Immobilized laccase on zinc oxide nanoarray for catalytic degradation of tertiary butyl alcohol

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.

Construction of Immobilized Laccase System Based on ZnO and Degradation of Mesotrione

Mesotrione (MES) is a new environmental pollutant. Some reports have indicated that microbial enzymes could be utilized for MES degradation. Laccase is a green biocatalyst whose potential use in environmental pollutant detoxification has been considered limited due to its poor stability and reusability. However, these issues may be addressed using enzyme immobilization. In the present study, we sought to optimize conditions for laccase immobilization, to analyze and characterize the characteristics of the immobilized laccase, and to compare its enzymatic properties to those of free laccase. In addition, we studied the ability of laccase to degrade MES, and analyzed the metabolic pathway of MES degradation by immobilized laccase. The results demonstrated that granular zinc oxide material (G-ZnO) was successfully used as the carrier for immobilization. G-ZnO@Lac demonstrated the highest recovery of enzyme activity and exhibited significantly improved stability compared with free laccase. Storage stability was also significantly improved, with the relative enzyme activity of G-ZnO@Lac remaining at about 54% after 28 days of storage (compared with only 12% for free laccase). The optimal conditions for the degradation of MES by G-ZnO@Lac were found to be 10 mg, 6 h, 30 °C, and pH 4; under these conditions, a degradation rate of 73.25% was attained. The findings of this study provide a theoretical reference for the laccase treatment of 4-hy-droxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide contamination.

Patterned Au@Ag nanoarrays with electrically stimulated laccase-mimicking activity for dual-mode detection of epinephrine

Epinephrine (EP) is a crucial neurotransmitter in the central nervous system. However, an abnormal level of EP in biological fluids can lead to various diseases. Therefore, it is essential to rapidly and accurately detect EP content. Herein, electrically stimulated patterned Au@Ag nanoarrays with laccase-mimicking activity were designed for the dual-mode detection of EP concentration. The patterned Au@Ag nanoarrays exhibit excellent electrochemical properties and electrically stimulated laccase-mimicking activity. They provide sensitive electrochemical responses for detecting EP content. Simultaneously, the Au@Ag nanoarrays can catalyze the oxidation of EP, enabling its detection through a colorimetric process. This dual-mode approach achieves the detection of EP content over a wide linear range of 0.5-200 μM, with a low detection limit of 0.152 μM. Furthermore, the utility of these nanoarrays for sensing EP in human serum was evaluated. This work provides a convenient method using patterned nanozyme array for the visible, rapid and accurate detection of EP content. It provides the important implication for the development of portable and reliable on-site analytical instruments.

In vitro assessment of the immobilized mannanase enzyme against infection-causing Candida

Background: Developing an effective treatment for fungal infections is among contemporary medicine's challenges. In this study we aimed to eradicate mannan in pathogenic Candidae's cell walls using a nontoxic method, mannanase. Materials & Methods: We investigated the in vitro antifungal activities of mannanase immobilized on zinc oxide nanoparticles (ZnONps) and reduced graphene oxide nanoparticles (RGONps), as well as therapeutics against Candidae. Mannanase was purified from Bacillus invictae (activity: 5.15 EU/ml; range: 60-80%) and then immobilized it to ZnO and RGO to enhance its effectiveness. Results: Mannanase immobilized on ZnONps had the highest activity, with a value of 4.97 EU/ml, more effective than amphotericin-B. However, it could not reach the inhibition rates of other antifungals. Conclusion: Mannanase immobilized on ZnONps could be an effective fungicide for Candida biocontrol.

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.

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%.

Catalyzed degradation of polycyclic aromatic hydrocarbons by recoverable magnetic chitosan immobilized laccase from Trametes versicolor

The capability of laccase to oxidate a broad range of polyphenols and aromatic substrates in vitro offers a new technological option for the remediation of polycyclic aromatic hydrocarbon (PAH) pollution with high cytotoxicity. However, laccase application in the remediation of PAH-contaminated sites mainly suffers from a low oxidation rate and high cost because of the difficulty in its recovery. In this study, laccases were immobilized on magnetic Fe₃O₄ particles coated with chitosan (Fe₃O₄@SiO₂-chitosan) to improve the operational stability and reusability in the treatment of PAH pollution. The enzyme fixation capacity reached 158 mg g^-1, and 79.1% of free laccase activities were reserved under the optimum immobilized condition of 4% glutaraldehyde, 1.0 mg mL^-1 laccase, 2 h covalent bonding time, and 6 h fixation time. The degradation efficiencies of anthracene (ANT) and benzo[a]pyrene (B(a)P) by Fe₃O₄@SiO₂-chitosan immobilized laccase in 48 h were 81.9% and 69.2%, respectively. Furthermore, it is very easy to magnetically recover the immobilized laccase from reaction systems and reuse it in a new batch. The relative activities of immobilized laccase were over 50% for the degradation of ANT and B(a)P in three catalytic runs, reaching the goal of substantially reducing cost in practice. According to the results from quantum calculations and mass spectrum analyses, the degradation products of ANT and B(a)P by laccase were anthraquinone and B(a)P-dione, respectively. The findings from this study provide valuable insight in promoting the application of immobilized laccase technology in the remediation of PAH contamination.

Nanobioremediation: A sustainable approach for the removal of toxic pollutants from the environment

In recent years, the proportion of organic and inorganic contaminants has increased rapidly due to growing human interference and represents a threat to ecosystems. The removal of these toxic pollutants from the environment is a difficult task. Physical, chemical and biological methods are implemented for the degradation of toxic pollutants from the environment. Among existing technologies, bioremediation in combination with nanotechnology is the most promising and cost-effective method for the removal of pollutants. Numerous studies have shown that exceptional characteristics of nanomaterials such as improved catalysis and adsorption properties as well as high reactivity have been subjects of great interest. There is an emerging trend of employing bacterial, fungal and algal cultures and their components, extracts or biomolecules as catalysts for the sustainable production of nanomaterials. They can serve as facilitators in the bioremediation of toxic compounds by immobilizing or inducing the synthesis of remediating microbial enzymes. Understanding the association between microorganisms, contaminants and nanoparticles (NPs) is of crucial importance. In this review, we focus on the removal of toxic pollutants using the cumulative effects of nanoparticles with microbial technology and their applications in different domains. Besides, we discuss how this novel nanobioremediation technique is significant and contributes towards sustainability.

Immobilized fungal enzymes: Innovations and potential applications in biodegradation and biosynthesis

Microbial enzymes catalyze various reactions inside and outside living cells. Among the widely studied enzymes, fungal enzymes have been used for some of the most diverse purposes, especially in bioremediation, biosynthesis, and many nature-inspired commercial applications. To improve their stability and catalytic ability, fungal enzymes are often immobilized on assorted materials, conventional as well as nanoscale. Recent advances in fungal enzyme immobilization provide effective and sustainable approaches to achieve improved environmental and commercial outcomes. This review aims to provide a comprehensive overview of commonly studied fungal enzymes and immobilization technologies. It also summarizes recent advances involving immobilized fungal enzymes for the degradation or assembly of compounds used in the manufacture of products, such as detergents, food additives, and fossil fuel alternatives. Furthermore, challenges and future directions are highlighted to offer new perspectives on improving existing technologies and addressing unexplored fields of applications.