Enhancing catalytic functionality of Trametes versicolor IBL-04 laccase by immobilization on chitosan microspheres

Simultaneous Degradation of AFB1 and ZEN by CotA Laccase from Bacillus subtilis ZJ-2019-1 in the Mediator-Assisted or Immobilization System

The global prevalence of aflatoxin B1 (AFB1) and zearalenone (ZEN) contamination in food and feed poses a serious health risk to humans and animals. Recently, enzymatic detoxification has received increasing attention, yet most enzymes are limited to degrading only one type of mycotoxin, and free enzymes often exhibit reduced stability and activity, limiting their practicality in real-world applications. In this study, the laccase CotA gene from ZEN/AFB1-degrading Bacillus subtilis ZJ-2019-1 was cloned and successfully expressed in Escherichia coli BL21, achieving a protein yield of 7.0 mg/g. The recombinant CotA (rCotA) completely degraded AFB1 and ZEN, with optimal activity at 70 °C and pH 7.0. After rCotA treatment, neither AFB1 nor ZEN showed significantly cytotoxicity to mouse macrophage cell lines. Additionally, the AFB1/ZEN degradation efficiency of rCotA was significantly enhanced by five natural redox mediators: acetosyringone, syringaldehyde, vanillin, matrine, and sophoridin. Among them, the acetosyringone-rCotA was the most effective mediator system, which could completely degrade 10 μg of AFB1 and ZEN within 1 h. Furthermore, the chitosan-immobilized rCotA system exhibited higher degradation activity than free rCotA. The immobilized rCotA degraded 27.95% of ZEN and 41.37% of AFB1 in contaminated maize meal within 12 h, and it still maintained more than 40% activity after 12 reuse cycles. These results suggest that media-assisted or immobilized enzyme systems not only boost degradation efficiency but also demonstrate remarkable reusability, offering promising strategies to enhance the degradation efficiency of rCotA for mycotoxin detoxification.

Zearalenone degradation by peptide-based enzyme mimics attached membrane reactor: Performance and mechanism

Zearalenone (ZEN) is a nonsteroidal estrogenic mycotoxin with widespread contamination. Inspired by lactone hydrolases, a peptide-based enzyme mimetic material for degrading ZEN was developed by combining serine, histidine and glutamate (S/H/E) catalytic triad with pro-hydrophobic self-assembling sequences and oxyanion hole site. Chitosan hybrid membranes were prepared, followed by immobilizing enzyme mimic on the membrane surface to fabricate biocatalytic membrane reactor. The membrane reactor, with good thermal stability and high catalytic activity after repeated use, can be applied to the degradation of ZEN in food. Computer simulation studies of the degradation mechanism indicated that the carbon atom on the lactone bond within ZEN molecule was susceptible to catalytic triplex attack, leading to lactone bond broken, followed by spontaneous decarboxylation to produce dihydroxyphenyl derivatives with greatly reduced binding capacity to the estrogen receptors. This kind of peptide-based enzyme mimetic material would be very promising in degrading mycotoxins in food safety field.

Decolorization of Textile Azo Dye via Solid-State Fermented Wheat Bran by Lasiodiplodia sp. YZH1

Textile dyes are one of the major water pollutants released into water in various ways, posing serious hazards for both aquatic organisms and human beings. Bioremediation is a significantly promising technique for dye decolorization. In the present study, the fungal strain Lasiodiplodia sp. was isolated from the fruiting bodies of Schizophyllum for the first time. The isolated fungal strain was examined for laccase enzyme production under solid-state fermentation conditions with wheat bran (WB) using ABTS and 2,6-Dimethoxyphenol (DMP) as substrates, then the fermented wheat bran (FWB) was evaluated as a biosorbent for Congo red dye adsorption from aqueous solutions in comparison with unfermented wheat bran. A Box-Behnken design was used to optimize the dye removal by FWB and to analyze the interaction effects between three factors: fermentation duration, pH, and dye concentration. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were applied to study the changes in the physical and chemical characteristics of wheat bran before and after fermentation. An additional experiment was conducted to investigate the ability of the Lasiodiplodia sp. YZH1 to remove Congo red in the dye-containing liquid culture. The results showed that laccase was produced throughout the cultivation, reaching peak activities of ∼6.2 and 22.3 U/mL for ABTS and DMP, respectively, on the fourth day of cultivation. FWB removed 89.8% of the dye (100 mg L-1) from the aqueous solution after 12 h of contact, whereas WB removed only 77.5%. Based on the Box-Behnken design results, FWB achieved 93.08% dye removal percentage under the conditions of 6 days of fermentation, pH 8.5, and 150 mg L-1 of the dye concentration after 24 h. The fungal strain removed 95.3% of 150 mg L-1 of the dye concentration after 8 days of inoculation in the dye-containing liquid culture. These findings indicate that this strain is a worthy candidate for dye removal from environmental effluents.

Exploiting fungi in bioremediation for cleaning-up emerging pollutants in aquatic ecosystems

Aquatic pollution negatively affects water bodies, marine ecosystems, public health, and economy. Restoration of contaminated habitats has attracted global interest since protecting the health of marine ecosystems is crucial. Bioremediation is a cost-effective and eco-friendly way of transforming hazardous, resistant contaminants into environmentally benign products using diverse biological treatments. Because of their robust morphology and broad metabolic capabilities, fungi play an important role in bioremediation. This review summarizes the features employed by aquatic fungi for detoxification and subsequent bioremediation of different toxic and recalcitrant compounds in aquatic ecosystems. It also details how mycoremediation may convert chemically-suspended matters, microbial, nutritional, and oxygen-depleting aquatic contaminants into ecologically less hazardous products using multiple modes of action. Mycoremediation can also be considered in future research studies on aquatic, including marine, ecosystems as a possible tool for sustainable management, providing a foundation for selecting and utilizing fungi either independently or in microbial consortia.

Immobilized laccase: an effective biocatalyst for industrial dye degradation from wastewater

Environmental concerns due to the release of industrial wastewater contaminated with dyes are becoming more and more intense with the increasing industrialization. Decolorization of industrial effluents has become the top priority due to the continuous demand for color-free discharge into the receiving water bodies. Different dye removal techniques have been developed, among which biodegradation by laccase enzyme is competitive. Laccase, as a green catalyst, has a high catalytic activity, generates less toxic by-products, and has been extensively researched in the field of remediation of dyes. However, laccase's significant catalytic activity could only be achieved after an effective immobilization step. Immobilization helps strengthen and stabilize the protein structure of laccase, thus enhancing its functional properties. Additionally, the reusability of immobilized laccase makes it an attractive alternative to traditional dye degradation technologies and in the realistic applications of water treatment, compared with free laccase. This review has elucidated different methods and the carriers used to immobilize laccase. Furthermore, the role of immobilized laccase in dye remediation and the prospects have been discussed.

Efficiency Assessment between Entrapment and Covalent Bond Immobilization of Mutant β-Xylosidase onto Chitosan Support

The Y509E mutant of β-xylosidase from Geobacillus stearothermophilus (XynB2Y509E) (which also bears xylanase activity) has been immobilized in chitosan spheres through either entrapment or covalent bond formation methods. The maximum immobilization yield by entrapment was achieved by chitosan beads developed using a 2% chitosan solution after 1 h of maturation time in CFG buffer with ethanol. On the other hand, the highest value in covalent bond immobilization was observed when employing chitosan beads that were prepared from a 2% chitosan solution after 4 h of activation in 1% glutaraldehyde solution at pH 8. The activity expressed after immobilization by covalent bonding was 23% higher compared to the activity expressed following entrapment immobilization, with values of 122.3 and 99.4 IU.g-1, respectively. Kinetic data revealed that catalytic turnover values were decreased as compared to a free counterpart. Both biocatalysts showed increased thermal and pH stability, along with an improved storage capacity, as they retained 88% and 40% of their activity after being stored at 4 °C for two months. Moreover, XynB2Y509E immobilized by covalent binding also exhibited outstanding reusability, retaining 92% of activity after 10 cycles of reuse. In conclusion, our results suggest that the covalent bond method appears to be the best choice for XynB2Y509E immobilization.

Bactericidal and biocatalytic temperature responsive microgel based self-cleaning membranes for water purification

The present study focuses on creating an antimicrobial and biocatalytic smart gating membrane by synthesizing unique core-shell microgels. The core-shell microgels are synthesized by grafting short chains of poly(ethylenimine) (PEI) onto a poly((N-isopropyl acrylamide)-co-glycidyl methacrylate)) (P(NIPAm-co-GMA)) core. Subsequently, the produced microgels are utilized as a substrate for synthesizing and stabilizing silver nanoparticles (Ag NPs) through an in-situ approach. These Ag NPs immobilized microgels are then suction filtered over a polyethylene terephthalate (PET) track-etched support to create cross-linked composite microgel membranes (CMMs). After structural and permeation characterization of the prepared CMMs, the laccase enzyme is then covalently grafted to the surface of the membrane and tested for its effectiveness in degrading Reactive red-120 dye. The laccase immobilized biocatalytic CMMs show effective degradation of the Reactive red-120 by 71%, 48%, and 34% at pH 3, 4, and 5, respectively. Furthermore, the immobilized laccase enzyme showed better activity and stability in terms of thermal, pH, and storage compared to the free laccase, leading to increased reusability. The unique combination of Ag NPs and laccase on a thermoresponsive microgel support resulted in a responsive self-cleaning membrane with excellent antimicrobial and dye degradation capabilities for environmentally friendly separation technology.

Bioremediation of multifarious pollutants using laccase immobilized on magnetized and carbonyldiimidazole-functionalized cellulose nanofibers

An easily recyclable biocatalyst (Lac@CDI-MCNFs) was synthesized by immobilizing laccase on rice straw-derived carbonyldiimidazole mediated magnetized cellulose nanofibers (MCNFs). Lac@CDI-MCNFs were utilized for bioremediation of cefixime antibiotic (CT), carbofuran pesticide (CF) and safranin O dye (SO) via oxidation-reduction reactions in wastewater. MCNFs provided enhanced pH, temperature and storage stability to laccase and allowed reusability for up to 25 cycles with mere 20 % decline in efficacy. The Lac@CDI-MCNFs effectively degraded 98.2 % CT and 96.8 % CF into benign metabolites within 20 h and completely degraded SO in just 7 h. Response surface modelling (RSM) was employed based on the Box Behnken Design to evaluate the effect of various parameters i.e. pH, catalyst dosage and the pollutants concentration which was further validated with experimental studies. The degradation products were identified using LCMS, which allowed the degradation pathway of the pollutants to be determined. The degradation of all pollutants followed first- order kinetics with rate constants of 0.1775, 0.0832 and 0.958 h^-1 and half-life of 3.9, 5.0 and 0.723 h for CT, CF and SO, respectively. Lac@CDI-MCNFs was demonstrated to be an effective catalyst for the degradation of multifarious pollutants.

Four Decades of Laccase Research for Wastewater Treatment: Insights from Bibliometric Analysis

Increasing trends of environmental pollution and emerging contaminants from anthropogenic activities have urged researchers to develop innovative strategies in wastewater management, including those using the biocatalyst laccase (EC 1.10.3.2). Laccase works effectively against a variety of substrates ranging from phenolic to non-phenolic compounds which only require molecular oxygen to be later reduced to H2O as the final product. In this study, we performed a bibliometric analysis on the metadata of literature acquired through the Scopus database (24 October 2022) with keyword combination "Laccase" AND "Pollutant" OR "Wastewater". The included publications were filtered based on year of publication (1978-2022), types of articles (original research articles and review articles) and language (English). The metadata was then exported in a CSV (.csv) file and visualized on VosViewer software. A total of 1865 publications were identified, 90.9% of which were original research articles and the remaining 9.1% were review articles. Most of the authors were from China (n = 416; 22.3%) and India (n = 276; 14.79%). In the case of subject area, 'Environmental Science' emerged with the highest published documents (n = 1053; 56.46%). The identified papers mostly cover laccase activity in degrading pollutants, and chitosan, which can be exploited for the immobilization. We encourage more research on laccase-assisted wastewater treatment, especially in terms of collaborations among organizations.

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.

Esterases as emerging biocatalysts: Mechanistic insights, genomic and metagenomic, immobilization, and biotechnological applications

Esterase enzymes are a family of hydrolases that catalyze the breakdown and formation of ester bonds. Esterases have gained a prominent position in today's world's industrial enzymes market. Due to their unique biocatalytic attributes, esterases contribute to environmentally sustainable design approaches, including biomass degradation, food and feed industry, dairy, clothing, agrochemical (herbicides, insecticides), bioremediation, biosensor development, anticancer, antitumor, gene therapy, and diagnostic purposes. Esterases can be isolated by a diverse range of mammalian tissues, animals, and microorganisms. The isolation of extremophilic esterases increases the interest of researchers in the extraction and utilization of these enzymes at the industrial level. Genomic, metagenomic, and immobilization techniques have opened innovative ways to extract esterases and utilize them for a longer time to take advantage of their beneficial activities. The current study discusses the types of esterases, metagenomic studies for exploring new esterases, and their biomedical applications in different industrial sectors.

Laccase-loaded magnetic dialdehyde inulin nanoparticles as an efficient heterogeneous natural polymer-based biocatalyst for removal and detoxification of ofloxacin

An efficient heterogeneous natural polymer-based biocatalyst was fabricated through the immobilization of laccase onto dialdehyde inulin (DAI)-coated silica-caped magnetic nanoparticles (laccase@DAI@SiO₂@Fe₃O₄⋅MNPs). The carrier was developed using SiO₂@Fe₃O₄⋅MNPs and functionalized with DAI. The construction of immobilized laccase was confirmed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Immobilization yield and efficiency were calculated as 61.0 ± 0.3% and 93.0 ± 0.6%, respectively. The immobilized laccase maintained 50% and 85% of its relative activity after 25 repeated cycles and 20 days of storage at 4 °C, respectively. The prepared biocatalyst effectively eliminated ofloxacin, a fluoroquinolone-type antibiotic, with a 63% removal capacity. Besides, antimicrobial activity study on some soil microorganisms involved in the biodegradation of xenobiotics revealed that the laccase-treated ofloxacin resulted in less toxic metabolites. The obtained data indicated that the fabricated biocatalyst is promising for the removal of ofloxacin or other analogs of fluoroquinolones in the environment.

Laccase immobilized on amino-functionalized magnetic Fe3O4-SiO2 core-shell material for 2,4-dichlorophenol removal

In this study, an amino-functionalized magnetic silica microsphere material (Fe₃O₄-SiO₂-NH₂) was prepared. Using glutaraldehyde as a cross-linking agent, Trametes versicolor laccase was adsorbed-covalently bonded and immobilized on the material to prepare Laccase @ Fe₃O₄-SiO₂. In addition, the materials were characterized and analysed by SEM, TEM, XRD, FT-IR and VSM. Finally, the thermal inactivation dynamics of immobilized laccase in polar/non-polar/toxic systems and the adsorption and degradation of 2,4-DCP were studied. The results showed that Laccase @ Fe₃O₄-SiO₂ under the optimal conditions (pH 6, temperature 65°C, initial concentration of 2,4-DCP 10 mg/L), the removal rate was as high as 81.6%. Moreover, compared with free laccase, immobilized laccase had good tolerance under low pH and high-temperature conditions, and storage stability was also greatly improved. After repeated use for 7 times, Laccase @ Fe₃O₄-SiO₂ can still maintain 59% removal rate of 2,4-DCP, which gives it the potential for industrial applications.

Homologous amino acids promoted co-immobilization of laccase and mediator onto geopolymer microspheres for enhancing degradation of dyes in water

A new strategy for co-immobilization of laccase (Lac) and mediator 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) on geopolymer microspheres (GM) was reported in this work, which was promoted by pre-embedded homologous amino acids, i.e., histidine (His) and cysteine (Cys). The GM-H₂C₁ produced with a His/Cys ratio of 2:1 was highly efficient in co-immobilizing Lac and ABTS. The as-prepared composite biocatalyst (Lac-ABTS@GM-H₂C₁) exhibited the highest degradation rate (94.78%) to the model pollutant (Congo Red, CR), which was superior to free Lac-ABTS (79.23%) and Lac@GM-H₂C₁ (53.82%). The enhanced degradation efficiency of CR by the Lac-ABTS@GM-H₂C₁ was due to the promoted electron transfer and shortened mass transfer distance. Moreover, Lac-ABTS@GM-H₂C₁ demonstrated good pH resistance, competitive storage stability, and good reusability during ten cycles of CR degradation.

Immobilization of Laccase on Hybrid Super-Structured Nanomaterials for the Decolorization of Phenolic Dyes

In the present work, hybrid super-structured nanomaterials were synthesized by the combination of smectite nanoclays with various carbon-based nanomaterials (graphene oxide, carbon nanotubes and adamantylamine) and were used as nanosupports for the covalent and non-covalent immobilization of laccase from Trametes versicolor (TvL). TvL was successfully immobilized on these hybrid nanomaterials, achieving high immobilization yields (up to 85%), while its conformation remained unaltered upon immobilization. The apparent kinetic constants Vmax and Km of the immobilized enzymes strongly depended on the immobilization procedure and the composition of hybrid nanomaterials. Immobilized TvL preserved up to 50% of its initial activity after 24 h of incubation at 60 °C, while free enzyme was totally deactivated. The TvL-hybrid nanomaterials bioconjugates were efficiently applied for the degradation of various synthetic dyes, exhibiting excellent decolorization capacity, as well as high reusability (up to 11 successive catalytic cycles), providing insights into the use of these bionanoconjugates on applications with environmental, and industrial interest.

Biocatalytic remediation of pharmaceutically active micropollutants for environmental sustainability

The discharge of an alarming number of recalcitrant pollutants from various industrial activities presents a serious threat to environmental sustainability and ecological integrity. Bioremediation has gained immense interest around the world due to its environmentally friendly and cost-effective nature. In contrast to physical and chemical methods, the use of microbial enzymes, particularly immobilized biocatalysts, has been demonstrated as a versatile approach for the sustainable mitigation of environmental pollution. Considerable attention is now devoted to developing novel enzyme engineering approaches and state-of-the-art bioreactor design for ameliorating the overall bio-catalysis and biodegradation performance of enzymes. This review discusses the contemporary and state of the art technical and scientific progress regarding applying oxidoreductase enzyme-based biocatalytic systems to remediate a vast number of pharmaceutically active compounds from water and wastewater bodies. A comprehensive insight into enzyme immobilization, the role of mediators, bioreactors designing, and transformation products of pharmaceuticals and their associated toxicity is provided. Additional studies are necessary to elucidate enzymatic degradation mechanisms, monitor the toxicity levels of the resulting degraded metabolites and optimize the entire bio-treatment strategy for technical and economical affordability.

Occurrence, environmental fate, ecological issues, and redefining of endocrine disruptive estrogens in water resources

The growing persistence of estrogenic pollutants in water resources is a worrying concern because of their endocrine disrupting activities and potentially hazardous consequences on the environmental matrices, ecology, and human health, even at low concentration. The long-term persistence of steroidal estrogens leads to their bioaccumulation in aquatic organisms that can further reach to humans via food chain route. Considering the toxicity of steroidal estrogens, it is important to mitigate these environmentally related hazardous contaminants. So far, several treatment methods, like adsorption, oxidation, irradiation, and electrochemical techniques have been proposed to eliminate estrogens from aqueous ecosystems. Nevertheless, high operational costs, insufficient removal, generation of toxic sludge, and the necessity of skilled maintenance and operating workers are the major hindrances associated with large scale applications. Bioremediation of steroidal estrogens using enzyme-based biocatalytic system has recently emerged as a promising alternative to remove and bio-transform estrogens from aqueous systems. However, the current literature lacks a critique focusing specifically and comprehensively on steroidal estrogens. The presented review is a critical assessment of the existing literature on steroid-based endocrine disruptive estrogens. A detailed description about the occurrence and eco-fate of steroidal estrogens is given with representative examples. The later half of the review stresses on the redefining (removal) of endocrine disruptive estrogens in water resources with particular reference to enzyme-based approaches.

Immobilization of Trametes versicolor laccase on chitosan/halloysite as a biocatalyst in the Remazol Red RR dye

In this study, the laccase obtained from Trametes versicolor was immobilized onto the chitosan(CTS)/halloysite (HNT) beads. In the immobilization step, the effects of chitosan (1-3% w/v), halloysite (0-2% w/v), glutaraldehyde (0.5-1.5% v/v) and enzyme concentrations (1-3%) on loading and immobilization efficiency were investigated. SEM, FT-IR, XRD, TGA and XPS analyses were performed to examine the structure of beads. In addition, the effects of parameters such as pH (4-10), temperature (25-55 °C), storage life on the activity of free and immobilized laccase were also investigated. The activities of free and immobilized laccase preserved 23% and 56% of its initial activity at the end of 59 days of storage. The effects of mediators such as 2.2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 1-Hydroxybenzotriazole hydrate (HBT), 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO) and violuric acid (VLA) on the dye removal efficiency were investigated. Reusability of the CTS/HNT/Lac in the presence of HBT and VLA mediators, which enable the highest dye removal, was tested. After 15 cycles, 42% and 54% dye removal were achieved with the CTS/HNT/Lac in the medium containing HBT and VLA, and 42% and 49% of the activity is preserved, respectively. This study showed that CTS/HNT/Lac can be used repeatedly for Remazol Red RR dye removal.

Enzyme polymer engineered structure strategy to enhance cross-linked enzyme aggregate stability: a step forward in laccase exploitation for cannabidiol removal from wastewater

Despite all its advantages and potential, cross-linking enzyme aggregate (CLEA) technology is still not applied at an industrial scale for enzyme insolubilization for bioremediation purposes. In this study, the enzyme polymer engineered structure (EPES) method was used to enhance CLEA stability and reuse. A crude laccase from Trametes hirsuta was successfully insolubilized to form EPES-CLEAs. The polymeric network provided excellent stability (> 90%) to CLEAs after a 24-h incubation in a non-buffered municipal wastewater effluent (WW), and the biocatalysts were recycled using a centrifugation process. While CLEAs activity dropped to 17%, EPES-CLEAs showed a laccase activity retention of 67% after five cycles of 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) oxidation. After 8 h of treatment in WW, the EPES-CLEAs were equally as effective in removing cannabidiol (CBD) as the free-LAC (~ 37%). This research demonstrates that the EPES method is a promising alternative for CLEA stabilization and reuse in environmental conditions.

A comprehensive insight into the application of white rot fungi and their lignocellulolytic enzymes in the removal of organic pollutants

Environmental problems resultant from organic pollutants are a major current challenge for modern societies. White rot fungi (WRF) are well known for their extensive organic compound degradation abilities. The unique oxidative and extracellular ligninolytic systems of WRF that exhibit low substrate specificity, enable them to display a considerable ability to transform or degrade different environmental contaminants. In recent decades, WRF and their ligninolytic enzymes have been widely applied in the removal of polycyclic aromatic hydrocarbons (PAHs), pharmaceutically active compounds (PhACs), endocrine disruptor compounds (EDCs), pesticides, synthetic dyes, and other environmental pollutants, wherein promising results have been achieved. This review focuses on advances in WRF-based bioremediation of organic pollutants over the last 10 years. We comprehensively document the application of WRF and their lignocellulolytic enzymes for removing organic pollutants. Moreover, potential problems and intriguing observations that are worthy of additional research attention are highlighted. Lastly, we discuss trends in WRF-remediation system development and avenues that should be considered to advance research in the field.

Exploring current tendencies in techniques and materials for immobilization of laccases - A review

Nanotechnology has transformed the science behind many biotechnological sectors, and applied bio-catalysis is not the exception. In 2017, the enzyme industry was valued at more than 7 billion USD and projected to 10.5 billion by 2024. The laccase enzyme is an oxidoreductase capable of oxidizing phenolic and non-phenolic compounds that have been considered an essential tool in the fields currently known as white biotechnology and green chemistry. Laccase is one of the most robust biocatalysts due to its wide applications in different environmental processes such as detecting and treating chemical pollutants and dyes and pharmaceutical removal. However, these biocatalytic processes are usually limited by the lack of stability of the enzyme, the half-life time, and the application feasibility at an industrial scale. Physical or chemical approaches have performed different laccase's immobilization methods to improve its catalytic properties and reuse. Emerging technologies have been proven to reduce the manufacturing process cost and increase application feasibility while looking for ecological and economical materials that can be used as support. Therefore, this review discusses the trends of enzyme immobilization recently studied, analyzing biomaterials and agro-industrial waste used for that intention, their advantages, and disadvantages. Finally, the work also highlights the performance obtained with these materials and current challenges and potential alternatives.

Myco-remediation of Chlorinated Pesticides: Insights Into Fungal Metabolic System

Synthetic chemicals including organochlorine pesticides pose environment and health hazard due to persistent and bio-accumulation property. Majority of them are recognized as endocrine disruptors. Fungi are ubiquitous in nature and employs efficient enzymatic machinery for the biotransformation and degradation of toxic, recalcitrant pollutants. This review critically discusses the organochlorine biotransformation process mediated by fungi and highlights the role of enzymatic system responsible for biotransformation, especially distribution of dehalogenase homologs among fungal classes. It also explores the potential use of fungal derived biomaterial, mainly chitosan as an adsorbing biomaterial for pesticides and heavy metals removal. Further, prospects of employing fungus to over-come the existing bioremediation limitations are discussed. The study highlights the potential scope of utilizing fungi for initial biotransformation purposes, preceding final biodegradation by bacterial species under environmental conditions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-021-00940-8.

Enhancement of laccase immobilization onto wet chitosan microspheres using an iterative protocol and its potential to remove micropollutants

This study was focused on creating a new and effective immobilization method for Trametes versicolor laccase (Lc) by using chitosan (CS) microspheres activated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride. The activation of the support alternated with immobilization of the enzyme, in repetitive procedures, led to obtaining three different products. Also, the physicochemical properties of the new products were investigated and compared with those of free laccase. The discoloration and reusability properties of the immobilized Lc were evaluated using indigo carmine (IC) as a model micropollutant. The ESEM and FT-IR methods demonstrated that the Lc was successfully immobilized. The relative reaction rate and the total amount of immobilized Lc were tripled using the iterative protocol as proved by specific and Bradford assays. The maximum amount of immobilized Lc was 8.4 mg Lc/g CS corresponding to the third immobilization procedure. Compared to the free Lc, the operational stability of the immobilized Lc was significantly improved, presenting a maximum activity plateau over a pH range of 3-5 and a temperature range of 25-50 °C. The thermal inactivation study at 55 °C proved that the immobilized enzyme is three times more stable than the free Lc. The isoconversional and Michaelis-Menten methods showed that the immobilization did not affect the enzyme catalytic properties. After 32 days of storage, the residual activities are 85% for the immobilized laccase and 40% for the free one. In similar conditions, the free and immobilized Lc (2.12 x 10^-6 M) completely decolorized IC (7.15 x 10^-5 M) within 14 min. The immobilized Lc activity remained almost constant (80%) during 10 reusability cycles. All these results highlight the substantial advantages of the new immobilization protocol and demonstrate that immobilized Lc can be used as a promising micropollutant removal from real wastewater.

Degradation of a leather-dye by the combination of depolymerised wood-chip biochar adsorption and solid-state fermentation with Trametes villosa SCS-10

Adsorption into biochar-derived materials and mycoremediation are promising technologies for removing dyes from solid and liquid matrices. This study presents a combined treatment with adsorption into wood-chip biochar and mycodegradation under solid-state fermentation by Trametes villosa for removing the leather-dye Acid Blue 161. In the first stage, untreated wood-chip biochar, NaOH–depolymerised biochar and KMnO4–depolymerised biochar were assessed for their dye removal efficiency by adsorption. KMnO4–depolymerised biochar exhibited the highest adsorption (85.1 ± 1.9%) after 24 h of contact. KMnO4–depolymerisation modified some physical and chemical properties on the untreated wood-chip biochar, increasing the surface area (50.4 m2 g–1), pore size (1.9 nm), and presence of surface functional groups. Response surface methodology coupled with a Box–Behnken design was used to optimise the AB161 adsorption into the KMnO4–depolymerised biochar. The optimised conditions, pH 3.0, dye concentration 100 mg L–1 and sorbent dosage 2 g L–1, led to a higher dye removal efficiency by adsorption (91.9 ± 1.0%). In a second stage, the wood-chip biochar supplemented with nutrients (1% malt extract and 0.5% peptone) was employed as a solid matrix for growing T. villosa and regenerating the dye-saturated material. After 15 days, T. villosa was able to grow (86.8 ± 0.8%), exhibit laccase activity (621.9 ± 62.3 U L–1), and biodegrade (91.4 ± 1.3%) the dye adsorbed into the KMnO4–depolymerised biochar. Finally, the mycoregenerated biochar was reutilised in a new cycle of adsorption reaching 79.5 ± 2.0% of dye removal efficiency by adsorption. This study revealed the potential of the combined treatment and is an initial assessment for developing commercial alternatives for treating leather industry wastewaters.

Characterization and deployment of surface-engineered chitosan-triethylenetetramine nanocomposite hybrid nano-adsorbent for divalent cations decontamination

The latency of toxic cations in the ecosystem poses serious ecological problems due to its bioaccumulation potential and toxicity to living organisms. The effective removal of these wastewater cations releasing from multi-industries is a bottleneck issue. Therefore, an attempt has been made to design a suitable sorbent for cations sorption from the aqueous environment. The chitosan biopolymer was modified with triethylenetetramine to incorporate active sites in the polymeric sequence to boost up its cations sorption capacity. Triethylenetetramine molecule anchoring chitosan (CH-TET) was authenticated through elemental assay, Fourier-transform infrared spectroscopy and ¹³C NMR in solid-state, scanning electron microscopy and thermal analysis. The sorption of lead (1.94 mmol g^-1), copper (2.79 mmol g^-1) and nickel (1.53 mmol g^-1) was carried out using the functionalized chitosan from aqueous solution, which showed higher sorption capacity for lead and copper than the pristine chitosan in terms of Langmuir sorption isotherm. To scrutinize the mechanism of sorption and energy of interaction between sorbent and sorbate, Langmuir, Temkin, and Freundlich isotherm models were used for sorption study. The Langmuir model showed the best fitting to the results based on lower error function values and a higher correlation coefficient (R²). It can be concluded that the triethylenetetramine-modified chitosan might be considered as an effective sorbent for cations removal from industrial wastewater.

Overview of Recent Advances in Immobilisation Techniques for Phenol Oxidases in Solution

Over the past two decades, phenol oxidases, particularly laccases and tyrosinases, have been extensively used for the removal of numerous pollutants in wastewaters due to their broad substrate specificity and their ability to use readily accessible molecular oxygen as the essential cofactor. As for other enzymes, immobilisation of laccases and tyrosinases has been shown to improve the performance and efficiency of the biocatalysts in solution. Several reviews have addressed the enzyme immobilisation techniques and the application of phenol oxidases to decontaminate wastewaters. This paper offers an overview of the recent publications, mainly from 2012 onwards, on the various immobilisation techniques applied to laccases and tyrosinases to induce and/or increase the performance of the biocatalysts. In this paper, the emphasis is on the efficiencies achieved, in terms of structural modifications, stability and resistance to extreme conditions (pH, temperature, inhibitors, etc.), reactivity, reusability, and broad substrate specificity, particularly for application in bioremediation processes. The advantages and disadvantages of several enzyme immobilisation techniques are also discussed. The relevance and effectiveness of the immobilisation techniques with respect to wastewater decontamination are critically assessed. A perspective on the future directions for large-scale application of the phenol oxidases in immobilised forms is provided.

Improving laccase activity and stability by HKUST-1 with cofactor via one-pot encapsulation and its application for degradation of bisphenol A

Enhancing the catalytic activity and stability of enzymes is of great importance in the development of green chemical and cost-effective application, with removal of bisphenol A (BPA) as a prominent example. Engineering immobilization carriers and immobilization methods of enzymes endows great potential to achieve above goal. Until now, these reports have focused on employing the metal-organic frameworks (MOFs) to increase the stability and reusability of enzymes, an enhancement in its catalytic activity has yet to be addressed. This work introduced a biomimetic mineralization process for facile synthesis of laccase@HKUST-1 biocomposite under mild condition. By exploiting the activity of laccase@HKUST-1, we demonstrated, for the first time, that the integration of laccase and HKUST-1 containing cofactor Cu²⁺ ions leaded to 1.5-fold enhancement in the catalytic activity compared with free laccase, which was due to the synergistic enhancement of substrate oxidation. Indeed, the laccase@HKUST-1 biocomposite could function as active biocatalysts under biologically challenging conditions, such as acidic condition, high temperature, organic solvent, and continuous operation. The oxidation of phenols, such as BPA, with laccase@HKUST-1 reached higher catalytic performance than free laccase, and gave 100% degradation efficiency within 4 h. This study provides a feasible method to improve the activity and stability of laccase, which enable completely remove of BPA from the environment.

Environmentally responsive and anti-bugs textile finishes - Recent trends, challenges, and future perspectives

Bugs, such as microorganisms and insects, are present in the environment and sometimes can be health-hazardous if the living environment is not maintained following proper hygienic regulations. In the present scenario of increasing public awareness, environmental consciousness, and growing demand for easy-care, and disinfected textiles, the manufacturing of protective and easy-to-care textiles has become a key necessity of the modern world. Comfortable, clean, hygienic, antimicrobial, and insect repelling properties of textile goods are gaining the accelerating research momentum as a basic requirement to produce multifunctional textiles. These functional finishes have numerous applications such as in-home textiles, bed nets, and tenting, camping gear as well as in military uniforms. Synthetic antimicrobial and insect repellents are quite effective against insects and microscopic organisms but are slightly toxic to the human being and the environment. To overcome these problems, researchers are considering natural agents for functional finishes, but their effectiveness is less durable to textile material. Besides needful advantages, the excessive use of dyes in finishing processes heavily required washing cycles and ultimately release various types of hazardous dyes or wasteful effluents in the environment. This review reports the chemical composition and recent developments in textile finishes, particularly antimicrobial and insect repellent textile finishes. A large number of commonly used antimicrobial agents (i.e. chitosan, zwitterionic compounds, silver and silver-based compounds, titanium dioxide nanoparticles, imidazolium salts, triclosan and quaternary ammonium salts) and insect repellent textile finishes (i.e. N‑N‑diethyl‑m‑toluamide, permethrin, cypermethrin, pyrethrum, picaridin, bioallethrin, citriodiol and essential oils) have been presented. Finally, the review is wrapped up with major research gaps/challenges, concluding remarks, and future opportunities in this area of research.

Sustainable bioconversion of food waste into high-value products by immobilized enzymes to meet bio-economy challenges and opportunities - A review

Over the past few years, food waste has intensified much attention from the local public, national and international organizations as well as a wider household territory due to increasing environmental, social and economic concerns, climate change and scarcity of fossil fuel resources. On one aspect, food-processing waste represents a substantial ecological burden. On the other hand, these waste streams are rich in carbohydrates, proteins, and lipids, thus hold significant potential for biotransformation into an array of high-value compounds. Indeed, the high sugar, protein, and fat content render food waste streams as attractive feedstocks for enzymatic valorization given the plentiful volumes generated annually. Enzymes as industrial biocatalysts offer unique advantages over traditional chemical processes with regard to eco-sustainability, and process efficiency. Herein, an effort has been made to delineate immobilized enzyme-driven valorization of food waste streams into marketable products such as biofuels, bioactive compounds, biodegradable plastics, prebiotics, sweeteners, rare sugars, surfactants, etc. Current challenges and prospects are also highlighted with respect to the development of industrially adaptable biocatalytic systems to achieve the ultimate objectives of sustainable manufacturing combined with minimum waste generation. Applications-based strategies to enzyme immobilization are imperative to design cost-efficient and sustainable industrially applicable biocatalysts. With a deeper apprehension of support material influences, and analyzing the extreme environment, enzymes might have significant potential in improving the overall sustainability of food processing.

Bio-Catalysis and Biomedical Perspectives of Magnetic Nanoparticles as Versatile Carriers

In recent years, magnetic nanoparticles (MNPs) have gained increasing attention as versatile carriers because of their unique magnetic properties, biocatalytic functionalities, and capabilities to work at the cellular and molecular level of biological interactions. Moreover, owing to their exceptional functional properties, such as large surface area, large surface-to-volume ratio, and mobility and high mass transference, MNPs have been employed in several applications in different sectors such as supporting matrices for enzymes immobilization and controlled release of drugs in biomedicine. Unlike non-magnetic carriers, MNPs can be easily separated and recovered using an external magnetic field. In addition to their biocompatible microenvironment, the application of MNPs represents a remarkable green chemistry approach. Herein, we focused on state-of-the-art two majorly studied perspectives of MNPs as versatile carriers for (1) matrices for enzymes immobilization, and (2) matrices for controlled drug delivery. Specifically, from the applied perspectives of magnetic nanoparticles, a series of different applications with suitable examples are discussed in detail. The second half is focused on different metal-based magnetic nanoparticles and their exploitation for biomedical purposes.

Hazardous contaminants in the environment and their laccase-assisted degradation - A review

In recent years, owing to the serious ecological risks and human health-related adverse effects, the wide occurrence of hazardous contaminants along with their potential to enter the environment have gained great public concerns. In this context, significant actions are urgently required to tackle the ignorance and inefficient monitoring/removal of emerging/(re)-emerging contaminants (ECs) in the environment from different routes of concerns, i.e., industrial waste, pharmaceutical, personal care products (PCPs), toxic effluents, etc. Laccases are multinuclear copper-containing oxidoreductases and can carry out one electron oxidation of a broad spectrum of environmentally related contaminants. In biotechnology, this group of versatile enzymes is known as a green catalyst/green tool with enormous potentialities to tackle ECs of high concern. In this review, we endeavored to present up-to-date literature concerning the potential use of immobilized laccases for the degradation and remediation of various types of environmental pollutants present in the environment. Both, pristine and immobilized, laccases have shown great capacity to oxidative degradation and mineralization of endocrine disrupting chemicals (EDs) in batch treatment processes as well as in large-scale continuous reactors. These properties make laccase as particularly attractive biocatalysts in environmental remediation processes, and their use might be advantageous over the conventional treatments. This review summarizes the most significant recent advances in the use of laccases and their future perspectives in environmental biotechnology.