Enhanced removal of hydroquinone by graphene aerogel-Zr-MOF with immobilized laccase

ZIF-67 and Biomass-Derived N, S-Codoped Activated Carbon Composite Derivative for High-Effective Removal of Hydroquinone from Water

Hydroquinone (HQ) in wastewater is of great concern, as it is harmful to human health and threatens the ecological environment. However, the existing adsorbents have low adsorption capacity for HQ. To improve the removal of HQ, N,S-codoped activated carbon-ZIF-67 (NSAC-ZIF-67@C) was synthesized in this study by in situ growth of ZIF-67 on N,S-codoped activated carbon (NSAC) and carbonization. The influence of pH, contact time, and initial concentration on the adsorption behaviors of NSAC-ZIF-67@C on HQ were investigated. Owing to the synergistic effect of abundant active sites and well-developed pore structure, the NSAC-ZIF-67@C achieved a prominent adsorption capacity of 962 mg·g-1 and can still retain high adsorption performance after 5 cycles for HQ, which is superior to that of reported other adsorbents. HQ adsorption follows the pseudo-second-order kinetics model (R2 = 0.99999) and the Freundlich isotherm model. X-ray photoelectron spectroscopy (XPS) analysis before and after adsorption as well as density functional theory (DFT) calculation results showed that pyridinic-N-termini were conducive to the π-π interactions and hydrogen-bonding interactions. Therefore, the adsorption mechanisms of NSAC-ZIF-67@C on HQ involve pore filling, electrostatic attraction, π-π interaction, and hydrogen bonding. This study is expected to provide a reference for designing highly effective adsorbents for wastewater treatment.

Green synthesis of NiO NPs for metagenome-derived laccase stabilization: Detoxifying pollutants and wastes

Laccases play a crucial role in neutralizing environmental pollutants, including antibiotics and phenolic compounds, by converting them into less harmful substances via a unique oxidation process. This study introduces an environmentally sustainable remediation technique, utilizing NiO nanoparticles (NPs) synthesized through green chemistry to immobilize a metagenome-derived laccase, PersiLac1, enhancing its application in pollutant detoxification. Salvadora persica leaf extract was used for the synthesis of NiO nanoparticles, utilizing its phytochemical constituents as reducing and capping agents, followed by characterization through different analyses. Characterization of NiO nanoparticles revealed distinctive FTIR absorption peaks indicating the nanoparticulate structure, while FESEM showed structured NiO with robust interconnections and dimensionality of about 50nm, confirmed by EDX analysis to have a consistent distribution of Ni and O. The immobilized PersiLac1 demonstrated enhanced thermal stability, with 85.55 % activity at 80 °C and reduced enzyme leaching, retaining 67.93 % activity across 15 biocatalytic cycles. It efficiently reduced rice straw (RS) phenol by 67.97 % within 210 min and degraded 70-78 % of tetracycline (TC) across a wide pH range (4.0-8.0), showing superior performance over the free enzyme. Immobilized laccase achieved up to 71 % TC removal at 40-80 °C, significantly outperforming the free enzyme. Notably, 54 % efficiency was achieved at 500 mg/L TC by immobilized laccase at 120 min. This research showed the potential of green-synthesized NiO nanoparticles to effectively immobilize laccase, presenting an eco-friendly approach to purify pollutants such as phenols and antibiotics. The durability and reusability of the immobilized enzyme, coupled with its ability to reduce pollutants, indicates a viable method for cleaning the environment. Nonetheless, the production costs and scalability of NiO nanoparticles for widespread industrial applications pose significant challenges. Future studies should focus on implementation at an industrial level and examine a wider range of pollutants to fully leverage the environmental clean-up capabilities of this innovative technology.

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.

Metal-Organic Framework for the Immobilization of Oxidoreductase Enzymes: Scopes and Perspectives

Oxidoreductases are a wide class of enzymes that can catalyze biological oxidation and reduction reactions. Nowadays, oxidoreductases play a vital part in most bioenergetic metabolic pathways, which have important applications in biodegradation, bioremediation, environmental applications, as well as biosensors. However, free oxidoreductases are not stable and hard to be recycled. In addition, cofactors are needed in most oxidoreductases catalyze reactions, which are so expensive and unstable that it hinders their industrial applications. Enzyme immobilization is a feasible strategy that can overcome these problems. Recently, metal-organic frameworks (MOFs) have shown great potential as support materials for immobilizing enzymes due to their unique properties, such as high surface-area-to-volume ratio, chemical stability, functional designability, and tunable pore size. This review discussed the application of MOFs and their composites as immobilized carriers of oxidoreductase, as well as the application of MOFs as catalysts and immobilized carriers in redox reactions in the perspective of the function of MOFs materials. The paper also focuses on the potential of MOF carrier-based oxidoreductase immobilization for designing an enzyme cascade reaction system.

An Up-to-Date Review on the Remediation of Dyes and Phenolic Compounds from Wastewaters Using Enzymes Immobilized on Emerging and Nanostructured Materials: Promises and Challenges

Addressing the critical issue of water pollution, this review article emphasizes the need to remove hazardous dyes and phenolic compounds from wastewater. These pollutants pose severe risks due to their toxic, mutagenic, and carcinogenic properties. The study explores various techniques for the remediation of organic contaminants from wastewater, including an enzymatic approach. A significant challenge in enzymatic wastewater treatment is the loss of enzyme activity and difficulty in recovery post-treatment. To mitigate these issues, this review examines the strategy of immobilizing enzymes on newly developed nanostructured materials like graphene, carbon nanotubes (CNTs), and metal-organic frameworks (MOFs). These materials offer high surface areas, excellent porosity, and ample anchoring sites for effective enzyme immobilization. The review evaluates recent research on enzyme immobilization on these supports and their applications in biocatalytic nanoparticles. It also analyzes the impact of operational factors (e.g., time, pH, and temperature) on dye and phenolic compound removal from wastewater using these enzymes. Despite promising outcomes, this review acknowledges the challenges for large-scale implementation and offers recommendations for future research to tackle these obstacles. This review concludes by suggesting that enzyme immobilization on these emerging materials could present a sustainable, environmentally friendly solution to the escalating water pollution crisis.

Three-Dimensional Mass Transfer Modeling of Hydroquinone Adsorption on Phragmites australis Biochar

In this work, the overall adsorption kinetic process of hydroquinone on Phragmites australis biochar (PAC) was analyzed in depth. A 3D mass transfer model of pore volume and surface diffusion was established, and the diffusion mechanism was analyzed. The characterization results show PAC has a higher porosity value, which is conducive to the adsorption of hydroquinone. The adsorption process modeling results show that the combined effect of pore volume diffusion and surface diffusion promotes the total diffusion process of hydroquinone in the PAC particles, and the two mechanisms of pore volume and surface diffusion exist simultaneously. Under the different operating concentrations, the range of surface diffusion coefficient D_s is 2.5 × 10^-10-1.74 × 10^-9 cm²/s, and the contribution rate of surface diffusion SDCP% is close to 100%, which is much larger than pore volume diffusion, revealing that regardless of the contact time and position, surface diffusion occupies the main position in intraparticle diffusion.

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.

Biomass-derived nanocellulose aerogel enable highly efficient immobilization of laccase for the degradation of organic pollutants

Laccase is a promising biocatalyst for pollutant degradation and water purification. However, laccase can only improve the stability of enzyme activity and achieve its significant catalytic effect after effective immobilization. Herein, we report a general strategy to integrate nanocellulose aerogel and laccase for high-efficiency degradation of organic pollutants. Biomass-derived functional bacterial cellulose (BC) aerogel with a nanonetwork structure and high porosity was prepared by biosynthesis, solvent replacement, and atom transfer radical polymerization (ATRP) procedures. Subsequently, a biocatalyst platform was fabricated by "coupling" ATRP-modified BC aerogel with abundant active sites with laccase through ion coordination. The results demonstrated the biocatalyst platform not only has good biological affinity, but also has high enzyme load and structural stability. Meanwhile, the degradation rates of reactive red X-3B and 2, 4-dichlorophenol reached 94.5% and 85.2% within 4 h, respectively. The strategy disclosed herein could provide a practical method for the degradation of organic pollutants.

Advanced MOFs@aerogel composites: Construction and application towards environmental remediation

Environmental pollution has drawn forth advanced materials and progressive techniques concentrating on sustainable development. Metal-organic frameworks (MOFs) have aroused vast interest resulting from their excellent property in structure and function. Conversely, powdery MOFs in highly crystalline follow with fragility, poor processability and recoverability. Aerogels distinguished by the unique three-dimensional (3D) interconnected pore structures with high porosity and accessible surface area are promising carriers for MOFs. Given these, combining MOFs with aerogels at molecule level to obtain advanced composites is excepted to further enhance their performance with higher practicability. Herein, we focus on the latest studies on the MOFs@aerogel composites. The construction of MOFs@aerogel with different synthetic routes and drying methods are discussed. To explore the connection between structure and performance, pore structure engineering and quantitation of MOFs content are outlined. Furthermore, various types of MOFs@aerogel composites and their carbonized derivatives are reviewed, as well as the applications of MOFs@aerogel for environmental remediation referring to water purification and air clearing. More importantly, outlooks towards these emerging advanced composites have been presented from the perspective of practical application and future development.

Enhancement of laccase production from a newly isolated Trichoderma harzianum S7113 using submerged fermentation: Optimization of production medium via central composite design and its application for hydroquinone degradation

Trichoderma harzianum S7113 as an efficient fungal isolate for laccase production was identified using the 18S rRNA sequencing. T. harzianum S7113 attained its maximal laccase production level on the 14^th day of static incubation at 28 °C and pH 5.0 using the inoculum size of 5 discs (14 mm), according to the one factor per time (OFT) method. The most appropriate carbon, organic and inorganic nitrogen sources to promote maximal laccase synthesis were glucose (15 g/L), beef extract (5 g/L), and ammonium chloride (4 g/L), respectively. Results of Response Surface Methodology (RSM) revealed that glucose, meat extract, and ammonium chloride concentrations of 17.54, 7.17, and 4.36 g/L respectively, at a pH value of 6.74 are the favorite conditions for high titer production. The ANOVA analysis highlighted an excellent match between the actual experimental results and the model predicted laccase production levels. The biodegradation of hydroquinone (HQ) by T. harzianum S7113 laccase was most efficient in the pH range of 5.0 to 6.5. The increase in laccase concentration led to a significant increase in the HQ conversion to get a biodegradation rate of 92 ± 2.6% with a laccase concentration of 0.75 U/mL after 3 h of reaction.

Remarkable adsorption of hydroquinone as an anion contaminant by using the magnetic supported bimetallic (NiCu-MOF@MAC) nanocomposites in aqueous solutions

The purposes of this work were to synthesize the core-shell magnetic and nonmagnetic supported bimetallic metal-organic frameworks (MOFs) on the walnut-based activated carbon by the facile preparation method to investigate the feasibility of the performance adsorption of hydroquinone in the aqueous solutions. Activated carbon as a substrate and nickel, copper, and trimesic acid were employed in the structure of the prepared MOFs. The adsorbents were characterized by XRD, FTIR, FESEM, EDX, TEM, BET, and VSM analysis. The goethite and magnetite phases were detected in the morphology of the magnetic adsorbent as confirmed by the XRD pattern. Increases in the pH value from 6 and the adsorption temperature led to a lower adsorption capacity of the samples. The maximum adsorption capacity for the well-dispersed nanoparticles of magnetic (NiCu-MOF@MAC and nonmagnetic (NiCu-MOF@AC) was calculated to be 303.03 and 454.54 mg/g by using linear Langmuir isotherm as an appropriate model, respectively. The achievements from the reusability evaluation illustrated that the magnetic bimetallic MOF nanocomposite could successfully be applied to remove hydroquinone from the wastewater on an industrial scale. The kinetic experimental data was in good agreement with the pseudo-second-order model.

MOF based engineered materials in water remediation: Recent trends

The significant upsurge in the demand for freshwater has prompted various developments towards water sustainability. In this context, several materials have gained remarkable interest for the removal of emerging contaminants from various freshwater sources. Among the currently investigated materials for water treatment, metal organic frameworks (MOFs), a developing class of porous materials, have provided excellent platforms for the separation of several pollutants from water. The structural modularity and the striking chemical/physical properties of MOFs have provided more room for target-specific environmental applications. However, MOFs limit their practical applications in water treatment due to poor processability issues of the intrinsically fragile and powdered crystalline forms. Nevertheless, growing efforts are recognized to impart macroscopic shapability to render easy handling shapes for real-time industrial applications. Furthermore, efforts have been devoted to improve the stabilities of MOFs that are subjected to fragile collapse in aqueous environments expanding their use in water treatment. Advances made in MOF based material design have headed towards the use of MOF based aerogels/hydrogels, MOF derived carbons (MDCs), hydrophobic MOFs and magnetic framework composites (MFCs) to remediate water from contaminants and for the separation of oils from water. This review is intended to highlight some of the recent trends followed in MOF based material engineering towards effective water regeneration.

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.

Dialysis membrane enclosed laccase catalysis combines a controlled conversion rate and recyclability without enzyme immobilization

Laccase is a versatile multicopper oxidase that holds great promise for many biotechnological applications. For such applications, it is essential to explore good biocatalytic systems for high activity and recyclability. The feasibility of membrane enclosed enzymatic catalysis (MEEC) for enzyme recycling with laccase was evaluated. The dialysis membrane enclosed laccase catalysis (DMELC) was tested for the conversion of the non-phenolic model substrate 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS). Trametes versicolor laccase was found to be completely retained by the dialysis membrane during the process. The ABTS total conversion after DMELC reached the same values as the batch reaction of the enzyme in solution. The efficiency of DMELC conversion of ABTS under different process conditions including shaking speed, temperature, ABTS concentration and pH was investigated. The repetitive dialysis minimally affected the activity and the protein content of the enclosed laccase. DMELC retained 70.3 ± 0.8% of its initial conversion after 5 cycles. The usefulness of MEEC extends to other enzymes with the benefit of superior activity of an enzyme in solution and the recyclability which is normally only obtained with immobilized enzymes.

Recent development in the application of immobilized oxidative enzymes for bioremediation of hazardous micropollutants - A review

During the past several years, abundant progresses has been made in the development of immobilized oxidative enzymes with focus on finding new support materials, improving the immobilization methods and their applications. Nowadays, immobilized oxidative enzymes are broadly accepted as a green way to face the challenge of high amounts of micropollutants in nature. Among all oxidative enzymes, laccases and horseradish peroxidase were used frequently in recent years as they are general oxidative enzymes with ability to oxidize various types of compounds. Immobilized laccase or horseradish peroxidase are showed better stability, and reusability as well as easy separation from reaction mixture that make them more favorable and economic in compared to free enzymes. However, additional improvements are still essential such as: development of the new materials for immobilization with higher capacity, easy preparation, and cheaper price. Moreover, immobilization methods are still need improving to become more efficient and avoid enzyme wasting during immobilization and enzyme leakage through working cycles.

Facile preparation of low-cost HKUST-1 with lattice vacancies and high-efficiency adsorption for uranium

In this work, we prepared HKUST-1 and HKUST-1 with lattice vacancies (HLV) using benzoic acid (BA) as a low-cost modulator to replace part of the traditional trimesic acid ligand (H₃BTC). The structure and morphology of the products were characterized by FTIR, XRD, SEM and XPS. The adsorption performance of the products for uranium from aqueous solutions was investigated. The results showed that the sorption of U(vi) on HKUST-1 and HLV agreed with the Langmuir isotherm model (R_HKUST-1² = 0.9867 and R_HLV² = 0.9828) and the maximum adsorption capacity was 430.98 mg g⁻¹ and 424.88 mg g⁻¹, respectively. According to kinetics studies, the adsorption fitted better with a pseudo-second-order model (R_HKUST-1² = 1.0000 and R_HLV² = 0.9978). The as-prepared adsorbents were used for the removal of uranium from real water samples as well. The results showed that HLV with lower cost is a promising adsorbent for uranium from aqueous solutions.

HLV was prepared using benzoic acid with lower cost as the modulator to replace part of the traditional ligand H₃BTC for uranium removal.