Immobilization of laccase by Cu(2+) chelate affinity interaction on surface-modified magnetic silica particles and its use for the removal of 2,4-dichlorophenol

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.

Plasma polymerized functional supermagnetic Fe3O4 nanostructured templates for laccase immobilization: A robust catalytic system for bio-inspired dye degradation

Fe3O4 magnetic nanoparticles, synthesized using co-precipitation method, were epoxy functionalized via plasma polymerization of 2,3-epoxypropylmethacrylate (EPMA) precursor. The EPMA-functionalized Fe3O4 nanoparticles (EPMA-f-MN) were employed as templates for facile, one-step covalent immobilization of laccase enzyme at room temperature. Samples were rigorously characterized by FTIR, TGA, SEM, TEM, XRD techniques, while Mössbauer spectroscopy (MöS) and vibrating sample magnetometry (VSM) confirmed the supermagnetic nature of Fe3O4 nanoparticles. Activities of free and immobilized laccase (ImLac) were assayed by spectrophotometrically monitoring the enzymatic reduction of substrate 2,2-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS) at 420 nm, corresponding to the λmax of ABTS.+. In addition to possessing higher thermal stability and a broader pH tolerance window compared to free laccase, the supermagnetic property of the Fe3O4 renders the ImLac system conveniently recoverable and recyclable. Practical applicability of ImLac towards catalytic degradation of industrial dyes was also ably demonstrated using Acid Blue 193 (AB 193) as a commercially used model textile dye, which belongs to the family of azo dyes. Over 95% degradation of the dye was achieved within a period of 4 hours. ImLac could be used for more than 10 dye degradation cycles with >90 % of retention in enzyme activity.

Degradation of 2,4-DCP by the immobilized laccase on the carrier of sodium alginate-sodium carboxymethyl cellulose

In this paper, sodium alginate-sodium carboxymethyl cellulose (SA-CMC) composite material was used as a carrier, and sodium alginate-embedded laccase (Lac@SC) was prepared by traditional embedding method. After that, ethylene glycol diglycidyl ether (EGDE) and glutaraldehyde (GLU) were used as cross-linking agents, two different cross-linking-embedded co-immobilized laccases (Lac@SCG and Lac@SCE) were innovatively prepared, respectively, and then these immobilized laccases were characterized by SEM, FT-IR and XRD, and the stability of the three immobilized laccases was explored. In addition, the effects of different factors on the removal of 2,4-DCP by immobilized laccase were studied, and the degradation kinetic models of three immobilized laccases on 2,4-DCP were summarized, the possible degradation pathways of pollutants were also given. Experimental results showed that compared to free laccase, the pH stability, thermal stability and storage stability of immobilized laccase were greatly improved. These immobilized laccases could maintain high activity at pH3~6, 45~55 °C. Lac@SCG had the best storage stability. After 30 days of storage, the relative enzyme activity was still more than 40%. Lac@SC had good reusability, the relative enzyme activity was still more than 50% after 5 uses. In the degradation of 2,4-DCP, all three immobilized laccases showed good performance, when Lac@SCE was at pH5, 35 °C, 25 h, the removal rate of 2,4-DCP could reach 95.2%; When at 45 °C, Lac@SC had the highest degradation rate which reach to 94%; At 45 °C, the degradation rate of Lac@SCG reached 83.2%.

Green remediation potential of immobilized oxidoreductases to treat halo-organic pollutants persist in wastewater and soil matrices - A way forward

The alarming presence of hazardous halo-organic pollutants in wastewater and soils generated by industrial growth, pharmaceutical and agricultural activities is a major environmental concern that has drawn the attention of scientists. Unfortunately, the application of conventional technologies within hazardous materials remediation processes has radically failed due to their high cost and ineffectiveness. Consequently, the design of innovative and sustainable techniques to remove halo-organic contaminants from wastewater and soils is crucial. Altogether, these aspects have led to the search for safe and efficient alternatives for the treatment of contaminated matrices. In fact, over the last decades, the efficacy of immobilized oxidoreductases has been explored to achieve the removal of halo-organic pollutants from diverse tainted media. Several reports have indicated that these enzymatic constructs possess unique properties, such as high removal rates, improved stability, and excellent reusability, making them promising candidates for green remediation processes. Hence, in this current review, we present an insight of green remediation approaches based on the use of immobilized constructs of phenoloxidases (e.g., laccase and tyrosinase) and peroxidases (e.g., horseradish peroxidase, chloroperoxidase, and manganese peroxidase) for sustainable decontamination of wastewater and soil matrices from halo-organic pollutants, including 2,4-dichlorophenol, 4-chlorophenol, diclofenac, 2-chlorophenol, 2,4,6-trichlorophenol, among others.

Highly effective enzymes immobilization on ceramics: Requirements for supports and enzymes

Enzyme immobilization is a well-known method for the improvement of enzyme reusability and stability. To achieve very high effectiveness of the enzyme immobilization, not only does the method of attachment need to be optimized, but the appropriate support must be chosen. The essential necessities addressed to the support applied for enzyme immobilization can be focused on the material features as well as on the stability and resistances in certain conditions. Ceramic membranes and nanoparticles are the most widespread supports for enzyme immobilization. Hence, the immobilization of enzymes on ceramic membrane and nanoparticles are summarized and discussed. The important properties of the supports are particle size, pore structure, active surface area, volume to surface ratio, type and number of reactive available groups, as well as thermal, mechanical, and chemical stability. The modifiers and the crosslinkers are crucial to the enzyme loading amount, the chemical and physical stability, and the reusability and catalytical activity of the immobilized enzymes. Therefore, the chemical and physical methods of modification of ceramic materials are presented. The most popular and used modifiers (e.g. APTES, CPTES, VTES) as well as activating agents (GA, gelatin, EDC and/or NHS) applied to the grafting process are discussed. Moreover, functional groups of enzymes are presented and discussed since they play important roles in the enzyme immobilization via covalent bonding. The enhanced physical, chemical, and catalytical properties of immobilized enzymes are discussed revealing the positive balance between the effectiveness of the immobilization process, preservation of high enzyme activity, its good stability, and relatively low cost.

Facile synthesis of recyclable laccase-mineral hybrid complexes with enhanced activity and stability for biodegradation of Evans Blue dye

Two morphologies of laccase-mineral hybrid complexes, i.e., laccase-mineral hybrid nanoflowers (La-HNF) and nanopetals (La-HNP), were synthesized via biomineralization using Cu₃ (PO₄)₂·3H₂O as the mineral for Evans Blue (EB) dye biodegradation. XRD patterns and FT-IR spectra results revealed the successful immobilization of laccase via in-situ formed Cu₃(PO₄)₂·3H₂O crystals. Compared with free laccase, laccase-mineral hybrid complexes showed higher enzymatic activity due to the activation effect induced by copper ions of Cu₃(PO₄)₂·3H₂O, further, the improved kinetic parameters of laccase-mineral hybrid complexes could be ascribed to nanoscale-dispersed laccase molecules within hybrid complexes. For EB dye biodegradation, the reason why the biodegradation efficiency (94.9%) of La-HNF was higher than that (86.8%) of La-HNP could be synergistic effect of immobilized laccase within 3D hierarchical structure of La-HNF. In addition, the optimized biodegradation conditions (pH 4.6 and 40 °C) of La-HNF were obtained, moreover, 93.2% and 48.1% of EB dye were biodegraded by La-HNF after stored for 30 days and reused for 10 cycles, respectively, demonstrating La-HNF have good practicability.

Enzymatic treatment of phenolic pollutants by a small laccase immobilized on APTES-functionalised magnetic nanoparticles

In this study, we have successfully synthesized magnetic nanoparticles (MNPs), functionalised them by silanization and used them for the covalent immobilization of a recombinant small laccase (rSLAC) from Streptomyces coelicolor. The immobilized recombinant laccase (MNP-rSLAC) was subsequently used for the treatment of phenol, 4-chlorophenol (4-CP) and 4-fluorophenol (4-FP). The enzyme completely degraded 80 µg/mL of the selected phenolic compounds within 2 h in the presence of a natural mediator, acetosyringone. The MNP-rSLAC retained > 73% of initial activity (2,6-dimethoxyphenol as substrate) after 10 catalytic cycles and could be easily recovered from the reaction mixture by the application of magnetic field. Furthermore, immobilised rSLAC exhibited better storage stability than its free counterpart. The Michaelis constant (K_m) value for the immobilised rSLAC was higher than free rSLAC, however the maximum velocity (V_max) of the immobilised SLAC was similar to that of the free rSLAC. Growth inhibition studies using Escherichia coli showed that rSLAC-mediated treatment of phenolic compounds reduced the toxicity of phenol, 4-CP and 4-FP by 90, 60 and 55%, respectively. Interestingly, the presence of selected metal ions (Co²⁺, Cu²⁺, Mn²⁺) greatly enhanced the catalytic activity of rSLAC and MNP-rSLAC. This study indicates that immobilized small laccase (MNP-rSLAC) has potential for treating wastewater contaminated with phenolic compounds.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02854-0.

A novel process for the covalent immobilization of laccases on silica gel and its application for the elimination of pharmaceutical micropollutants

In the present work, pharmaceutical micropollutant degradation by laccase immobilized on silica through an innovative process is proposed. The influence of different parameters on the immobilization conditions was evaluated by a 2³ full factorial design, and parameters leading to the highest activity were identified. Under these conditions, laccase activity reached 14 ± 2 U g^-1 of silica with a protein immobilization yield of 35%. The biocatalyst characterization did not show any change in pH and thermal stabilities but enhanced the long-term storage of laccases. Immobilized T. versicolor laccases were then tested to remove four pharmaceutical micropollutants (amoxicillin, ciprofloxacin, carbamazepine, and sulfamethoxazole) in the presence of redox mediators (syringaldehyde, p-coumaric acid, and ABTS). High removal yields (50-100% according to the pollutant) were obtained within 4 h of treatment due to the synergistic effect of laccase-mediator biotransformation and adsorption on the support. Overall, the pharmaceuticals' removal efficiency was highly influenced by their physicochemical properties; however, the presence of redox mediators impacted not only the oxidation mechanism but also the interactions between the biocatalyst and micropollutants. Finally, the reusability of the biocatalyst was proved during 7 degradation cycles.

Co-immobilization of laccase and ABTS onto amino-functionalized ionic liquid-modified magnetic chitosan nanoparticles for pollutants removal

This work aims to achieve the co-immobilization of laccase and 2,2-binamine-di-3-ethylbenzothiazolin-6-sulfonic acid (ABTS) to improve removal capability of the biocatalyst for pollutants while avoiding potential pollution caused by ABTS. The laccase was immobilized on magnetic chitosan nanoparticles modified with amino-functionalized ionic liquid containing ABTS (MACS-NIL) based on Cu ion chelation (MACS-NIL-Cu-lac). The carrier was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, x-ray diffraction and etc., and electron paramagnetic resonance confirmed the mediator molecule ABTS on the carrier could also play the role of electron transmission. MACS-NIL-Cu-lac presented relatively high immobilization capacity, enhanced activity (1.7-fold that of free laccase), improved pH and temperature adaptability, and increased thermal and storage stability. The removal performance assay found that MACS-NIL-Cu-lac had a good removal efficiency with 100.0 % for 2,4-dichlorophenol in water at 25 °C, even when the concentration reached 50 mg/L. Reusability study showed that after six catalytic runs, the removal efficiency of 2,4-dichlorophenol by MACS-NIL-Cu-lac could still reach 93.2 %. Additionally, MACS-NIL-Cu-lac exhibited higher catalytic efficiencies with 100.0 %, 70.5 % and 93.3 % for bisphenol A, indole, and anthracene, respectively. The high catalytic performance in pure water system obtained by the novel biocatalyst co-immobilizing laccase and electron mediator ABTS showed greater practical application value.

Immobilization of enzymes on nanoinorganic support materials: An update

Despite the widespread use in various industries, enzyme's instability and non-reusability limit their applications which can be overcome by immobilization. The nature of the enzyme's support material and method of immobilization affect activity, stability, and kinetics properties of enzymes. Here, we report a comparative study of the effects of inorganic support materials on immobilized enzymes. Accordingly, immobilization of enzymes on nanoinorganic support materials significantly improved thermal and pH stability. Furthermore, immobilizations of enzymes on the materials mainly increased K_m values while decreased the V_max values of enzymes. Immobilized enzymes on nanoinorganic support materials showed the increase in ΔG value, and decrease in both ΔH and ΔS values. In contrast to weak physical adsorption immobilization, covalently-bound and multipoint-attached immobilized enzymes do not release from the support surface to contaminate the product and thus the cost is decreased while the product quality is increased. Nevertheless, nanomaterials can enter the environment and increase health and environmental risks and should be used cautiously. Altogether, it can be predicated that hybrid support materials, directed immobilization methods, site-directed mutagenesis, recombinant fusion protein technology, green nanomaterials and trailor-made supports will be used increasingly to produce more efficient immobilized industrial enzymes in near future.

Developments in support materials for immobilization of oxidoreductases: A comprehensive review

Bioremediation, a biologically mediated transformation or degradation of persistent chemicals into nonhazardous or less-hazardous substances, has been recognized as a key strategy to control levels of pollutants in water and soils. The use of enzymes, notably oxidoreductases such as laccases, tyrosinases, various oxygenases, aromatic dioxygenases, and different peroxidases (all of EC class 1) is receiving significant research attention in this regard. It should be stated that immobilization is emphasized as a powerful tool for enhancement of enzyme activity and stability as well as for protection of the enzyme proteins against negative effects of harsh reaction conditions. As proper selection of support materials for immobilization and their performance is overlooked when it comes to comparing performance of immobilized enzyme in academic studies, this review summarizes the current state of knowledge regarding the materials used for enzyme immobilization of these oxidoreductase enzymes for environmental applications. In the presented study, thorough physicochemical characteristics of the support materials was presented. Moreover, various types of reactions and notably operational modes of enzymatic processes for biodegradation of harmful pollutants are summarized, and future trends in use of immobilized oxidoreductases for environmental applications are discussed. Our goal is to provide an improved foundation on which new technological advancements can be made to achieve efficient enzyme-assisted bioremediation.

Molecular and biochemical characterization of a new thermostable bacterial laccase from Meiothermus ruber DSM 1279

A new bacterial laccase gene (mrlac) fromMeiothermus ruberDSM 1279 was successfully overexpressed to produce a laccase (Mrlac) in soluble form inEscherichia coliduring simultaneous overexpression of a chaperone protein (GroEL/ES).

Reversible immobilization of laccase onto metal-ion-chelated magnetic microspheres for bisphenol A removal

Increasing attention has been given to nanobiocatalysis for commercial applications. In this study, laccase was reversibly immobilized onto Cu(ΙΙ)- and Mn(ΙΙ)-chelated magnetic microspheres and successfully applied to remove bisphenol A (BPA) from water. The results indicated that the loading of laccase onto the metal-ion-chelated magnetic microspheres was approximately 100mg/g. After five successive adsorption-desorption cycles, the laccase adsorption capacities did not change. In comparison with free laccase, the thermal and storage stabilities of immobilized laccase were significantly improved. Immobilized laccase exhibited a high removal efficiency for BPA under the combined actions of biodegradation and adsorption. Greater than 85% of BPA was removed under optimum conditions. The effects of various factors on the BPA removal efficiency of immobilized laccase were analysed. The results showed that metal-ion-chelated magnetic microspheres have great potential for industrial applications.

Immobilization as a strategy for improving enzyme properties-application to oxidoreductases

The main objective of the immobilization of enzymes is to enhance the economics of biocatalytic processes. Immobilization allows one to re-use the enzyme for an extended period of time and enables easier separation of the catalyst from the product. Additionally, immobilization improves many properties of enzymes such as performance in organic solvents, pH tolerance, heat stability or the functional stability. Increasing the structural rigidity of the protein and stabilization of multimeric enzymes which prevents dissociation-related inactivation. In the last decade, several papers about immobilization methods have been published. In our work, we present a relation between the influence of immobilization on the improvement of the properties of selected oxidoreductases and their commercial value. We also present our view on the role that different immobilization methods play in the reduction of enzyme inhibition during biotechnological processes.