Graphene oxide/CuFe2O4 nanocomposite as a novel scaffold for the immobilization of laccase and its application as a recyclable nanobiocatalyst for the green synthesis of arylsulfonyl benzenediols

Preparation, Structural Characterization, and Enzymatic Properties of Alginate Lyase Immobilized on Magnetic Chitosan Microspheres

Alginate lyase is an enzyme that catalyses the hydrolysis of alginate into alginate oligoalginates. To enhance enzyme stability and recovery, a facile strategy for alginate lyase immobilization was developed. Novel magnetic chitosan microspheres were synthesized and used as carriers to immobilize alginate lyase. The immobilization of alginate lyase on magnetic chitosan microspheres was successful, as proven by Fourier transform infrared spectroscopy and X-ray diffraction spectra. Enzyme immobilization exhibited the best performance at an MCM dosage of 1.5 g/L, adsorption time of 2.0 h, glutaraldehyde concentration of 0.2%, and immobilization time of 2.0 h. The optimal pH of the free alginate lyase was 7.5, and this pH value was shifted to 8.0 after immobilization. No difference was observed at the optimal temperature (45 °C) for the immobilized and free enzymes. The immobilized alginate lyase displayed better thermal stability than the free alginate lyase. The Km values of the free and immobilized enzymes were 0.05 mol/L and 0.09 mol/L, respectively. The immobilized alginate lyase retained 72% of its original activity after 10 batch reactions. This strategy was found to be a promising method for immobilizing alginate lyase.

Enhanced stability and catalytic performance of laccase immobilized on magnetic graphene oxide modified with ionic liquids

Graphite oxide (GO) is an excellent laccase immobilization material. However, the electrostatic interaction between graphene leads to the accumulation of GO, as well as the interaction with the surface of enzyme molecules causing protein denaturation and deactivation, which limits its further industrial application. In this study, the ionic liquids (ILs) modification strategy was proposed to improve the stability and catalytic performance of immobilized laccase. The laccase-ILs-MGO exhibited remarkable enzymatic properties, with significant enhancements in organic solvent tolerance, thermal and operational stability. The laccase-ILs-MGO system exhibited a remarkable removal efficiency of 95.5% towards 2,4-dichlorophenol (2,4-DCP) within 12 h and maintained over 70.0% removal efficiency after seven reaction cycles. In addition, the efficient elimination of other phenolic compounds and recalcitrant polycyclic aromatic hydrocarbons could also be accomplished. Molecular dynamics simulation and molecular docking studies demonstrated that immobilized laccase exhibited superior structural rigidity and stronger hydrogen bond interactions with substrates compared to free laccase, which was beneficial for the stability of both the laccase and substrate degradation efficiency. Therefore, this study proposed a simple and practical strategy for modifying GO with ILs, providing novel insights into developing efficient enzyme immobilization techniques.

Laccase immobilized on nanocomposites for wastewater pollutants degradation: current status and future prospects

The bio-enzyme degradation technology is a promising approach to sustainably remove pollution in the water and laccase is one of the most widely used enzymes in this area. Nevertheless, the further industrial application of laccase is limited by low stability, short service, low reusability and high price. The immobilization technology can significantly improve the stability and reusability of enzymes and thus promoting their industrial applications. Nanocomposite materials have been developed and applied in the efficient immobilization of laccase due to their superior physical, chemical, and biological performance. This paper presents a comprehensive review of various nanocomposite immobilization methods for laccase and the consequent changes in enzymatic properties post-immobilization. Additionally, a comprehensive analysis is conducted on the factors that impact laccase immobilization and its water removal efficiency. Furthermore, this review examines the effectiveness of common contaminants' removal mechanisms while summarizing and discussing issues related to laccase immobilization on nanocomposite carriers. This review aims to provide valuable guidance for enhancing laccase immobilization efficiency and enzymatic water pollutant removal.

Effects of co-modified biochar immobilized laccase on remediation and bacterial community of PAHs-contaminated soil

Considering the stability and economy of immobilized enzymes, this study prepared co-modified biochar immobilized laccase product named Fe₃O₄@NaBC@GA@LC via orthogonal experimental design and explored its possibility of remediating polycyclic aromatic hydrocarbons (PAHs) contaminated soil in steel plants. Compared with the free laccase treatment, the relative activity of Fe₃O₄@NaBC@GA@LC remained 60 % after 50 days of incubation at room temperature. The relative activity of Fe₃O₄@NaBC@GA@LC could still retain nearly 80 % after five reuses. In the process of simulating the PAHs-contaminated site treatment experiment in Hangzhou Iron and steel plant, immobilized laccase exhibited efficient adsorption and degradation performances and even the removal rate of 5-ring PAHs reached more than 90 % in 40 days, resulting in improving urease activity and dehydrogenase in the soil and promoted the growth of a PAH degrading bacteria (Massilia). Our results further explained the efficient degradation effects of Fe₃O₄@NaBC@GA@LC on PAHs, which make it a promising candidate for PAHs-contaminated soil remediation.

Laccase Immobilization on Copper-Magnetic Nanoparticles for Efficient Bisphenol Degradation

Laccase activity is influenced by copper (Cu) as an inducer. In this study, laccase was immobilized on Cu and Cu-magnetic (Cu/Fe₂O₄) nanoparticles (NPs) to improve enzyme stability and potential applications. The Cu/Fe₂O₄ NPs functionally activated by 3-aminopropyltriethoxysilane and glutaraldehyde exhibited an immobilization yield and relative activity (RA) of 93.1 and 140%, respectively. Under optimized conditions, Cu/Fe₂O₄ NPs showed high loading of laccase up to 285 mg/g of support and maximum RA of 140% at a pH 5.0 after 24 h of incubation (4°C). Immobilized laccase, as Cu/Fe₂O₄-laccase, had a higher optimum pH (4.0) and temperature (45°C) than those of a free enzyme. The pH and temperature profiles were significantly improved through immobilization. Cu/Fe₂O₄-laccase exhibited 25-fold higher thermal stability at 65°C and retained residual activity of 91.8% after 10 cycles of reuse. The degradation of bisphenols was 3.9-fold higher with Cu/Fe₂O₄-laccase than that with the free enzyme. To the best of our knowledge, Rhus vernicifera laccase immobilization on Cu or Cu/Fe₂O₄ NPs has not yet been reported. This investigation revealed that laccase immobilization on Cu/Fe₂O₄ NPs is desirable for efficient enzyme loading and high relative activity, with remarkable bisphenol A degradation potential.

Applications and immobilization strategies of the copper-centred laccase enzyme; a review

Laccase is a multi-copper enzyme widely expressed in fungi, higher plants, and bacteria which facilitates the direct reduction of molecular oxygen to water (without hydrogen peroxide production) accompanied by the oxidation of an electron donor. Laccase has attracted attention in biotechnological applications due to its non-specificity and use of molecular oxygen as secondary substrate. This review discusses different applications of laccase in various sectors of food, paper and pulp, waste water treatment, pharmaceuticals, sensors, and fuel cells. Despite the many advantages of laccase, challenges such as high cost due to its non-reusability, instability in harsh environmental conditions, and proteolysis are often encountered in its application. One of the approaches used to minimize these challenges is immobilization. The various methods used to immobilize laccase and the different supports used are further extensively discussed in this review.

3D hierarchical LDHs-based Janus micro-actuator for detection and degradation of catechol

Micro/nanomotors that combine the miniaturization and autonomous motion have attracted much research interest for environmental monitoring and water remediation. However, it is still challenging to develop a facile route to produce bifunctional micromotors that can simultaneously detect and remove organic pollutants from water. Herein, we developed a novel Janus micromotor with robust peroxide-like activity for simultaneously colorimetric detection and removal of catechol from water. Such laccase (Lac) functionalized Janus micromotor consisted of calcined MgAl-layered double hydroxides (MgAl-CLDHs) nanosheets and Co₃O₄-C nanoparticles (Lac-MgAl-CLDHs/Co₃O₄-C), revealing unique 3D hierarchical microstructure with highly exposed active sites. The obtained Janus micromotors exhibited autonomous motion with a maximum velocity of 171.83 ± 4.07 µm/s in the presence of 7 wt% H₂O₂ via a chemical propulsion mechanism based on the decomposition of H₂O₂ by Co₃O₄-C layer on the hemisphere surface of Janus micromotors. Owing to the combination of autonomous motion and high peroxide-like activity, Lac-MgAl-CLDHs/Co₃O₄-C Janus micromotors could sensitively detect catechol with the limit of detection of 0.24 μM. In addition, such Janus micromotors also could quickly degrade catechol by •OH generated from a Fenton-like reaction. It is a first step towards using autonomous micromotors for highly selective, sensitive, and facile detection and quick removal of catechol from water.

Modular configurations of living biomaterials incorporating nano-based artificial mediators and synthetic biology to improve bioelectrocatalytic performance: A review

Currently, the industrial application of bioelectrochemical systems (BESs) that are incubated with natural electrochemically active microbes (EABs) is limited due to inefficient extracellular electron transfer (EET) by natural EABs. Notably, recent studies have identified several novel living biomaterials comprising highly efficient electron transfer systems allowing unparalleled proficiency of energy conversion. Introduction of these biomaterials into BESs could fundamentally increase their utilization for a wide range of applications. This review provides a comprehensive assessment of recent advancements in the design of living biomaterials that can be exploited to enhance bioelectrocatalytic performance. Further, modular configurations of abiotic and biotic components promise a powerful enhancement through integration of nano-based artificial mediators and synthetic biology. Herein, recent advancements in BESs are synthesized and assessed, including heterojunctions between conductive nanomaterials and EABs, in-situ hybrid self-assembly of EABs and nano-sized semiconductors, cytoprotection in biohybrids, synthetic biological modifications of EABs and electroactive biofilms. Since living biomaterials comprise a broad range of disciplines, such as molecular biology, electrochemistry and material sciences, full integration of technological advances applied in an interdisciplinary framework will greatly enhance/advance the utility and novelty of BESs. Overall, emerging fundamental knowledge concerning living biomaterials provides a powerful opportunity to markedly boost EET efficiency and facilitate the industrial application of BESs to meet global sustainability challenges/goals.

Laccases as green and versatile biocatalysts: from lab to enzyme market-an overview

Laccases are multi-copper oxidase enzymes that catalyze the oxidation of different compounds (phenolics and non-phenolics). The scientific literature on laccases is quite extensive, including many basic and applied research about the structure, functions, mechanism of action and a variety of biotechnological applications of these versatile enzymes. Laccases can be used in various industries/sectors, from the environmental field to the cosmetics industry, including food processing and the textile industry (dyes biodegradation and synthesis). Known as eco-friendly or green enzymes, the application of laccases in biocatalytic processes represents a promising sustainable alternative to conventional methods. Due to the advantages granted by enzyme immobilization, publications on immobilized laccases increased substantially in recent years. Many patents related to the use of laccases are available, however, the real industrial or environmental use of laccases is still challenged by cost-benefit, especially concerning the feasibility of producing this enzyme on a large scale. Although this is a compelling point and the enzyme market is heated, articles on the production and application of laccases usually neglect the economic assessment of the processes. In this review, we present a description of laccases structure and mechanisms of action including the different sources (fungi, bacteria, and plants) for laccases production and tools for laccases evolution and prediction of potential substrates. In addition, we both compare approaches for scaling-up processes with an emphasis on cost reduction and productivity and critically review several immobilization methods for laccases. Following the critical view on production and immobilization, we provide a set of applications for free and immobilized laccases based on articles published within the last five years and patents which may guide future strategies for laccase use and commercialization.

Recent Developments in the Immobilization of Laccase on Carbonaceous Supports for Environmental Applications - A Critical Review

Τhe ligninolytic enzyme laccase has proved its potential for environmental applications. However, there is no documented industrial application of free laccase due to low stability, poor reusability, and high costs. Immobilization has been considered as a powerful technique to enhance laccase's industrial potential. In this technology, appropriate support selection for laccase immobilization is a crucial step since the support could broadly affect the properties of the resulting catalyst system. Through the last decades, a large variety of inorganic, organic, and composite materials have been used in laccase immobilization. Among them, carbon-based materials have been explored as a support candidate for immobilization, due to their properties such as high porosity, high surface area, the existence of functional groups, and their highly aromatic structure. Carbon-based materials have also been used in culture media as supports, sources of nutrients, and inducers, for laccase production. This study aims to review the recent trends in laccase production, immobilization techniques, and essential support properties for enzyme immobilization. More specifically, this review analyzes and presents the significant benefits of carbon-based materials for their key role in laccase production and immobilization.

Reversible immobilization of laccase onto glycopolymer microspheres via protein-carbohydrate interaction for biodegradation of phenolic compounds

It is challenging to regenerate enzyme carriers when covalently immobilized enzymes suffered from inactivation during continuous operations. Hence, it is urgent to develop a facile strategy to immobilize enzymes reversibly. Herein, the non-covalent interaction between protein and carbohydrate was used to adsorb and desorb enzymes reversibly. Laccase was immobilized onto glycopolymer microspheres via protein-carbohydrate interaction using lectins as the intermediates. The enzyme loading and immobilization yield were up to 49 mg/g and 77.1% with highly expressed activity of 107.9 U/mg. The immobilized laccase exhibited enhanced pH stability and high activity in catalyzing the biodegradation of paracetamol. During ten successive recoveries, the immobilized laccases could be recycled while maintaining relatively high enzyme activity. The glycopolymer microspheres could be efficiently regenerated by elution with an aqueous solution of mannose or acid for further enzyme immobilization. This glycopolymer microspheres has excellent potential to act as reusable carriers for the non-covalent immobilization of different enzymes.

Optimization and efficacy studies of Laccase immobilized on Zein-Polyvinyl pyrrolidone nano fibrous membrane in decolorization of Acid Red 1

Azo dyes are widely used in textile industries. A significant portion of these recalcitrant dyes are being discharged to the natural waters. Due to their low biodegradability they pose serious pollution problems if untreated. In this work, decolourization studies of Acid Red 1 (AR1) by laccase enzyme immobilized onto zein-polyvinyl pyrrolidone (PVP) composite nanofiber is done. The nanofibers were characterized by scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) analysis. pH and temperature profiles of immobilized enzyme were found to be broader than its free counterpart. The K_m value was found to be 0.243 mM for free laccase and 0.958 mM for immobilized laccase. Similarly, V_max for the free enzyme was 3.572 U/mg compared to 2.48 U/mg of immobilized laccase. The relative activity of immobilized laccase was 64.91% after storage for 30 days at room temperature while it was 28.64% for free laccase. The temperature and pH for AR 1 decolorization were optimized and was found to be 60 °C and 5, respectively. Also, decolorization percentage was found to be 91.67% for immobilized laccase and 72.03% of free laccase in the presence of natural mediators like vanillin. From phytotoxicity studies it was found that the germination rate, shoot and root length was increased compared to untreated dye. Therefore, zein-PVP nanofiber immobilized laccase could be an ideal candidate for the textile dye decolorization.

One-pot access to sulfonylated naphthalenediols/hydroquinones from naphthols/phenols with sodium sulfinates in an aqueous medium

A metal-free method towards sulfonylated hydroquinones/naphthalenediols under an ambient atmosphere has been developed with up to 97% yield.

Harnessing the biocatalytic attributes and applied perspectives of nanoengineered laccases-A review

In the recent past, numerous new types of nanostructured carriers, as support matrices, have been engineered to advance the traditional enzyme immobilization strategies. The current research aimed to develop a robust enzyme-based biocatalytic platform and its effective deployment in the industrial biotechnology sectors at large and catalysis area, in particular, as low-cost biocatalytic systems. Suitable coordination between the target enzyme molecules and surface pendent multifunctional entities of nanostructured carriers has led an effective and significant contribution in myriad novel industrial, biotechnological, and biomedical applications. As compared to the immobilization on planar two-dimensional (2-D) surface, the unique physicochemical, structural and functional attributes of nano-engineered matrices, such as high surface-to-volume ratio, surface area, robust chemical and mechanical stability, surface pendant functional groups, outstanding optical, thermal, and electrical characteristics, resulted in the concentration of the immobilized entity being substantially higher, which is highly requisite from applied bio-catalysis perspective. Besides inherited features, nanostructured materials-based enzyme immobilization aided additional features, such as (1) ease in the preparation or green synthesis route, (2) no or minimal use of surfactants and harsh reagents, (3) homogeneous and well-defined core-shell nanostructures with thick enzyme shell, and (4) nano-size can be conveniently tailored within utility limits, as compared to the conventional enzyme immobilization. Moreover, the growing catalytic needs can be fulfilled by multi-enzymes co-immobilization on these nanostructured materials-based support matrices. This review spotlights the unique structural and functional attributes of several nanostructured materials, including carbon nanotubes, graphene, and its derivate constructs, nanoparticles, nanoflowers, and metal-organic frameworks as robust matrices for laccase immobilization. The later half of the review focuses on the applied perspective of immobilized laccases for the degradation of emergent contaminants, biosensing cues, and lignin deconstruction and high-value products.

Laccase immobilized peroxidase mimicking magnetic metal organic frameworks for industrial dye degradation

In the present work, laccase was successfully immobilized in peroxidase mimicking magnetic metal organic frameworks (MMOFs) within 30 min using a facile approach. The integration of magnetic nanoparticles during synthesis significantly eases the separation of prepared biocatalyst using an external magnet. The immobilization of laccase was confirmed using different characterization techniques. The laccase@MMOFs found spherical in nature with an average particle size below 100 nm. The synthesized laccase embedded framework exhibits supermagnetic property with the saturation magnetization (Ms) of 34.12 emu/gm. The prepared bio-metallic frameworks maintain high surface area and thermal stability. The laccase@MMOFs was successfully exploited for the degradation of industrial dyes in batch and continuous mode with an average degradation efficiency of 95%. The prepared laccase structure had an excellent recyclability retaining upto 89% residual activity upto 10^th cycle and can be stored at room temperature upto 30 days without any significant loss of activity.

Rhus vernicifera Laccase Immobilization on Magnetic Nanoparticles to Improve Stability and Its Potential Application in Bisphenol A Degradation

In the present study, Rhus vernicifera laccase (RvLac) was immobilized through covalent methods on the magnetic nanoparticles. Fe₂O₃ and Fe₃O₄ nanoparticles activated by 3-aminopropyltriethoxysilane followed with glutaraldehyde showed maximum immobilization yields and relative activity up to 81.4 and 84.3% at optimum incubation and pH of 18 h and 5.8, respectively. The maximum RvLac loading of 156 mg/g of support was recorded on Fe₂O₃ nanoparticles. A higher optimum pH and temperature of 4.0 and 45 °C were noted for immobilized enzyme compared to values of 3.5 and 40 °C for free form, respectively. Immobilized RvLac exhibited better relative activity profiles at various pH and temperature ranges. The immobilized enzyme showed up to 16-fold improvement in the thermal stability, when incubated at 60 °C, and retained up to 82.9% of residual activity after ten cycles of reuses. Immobilized RvLac exhibited up to 1.9-fold higher bisphenol A degradation efficiency potential over free enzyme. Previous reports have demonstrated the immobilization of RvLac on non-magnetic supports. This study has demonstrated that immobilization of RvLac on magnetic nanoparticles is very efficient especially for achieving high loading, better pH and temperature profiles, and thermal- and solvents-stability, high reusability, and higher degradation of bisphenol A.

Development of a CuFe2O4 - Reduced Graphene Oxide-Based Electrochemical Sensor for Malathion

A portable non-enzymatic electrochemical sensor for malathion detection based on CuFe2O4 and reduced graphene oxide nanocomposites was developed. CuFe2O4-rGO nanocomposites were synthesized using a facile one-pot co-precipitation method. X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy confirmed successful synthesis of the nanocomposites. Square wave voltammetry was performed using a portable potentiostat (CheapStat) and a three-electrode setup in order to determine the electrochemical behavior of the nanocomposite and its interaction with malathion. Maximum inhibition was observed at conditions corresponding to 15% rGO loading, pH 4 buffer solution, and five-minute accumulation time. Calibration of the sensor established a linear detection range of 0.5-8 ppm and a detection limit of 0.992 ± 0.007 ppm. Altogether, the performance parameters indicate good selectivity and potential applicability of the system for malathion monitoring particularly in agricultural products.

Electrospun poly(methyl methacrylate)/polyaniline fibres as a support for laccase immobilisation and use in dye decolourisation

Novel electrospun poly(methyl methacrylate)/polyaniline electrospun fibres were produced, characterised, modified, and used as a support for laccase immobilisation by two methods: adsorption and covalent binding. Effective deposition of laccase by both methods was confirmed by FTIR and CLSM results. Nevertheless, the main objective of the study was to select the most favourable immobilisation conditions and prepare heterogeneous biocatalysts with the best possible catalytic properties. The highest relative activity of enzymes immobilised by adsorption and covalent binding were obtained after 1 h of immobilisation using laccase solution at a concentration of 1 mg/mL, at pH 5 and 25 °C. It was found that the immobilised enzymes, which were present in amounts of 110 mg/g and 185 mg/g for systems with adsorbed and covalently bonded laccase respectively, exhibited slightly lower substrate affinity, and in consequence also a lower maximum reaction rate, than the free enzyme. The stability of laccase improved significantly upon immobilisation: both heterogeneous biocatalysts retained over 80% relative activity even after 10 repeated catalytic cycles and 30 days of storage. The obtained systems were used for decolourisation of Remazol Brilliant Blue R dye from a model aqueous solution, resulting in removal efficiencies of 87% and 58% using adsorbed and covalently bonded laccase, respectively. The described approach to the removal of textile dye from model solution is significant for the sustainable and environmentally friendly decolourisation of various compounds from wastewater.

Laccase Immobilized Fe3O4-Graphene Oxide Nanobiocatalyst Improves Stability and Immobilization Efficiency in the Green Preparation of Sulfa Drugs

This paper, reports on the novel and green synthesis procedure for sulfonamides that involved the immobilization of Trametes Versicolor laccase onto the Fe3O4–graphene nanocomposite via glutaraldehyde (GA) crosslinking (Lac/Fe3O4/GO). Various parameters, mainly, activation time, GA, and laccase concentration were investigated and optimized. The results showed that the optimal contact time was 4 h, GA concentration was 5% while laccase concentration was 5 mg·mL−1, at which a high enzyme activity recovery was achieved (86%). In terms of the stability of immobilized laccase to temperature and storage conditions, the performance of the nanobiocatalyst was found to significantly exceed that of free laccase. The results have indicated that nearly 70% of relative activity for immobilized laccase remained after the incubation period of 2 h at 55 °C, but only 48% of free laccase remained within the same time period. Moreover, the immobilized laccase retained 88% of its initial activity after storage for 20 days. In case of the free laccase, the activity retained within the same time period was 32%. In addition, the nanobiocatalyst possessed better recycling performance as evidenced from the observation that after eight cycles of repeated use, it retained 85% of its original activity.