Textile Dye Biodecolorization by Manganese Peroxidase: A Review

Adsorption potential of ionic liquid-modified ZnO nanoparticles for highly efficient removal of azo dye: detailed isotherms and kinetics

In this study, bare and ionic liquid-modified ZnO nanoparticles have been fabricated using microwave irradiation method. The fabricated nanoparticles were characterized by different techniques, viz. XRD, FT-IR, FESEM, and UV-Visible spectroscopy, and were explored as adsorbent for effective sequestration of azo dye (Brilliant Blue R-250) from aqueous media. Various factors affecting the adsorption efficiency of synthesized nanoparticles (bare/ionic liquid-modified) such as concentration of dye, pH of reaction media, dose of nanoparticles, and reaction time were thoroughly investigated with varying experimental conditions; on a magnetic stirrer and in a sonicator. The results exhibited a high adsorption efficiency of ionic liquid-modified nanoparticles for removal of dye as compared to the bare one. Also, an enhanced adsorption was observed via sonication in comparison with magnetic stirring. Different isotherms such as Langmuir, Freundlich, and Tempkin were elaborated. Evaluation of adsorption kinetics showed a linear pseudo-second-order equation for adsorption process. The exothermic and spontaneous nature of adsorption was further confirmed by thermodynamic investigations. As per the results obtained, it is suggested that the fabricated ionic liquid-modified ZnO nanoparticles could successfully remediate the toxic anionic dye from aqueous media. Hence, this system can be utilized for large-scale industrial applications.

Biodegradation strategies of veterinary medicines in the environment: Enzymatic degradation

One Health closely integrates healthy farming, human medicine, and environmental ecology. Due to the ecotoxicity and risk of transmission of drug resistance, veterinary medicines (VMs) are regarded as emerging environmental pollutants. To reduce or mitigate the environmental risk of VMs, developing friendly, safe, and effective removal technologies is an important means of environmental remediation for VMs. Many previous studies have proved that biodegradation has significant advantages in removing VMs, and biodegradation based on enzyme catalysis presents higher operability and specificity. This review focused on biodegradation strategies of environmental pollutants and reviewed the enzymatic degradation of VMs including antimicrobial drugs, insecticides, and disinfectants. We reviewed the sources and catalytic mechanisms of peroxidase, laccase, and organophosphorus hydrolases, and summarized the latest research status of immobilization methods and bioengineering techniques in improving the performance of degrading enzymes. The mechanism of enzymatic degradation for VMs was elucidated in the current research. Suggestions and prospects for researching and developing enzymatic degradation of VMs were also put forward. This review will offer new ideas for the biodegradation of VMs and have a guide significance for the risk mitigation and detoxification of VMs in the environment.

Conversion of Corn Stover for Microbial Enzymes Production by Phanerochaete chrysosporium

Phanerochaete chrysosporium, a white rot fungus, exhibits remarkable capabilities in producing various extracellular enzymes. These microbial enzymes find extensive applications in disrupting the intricate structure of plant cell walls, decolorizing synthetic dyes, and facilitating pulp extraction, among other functions. The process of solid-state fermentation stands out as an economical and sustainable approach, ideal for achieving high yields in enzyme production using lignocellulosic biomass as a substrate. In this research paper, both untreated and alkali pretreated corn stover materials served as substrates for enzyme production, leveraging the fungal strain's capacity to generate enzymes like cellulases and manganese peroxidase. The maximum production of endoglucanase was notably observed, reaching 121.21 ± 0.90 U/gds on the 9th day for untreated biomass and 79.75 ± 0.57 U/gds on the 6th day for treated biomass. Similarly, the peak exoglucanase production was recorded at 2.46 ± 0.008 FPU/ml on the 3rd day for untreated biomass and 0.92 ± 0.002 FPU/ml on the 6th day for treated biomass. Furthermore, the highest production of manganese peroxidase was achieved, with values of 5076.81 U/l on the 6th day for untreated biomass and 1127.58 ± 0.23 U/l on the 3rd day for treated biomass. These results collectively emphasize the potential of corn stover as a renewable and promising substrate for the production of essential enzymes.

Lignocellulolytic extremozymes and their biotechnological applications

Lignocellulolytic enzymes are used in different industrial and environmental processes. The rigorous operating circumstances of these industries, however, might prevent these enzymes from performing as intended. On the other side, extremozymes are enzymes produced by extremophiles that can function in extremely acidic or basic; hot or cold; under high or low salinity conditions. These severe conditions might denature the normal enzymes that are produced by mesophilic microorganisms. The increased stability of these enzymes has been contributed to a number of conformational modifications in their structures. These modifications may result from a few amino acid substitutions, an improved hydrophobic core, the existence of extra ion pairs and salt bridges, an increase in compactness, or an increase in positively charged amino acids. These enzymes are the best option for industrial and bioremediation activities that must be carried out under difficult conditions due to their improved stability. The review, therefore, discusses lignocellulolytic extremozymes, their structure and mechanisms along with industrial and biotechnological applications.

Dye Decolorization by a Miniaturized Peroxidase Fe-MimochromeVI*a

Oxidases and peroxidases have found application in the field of chlorine-free organic dye degradation in the paper, toothpaste, and detergent industries. Nevertheless, their widespread use is somehow hindered because of their cost, availability, and batch-to-batch reproducibility. Here, we report the catalytic proficiency of a miniaturized synthetic peroxidase, Fe-Mimochrome VI*a, in the decolorization of four organic dyes, as representatives of either the heterocyclic or triarylmethane class of dyes. Fe-Mimochrome VI*a performed over 130 turnovers in less than five minutes in an aqueous buffer at a neutral pH under mild conditions.

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

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 frameworks, built upon artificial intelligence (AI) and machine learning (ML), has been emphasized as a recent milestone in environmental research.

Manganese peroxidases as robust biocatalytic tool - An overview of sources, immobilization, and biotechnological applications

With robust catalytic features, manganese peroxidases (MnPs) from various sources, including fungi and bacteria, have gained much consideration in many biotechnological applications with particular emphasis on environmental remediation. MnP is a heme-containing enzyme that belongs to the oxidoreductases that can catalyze the degradation of various organic pollutants, such as chlorophenols, nitroaromatic compounds, industrial dyes, and polycyclic aromatic hydrocarbons. To spotlight the MnP as biocatalytic tool, an effort has been put forward to cover the four major compartments. For instance, following a brief introduction, first, various microbial sources of MnP are discussed with examples. Second, structural attributes and biocatalytic features of MnP are given with examples. Third, different MnP immobilization strategies, including adsorption, covalent linking, entrapment, and cross-linking, are discussed with a significant motive to strengthen the enzyme's stability against diverse deactivation agents by restricting the conformational mobility of molecules. Compared to free counterparts, immobilized MnP fractions perform well in hostile environments. Finally, various biotechnological applications, such as fuel ethanol production, de-lignification, textile industry, pulp and paper industry, degradation of phenolic and non-phenolic compounds, and pharmaceutical and pesticide degradation, are briefly discussed.

A mutant R70V/E166A of short manganese peroxidase showing Mn2+-independent dye decolorization

Il-MnP1, a short-type manganese peroxidase from Irpex lacteus F17, can oxidize some substrates in the absence of Mn²⁺, but the catalysis was much lower than in the presence of Mn²⁺. Here, we report a mutant R70V/E166A of Il-MnP1 with some unique properties, which possessed clearly higher catalysis for the decolorization of anthraquinone and azo dyes in the absence of Mn²⁺ than that of Il-MnP1. Importantly, the optimum pH of R70V/E166A for decolorization of anthraquinone dyes (Reactive Blue 19, RB19) was 6.5, and the mutant achieved high decolorization activities in the range of pH 4.0-7.0, whereas Il-MnP1 only showed decolorization for RB19 at pH 3.5-4.0. In addition, the optimum H₂O₂ concentration of R70V/E166A for RB19 decolorization was eight times that of Il-MnP1 and the H₂O₂ stability has improved 1.4 times compared with Il-MnP1. Furthermore, Mn²⁺ competitively inhibited the oxidation of RB19 by R70V/E166A, explaining the higher catalytic activity of the mutant R70V/E166A in the absence of Mn²⁺. Molecular docking results suggested that RB19 binds to the distal side of the heme plane in mutant R70V/E166A, which extended from the heme δ-side to the heme γ-side, and close to the mutated residues of R70V and E166A, whereas RB19 could not access the heme pocket of Il-MnP1 due to the steric hindrance of the side-chain group of Arg 70. Thus, this study constructed a useful mutant R70V/E166A and analyzed its higher Mn²⁺-independent activity, which is very important for better understanding the Mn²⁺-independent catalytic mechanism for short manganese peroxidases. KEY POINTS: • The mutant R70V/E166A of atypical MnP1 of I. lacteus F17 shows unique catalytic properties. • At pH 6.5, the R70V/E166A had a strong ability to decolorize anthraquinone dyes in the absence of Mn²⁺. • The binding sites of Reactive Blue 19 in mutant R70V/E166A were elucidated.

Artificial microbial consortium producing oxidases enhanced the biotransformation efficiencies of multi-antibiotics

Antibiotic mixtures in the environment result in the development of bacterial strains with resistance against multiple antibiotics. Oxidases are versatile that can bio-remove antibiotics. Various laccases (LACs), manganese peroxidases (MNPs), and versatile peroxidase (VP) were reconstructed in Pichia pastoris. For the single antibiotics, over 95.0% sulfamethoxazole within 48 h, tetracycline, oxytetracycline, and norfloxacin within 96 h were bio-removed by recombinant VP with α-signal peptide, respectively. In a mixture of the four antibiotics, 80.2% tetracycline and 95.6% oxytetracycline were bio-removed by recombinant MNP2 with native signal peptide (NSP) within 8 h, whereas < 80.0% sulfamethoxazole was bio-removed within 72 h, indicating that signal peptides significantly impacted removal efficiencies of antibiotic mixtures. Regarding mediators for LACs, 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) resulted in better removal efficiencies of multi-antibiotic mixtures than 1-hydroxybenzotriazole or syringaldehyde. Furthermore, artificial microbial consortia (AMC) producing LAC2 and MNP2 with NSP significantly improved bio-removal efficiency of sulfamethoxazole (95.5%) in four-antibiotic mixtures within 48 h. Tetracycline and oxytetracycline were completely bio-removed by AMC within 48 and 72 h, respectively, indicating that AMC accelerated sulfamethoxazole, tetracycline, and oxytetracycline bio-removals. Additionally, transformation pathways of each antibiotic by recombinant oxidases were proposed. Taken together, this work provides a new strategy to simultaneously remove antibiotic mixtures by AMC.

High Potential Decolourisation of Textile Dyes from Wastewater by Manganese Peroxidase Production of Newly Immobilised Trametes hirsuta PW17-41 and FTIR Analysis

Coloured wastewater from the textile industry is a very serious global problem. Among 16 different white-rot fungal isolates, Trametes hirsuta PW17-41 revealed high potential for decolourisation of mixed textile dyes (Navy EC-R, Ruby S3B and Super Black G) from real industrial wastewater samples. The efficiency of dye decolourisation was evaluated using the American Dye Manufacturers’ Institute (ADMI) standard methodology. The suitable support for fungal mycelium immobilisation was nylon sponges. The optimal dye decolourisation (95.39%) was achieved by using palm sugar and ammonium nitrate as carbon and nitrogen sources, respectively. The initial pH was 5 and the agitation speed was 100 rpm at 30 °C. The ADMI values of textile dyes decreased from 2475 to 114 within two days, reducing the treatment time from seven days before optimisation. The major mechanism of dye decolourisation was biodegradation, which was confirmed by UV–visible and FTIR spectra. Manganese peroxidase (MnP) (4942 U L⁻¹) was found to be the main enzyme during the decolourisation process at an initial dye concentration of 21,200 ADMI. The results indicated the strong potential of immobilised fungal cells to remove high concentrations of textile dyes from industrial wastewater and their potential ability to produce high MnP and laccase activities that can be used in further application.

Exploring the potential of a newly constructed manganese peroxidase-producing yeast consortium for tolerating lignin degradation inhibitors while simultaneously decolorizing and detoxifying textile azo dye wastewater

MnP-YC4, a newly constructed manganese peroxidase-producing yeast consortium, has been developed to withstand lignin degradation inhibitors while degrading and detoxifying azo dye. MnP-YC4 tolerance to major biomass-derived inhibitors was promising. MnP induced by lignin was found to be highly related to dye decolorization by MnP-YC4. Simulated azo dye-containing wastewater supplemented with a lignin co-substrate (3,5-Dimethoxy-4-hydroxybenzaldehyde) decolorized up to 100, 91, and 76% at final concentrations of 20, 40, and 60%, respectively. MnP-YC4 effectively decolorized the real textile wastewater sample, reaching up to 91.4%, and the COD value decreased significantly during the decolorization, reaching 7160 mg/l within 7 days. A possible dye biodegradation pathway was proposed based on the degradation products identified by UV-vis, FTIR, GC/MS, and HPLC techniques, beginning with azo bond cleavage and eventually mineralized to CO₂ and H₂O. When compared to the phytotoxic original dye, the phytotoxicity of MnP-YC4 treated dye-containing wastewater samples confirmed the nontoxic nature.

Carrier-Free Cross-linked Laccase Crystals for Biocatalytic Degradation of Textile Industrial Effluents

Herein, laccase from Trametes versicolor was used to fabricate carrier-free cross-linked laccase crystals (CLLCs) and deployed as a robust catalyst for waste effluent treatment. The surface morphology and involvement of functional group attributes of CLLCs were scrutinized by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). As fabricated CLLCs were subjected to kinetic characterization by assessing the effects of pH environment, thermal profile, and substrate (determination of K_m and V_max) on the activity. A fully characterized CLLCs fraction was used to treat synthetic dyes containing waste effluents taken from various industries, i.e., Chenab Textile Industry, M-tax, Sitara, and National Silk & Rayon Mills. Degradation profile revealed 36.8%, 27.6%, 39.9%, and 26.4% degradation of Chenab Textile Industry, M-tax, Sitara, and National Silk & Rayon Mills, respectively, by the free form of laccase, whereas the biocatalytic activity of CCLCs led to 78.6%, 75.6%, 85.5%, and 63.3% degradation of those effluents. The decrease in peak and mass region alongside the presence of new peaks in GC-MS affirms the effective decolorization of contaminated waste effluents. CLLCs retained over 70% and 50% of their degradation activity after 3 and 5 cycles, respectively. In conclusion, CLLCs might represent a robust bioprocess to improve the usability of laccase for various synthetic dyes containing waste effluents to diminish environmental pollution from the dye-based industries.

An innovative approach of bioremediation in enzymatic degradation of xenobiotics

Worldwide, environmental pollution due to a complex mixture of xenobiotics has become a serious concern. Several xenobiotic compounds cause environmental contamination due to their severe toxicity, prolonged exposure, and limited biodegradability. From the past few decades, microbial-assisted degradation (bioremediation) of xenobiotic pollutants has evolved as the most effective, eco-friendly, and valuable approach. Microorganisms have unique metabolism, the capability of genetic modification, diversity of enzymes, and various degradation pathways necessary for the bioremediation process. Microbial xenobiotic degradation is effective but a slow process that limits its application in bioremediation. However, the study of microbial enzymes for bioremediation is gaining global importance. Microbial enzymes have a huge ability to transform contaminants into non-toxic forms and thereby reduce environmental pollution. Recently, various advanced techniques, including metagenomics, proteomics, transcriptomics, metabolomics are effectively utilized for the characterization, metabolic machinery, new proteins, metabolic genes of microorganisms involved in the degradation process. These advanced molecular techniques provide a thorough understanding of the structural and functional aspects of complex microorganisms. This review gives a brief note on xenobiotics and their impact on the environment. Particular attention will be devoted to the class of pollutants and the enzymes such as cytochrome P450, dehydrogenase, laccase, hydrolase, protease, lipase, etc. capable of converting these pollutants into innocuous products. This review attempts to deliver knowledge on the role of various enzymes in the biodegradation of xenobiotic pollutants, along with the use of advanced technologies like recombinant DNA technology and Omics approaches to make the process more robust and effective.

Enzymatic Bioprospecting of Fungi Isolated from a Tropical Rainforest in Mexico

The humid tropical environment provides an ideal place for developing a high diversity of plants; this is why it is an interesting site for the enzymatic bioprospecting of fungi that are responsible for the recycling of organic matter in an efficient and accelerated way and whose enzymes could have multiple biotechnological applications. For this study, 1250 isolates of macroscopic and microscopic fungal morphotypes were collected from soil, leaf litter, and wood. One hundred and fifty strains (50 from each source) were selected for the enzymatic screening. From the first phase, 51 strains with positive activity for laccase, protease, amylase, xylanase, and lipase enzymes were evaluated, of which 20 were isolated from leaf litter, 18 from the soil, and 13 from wood. The 10 best strains were selected for the enzymatic quantification, considering the potency index and the production of at least two enzymes. High laccase activity was detected for Trametes villosa FE35 and Marasmius sp. CE25 (1179 and 710.66 U/mg, respectively), while Daedalea flavida PE47 showed laccase (521.85 U/mg) and protease activities (80.66 U/mg). Fusarium spp. PH79 and FS400 strains had amylase (14.0 U/mg, 49.23 U/mg) and xylanase activities (40.05 U/mg, 36.03 U/mg) respectively. These results confirm the enzymatic potential of fungi that inhabit little-explored tropical rainforests with applications in industry.