constant (k_CAT), and catalytic efficiency (k_CAT/K_M), were determined by spectroscopic measurements in the micellar system and in homogeneous aqueous medium. The distribution of the substrate in two pseudo-phases (micelle and organic solvent) was taking into account in the kinetic parameters' determinations. The results obtained indicate that the nano-aggregate system confers a solubilization media in the water core of the micelle, both for the enzyme and the substrate, in which the catalytic function of the enzyme is preserved. On the other hand, in homogeneous aqueous medium k_CAT/K_M value, it is reduced by ~50% after UVB irradiation of the enzyme, while in micellar medium, less than 10% of the activity was affected. This mean that the enzyme achieves a considerably photo-protection when it is irradiated with UVB light in reverse micelles as compared with the homogeneous aqueous medium. This phenomenon can be mainly due to the confinement of the biomolecule inside the micelle. Physical properties of the nano-environment could affect photochemical reactions.

A critical review on application of organic, inorganic and hybrid nanophotocatalytic assemblies for photocatalysis of methyl orange dye in aqueous medium

Methyl orange (MO) is a highly carcinogenic and harmful contaminant, which has been extensively reported for its detrimental impact on human and aquatic life. The photodegradation of MO into less toxic products has gained much attention over the past few decades. Herein we have reviewed the recent advancement in designing of nanomaterials (NMs) stabilized on different fabricating assemblies and their application in photocatalysis of MO dye. These photocatalytic systems possess various advantages and disadvantages. Graphene-based supported materials on different NMs are highly reported photocatalysts for photocatalysis of MO dye. Recent advancement, parameters affecting photocatalytic studies, kinetics and photocatalytic mechanism of MO have been thoroughly explained in this review. Future outcomes are also provided for extending the development of scientific research in this field.

Azo dyes degradation by microorganisms - An efficient and sustainable approach

Synthetic aromatic compounds consisting of various functional groups are known as dyes. These colored compounds are often discharged in effluents, and they are very dangerous to aquatic life. Basically, the dye industry started by using natural plant and insect sources, and then suddenly turned into artificial manufacturing. Natural equilibrium of our environment gets changed by the reduction in photosynthetic activity due to the dyes. In China 900,000 tons of all kinds of dyes are usually produced, which are used in many industries like food, textile, food, paper and leather. Untreated wastewater contaminates aquatic bodies by causing eutrophication, change in water color, oxygen depletion which affect aquatic organisms to a great extent. Dye wastewater is now the key environmental pollution form. In recent eras an extensive study line has been developed to explore the dye decolorization and biodegradation under both aerobic as well as anaerobic conditions. In this review, the chemistry, toxicity and microbial biodegradation/decolorization are presented. Some recent studies along with the new techniques and methodologies of remediating the dye pollution are also discussed to provide the bases of their handling. Overall, efficient and high biodegradation potential make microbes an impending foundation for green chemistry to eradicate toxic dyes from industrial wastewater.

Site-Specific Covalent Immobilization of Methylobacterium extorquens Non-Blue Laccse Melac13220 on Fe3O4 Nanoparticles by Aldehyde Tag

In the present study, the non-blue laccase Melac13220 from Methylobacterium extorquens was immobilized using three methods to overcome problems related to the stability and reusability of the free enzyme: entrapment of the enzyme with sodium alginate, crosslinking of the enzyme with glutaraldehyde and chitosan-, and site-specific covalent immobilization of the enzyme on Fe3O4 nanoparticles by an aldehyde tag. The site-specific covalent immobilization method showed the highest immobilization efficiency and vitality recovery. The optimum temperature of Melac13220 was increased from 65 °C to 80 °C. Immobilized Melac13220 showed significant tolerance to some organic solvents and maintained approximately 80% activity after 10 cycles of use. Differential scanning calorimetry (DSC) indicated that the melting temperature of the enzyme was increased (from 57 °C to 79 °C). Immobilization of Melac13220 also led to improvement in dye decolorization such that Congo Red was completely decolorized within 10 h. The immobilized enzyme can be easily prepared without purification, demonstrating the advantages of using the aldehyde tag strategy and providing a reference for the practical application of different immobilized laccase methods in the industrial field.

Enhanced adsorption of Congo red dye onto polyethyleneimine-impregnated biochar derived from pine needles

Biochar derived from waste pine needles was chemically modified using polyethyleneimine (PEI) to increase its adsorptive potential for withdrawal of anionic dye Congo red from aqueous solution. PEI impregnation on biochar was confirmed from scanning electron microscopy and energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The surface area of biochar decreased after PEI treatment, but the amine groups increased on biochar surface. PEI-treated biochar displayed considerable increase in adsorption at acidic conditions. Adsorption isotherm was best explained by Langmuir model (R² > 99) and the adsorption kinetics agrees well with pseudo-second-order model. The maximum adsorption capacity of PEI-treated biochar was observed to be 294.11 mg g^-1 and 30.76 mg g^-1 for pristine biochar displaying a 9.5-fold increase. The positive value of standard enthalpy of adsorption (∆H° = 14.96 KJmole^-1) indicated the endothermic nature of adsorption, and positive value of entropy (∆S° = 74.43 Jmole^-1 K^-1) revealed the affinity of biochar towards dye molecules. Negative value of Gibb's free energy ∆G° (- 7.2 KJmole^-1) revealed that the process was spontaneous. Electrostatic interaction appeared to be the key mechanism governing the adsorption process. Thus, PEI-impregnated biochar represents novel low-cost sorbent that can effectively remove anionic dyes which are poorly removed by pristine biochar.

Biodegradation of Congo Red Using Co-Culture Anode Inoculum in a Microbial Fuel Cell

Congo red is an azo dye widely used as a colouring agent in textile industries. It is a serious threat due to its carcinogenic effects. Its degradation has been challenging due to its complex yet stable structure. The present study was aimed to investigate the effective degradation of Congo red by bioremediating bacteria isolated from different environments. To investigate predominant microorganisms that degrade Congo red and its functions in microbial fuel cells (MFCs), strains isolated from cow dung (Enterococcus faecalis SUCR1) and soil (Pseudomonas aeruginosa PA1_NCHU) were used as a co-culture inocula. The remarkable results establish that E. faecalis as an excellent microbial source for the biological degradation of dye-contaminated wastewater treatment alongside bioactive treating wastewater with varied concentrations of congo red dye. The highest efficiency percentage of dye degradation was 98% after 3 days of incubation at pH 7 and 37 °C, whereas findings have shown that the decolorization at pH 5 and 6 was lower at 66% and 83.3%, respectively, under the same incubation conditions. Furthermore, the co-culture of E. faecalis SUCR1 and P. aeruginosa at a 1:1 ratio demonstrated improved power generation in MFCs. The maximum power density of 7.4 W/m3 was recorded at a 150 mg L−1 concentration of Congo red, indicating that the symbiotic relation between these bacterium resulted in improved MFCs performance simultaneous to dye degradation.

Automated monitoring the kinetics of homogeneous and heterogeneous chemical processes using a smartphone

Heterogeneous chemical processes occupy a pivotal position in many fields of applied chemistry. Monitoring reaction kinetics in such heterogeneous systems together with challenges associated with ex-situ analytical methodologies can lead to inaccurate information about the nature of the catalyst surfaces as well as information about the steps involved. The present work explores the possibility of kinetic measurements of chemical reactions and adsorption processes of homogeneous and heterogeneous systems through the variation of RGB intensities of digital images using a smartphone combined with a program written in Python to accelerate and facilitate data acquisition. In order to validate the method proposed, the base promoted hydrolysis of 4-nitrophenyl acetate was initially investigated. The rate constants obtained through RGB analysis (0.01854 min^-1) is almost identical to that using traditional UV-Vis spectroscopy (0.01848 min^-1). The proposed method was then applied to monitor the kinetics of three heterogeneous processes: (1) reduction of 4-nitrophenolate in the presence of dispersed Pd/C; (2) decomposition of methyl orange with TiO₂; and (3) adsorption of rhodamine on montmorillonite. In general, the method via digital images showed high reproducibility and analytical frequency, allowing the execution of simultaneous analyses, with an accuracy comparable to UV-Vis spectrophotometry. The method developed herein is a practical and valuable alternative for obtaining kinetic data of heterogeneous reactions and processes where a color change is involved, bypassing sampling collection and processing which decreases analytical frequency and may lead to data errors.

Characterization of a Novel Fe2+ Activated Non-Blue Laccase from Methylobacterium extorquens

Herein, a novel laccase gene, Melac13220, was amplified from Methylobacterium extorquens and successfully expressed in Escherichia coli with a molecular weight of approximately 50 kDa. The purified Melac13220 had no absorption peak at 610 nm and remained silent within electron paramagnetic resonance spectra, suggesting that Melac13220 belongs to the non-blue laccase group. Both inductively coupled plasma spectroscopy/optical emission spectrometry (ICP-OES) and isothermal titration calorimetry (ITC) indicated that one molecule of Melac13220 can interact with two iron ions. Furthermore, the optimal temperature of Melac13220 was 65 °C. It also showed a high thermolability, and its half-life at 65 °C was 80 min. Melac13220 showed a very good acid environment tolerance; its optimal pH was 1.5. Cu²⁺ and Co²⁺ can slightly increase enzyme activity, whereas Fe²⁺ could increase Melac13220′s activity five-fold. Differential scanning calorimetry (DSC) indicated that Fe²⁺ could also stabilize Melac13220. Unlike most laccases, Melac13220 can efficiently decolorize Congo Red and Indigo Carmine dyes even in the absence of a redox mediator. Thus, the non-blue laccase from Methylobacterium extorquens shows potential application value and may be valuable for environmental protection, especially in the degradation of dyes at low pH.

Synergistic action of laccase treatment and membrane filtration during removal of azo dyes in an enzymatic membrane reactor upgraded with electrospun fibers

Nowadays, the increasing amounts of dyes present in wastewaters and even water bodies is an emerging global problem. In this work we decided to fabricate new biosystems made of nanofiltration or ultrafiltration membranes combined with laccase entrapped between polystyrene electrospun fibers and apply them for decolorization of aqueous solutions of three azo dyes, C.I. Acid Yellow 23 (AY23), C.I. Direct Blue 71 (DB71) and C.I. Reactive Black 5 (RB5). Besides effective decolorization of the permeate stream, the biosystems also allowed removal of dyes from the retentate stream as a result of enzymatic action. The effect of pH and applied pressure on decolorization efficiencies was investigated, and pH 5 and pressure of 2 bar gave the highest removal efficiencies of 97% for AY23 and 100% for both DB71 and RB5 from permeate solutions while decolorization of retentate for RB5 reached 65% under these conditions. Almost 100% decolorization of all dyes was achieved after three consecutive enzyme membrane cycles. Decolorization was shown to be due to the synergistic action of membrane separation and bioconversion. The biocatalytic action also enabled significant reduction of permeate and retentate toxicity, which is one of the biggest environmental health issues for these types of streams.

Degradation and Detoxification of Chlorophenols with Different Structure by LAC-4 Laccase Purified from White-Rot Fungus Ganoderma lucidum

A laccase named LAC-4 was purified from Ganoderma lucidum. Firstly, the enzymatic properties of purified LAC-4 laccase, and the degradation of three chlorophenol pollutants 2,6-dichlorophenol (2,6-DCP), 2,3,6-trichlorophenol (2,3,6-TCP) and 3-chlorophenol (3-CP) by LAC-4 were systematically studied. LAC-4 had a strong ability for 2,6-DCP and 2,3,6-TCP degradation. The degradation ability of LAC-4 to 3-CP was significantly lower than that of 2,6-DCP and 2,3,6-TCP. LAC-4 also had a good degradation effect on the chlorophenol mixture (2,6-DCP + 2,3,6-TCP). The results of kinetics of degradation of chlorophenols by LAC-4 suggested that the affinity of LAC-4 for 2,6-DCP was higher than 2,3,6-TCP. The catalytic efficiency and the catalytic rate of LAC-4 on 2,6-DCP were also significantly higher than 2,3,6-TCP. During degradation of 2,6-DCP and 2,3,6-TCP, LAC-4 had a strong tolerance for high concentrations of different metal salts (such as MnSO₄, ZnSO₄, Na₂SO₄, MgSO₄, CuSO₄, K₂SO₄) and organic solvents (such as ethylene glycol and glycerol). Next, detoxification of chlorophenols by LAC-4 was also systematically explored. LAC-4 treatment had a strong detoxification ability and a good detoxification effect on the phytotoxicity of individual chlorophenols (2,6-DCP, 2,3,6-TCP) and chlorophenol mixtures (2,6-DCP + 2,3,6-TCP). The phytotoxicities of 2,6-DCP, 2,3,6-TCP and chlorophenol mixtures (2,6-DCP + 2,3,6-TCP) treated with LAC-4 were considerably reduced or eliminated. Finally, we focused on the degradation mechanisms and pathways of 2,6-DCP and 2,3,6-TCP degradation by LAC-4. The putative transformation pathway of 2,6-DCP and 2,3,6-TCP catalyzed by laccase was revealed for the first time. The free radicals formed by LAC-4 oxidation of 2,6-DCP and 2,3,6-TCP produced dimers through polymerization. LAC-4 catalyzed the polymerization of 2,6-DCP and 2,3,6-TCP, forming dimer products. LAC-4 catalyzed 2,6-DCP into two main products: 2,6-dichloro-4-(2,6-dichlorophenoxy) phenol and 3,3′,5,5′-tetrachloro-4,4′-dihydroxybiphenyl. LAC-4 catalyzed 2,3,6-TCP into two main products: 2,3,6-trichloro-4-(2,3,6-trichlorophenoxy) phenol and 2,2′,3,3′,5,5′-hexachloro-[1,1′-biphenyl]-4,4′-diol.

Novel laccase from Xylaria polymorpha and its efficiency in the biotransformation of pharmaceuticals: Optimization of operational conditions, comparative effect of redox-mediators and toxicity studies

The promising potentials of biocatalytic treatment processes in the removal of micropollutants whilst eliminating health and environmental hazards have attracted great attention in recent years. This current work investigated the biotransformation efficiency of a novel laccase from Xylaria polymorpha (XPL) in comparison with commercial laccases from Trametes versicolor (TVL) and Aspergillus sp. (ASL). XPL exhibited better oxidation performance (95.7%) on AMX than TVL (92.8%) and ASL (90.5%). Optimization of operational conditions revealed that AMX was best oxidized at pH 5, temperature (30 °C), and concentration (1.0 mg L^-1). The investigation carried out to determine the effect of redox mediators revealed violuric acid (VLA) as the best redox mediator. The laccase stability experiments elucidated that the oxidation of AMX is time and mediator concentration dependent with ABTS exhibiting highest deactivation of XPL active sites. Two metabolic products; amoxicillin penilloic acid and 5-hydroxy-6-(4-hydroxyphenyl)- 3-(1,3-thiazolidin-2-yl)piperazin-2-one of AMX were obtained through Liquid Chromatography-Mass Spectrometry (LC-MS) analyses. The toxicity assessments carried out after oxidation of AMX by XPL showed 94% and 97% reduced toxicity on Artemia salina and Aliivibrio fischeri respectively. The study further underscored the efficiency of biocatalytic-mediator technology in the transformation of complex micropollutants into less toxic substances in an eco-friendly way.