Immobilization of Peroxidase on Functionalized MWCNTs-Buckypaper/Polyvinyl alcohol Nanocomposite Membrane

Purification and characterization of recombinant human superoxide dismutase integrated with resilin-like polypeptide

Human superoxide dismutase (hSOD1) plays an important role in the aerobic metabolism and free radical eliminating process in the body. However, the production of existing SOD faces problems such as complex purification methods, high costs, and poor product stability. This experiment achieved low-cost, rapid, and simple purification of hSOD1 through ammonium sulfate precipitation method and heat resistance of recombinant protein. We constructed a recombinant protein hSOD1-LR containing a resilin-like polypeptide tag and expressed it. The interest protein was purified by ammonium sulfate precipitation method, and the results showed that the purification effect of 1.5 M (NH4)2SO4 was the best, with an enzyme activity recovery rate of 80 % after purification. Then, based on its thermal stability, further purification of the interest protein at 60 °C revealed a purification fold of up to 24 folds, and the purification effect was similar to that of hSOD1-6xHis purified by nickel column affinity chromatography. The stability of hSOD1-LR showed that the recombinant protein hSOD1-LR has better stability than hSOD-6xHis. hSOD1-LR can maintain 76.57 % activity even after 150 min of reaction at 70 °C. At same time, hSOD1-LR had activity close to 80 % at pH < 5, indicating good acid resistance. In addition, after 28 days of storage at 4 °C and 40 °C, hSOD1-LR retained 92 % and 87 % activity, respectively. Therefore, the method of purifying hSOD1-LR through salt precipitation may have positive implications for the study of SOD purification.

Horseradish Peroxidase Immobilized onto Mesoporous Magnetic Hybrid Nanoflowers for Enzymatic Decolorization of Textile Dyes: A Highly Robust Bioreactor and Boosted Enzyme Stability

Recently, hybrid nanoflowers (hNFs), which are accepted as popular carrier supports in the development of enzyme immobilization strategies, have attracted much attention. In this study, the horseradish peroxidase (HRP) was immobilized to mesoporous magnetic Fe3O4-NH2 by forming Schiff base compounds and the HRP@Fe3O4-NH2/hNFs were then synthesized. Under optimal conditions, 95.0% of the available HRP was immobilized on the Fe3O4-NH2/hNFs. Structural morphology and characterization of synthesized HRP@Fe3O4-NH2/hNFs were investigated. The results demonstrated that the average size of HRP@Fe3O4-NH2/hNFs was determined to be around 220 nm. The ζ-potential and magnetic saturation values of HRP@Fe3O4-NH2/hNFs were -33.58 mV and ∼30 emu/g, respectively. Additionally, the optimum pH, optimum temperature, thermal stability, kinetic parameters, reusability, and storage stability were examined. It was observed that the optimum pH value shifted from 5.0 to pH 8.0 after immobilization, while the optimum temperature shifted from 30 to 80 °C. K m values were calculated to be 15.5502 and 7.6707 mM for free HRP and the HRP@Fe3O4-NH2/hNFs, respectively, and V max values were calculated to be 0.0701 and 0.0038 mM min-1. The low K m value observed after immobilization indicated that the affinity of HRP for its substrate increased. The HRP@Fe3O4-NH2/hNFs showed higher thermal stability than free HRP, and its residual activity after six usage cycles was approximately 45%. While free HRP lost all of its activity within 120 min at 65 °C, the HRP@Fe3O4-NH2/hNFs retained almost all of its activity during the 6 h incubation period at 80 °C. Most importantly, the HRP@Fe3O4-NH2/hNFs demonstrated good potential efficiency for the biodegradation of methyl orange, phenol red, and methylene blue dyes. The HRP@Fe3O4-NH2/hNFs were used for a total of 8 cycles to degrade methyl orange, phenol red, and methylene blue, and degradation of around 81, 96, and 56% was obtained in 8 h, respectively. Overall, we believe that the HRP@Fe3O4-NH2/hNFs reported in this work can be potentially used in various industrial and environmental applications, particularly for the biodegradation of recalcitrant compounds, such as textile dyes.

Utilizing immobilized recombinant serine alkaline protease from Bacillus safensis lab418 in wound healing: Gene cloning, heterologous expression, optimization, and characterization

Microbial proteases have proven their efficiency in various industrial applications; however, their application in accelerating the wound healing process has been inconsistent in previous studies. In this study, heterologous expression was used to obtain an over-yielding of the serine alkaline protease. The serine protease-encoding gene aprE was isolated from Bacillus safensis lab 418 and expressed in E. coli BL21 (DE3) using the pET28a (+) expression vector. The gene sequence was assigned the accession number OP610065 in the NCBI GenBank. The open reading frame of the recombinant protease (aprEsaf) was 383 amino acids, with a molecular weight of 35 kDa. The yield of aprEsaf increased to 300 U/mL compared with the native serine protease (SAFWD), with a maximum yield of 77.43 U/mL after optimization conditions. aprEsaf was immobilized on modified amine-functionalized films (MAFs). By comparing the biochemical characteristics of immobilized and free recombinant enzymes, the former exhibited distinctive biochemical characteristics: improved thermostability, alkaline stability over a wider pH range, and efficient reusability. The immobilized serine protease was effectively utilized to expedite wound healing. In conclusion, our study demonstrates the suitability of the immobilized recombinant serine protease for wound healing, suggesting that it is a viable alternative therapeutic agent for wound management.

Carbon nanotubes buckypapers: A new frontier in wastewater treatment technology

Occurrence of contaminants in water is one of the major global concerns humanity is still facing today: most of them are extremely toxic and dangerous for human health, obliging their removal for a proper and correct process of sanitation. Among wastewater treatment technologies, in the view of development of sustainable and environmentally friendly processes, membrane adsorption has proved to be a fast and simple method in the removal of pollutants, offering great contaminants recovery percentages, fast adsorbent regeneration and recycle, and easy scale-up. Due to their large surface area and tunable chemistry, carbon nanotubes (CNTs)-based materials revealed to be extraordinary adsorbents, exceeding by far performances of ordinary organic and inorganic membranes such as polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, ceramics, currently employed in membrane technologies for wastewater treatment. In consideration of this, the review aims to summarize recent developments in the field of carbon nanotubes-based materials for pollutants recovery from water through adsorption processes. After a brief introduction concerning what adsorption phenomenon is and how it is performed and governed by using carbon nanotubes-based materials, the review discusses into detail the employment of three common typologies of CNTs-based materials (CNTs powders, CNTs-doped polymeric membranes and CNTs membranes) in adsorption process for the removal of water pollutants. Particularly focus will be devoted on the emergent category of self-standing CNTs membranes (buckypapers), made entirely of carbon nanotubes, exhibiting superior performances than CNTs and CNTs-doped polymeric membranes in terms of preparation strategy, recovery percentages of pollutants and regeneration possibilities. The extremely encouraging results presented in this review aim to support and pave the way to the introduction of alternative and more efficient pathways in wastewater treatment technologies to contrast the problem of water pollution.

Alloyed Trimetallic Nanocomposite as an Efficient and Recyclable Solid Matrix for Ideonella sakaiensis Lipase Immobilization

In this work, a trimetallic (Ni/Co/Zn) organic framework (tMOF), synthesized by a solvothermal method, was calcinated at 400 and 600 °C and the final products were used as a support for lipase immobilization. The material annealed at 400 °C (Ni-Co-Zn@400) had an improved surface area (66.01 m2/g) and pore volume (0.194 cm3/g), which showed the highest enzyme loading capacity (301 mg/g) with a specific activity of 0.196 U/mg, and could protect the enzyme against thermal denaturation at 65 °C. The optimal pH and temperature for the lipase were 8.0 and 45 °C but could tolerate pH levels 7.0-8.0 and temperatures 40-60 °C. Moreover, the immobilized enzyme (Ni-Co-Zn@Lipase, Ni-Co-Zn@400@Lipase, or Ni-Co-Zn@600@Lipase) could be recovered and reused for over seven cycles maintaining 80, 90, and 11% of its original activity and maintained a residual activity >90% after 40 storage days. The remarkable thermostability and storage stability of the immobilized lipase suggest that the rigid structure of the support acted as a protective shield against denaturation, while the improved pH tolerance toward the alkaline range indicates a shift in the ionization state attributed to unequal partitioning of hydroxyl and hydrogen ions within the microenvironment of the active site, suggesting that acidic residues may have been involved in forming an enzyme-support bond. The high enzyme loading capacity, specific activity, encouraging stability, and high recoverability of the tMOF@Lipase indicate that a multimetallic MOF could be a better platform for efficient enzyme immobilization.

Display of Lignin Peroxidase on the Surface of Bacillus subtilis

Lignin peroxidase (LiP) has a good application prospect in lignin degradation, environmental treatment, straw feed, and other industries. However, its application is constrained by the high price and low stability of enzyme preparation. In this study, the Escherichia coli-Bacillus subtilis (E. coli-B. subtilis) shuttle expression vector pHS-cotG-lip was constructed and displayed on the surface of Bacillus subtilis spores. The analysis of enzymatic properties showed that the optimal catalytic temperature and pH of the immobilized LiP were 55 °C and 4.5, respectively. Compared with free LiP (42 °C and pH4.0), the optimal reaction temperature increased by 13 °C. After incubation at 70 °C for 1 h, its activity remained above 30%, while the free LiP completely lost its activity under the same conditions. Adding Mn2+, DL-lactic acid, and PEG-4000 increased the CotG-LiP enzyme activity to 313%, 146%, and 265%, respectively. The recyclability of spore display made the fusion protein CotG-LiP retain more than 50% enzyme activity after four cycles. The excellent recycling rate indicated that LiP displayed on the spore surface had a good application prospect in sewage treatment and other fields, and also provided a reference for the rapid and low-cost immobilized production of enzyme preparations.

Biodegradation strategies of veterinary medicines in the environment: Enzymatic degradation

One Health closely integrates healthy farming, human medicine, and environmental ecology. Due to the ecotoxicity and risk of transmission of drug resistance, veterinary medicines (VMs) are regarded as emerging environmental pollutants. To reduce or mitigate the environmental risk of VMs, developing friendly, safe, and effective removal technologies is an important means of environmental remediation for VMs. Many previous studies have proved that biodegradation has significant advantages in removing VMs, and biodegradation based on enzyme catalysis presents higher operability and specificity. This review focused on biodegradation strategies of environmental pollutants and reviewed the enzymatic degradation of VMs including antimicrobial drugs, insecticides, and disinfectants. We reviewed the sources and catalytic mechanisms of peroxidase, laccase, and organophosphorus hydrolases, and summarized the latest research status of immobilization methods and bioengineering techniques in improving the performance of degrading enzymes. The mechanism of enzymatic degradation for VMs was elucidated in the current research. Suggestions and prospects for researching and developing enzymatic degradation of VMs were also put forward. This review will offer new ideas for the biodegradation of VMs and have a guide significance for the risk mitigation and detoxification of VMs in the environment.

Support Materials of Organic and Inorganic Origin as Platforms for Horseradish Peroxidase Immobilization: Comparison Study for High Stability and Activity Recovery

In the presented study, a variety of hybrid and single nanomaterials of various origins were tested as novel platforms for horseradish peroxidase immobilization. A thorough characterization was performed to establish the suitability of the support materials for immobilization, as well as the activity and stability retention of the biocatalysts, which were analyzed and discussed. The physicochemical characterization of the obtained systems proved successful enzyme deposition on all the presented materials. The immobilization of horseradish peroxidase on all the tested supports occurred with an efficiency above 70%. However, for multi-walled carbon nanotubes and hybrids made of chitosan, magnetic nanoparticles, and selenium ions, it reached up to 90%. For these materials, the immobilization yield exceeded 80%, resulting in high amounts of immobilized enzymes. The produced system showed the same optimal pH and temperature conditions as free enzymes; however, over a wider range of conditions, the immobilized enzymes showed activity of over 50%. Finally, a reusability study and storage stability tests showed that horseradish peroxidase immobilized on a hybrid made of chitosan, magnetic nanoparticles, and selenium ions retained around 80% of its initial activity after 10 repeated catalytic cycles and after 20 days of storage. Of all the tested materials, the most favorable for immobilization was the above-mentioned chitosan-based hybrid material. The selenium additive present in the discussed material gives it supplementary properties that increase the immobilization yield of the enzyme and improve enzyme stability. The obtained results confirm the applicability of these nanomaterials as useful platforms for enzyme immobilization in the contemplation of the structural stability of an enzyme and the high catalytic activity of fabricated biocatalysts.

A pushed biosynthesis of 2,6-dihydroxybenzoic acid by the recombinant 2,3-dihydroxybenzoic acid decarboxylase immobilized on novel amino-modified lignin-containing cellulose nanocrystal aerogel

Production of 2,6-dihydroxybenzoic acid (2,6-DHBA) via enzymatic carboxylation of resorcinol by decarboxylases is of great promising but shows depressed equilibrium conversion. In this study, 2,3-dihydroxybenzoic acid decarboxylase from Aspergillus oryzae (2,3-DHBD_Ao) pushing the conversion towards carboxylation for efficient 2,6-DHBA biosynthesis was achieved. Meanwhile, a novel amino-modified and lignin-doped cellulose nanocrystal aerogel (A-LCNCA) with high specific surface area and prominent CO2 capture was prepared for 2,3-DHBD_Ao immobilization. 2,3-DHBD_Ao@A-LCNC contributed a further enhanced conversion of carboxylation with the maximal conversion of 76.2 %, which was correlated to both the activity of 2,3-DHBD_Ao and the high CO2 loading capacity of A-LCNCA. Moreover, 2,3-DHBD_Ao@A-LCNC exhibited superior performances in a wider range of temperature and higher concentrations of substrate, with a prolonged storage period longer than 30 days. After seven cycles reuse, 2,3-DHBD_Ao@A-LCNCA could retain 85.3 % of its original activity. These results suggest a considerable potential of 2,3-DHBD_Ao@A-LCNCA in the selective biosynthesis of 2,6-DHBA.

Development of chia gum/alginate-polymer support for horseradish peroxidase immobilization and its application in phenolic removal

Chia gum's molecular structure with distinctive properties as well as the alginate-based hydrogel's three-dimensionally cross-linked structure can provide a potent matrix for immobilization of enzyme. Herein, chia gum (CG)/alginate (A)-polymeric complex was synthesized and employed as a support material for the immobilization of horseradish peroxidase (HRP). HRP was successfully immobilized on the developed ACG-polymeric support, and the highest immobilization recovery (75%) was observed at 1.0% CG and 2% A, pH 7.0, and 50 units of the enzyme. The structure, morphology, and thermal properties of the prepared ACG-HRP were demonstrated using Fourier Transform Infrared (FTIR), Scanning Electron Microscope, and Thermogravimetric (TGA) analyses. ACG-HRP showed a good reusability (60%) over ten reuses. The immobilized ACG-HRP displayed an acidic pH optimum (6.0), a higher temperature optimum (50 °C), and improved thermal stability (30-50 °C) compared to the soluble HRP at pH 7.0, 40 °C and (30-40 °C), respectively. ACG-HRP has a lower affinity for hydrogen peroxide (H2O2) and guaiacol and a higher oxidizing affinity for a number of phenolic substrates. The ACG-HRP demonstrated greater resistance to heavy metals, isopropanol, urea, Triton X-100, and urea, as well as improved efficiency for eliminating phenol and p-chlorophenol. The developed ACG-polymeric support provided improved enzyme properties, allowed the reuse of the immobilized HRP in 10 cycles, and made it promising for several biotechnological applications.

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.

The s-oph enzyme for efficient degradation of polyvinyl alcohol: soluble expression and catalytic properties

BACKGROUND

Polyvinyl alcohol (PVA) is one of the most widely used water-soluble polymers with remarkable mechanical properties. However, water-soluble polymers are among the major organic pollutants of streams, river, and marine ecosystems. Once dispersed in aqueous systems, they can directly interfere with the life cycle of aquatic organisms via direct toxic effects. There is thus an urgent need for microorganisms or enzymes that can efficiently degrade them. Oxidized PVA hydrolase plays an important role in the pathway of PVA biodegradation. It is the key enzyme in the second step of the pathway for complete degradation of PVA.

METHODS AND RESULTS

The s-oph gene was cloned from the laboratory-isolated strain Sphingopyxis sp. M19. This gene was expressed in the Escherichia coli system pET32a/s-oph expression vector, with the products forming an inclusion body. By binding with a molecular chaperone, pET32a/s-oph/BL21 (DE3)/pGro7 was successfully constructed, which enabled the s-oph gene to be solubly expressed in E. coli. The protein encoded by the s-oph gene was purified at a yield of 16.8 mg L-1, and its catalytic activity reached 852.71 U mg-1. In the s-oph enzyme reaction system, the efficiency of PVA degradation was increased to 233.5% compared with that of controls.

CONCLUSIONS

The s-oph enzyme exhibited the characteristics of being able to degrade PVA with high efficiency, specificity, and stability. This enzyme has good potential for practical application in ameliorating plastic pollution and protecting the environment.

Carbon nanotubes: a powerful bridge for conductivity and flexibility in electrochemical glucose sensors

The utilization of nanomaterials in the biosensor field has garnered substantial attention in recent years. Initially, the emphasis was on enhancing the sensor current rather than material interactions. However, carbon nanotubes (CNTs) have gained prominence in glucose sensors due to their high aspect ratio, remarkable chemical stability, and notable optical and electronic attributes. The diverse nanostructures and metal surface designs of CNTs, coupled with their exceptional physical and chemical properties, have led to diverse applications in electrochemical glucose sensor research. Substantial progress has been achieved, particularly in constructing flexible interfaces based on CNTs. This review focuses on CNT-based sensor design, manufacturing advancements, material synergy effects, and minimally invasive/noninvasive glucose monitoring devices. The review also discusses the trend toward simultaneous detection of multiple markers in glucose sensors and the pivotal role played by CNTs in this trend. Furthermore, the latest applications of CNTs in electrochemical glucose sensors are explored, accompanied by an overview of the current status, challenges, and future prospects of CNT-based sensors and their potential applications.

Macromolecular assembly of bioluminescent protein nanoparticles for enhanced imaging

Bioluminescence imaging has advantages over fluorescence imaging, such as minimal photobleaching and autofluorescence, and greater signal-to-noise ratios in many complex environments. Although significant achievements have been made in luciferase engineering for generating bright and stable reporters, the full capability of luciferases for nanoparticle tracking has not been comprehensively examined. In biocatalysis, enhanced enzyme performance after immobilization on nanoparticles has been reported. Thus, we hypothesized that by assembling luciferases onto a nanoparticle, the resulting complex could lead to substantially improved imaging properties. Using a modular bioconjugation strategy, we attached NanoLuc (NLuc) or Akaluc bioluminescent proteins to a protein nanoparticle platform (E2), yielding nanoparticles NLuc-E2 and Akaluc-E2, both with diameters of ∼45 ​nm. Although no significant differences were observed between different conditions involving Akaluc and Akaluc-E2, free NLuc at pH 5.0 showed significantly lower emission values than free NLuc at pH 7.4. Interestingly, NLuc immobilization on E2 nanoparticles (NLuc-E2) emitted increased luminescence at pH 7.4, and at pH 5.0 showed over two orders of magnitude (>200-fold) higher luminescence (than free NLuc), expanding the potential for imaging detection using the nanoparticle even upon endocytic uptake. After uptake by macrophages, the resulting luminescence with NLuc-E2 nanoparticles was up to 7-fold higher than with free NLuc at 48 ​h. Cells incubated with NLuc-E2 could also be imaged using live bioluminescence microscopy. Finally, biodistribution of nanoparticles into lymph nodes was detected through imaging using NLuc-E2, but not with conventionally-labeled fluorescent E2. Our data demonstrate that NLuc-bound nanoparticles have advantageous properties that can be utilized in applications ranging from single-cell imaging to in vivo biodistribution.

Advances in the application of immobilized enzyme for the remediation of hazardous pollutant: A review

Nowadays, ecofriendly, low-cost, and sustainable alternatives techniques have been focused on the effective removal of hazardous pollutants from the water streams. In this context, enzyme immobilization seems to be of specific interest to several researchers to develop novel, effective, greener, and hybrid strategies for the removal of toxic contaminants. Immobilization is a biotechnological tool, anchoring the enzymes on support material to enhance the stability and retain the structural conformation of enzymes for catalysis. Recyclability and reusability are the main merits of immobilized enzymes over free enzymes. Studies showed that immobilized enzyme laccase can be used up to 7 cycles with 66% efficiency, peroxidase can be recycled to 2 cycles with 50% efficiency, and also cellulase to 3 cycles with 91% efficiency. In this review, basic concepts of immobilization, different immobilization techniques, and carriers used for immobilization are summarized. In addition to that, the potential of immobilized enzymes as the bioremediation agents for the effective degradation of pollutants from the contaminated zone and the impact of different operating parameters are summarized in-depth. Further, this review provides future trends and challenges that have to be solved shortly for enhancing the potential of immobilized systems for large-scale industrial wastewater treatment.

Epoxy functionalized iron oxide magnetic nanoparticles for catalase enzyme covalent immobilization

An aqueous solution of magnetite (Fe3O4) nanoparticles was synthesized using the method of co-precipitation. The nanoparticles were activated with epichlorohydrin for covalently immobilizing the catalase enzyme. The immobilization conditions were optimized as 0.07 mg/ml catalase for 1 h contact time. The properties of free and immobilized catalase were also investigated. The immobilized enzyme showed enhanced activity at alkaline pH and retained about 90% of its relative activity between pH (6–8) and resisted the high temperature and retained 90% of its relative activity at 50 °C. Kinetic parameters of free and immobilized catalase were investigated. While the Vmax value of the immobilized enzyme was reduced 2.4 fold compared to the free enzyme, the KM value of the immobilized catalase was higher by 2.2 fold than the free enzyme. The formulated matrix enhanced the velocity of the immobilized catalase more than the free one and was able to be used for about 18 cycles with retention of 80% of its activity. The immobilized catalase on epoxy functionalized iron oxide nanoparticles is promising as a nano-bio-catalyst carrying out in many industries and different fields.

Carbon Nanomaterials (CNMs) and Enzymes: From Nanozymes to CNM-Enzyme Conjugates and Biodegradation

Carbon nanomaterials (CNMs) and enzymes differ significantly in terms of their physico-chemical properties—their handling and characterization require very different specialized skills. Therefore, their combination is not trivial. Numerous studies exist at the interface between these two components—especially in the area of sensing—but also involving biofuel cells, biocatalysis, and even biomedical applications including innovative therapeutic approaches and theranostics. Finally, enzymes that are capable of biodegrading CNMs have been identified, and they may play an important role in controlling the environmental fate of these structures after their use. CNMs’ widespread use has created more and more opportunities for their entry into the environment, and thus it becomes increasingly important to understand how to biodegrade them. In this concise review, we will cover the progress made in the last five years on this exciting topic, focusing on the applications, and concluding with future perspectives on research combining carbon nanomaterials and enzymes.

Impacts of horseradish peroxidase immobilization onto functionalized superparamagnetic iron oxide nanoparticles as a biocatalyst for dye degradation

To enhance the dye removal efficiency by natural enzyme, horseradish peroxidase (HRP) was immobilized onto amine-functionalized superparamagnetic iron oxide and used as a biocatalyst for the oxidative degradation of acid black-HC dye. The anchored enzyme was characterized by vibrating sample magnetometry, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry, scanning electron microscopy, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda methods, nitrogen adsorption-desorption measurements, Zeta potential, energy dispersive X-ray spectroscopy, and transmission electron microscopy. The Michaelis constant values of free and immobilized HRP were determined to be 4.5 and 5 mM for hydrogen peroxide and 12.5 and 10 mM for guaiacol, respectively. Moreover, the maximum values of free and immobilized HRP were 2.4 and 2 U for H₂O₂, respectively, and 1.25 U for guaiacol. The immobilized enzyme was thermally stable up to 60°C, whereas the free peroxidase was stable only up to 40°C. In the catalytic experiment, the immobilized HRP exhibited superior catalytic activity compared with that of free HRP for the oxidative decolorization and removal of acid black-HC dye. The influence of experimental parameters such as the catalyst dosage, pH, H₂O₂ concentration, and temperature on the removal efficiency was investigated. The reaction followed second-order kinetics, and the thermodynamic activation parameters were determined.

Recent advances in carbon nanotubes-based biocatalysts and their applications

Enzymes have been incorporated into a wide variety of fields and industries as they catalyze many biochemical and chemical reactions. The immobilization of enzymes on carbon nanotubes (CNTs) for generating nano biocatalysts with high stability and reusability is gaining great attention among researchers. Functionalized CNTs act as excellent support for effective enzyme immobilization. Depending on the application, the enzymes can be tailored using the various surface functionalization techniques on the CNTs to extricate the desirable characteristics. Aiming at the preparation of efficient, stable, and recyclable nanobiocatalysts, this review provides an overview of the methods developed to immobilize the various enzymes. Various applications of carbon nanotube-based biocatalysts in water purification, bioremediation, biosensors, and biofuel cells have been comprehensively reviewed.

Fabrication of Cellulase Catalysts Immobilized on a Nanoscale Hybrid Polyaniline/Cationic Hydrogel Support for the Highly Efficient Catalytic Conversion of Cellulose

A novel conductive nanohydrogel hybrid support was prepared by in situ polymerization of polyaniline nanorods on an electrospun cationic hydrogel of poly(ε-caprolactone) and a cationic phosphine oxide macromolecule. Subsequently, the cellulase enzyme was immobilized on the hybrid support. Field-emission scanning electron microscopy and Brunauer-Emmett-Teller analyses confirmed a mesoporous, rod-like structure with a slit-like pore geometry for the immobilized support and exhibiting a high immobilization capacity and reduced diffusion resistance of the substrate. For comparison, the catalytic activity, storage stability, and reusability of the immobilized and free enzymes were evaluated. The results showed that the immobilized enzymes have higher thermal stability without changes in the optimal pH (5.5) and temperature (55 °C) for enzyme activity. A high immobilization efficiency (96%) was observed for the immobilized cellulose catalysts after optimization of parameters such as the pH, temperature, incubation time, and protein concentration. The immobilized enzyme retained almost 90% of its original activity after 4 weeks of storage and 73% of its original activity after the ninth reuse cycle. These results strongly suggest that the prepared hybrid support has the potential to be used as a support for protein immobilization.

Cross-linked tannase-carbon nanotubes composite in elevating antioxidative potential of green tea extract

Multi-walled carbon nanotubes (MWCNT)-tannase composite was investigated as an immobilized biocatalyst on the basis of its facile preparation, low cost, and excellent aqueous dispersibility. Cross-linked tannase enzymes, obtained in the presence of glutaraldehyde, were composited with MWCNT via physical adsorption. Multiple techniques were applied to investigate, and corroborate the successful adsorption of cross-linked tannase onto the MWCNT structure. Green tea infusion extract post-treatment using the composite preparation showed elevated radical scavenging activities relative to the control. Green tea infusion extract exhibited a markedly reduced EC₅₀ value on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals following its treatment with the enzyme composite, which represents 20%-34% enhancement in its free radical scavenging capacity. Stoichiometry and number of reduced DPPH were determined and compared. The antioxidative potential of a widely consumed, health-beneficial green tea is elevated by the treatment with MWCNT-tannase composite. PRACTICAL APPLICATIONS: Cross-linked tannase enzymes were composited with pristine multi-walled carbon nanotubes via simple physical adsorption. The composite presents key advantages such as low specific volume compared to other well-known immobilization media, inert, facile enzyme composition, and ease of recovery for repeated use. The work demonstrated carbon nanotube prosthetic utility in the biotransformation of food-based health commodity sought after for its nutritional benefits. The approach is of both industrial- and agricultural importance, and is a promising and viable strategy to obtain a natural, functional food supplement for the multi-billion dollar well-being and health-related industries.

Decellularized spinal cord meninges extracellular matrix hydrogel that supports neurogenic differentiation and vascular structure formation

Decellularization of extracellular matrices offers an alternative source of regenerative biomaterials that preserve biochemical structure and matrix components of native tissues. In this study, decellularized bovine spinal cord meninges (dSCM)-derived extracellular matrix hydrogel (MeninGEL) is fabricated by employing a protocol that involves physical, chemical, and enzymatic processing of spinal meninges tissue and preserves the biochemical structure of meninges. The success of decellularization is characterized by measuring the contents of residual DNA, glycosaminoglycans, and hydroxyproline, while a proteomics analysis is applied to reveal the composition of MeninGEL. Frequency and temperature sweep rheometry show that dSCM forms self-supporting hydrogel at physiological temperature. The MeninGEL possesses excellent cytocompatibility. Moreover, it is evidenced with immuno/histochemistry and gene expression studies that the hydrogel induces growth-factor free differentiation of human mesenchymal stem cells into neural-lineage cells. Furthermore, MeninGEL instructs human umbilical vein endothelial cells to form vascular branching. With its innate bioactivity and low batch-to-batch variation property, the MeninGEL has the potential to be an off-the-shelf product in nerve tissue regeneration and restoration.

Evaluating the activity and stability of sonochemically produced hemoglobin-copper hybrid nanoflowers against some metallic ions, organic solvents, and inhibitors

The disadvantage of the conventional protein-inorganic hybrid nanoflower production method is the long incubation period of the synthesis method. This period is not suitable for practical industrial use. Herein, protein-inorganic hybrid nanoflowers were synthesized using hemoglobin and copper ion by fast sonication method for 10 min. The synthesized nanoflowers were characterized via scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fouirer-transform infrared spectroscopy. The activity and stability of the nanoflowers in the presence of different metal ions, organic solvents, inhibitors, and storage conditions were also evaluated by comparing with free hemoglobin. According to obtained results, the optimum pH and temperatures of both hybrid nanoflower and free hemoglobin were pH 5 and 40 °C, respectively. At all pH levels, nanoflower was more stable than free protein and it was also more stable than the free hemoglobin at temperatures ranging between 50 °C and 80 °C. The free protein lost more than half of its activity in the presence of acetone, benzene, and N,N-dimethylformamide, while the hybrid nanoflower retained more than 70% of its activity for 2 h at 40 °C. The hybrid nanoflower activity was essentially increased in the presence of Ca²⁺, Zn²⁺, Fe²⁺, Cu²⁺ and Ni²⁺ (132%, 161%, 175%, 185% and 106%, respectively) at 5 mM concentration. The nanoflower retained more than 85% of its initial activity in the presence of all inhibitors. In addition, it retained all its activity for 3 days under different storage conditions, unlike free hemoglobin. The results demonstrated that new hybrid nanoflowers may be promising in different biotechnological applications such as catalytic biosensors and environmental or industrial catalytic processes.

A comprehensive review on magnetic carbon nanotubes and carbon nanotube-based buckypaper for removal of heavy metals and dyes

Industrial effluents contain several organic and inorganic contaminants. Among others, dyes and heavy metals introduce a serious threat to drinking waterbodies. These pollutants can be noxious or carcinogenic in nature, and harmful to humans and different aquatic species. Therefore, it is of high importance to remove heavy metals and dyes to reduce their environmental toxicity. This has led to an extensive research for the development of novel materials and techniques for the removal of heavy metals and dyes. One route to the removal of these pollutants is the utilization of magnetic carbon nanotubes (CNT) as adsorbents. Magnetic carbon nanotubes hold remarkable properties such as surface-volume ratio, higher surface area, convenient separation methods, etc. The suitable characteristics of magnetic carbon nanotubes have led them to an extensive search for their utilization in water purification. Along with magnetic carbon nanotubes, the buckypaper (BP) membranes are also favorable due to their unique strength, high porosity, and adsorption capability. However, BP membranes are mostly used for salt removal from the aqueous phase and limited literature shows their applications for removal of heavy metals and dyes. This study focuses on the existence of heavy metal ions and dyes in the aquatic environment, and methods for their removal. Various fabrication approaches for the development of magnetic-CNTs and CNT-based BP membranes are also discussed. With the remarkable separation performance and ultra-high-water flux, magnetic-CNTs, and CNT-based BP membranes have a great potential to be the leading technologies for water treatment in future.

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

Laccase is an effective biocatalyst in bioremediation process; however, the application of the enzyme is limited due to its cost, recovery, and stability. In this study, we developed, characterized and evaluated the efficiency of immobilized laccase on zinc oxide nanostructure to catalyze biodegradation of TBA in comparison to the suspended enzyme. The results showed that both immobilized and suspended laccase were capable of catalyzing TBA biodegradation; however, the efficiency of the immobilized laccase on TBA removal was higher than that of the suspended enzyme. The repeatability testing revealed the potential of the immobilized laccase for repeatedly catalyzing TBA biodegradation with storage capacity. While the V_max of immobilized enzyme was higher than suspended laccase (2.25 ± 0.542 mg TBA/h∙U vs. 1.47 ± 0.185 mg TBA/h∙U), the k_m of the immobilized enzyme was higher than the suspended laccase (67.9 ± 20.5 mg TBA/L vs. 33.5 ± 7.10 mg TBA/L). This suggests that the immobilized laccase is better in TBA removal, but has lower affinity with TBA than the suspended enzyme. Thus, immobilization of the enzyme can be applied to increase the efficiency and minimize the use of laccase for TBA remediation.

Extraction of ingredients from tea leaves using oxidative enzymatic reaction and optimization of extraction conditions

Peroxidase (POD) and polyphenol oxidase (PPO) are used as biocatalyst in many processes such as oxidization reactions, wastewater treatment, phenol synthesis and so on. The purpose of current study is enzymes extraction from biomass (tea leaves) as well as evaluation of their activation. Different parameters including temperature, buffer concentration, buffer type, buffer/tea leaves ratio, addition of high molecular weight polymers and emulsifiers, and pH were optimized in order to obtain the highest enzymes activity. Response Surface Methodology (RSM) procedure is employed for statistical analysis of enzymes extraction. It is understood from the result that PPO and POD possess the highest activity at temperatures of 25 °C and 50 °C, pH 7 and 5, buffer molarity of 0.1, and 0.05, buffer/tea leaves ratio = 5 for both, contact time = 20 min and 10 min, and presence of 6% and 3% PVP, 5% and 0% Tween 80 for PPO and POD, respectively. Amounts of highest activity for PPO and POD biocatalysts were calculated 0.42 U/mL and 0.025493 U/mL, respectively. Moreover, the entire inactivation of PPO took place after 30 min at 40 °C and 60 °C and 20 min at 80 °C. However, POD lost 35% of its activity after 30 min at 40 °C and 60 °C. The amount of 6% POD activity was kept after 45 min at 80 °C. Generally, it was indicated that POD was more resistant to thermal treatment than PPO.

Improvement of Laccase Activity Via Covalent Immobilization over Mesoporous Silica Coated Magnetic Multiwalled Carbon Nanotubes for the Discoloration of Synthetic Dyes

Due to its environmental friendliness and biodegradable ability, the enzymatic decolorization of azo dyes is the best option. However, the free enzyme suffers from various limitations, including poor stability, no repeatable use, and a high expense, which is the key drawback for its practical use. In this analysis, the laccase enzyme was immobilized in mesoporous silica coated magnetic multiwalled carbon nanotubes (Fe₃O₄-MWCNTs@SiO₂) by a glutaraldehyde cross-linker to create an easily separable and stable enzyme. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the as-synthesized Fe₃O₄-MWCNTs@SiO₂. Laccase immobilized in Fe₃O₄-MWCNTs@SiO₂ showed a good improvement in temperature, pH, and storage stability. Moreover, the operational stability of the biocatalyst was improved, retaining 87% of its original activity even after 10 cycles of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) oxidation. The biocatalysts were applied for the decolorization of selected azo dyes without a mediator, and up to 99% of Eriochrome Black T (EBT), 98% of Acid Red 88 (AR 88), and 66% of Reactive Black 5 (RB5) were decolorized. Based on these properties, the biocatalysts can be potentially utilized in various environmental and industrial applications.

Graphene/PVA buckypaper for strain sensing application

Strain sensors in the form of buckypaper (BP) infiltrated with various polymers are considered a viable option for strain sensor applications such as structural health monitoring and human motion detection. Graphene has outstanding properties in terms of strength, heat and current conduction, optics, and many more. However, graphene in the form of BP has not been considered earlier for strain sensing applications. In this work, graphene-based BP infiltrated with polyvinyl alcohol (PVA) was synthesized by vacuum filtration technique and polymer intercalation. First, Graphene oxide (GO) was prepared via treatment with sulphuric acid and nitric acid. Whereas, to obtain high-quality BP, GO was sonicated in ethanol for 20 min with sonication intensity of 60%. FTIR studies confirmed the oxygenated groups on the surface of GO while the dispersion characteristics were validated using zeta potential analysis. The nanocomposite was synthesized by varying BP and PVA concentrations. Mechanical and electrical properties were measured using a computerized tensile testing machine, two probe method, and hall effect, respectively. The electrical conducting properties of the nanocomposites decreased with increasing PVA content; likewise, electron mobility also decreased while electrical resistance increased. The optimization study reports the highest mechanical properties such as tensile strength, Young’s Modulus, and elongation at break of 200.55 MPa, 6.59 GPa, and 6.79%, respectively. Finally, electrochemical testing in a strain range of ε ~ 4% also testifies superior strain sensing properties of 60 wt% graphene BP/PVA with a demonstration of repeatability, accuracy, and preciseness for five loading and unloading cycles with a gauge factor of 1.33. Thus, results prove the usefulness of the nanocomposite for commercial and industrial applications.

A comprehensive review on incredible renewable carriers as promising platforms for enzyme immobilization & thereof strategies

Enzymes are the highly versatile bio-catalysts having the potential for being employed in biotechnological and industrial sectors to catalyze biosynthetic reactions over a commercial point of view. Immobilization of enzymes has improved catalytic properties, retention activities, thermal and storage stabilities as well as reusabilities of enzymes in synthetic environments that have enthralled significant attention over the past few years. Dreadful efforts have been emphasized on the renewable and synthetic supports/composite materials to reserve their inherent characteristics such as biocompatibility, non-toxicity, accessibility of numerous reactive sites for profitable immobilization of biological molecules that often serve diverse applications in the pharmaceutical, environmental, and energy sectors. Supports should be endowed with unique physicochemical properties including high specific surface area, hydrophobicity, hydrophilicity, enantioselectivities, multivalent functionalization which professed them as competent carriers for enzyme immobilization. Organic, inorganic, and nano-based platforms are more potent, stable, highly recovered even after used for continuous catalytic processes, broadly renders the enzymes to get efficiently immobilized to develop an inherent bio-catalytic system that displays higher activities as compared to free-counter parts. This review highlights the recent advances or developments on renewable and synthetic matrices that are utilized for the immobilization of enzymes to deliver emerging applications around the globe.

Removal of dye using peroxidase-immobilized Buckypaper/polyvinyl alcohol membrane in a multi-stage filtration column via RSM and ANFIS

The feasibility and performance of Jicama peroxidase (JP) immobilized Buckypaper/polyvinyl alcohol (BP/PVA) membrane for methylene blue (MB) dye removal was investigated in a customized multi-stage filtration column under batch recycle mode. The effect of independent variables, such as influent flow rate, ratio of H₂O₂/MB dye concentration, and contact time on the dye removal efficiency, were investigated using response surface methodology (RSM). To capture the inherent characteristics and better predict the removal efficiency, a data-driven adaptive neuro-fuzzy inference system (ANFIS) is implemented. Results indicated that the optimum dye removal efficiency of 99.7% was achieved at a flow rate of 2 mL/min, 75:1 ratio of H₂O₂/dye concentration with contact time of 183 min. The model predictions of ANFIS are significantly good compared with RSM, thus resulting in R² values of 0.9912 and 0.9775, respectively. The enzymatic kinetic parameters, K_m and V_max, were evaluated, which are 1.98 mg/L and 0.0219 mg/L/min, respectively. Results showed that JP-immobilized BP/PVA nanocomposite membrane can be promising and cost-effective biotechnology for the practical application in the treatment of industrial dye effluents.

A preliminary study on the development of a novel biomatrix by decellularization of bovine spinal meninges for tissue engineering applications

Here, we aim at developing a novel biomatrix from decellularized bovine spinal meninges for tissue engineering and regenerative medicine applications. Within this concept, the bovine spinal meninges were decellularized using 1% Triton X-100 for 48 h, and residual nuclear content was determined with double-strand DNA content analysis and agarose gel electrophoresis. The major matrix components such as sulfated GAGs and collagen before and after the decellularization process were analyzed with DMMB, hydroxyproline assay and SDS-PAGE. Subsequently, the native bovine spinal meninges (nBSM) and decellularized BSM (dBSM) were physiochemically characterized via ATR-FTIR spectroscopy, TGA, DMA and tensile strength test. The dsDNA content in the nBSM was 153.39 ± 53.93 ng/mg dry weight, versus in the dBSM was 39.47 ± 4.93 ng/mg (n = 3) dry weight and DNA fragments of more than 200 bp in length were not detected in the dBSM by agarose gel electrophoresis. The sulfated GAGs contents for nBSM and dBSM were observed to be 10.87 ± 1.2 and 11.42 ± 2.01 μg/mg dry weight, respectively. The maximum strength of dBSM in dry and wet conditions was found to be 19.67 ± 0.21 MPa and 13.97 ± 0.17 MPa, while nBSM (dry) was found to be 26.26 ± 0.28 MPa. MTT, SEM, and histology results exhibited that the cells attached to the surface of dBSM, and proliferated on the dBSM. In conclusion, the in vitro preliminary study has demonstrated that the dBSM might be a proper and new bioscaffold for tissue engineering and regenerative medicine applications.

A Novel Fungal Lipase With Methanol Tolerance and Preference for Macaw Palm Oil

Macaw palm is a highly oil-producing plant, which presents high contents of free fatty acids, being a promising feedstock for biofuel production. The current chemical routes are costly and complex, involving highly harsh industrial conditions. Enzymatic processing is a potential alternative; however, it is hampered by the scarce knowledge on biocatalysts adapted to this acidic feedstock. This work describes a novel lipase isolated from the thermophilic fungus Rasamsonia emersonii (ReLip), which tolerates extreme conditions such as the presence of methanol, high temperatures, and acidic medium. Among the tested feedstocks, the enzyme showed the highest preference for macaw palm oil, producing a hydrolyzate with a final free fatty acid content of 92%. Crystallographic studies revealed a closed conformation of the helical amphipathic lid that typically undergoes conformational changes in a mechanism of interfacial activation. Such conformation of the lid is stabilized by a salt bridge, not observed in other structurally characterized homologs, which is likely involved in the tolerance to organic solvents. Moreover, the lack of conservation of the aromatic cluster IxxWxxxxxF in the lid of ReLip with the natural mutation of the phenylalanine by an alanine might be correlated with the preference of short acyl chains, although preserving catalytic activity on insoluble substrates. In addition, the presence of five acidic amino acids in the lid of ReLip, a rare property reported in other lipases, may have contributed to its ability to tolerate and be effective in acidic environments. Therefore, our work describes a new fungal biocatalyst capable of efficiently hydrolyzing macaw oil, an attractive feedstock for the production of "drop-in" biofuels, with high desirable feature for industrial conditions such as thermal and methanol tolerance, and optimum acidic pH. Moreover, the crystallographic structure was elucidated, providing a structural basis for the enzyme substrate preference and tolerance to organic solvents.

Modeling and optimization by particle swarm embedded neural network for adsorption of methylene blue by jicama peroxidase immobilized on buckypaper/polyvinyl alcohol membrane

Jicama peroxidase (JP) immobilized functionalized Buckypaper/Polyvinyl alcohol (BP/PVA) membrane was synthesized and evaluated as a promising nanobiocomposite membrane for methylene blue (MB) dye removal from aqueous solution. The effects of independent process variables, including pH, agitation speed, initial concentration of hydrogen peroxide (H₂O₂), and contact time on dye removal efficiency were investigated systematically. Both Response Surface Methodology (RSM) and Artificial Neural Network coupled with Particle Swarm Optimization (ANN-PSO) approaches were used for predicting the optimum process parameters to achieve maximum MB dye removal efficiency. The best optimal topology for PSO embedded ANN architecture was found to be 4-6-1. This optimized network provided higher R² values for randomized training, testing and validation data sets, which are 0.944, 0.931 and 0.946 respectively, thus confirming the efficacy of the ANN-PSO model. Compared to RSM, results confirmed that the hybrid ANN-PSO shows superior modeling capability for prediction of MB dye removal. The maximum MB dye removal efficiency of 99.5% was achieved at pH-5.77, 179 rpm, ratio of H₂O₂/MB dye of 73.2:1, within 229 min. Thus, this work demonstrated that JP-immobilized BP/PVA membrane is a promising and feasible alternative for treating industrial effluent.

Modelling of methylene blue adsorption using peroxidase immobilized functionalized Buckypaper/polyvinyl alcohol membrane via ant colony optimization

Jicama peroxidase (JP) was covalently immobilized onto functionalized multi-walled carbon nanotube (MWCNT) Buckypaper/Polyvinyl alcohol (BP/PVA) membrane and employed for degradation of methylene blue dye. The parameters of the isotherm and kinetic models are estimating using ant colony optimization (ACO), which do not meddle the non-linearity form of the respective models. The proposed inverse modelling through ACO optimization was implemented, and the parameters were evaluated to minimize the non-linear error functions. The adsorption of MB dye onto JP-immobilized BP/PVA membrane follows Freundlich isotherm model (R² = 0.99) and the pseudo 1st order or 2nd kinetic model (R² = 0.980 & 0.968 respectively). The model predictions from the parameters estimated by ACO resulted values close the experimental values, thus inferring that this approach captured the inherent characteristics of MB adsorption. Moreover, the thermodynamic studies indicated that the adsorption was favourable, spontaneous, and exothermic in nature. The comprehensive structural analyses have confirmed the successful binding of peroxidase onto BP/PVA membrane, as well as the effective MB dye removal using immobilized JP membrane. Compared to BP/PVA membrane, the reusability test revealed that JP-immobilized BP/PVA membrane has better dye removal performances as it can retain 64% of its dye removal efficiency even after eight consecutive cycles. Therefore, the experimental results along with modelling results demonstrated that JP-immobilized BP/PVA membrane is expected to bring notable impacts for the development of effective green and sustainable wastewater treatment technologies.

Covalent immobilization of trypsin on polyvinyl alcohol-coated magnetic nanoparticles activated with glutaraldehyde

Magnetic nanoparticles were coated with polyvinyl alcohol and activated with glutaraldehyde for trypsin immobilization. The prepared magnetic nanoparticles were characterized by transmission electron microscopy, fourier transform infrared spectroscopy, thermal gravimetric analysis, zeta potential meter and vibrating sample magnetometer. Free and immobilized trypsin showed optimum activity at pH 6.0, 30 °C and pH 7.0, 40 °C, respectively. Immobilized trypsin was more stable than the free enzyme at 40 °C. After immobilization, K_m of the immobilized trypsin increased, however, V_max value was almost the same with free trypsin. According to the results, the immobilized trypsin retained 50 % of its initial activity, whereas free trypsin retained 19 % of its initial activity after 12-days at 4 °C. Immobilized trypsin sustained 56 % of its initial activity after eight times of successive reuse. The performance of the immobilized trypsin was evaluated by digestion of cytochrome c. The peptide fragments in digest solution were determined by using MALDI-TOF mass spectrometry. Immobilized trypsin showed effective proteolytic activity in shorter time (15 min) than free trypsin (24 h). Hence, immobilized trypsin on the polyvinyl alcohol coated magnetic nanoparticles could be promising biocatalyst for large-scale proteomics studies and practical applications.

Encapsulation of HRP Enzyme onto a Magnetic Fe3O4 Np–PMMA Film via Casting with Sustainable Biocatalytic Activity

Horseradish peroxidase (HRP) enzyme was effectively encapsulated onto an Fe3O4 nanoparticle–polymethyl methacrylate (PMMA) film via the casting method. The HRP was immobilized on the 0.5% Fe3O4Np–PMMA film and characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Moreover, the reusability, thermal stability, optimum pH, optimum temperature, the influence of metal ions, and the effects of detergent and organic solvent were investigated. After optimizing the immobilization conditions, the highest efficiency of the immobilized enzyme was 88.4% using 0.5% Fe3O4Np–PMMA. The reusability of the immobilized HRP activity was 78.5% of its initial activity after being repeatedly used for 10 cycles. When comparing the free and immobilized forms of the HRP enzyme, changes in the optimum temperature and optimum pH from 30 to 40 °C and 7.0 to 7.5, respectively, were observed. The Km and Vmax for the immobilized HRP were estimated to be 41 mM, 0.89 U/mL for guaiacol and 5.84 mM, 0.66 U/mL for H2O2, respectively. The high stability of the immobilized HRP enzyme was obtained using metal ions, a high urea concentration, isopropanol, and Triton X-100. In conclusion, the applicability of immobilized HRP involves the removal of phenol in the presence of hydrogen peroxide, therefore, it could be a potential catalyst for the removal of wastewater aromatic pollutants.