Enhancement of catalytic performance of porcine pancreatic lipase immobilized on functional ionic liquid modified Fe3O4-Chitosan nanocomposites

Boosting catalytic efficiency of lipase by regulating amphiphilic microenvironment through reversible addition-fragmentation chain transfer polymerized modifications on polyacrylonitrile fiber

Lipases are increasingly attracting attention in green and sustainable biodiesel production. Currently, the research emphasis lies in immobilizing unstable lipase onto carriers to enhance its performance. Polyacrylonitrile fiber (PANF) is considered to be a promising material for lipase immobilization due to its excellent properties. In this study, functional carriers with regulated surface hydrophobicity were obtained by loading functional groups on PANF via reversible addition-fragmentation chain transfer (RAFT) polymerized modification, and Candida rugosa lipase (CRL) was covalently immobilized on the carrier with glutaraldehyde as a linker. By employing this optimized biocatalyst PANF@BMA&2VImBr-NH2-CRL in the transesterification process, the yield of biodiesel derived from soybean oil reached an impressive 92.7 %. The outstanding performance can be attributed to the activation of lipase interface induced by hydrophobic microenvironment derived from alkyl ester on the carrier skeleton. Moreover, the stability and storage performance of immobilized lipase were significantly improved. The immobilized lipase exhibited facile recovery and maintained a consistent biodiesel yield of 80.9 % even after undergoing 5 cycles of reuse, thereby highlighting its potential for sustainable production. To sum up, our research demonstrates that the designed and prepared process of PANF-supported lipase offers a promising approach for enzyme immobilization, thereby presenting extensive potential applications in the field of biotechnology.

Enzyme immobilization with nanomaterials for hydrolysis of lignocellulosic biomass: Challenges and future Perspectives

Enzyme immobilization has emerged as a prodigious strategy in the enzymatic hydrolysis of lignocellulosic biomass (LCB) promising enhanced efficacy and stability of the enzymes. Further, enzyme immobilization on magnetic nanoparticles (MNPs) facilitates the easy recovery and reuse of biocatalysts. This results in the development of a nanobiocatalytic system, that serves as an eco-friendly and inexpensive LCB deconstruction approach. This review provides an overview of nanomaterials used for immobilization with special emphasis on the nanomaterial-enzyme interactions and strategies of immobilization. After the succinct outline of the immobilization procedures and supporting materials, a comprehensive assessment of the catalysis enabled by nanomaterial-immobilized biocatalysts for the conversion and degradation of lignocellulosic biomasses is provided by gathering state-of-the-art examples. The challenges and future directions associated with this technique providing a potential solution in the present article. Insight on the recent advancements in the process of nanomaterial-based immobilization for the hydrolysis of lignocellulosic biomass has also been highlighted in the article.

Nanodiamonds and natural deep eutectic solvents as potential carriers for lipase

This study investigates the use of nanodiamonds (ND) as a promising carrier for enzyme immobilization and compares the effectiveness of immobilized and native enzymes. Three different enzyme types were tested, of which Rhizopus niveus lipase (RNL) exhibited the highest relative activity, up to 350 %. Under optimized conditions (1 h, pH 7.0, 40 °C), the immobilized ND-RNL showed a maximum specific activity of 0.765 U mg-1, significantly higher than native RNL (0.505 U mg-1). This study highlights a notable enhancement in immobilized lipase; furthermore, the enzyme can be recycled in the presence of a natural deep eutectic solvent (NADES), retaining 76 % of its initial activity. This aids in preserving the native conformation of the protein throughout the reusability process. A test on brine shrimp revealed that even at low concentrations, ND-RNL had minimal toxicity, indicating its low cytotoxicity. The in silico molecular dynamics simulations performed in this study offer valuable insights into the mechanism of interactions between RNL and ND, demonstrating that RNL immobilization onto NDs enhances its efficiency and stability. All told, these findings highlight the immense potential of ND-immobilized RNL as an excellent candidate for biological applications and showcase the promise of further research in this field.

Melamine phosphate-modified magnetic chitosan: a novel biocompatible catalyst for the synthesis of biological tetrahydrodipyrazolopyridine and pyrazolopyranopyrimidine derivatives

A novel biocompatible composite was fabricated by the functionalization of magnetic chitosan with the melamine phosphate (MP) ionic compound to serve as a recoverable and bifunctional catalyst, aiming at the diversity-oriented generation of biological tetrahydropyrazolopyridine and pyrazolopyrimidine derivatives. This involved a meticulously orchestrated reaction, exploiting the in situ generated pyrazole alongside aromatic aldehydes, ammonium acetate, and (thio) barbituric acid. The present work manifests outstanding advantages, offering a novel and great method for the optimal synthesis of two valuable heterocyclic series especially five new derivatives. The resulting novel biocompatible composite was comprehensively characterized through a range of analytical techniques, including FT-IR, NH3 and CO2-TPD, XRD, TEM, FE-SEM, VSM, EDX, elemental CHNS analysis, ICP-MS, and NMR spectroscopy. Notably, the study represents a critical step in the preparation of advanced materials from accessible and cost-effective precursors.

Tailoring the interfacial microenvironment of magnetic metal-organic frameworks using amino-acid-based ionic liquids for lipase immobilization

Modifying the carrier interface is a promising method to improve the microenvironment of immobilized enzymes and enhance their activity and stability. In this work, using proline as amino acid, magnetic metal-organic frameworks (MOFs) were modified with an amino-acid-based ionic liquid (AAIL) with two hydroxyl groups followed by adsorption of porcine pancreatic lipase (PPL). The activity recovery of the prepared immobilized lipase (MMOF-AAIL/PPL) was up to 162 % higher than that of MMOF-PPL (70.8 %). The Michaelis constant of MMOF-AAIL/PPL was 0.0742 mM lower than that of MMOF-PPL, but the catalytic efficiency was 0.0223 min-1 which was higher than MMOF-PPL. Furthermore, MMOF-AAIL/PPL maintained 85.6 % residual activity after stored for 40 days and its residual activity was 71.9 % while that for MMOF-PPL was 58.8 % after incubated in 6 M urea for 2 h. Particularly, after ten consecutive cycles, the residual activity of MMOF-AAIL/PPL still reached 84.4 %. In addition, the magnetic properties of the support facilitate the separation process which improves the utilization efficiency of immobilized enzymes.

Recent applications and future prospects of magnetic biocatalysts

Magnetic biocatalysts combine magnetic properties with the catalytic activity of enzymes, achieving easy recovery and reuse in biotechnological processes. Lipases immobilized by magnetic nanoparticles dominate. This review covers an advanced bibliometric analysis and an overview of the area, elucidating research advances. Using WoS, 34,949 publications were analyzed and refined to 450. The prominent journals, countries, institutions, and authors that published the most were identified. The most cited articles showed research hotspots. The analysis of the themes and keywords identified five clusters and showed that the main field of research is associated with obtaining biofuels derived from different types of sustainable vegetable oils. The overview of magnetic biocatalysts showed that these materials are also employed in biosensors, photothermal therapy, environmental remediation, and medical applications. The industry shows a significant interest, with the number of patents increasing. Future studies should focus on immobilizing new lipases in unique materials with magnetic profiles, aiming to improve the efficiency for various biotechnological applications.

Magnetic Polyethyleneimine Nanoparticles Fabricated via Ionic Liquid as Bridging Agents for Laccase Immobilization and Its Application in Phenolic Pollutants Removal

In this study, polyethyleneimine was combined with magnetic Fe₃O₄ nanoparticles through the bridging of carboxyl-functionalized ionic liquid, and laccase was loaded onto the carrier by Cu²⁺ chelation to achieve laccase immobilization (MCIL-PEI-Cu-lac). The carrier was characterized by Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, X-ray diffraction analysis, magnetic hysteresis loop and so on. MCIL-PEI-Cu-lac has good immobilization ability; its loading and activity retention could reach 52.19 mg/g and 91.65%, respectively. Compared with free laccase, its thermal stability and storage stability have been significantly improved, as well. After 6 h of storage at 60 °C, 51.45% of the laccase activity could still be retained, and 81.13% of the laccase activity remained after 1 month of storage at 3 °C. In the pollutants removal test, the removal rate of 2,4-dichlorophenol (10 mg/L) by MCIL-PEI-Cu-lac could reach 100% within 10 h, and the removal efficiency could still be maintained 60.21% after repeated use for 8 times. In addition, MCIL-PEI-Cu-lac also has a good removal effect on other phenolic pollutants (such as bisphenol A, phenol, 4-chlorophenol, etc.). Research results indicated that an efficient strategy for laccase immobilization to biodegrade phenolic pollutants was developed.

Co-immobilization of electron mediator and laccase onto dialdehyde starch cross-linked magnetic chitosan nanomaterials for organic pollutants’ removal

In this study, an amino-functionalized ionic liquid-modified magnetic chitosan (MACS-NIL) containing 2,2-diamine-di-3-ethylbenzothiazolin-6-sulfonic acid (ABTS) was used as a carrier, and dialdehyde starch (DAS) was used as a cross-linking agent to covalently immobilize laccase (MACS-NIL-DAS-lac), which realized the co-immobilization of laccase and ABTS. The carrier was characterized by Fourier infrared transform spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction analysis, electron paramagnetic resonance, etc. The immobilization efficiency and activity retention of MACS-NIL-DAS-lac could reach 76.7% and 69.8%, respectively. At the same time, its pH stability, thermal stability, and storage stability had been significantly improved. In the organic pollutant removal performance test, the removal rate of 2,4-dichlorophenol (10 mg/L) by MACS-NIL-DAS-lac (1 U) could reach 100% within 6 h, and the removal efficiency could still reach 88.6% after six catalytic runs. In addition, MACS-NIL-DAS-lac also showed excellent degradation ability for other conventional phenolic pollutants and polycyclic aromatic hydrocarbons. The research results showed that MACS-NIL-DAS fabricated by the combination inorganic material, organic biomacromolecules, ionic liquid, and electron mediator could be used as a novel carrier for laccase immobilization and the immobilized laccase showed excellent removal efficiency for organic pollutants.

Unprecedented enhancement and preservation of the peroxidase activity of cytochrome-c packaged with ionic liquid-modified gold nanoparticles by offsetting temperature and time stresses

Inspired by the biocompatibility of ionic liquids and their dexterousness for the preservation of enzyme structure and activity, herein, the interactions of Cyt-c with naked AuNPs and four IL-mediated AuNPs, which were formed by the fabrication of ILs with common cation 1-ethyl-3-methyl-imidazolium (EMIM) and different anions, to obtain AuNP-IL1 [(BF4)^-1 anion], AuNP-IL2 [(CH₃OSO₃)^-1 anion], AuNP-IL3 [(CH₃CH₂OSO₃)^-1 anion], and (AuNP-IL4) [Cl^-1 anion], were studied. Through this work, the peroxidase activity observed in the presence of a lower concentration IL-AuNPs is exceptionally increased (16 fold). IL-AuNPs preferentially counteract the temperature gradient change and long-term solvent preservation effects while persistently maintaining the Cyt-c peroxidase activity without much depreciation. The hydrodynamic diameter (d_H) of the Cyt-c-AuNP system was obtained, which supported the TEM results. Furthermore, to evaluate the effect of Cyt-c interaction with the AuNPs, a Zeta potential analysis was performed. Taken together, the binding of IL-AuNPs with Cyt-c, diameter size analysis, zeta potential, structural integrity evaluation using the DichroWeb software and morphology results suggest the interaction order of the IL-AuNPs to be in a sequence of AuNP-IL2 > AuNP-IL3 > AuNP- IL4 > AuNP-IL1 > Naked AuNPs. Moreover, results indicate that the IL anions play a dominating role in the modulation of interactions between IL-mediated AuNPs and Cyt-c. The study strongly supports the promising character of sulfur-containing IL-mediated AuNPs for Cyt-c immobilization simultaneously opening new avenues for the application of greener and biocompatible nanoparticles with drug delivery and therapeutic applications.

Ionic liquid based composites: A versatile materials for remediation of aqueous environmental contaminants

Water pollution is one of the most aggravated problems threatening the sustainability of human race and other life forms due to the rapid pace of civilization and industrialization. A long history exists of release of hazardous pollutants into the water bodies due to selfish human activities since the Industrial Revolution, but no effort has been completely successful in curbing the activities that result in the degradation of our environment. These pollutants are harmful, carcinogenic and have adverse health effects to all forms of life. Thus, remarkable efforts have been geared up to obtain clean water by exploiting science and technology. The application of Ionic liquids (ILs) as sustainable materials have received widespread attention since the last decade. Their interesting properties, simplicity in operation and satisfactory binding capacities in elimination of the contaminants makes them a valuable prospect to be utilized in wastewater treatment. Immobilizing and grafting the solid supports with ILs have fetched efficient results to exploit their potential in the adsorptive removal processes. This review provides an understanding of the recent developments and outlines the possible utility of IL based nano adsorbents in the removal of organic compounds, dyes and heavy metal ions from aqueous medium. Effect of several parameters such as sorbent dosage, pH and temperature on the removal efficiency has also been discussed. Moreover, the adsorption isotherms, thermodynamics and mechanism are comprehensively studied. It is envisioned that the literature gathered in this article will guide the budding scientists to put their interest in this area of research in the days to come.

Immobilization of Interfacial Activated Candida rugosa Lipase Onto Magnetic Chitosan Using Dialdehyde Cellulose as Cross-Linking Agent

Candidarugosa lipase (CRL) was activated with surfactants (sodium dodecyl sulfate [SDS]) and covalently immobilized onto a nanocomposite (Fe₃O₄-CS-DAC) fabricated by combining magnetic nanoparticles Fe₃O₄ with chitosan (CS) using polysaccharide macromolecule dialdehyde cellulose (DAC) as the cross-linking agent. Fourier transform infrared spectroscopy, transmission electron microscope, thermogravimetric analysis, and X-ray diffraction characterizations confirmed that the organic–inorganic nanocomposite support modified by DAC was successfully prepared. Enzymology experiments confirmed that high enzyme loading (60.9 mg/g) and 1.7 times specific enzyme activity could be obtained under the optimal immobilization conditions. The stability and reusability of immobilized CRL (Fe₃O₄-CS-DAC-SDS-CRL) were significantly improved simultaneously. Circular dichroism analysis revealed that the active conformation of immobilized CRL was maintained well. Results demonstrated that the inorganic–organic nanocomposite modified by carbohydrate polymer derivatives could be used as an ideal support for enzyme immobilization.

Non-magnetic and magnetically responsive support materials immobilized peroxidases for biocatalytic degradation of emerging dye pollutants-A review

In recent years, the removal of hazardous pollutants from many industries has become a significant challenge for mankind as a growing number of contaminants, including a wide range of organic pollutants, synthetic dyes, and polycyclic aromatic hydrocarbons (PAHs), have inevitably led to an increased anthropogenic impact on the biosphere. Due to the complex aromatic structure, most synthetic dyes show resistance to degrade by the classical approaches, such as coagulation, flotation, adsorption, membrane process, and reverse osmosis. Enzyme-assisted biodegradation of pollutants offers an eco-friendlier and cost-effective alternative to remediate dyes, dyes-based effluents, other toxins, etc. Various plant and microbial oxidoreductase (Horseradish and manganese peroxidase) have recently received more attention for degrading and detoxifying a wide range of dyes either by opening the aromatic ring structure or by precipitation due to their high activity under milder conditions, high substrate specificity, and biodegradable nature. To enhance the efficiency, stability and recyclability, enzymes were immobilized on various support media such as sodium alginate, agarose, chitin/chitosan, polyvinyl alcohol, polyacrylamide, macroporous exchange resins, hydrophobic sol-gels, and nanoporous silica gel, including magnetically separatable media. Among various types of magnetic nanoparticles (MNPs), iron oxide magnetic nanoparticles, such as hematite, magnetite, and maghemite, have gained great attention due to their properties like small size, superparamagnetism, high surface area to volume ratio, and ease of separation for repeated cycles of uses. These carriers can be separated easily and rapidly from the reaction medium by an external magnetic field without being subjected to mechanical stress than centrifugation or filtration. Various methods have been employed for immobilizing oxidoreductase on different media, such as adsorption, covalent binding, entrapment, and encapsulation using different cross-linking agents. Compared to the free enzyme, insolubilized enzymes reduce production costs by enzyme reusability, tolerance to unfavorable environmental conditions, and high catalytic stability. Here, we review various immobilization methods and biocatalytic degradation of emerging dye pollutants, focusing on various non-magnetically and magnetically responsive supports to immobilize peroxidases. Conclusively, magnetically separatable peroxidases show more stability towards extreme temperature and pH conditions and can be used for repeated cycles than free and non-magnetically separatable peroxidase.

Photo-induced adhesive carboxymethyl chitosan-based hydrogels with antibacterial and antioxidant properties for accelerating wound healing

Designing adhesive hydrogel wound dressings with inherent antibacterial and antioxidant properties is desirable to treat cutaneous full-thickness injuries in clinical care. Herein, a series of photo-induced Schiff base crosslinking-based adhesive hydrogels with promising traits are designed and prepared through Diels-Alder (DA) reactions between functional groups-grafted carboxymethyl chitosan (CMCS) and a photo-responsive polyethylene glycol (PEG) crosslinker. The quaternary ammonium and phenol groups in modified CMCS endows hydrogels excellent antibacterial and antioxidant properties. Upon UV (365 nm) irradiation, the generated o-nitrosobenzaldehyde from the photo-isomerization of o-nitrobenzyl in PEG derivative can subsequently crosslink with amino groups on tissue interfaces via Schiff base, endowing the hydrogel with well adhesiveness. Additionally, the hydrogel exhibits good BSA adsorption capacity, cytocompatibility and hemostatic property. The in vivo full-thickness skin defect study on mice indicates that the multi-functional hydrogel with considerable collagen deposition and vascularization capacities can be an effective and promising adhesive dressing for improving wound healing.

Improved catalytic performance of carrier-free immobilized lipase by advanced cross-linked enzyme aggregates technology

The cross-linked enzyme aggregates (CLEAs) are one of the technologies that quickly immobilize the enzyme without a carrier. In this study, ionic liquid with amino group (1-aminopropyl-3-methylimidazole bromide, FIL) was used as the novel functional surface molecule to modify CRL (Candida rugosa lipase, CRL). The enzymatic properties of CRL-FIL-CLEAs were investigated. The activity of CRL-FIL-CLEAs (5.51 U/mg protein) was 1.9 times higher than that of CRL-CLEAs (2.86 U/mg protein) without surface modification. After incubating in a centrifuge tube for 50 min at 60 °C, CRL-FIL-CLEAs still maintained 61% of its initial activity, while the value for CRL-CLEAs was only 22%. After repeated use for five times, compared with the 22% residual activity of CRL-CLEAs, the value of CRL-FIL-CLEAs was 51%. Based on the above results, it was indicated that this method provided a new idea for the effective synthesis of immobilized enzyme.

Recent Advances in Ionic Liquids in Biomedicine

The use of ionic liquids and deep eutectic solvents in biomedical applications has grown dramatically in recent years due to their unique properties and their inherent tunability. This review will introduce ionic liquids and deep eutectics and discuss their biomedical applications, namely solubilization of drugs, creation of active pharmaceutical ingredients, delivery of pharmaceuticals through biological barriers, stabilization of proteins and other nucleic acids, antibacterial agents, and development of new biosensors. Current challenges and future outlooks are discussed, including biocompatibility, the potential impact of the presence of impurities, and the importance of understanding the microscopic interactions in ionic liquids in order to design task-specific solvents.

Magnetic Nanoparticle-Containing Supports as Carriers of Immobilized Enzymes: Key Factors Influencing the Biocatalyst Performance

In this short review (Perspective), we identify key features of the performance of biocatalysts developed by the immobilization of enzymes on the supports containing magnetic nanoparticles (NPs), analyzing the scientific literature for the last five years. A clear advantage of magnetic supports is their easy separation due to the magnetic attraction between magnetic NPs and an external magnetic field, facilitating the biocatalyst reuse. This allows for savings of materials and energy in the biocatalytic process. Commonly, magnetic NPs are isolated from enzymes either by polymers, silica, or some other protective layer. However, in those cases when iron oxide NPs are in close proximity to the enzyme, the biocatalyst may display a fascinating behavior, allowing for synergy of the performance due to the enzyme-like properties shown in iron oxides. Another important parameter which is discussed in this review is the magnetic support porosity, especially in hierarchical porous supports. In the case of comparatively large pores, which can freely accommodate enzyme molecules without jeopardizing their conformation, the enzyme surface ordering may create an optimal crowding on the support, enhancing the biocatalytic performance. Other factors such as surface-modifying agents or special enzyme reactor designs can be also influential in the performance of magnetic NP based immobilized enzymes.

Ionic Liquids for Development of Heterogeneous Catalysts Based on Nanomaterials for Biocatalysis

The development of effective methods of enzyme stabilization is key for the evolution of biocatalytic processes. An interesting approach combines the stabilization process of proteins in ionic liquids and the immobilization of the active phase on the solid support. As a result, stable, active and heterogeneous biocatalysts are obtained. There are several benefits associated with heterogeneous processes, as easy separation of the biocatalyst from the reaction mixture and the possibility of recycling. Accordingly, this work focused on the supported ionic liquid phases as the efficient enzyme stabilization carriers, and their application in both continuous flow and batch biocatalytic processes.

Enhancing bio-catalytic performance of lipase immobilized on ionic liquids modified magnetic polydopamine

In this study, imidazolium-based ionic liquid with [tf₂N]^- as the anion was successfully grafted to magnetic polydopamine nanoparticles (MPDA). The prepared materials were well characterized and used as supports for lipase immobilization. The immobilized lipase (PPL-ILs-MPDA) exhibited excellent activity and stability. The specific activity of PPL-ILs-MPDA was 2.15 and 1.49 folds higher than that of free PPL and PPL-MPDA. In addition, after 10 rounds of reuse, the residual activity of PPL-ILs-MPDA was 86.2 % higher than that of PPL-MPDA (75.4 %). Furthermore, the kinetic assay indicated that the affinity between PPL-ILs-MPDA and substrate had increased. Analysis of the secondary structure using circular dichroism was used to explain the mechanism underlying the improvement in the performance of PPL-ILs-MPDA. In addition, the immobilized lipase can be easily separated from the reaction system with a magnet. The observations regarding the development of new supports for lipase immobilization may provide new ideas regarding further studies in this field.

Different strategies for the lipase immobilization on the chitosan based supports and their applications

Immobilized enzymes have received incredible interests in industry, pharmaceuticals, chemistry and biochemistry sectors due to their various advantages such as ease of separation, multiple reusability, non-toxicity, biocompatibility, high activity and resistant to environmental changes. This review in between various immobilized enzymes focuses on lipase as one of the most practical enzyme and chitosan as a preferred biosupport for lipase immobilization and provides a broad range of studies of recent decade. We highlight several aspects of lipase immobilization on the surface of chitosan support containing various types of lipase and immobilization techniques from physical adsorption to covalent bonding and cross-linking with their benefits and drawbacks. The recent advances and future perspectives that can improve the present problems with lipase and chitosan such as high-price of lipase and low mechanical resistance of chitosan are also discussed. According to the literature, optimization of immobilization methods, combination of these methods with other techniques, physical and chemical modifications of chitosan, co-immobilization and protein engineering can be useful as a solution to overcome the mentioned limitations.

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

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

Immobilization in Ionogel: A New Way to Improve the Activity and Stability of Candida antarctica Lipase B

New Candida antarctica lipase B derivatives with higher activity than the free enzyme were obtained by occlusion in an organogel of an ionic liquid (ionogel) based on the ionic liquid [Omim][PF₆] and polyvinyl chloride. The inclusion of glutaraldehyde as a crosslinker improved the properties of the ionogel, allowing the enzymatic derivative to reach 5-fold higher activity than the free enzyme and also allowing it to be reused at 70 °C. The new methodology allows enzymatic derivatives to be designed by changing the ionic liquid, thus providing a suitable microenvironment for the enzyme. The ionic liquid may act on substrates to increase their local concentration, while reducing water activity in the enzyme's microenvironment. All this allows the activity and selectivity of the enzyme to be improved and greener processes to be developed. The chemical composition and morphology of the ionogel were also studied by scanning electron microscopy-energy dispersive X-ray spectroscopy, finding that porosity, which was related with the chemical composition, was a key factor for the enzyme activity.

Recent Trends in Biomaterials for Immobilization of Lipases for Application in Non-Conventional Media

The utilization of biomaterials as novel carrier materials for lipase immobilization has been investigated by many research groups over recent years. Biomaterials such as agarose, starch, chitin, chitosan, cellulose, and their derivatives have been extensively studied since they are non-toxic materials, can be obtained from a wide range of sources and are easy to modify, due to the high variety of functional groups on their surfaces. However, although many lipases have been immobilized on biomaterials and have shown potential for application in biocatalysis, special features are required when the biocatalyst is used in non-conventional media, for example, in organic solvents, which are required for most reactions in organic synthesis. In this article, we discuss the use of biomaterials for lipase immobilization, highlighting recent developments in the synthesis and functionalization of biomaterials using different methods. Examples of effective strategies designed to result in improved activity and stability and drawbacks of the different immobilization protocols are discussed. Furthermore, the versatility of different biocatalysts for the production of compounds of interest in organic synthesis is also described.

Lipase immobilized on functionalized superparamagnetic few-layer graphene oxide as an efficient nanobiocatalyst for biodiesel production from Chlorella vulgaris bio-oil

BACKGROUND

Microalgae, due to its well-recognized advantages have gained renewed interest as potentially good feedstock for biodiesel. Production of fatty acid methyl esters (FAMEs) as a type of biodiesel was carried out from Chlorella vulgaris bio-oil. Biodiesel was produced in the presence of nano-biocatalysts composed of immobilized lipase on functionalized superparamagnetic few-layer graphene oxide via a transesterification reaction. A hybrid of few-layer graphene oxide and Fe3O4 (MGO) was prepared and characterized. The MGO was functionalized with 3-aminopropyl triethoxysilane (MGO-AP) as well as with a couple of AP and glutaraldehyde (MGO-AP-GA). The Rhizopus oryzae lipase (ROL) was immobilized on MGO and MGO-AP using electrostatic interactions as well as on MGO-AP-GA using covalent bonding. The supports, MGO, MGO-AP, and MGO-AP-GA, as well as nano-biocatalyst, ROL/MGO, ROL/MGO-AP, and ROL/MGO-AP-GA, were characterized using FESEM, VSM, FTIR, and XRD. The few-layer graphene oxide was characterized using AFM and the surface charge of supports was evaluated with the zeta potential technique. The nano-biocatalysts assay was performed with an evaluation of kinetic parameters, loading capacity, relative activity, time-course thermal stability, and storage stability. Biodiesel production was carried out in the presence of nano-biocatalysts and their reusability was evaluated in 5 cycles of transesterification reaction.

RESULTS

The AFM analysis confirmed the few-layer structure of graphene oxide and VSM also confirmed that all supports were superparamagnetic. The maximum loading of ROL (70.2%) was related to MGO-AP-GA. The highest biodiesel conversion of 71.19% achieved in the presence of ROL/MGO-AP-GA. Furthermore, this nano-biocatalyst could maintain 58.77% of its catalytic performance after 5 cycles of the transesterification reaction and was the best catalyst in the case of reusability.

CONCLUSIONS

In this study, the synthesized nano-biocatalyst based on bare and functionalized magnetic graphene oxide was applied and optimized in the process of converting microalgae bio-oil to biodiesel for the first time and compared with bare lipase immobilized on magnetic nanoparticles. Results showed that the loading capacity, kinetic parameters, thermal stability, and storage stability improved by the functionalization of MGO. The biocatalysts, which were prepared via covalent bonding immobilization of enzyme generally, showed better characteristics.

Magnetic multiwalled carbon nanotubes with controlled release of epirubicin: an intravesical instillation system for bladder cancer

Background

Traditional intravesical instillation treatment in bladder cancer has limited efficacy, which results in a high frequency of recurrence.

Purpose

The aim of this study was to report on an epirubicin (EPI)-loaded magnetic multi-walled carbon nanotube (mMWCNTs-EPI) system for intravesical instillation in place of the current formulation.

Methods

The mMWCNTs-EPI system was formulated with carboxylated MWCNTs, Fe₃O₄ magnetic nanoparticles, and EPI. Features and antitumor activity of the system were investigated.

Results

Under the effect of external magnets, the mMWCNTs-EPI system showed sustained release and prolonged retention behavior and better antitumor activity than free EPI. The mMWCNTs-EPI system had higher efficiency in enhancing cytotoxicity and inhibiting proliferation in vitro and in vivo than free EPI. Our studies also revealed the atoxic nature of mMWCNTs.

Conclusion

These findings suggested that mMWCNTs are effective intravesical instillation agents with great potential for clinical application.

A robust nanobiocatalyst based on high performance lipase immobilized to novel synthesised poly(o-toluidine) functionalized magnetic nanocomposite: Sterling stability and application

Herein, as a promising support, a magnetic enzyme nanoformulation have been designed and fabricated by a poly-o-toluidine modification approach. Owing to the magnetic nature and the existence of amine functionalized groups, the as-synthesised poly(o-toluidine) functionalized magnetic nanocomposite (Fe₃O₄@POT) was employed as potential support for Candida rugosa lipase (CRL) immobilization to explore its application in fruit flavour esters synthesis. The morphology and structure of the Fe₃O₄@POT NC were examined through various analytical tools. Hydrolytic activity assays disclose that immobilized lipase demonstrated an activity yield of 120%. It is worth mentioning that CRL#Fe₃O₄@POT showed superior resistance to extremes of temperature and pH and different organic solvents in contrast to free CRL. The magnetic behaviour of the as-synthesised NC was affirmed by alternating gradient magnetometer analysis. It was found to own facile immobilization process, enhanced catalytic performance for the immobilized form which may be stretched to the immobilization of various vital industrial enzymes. Moreover, it retained improved recycling performance. After 10 cycles of repetitive uses, it still possessed around 90% of its initial activity for the hydrolytic reaction, since the enzyme-magnetic nanoconjugate was effortlessly obtained using a magnet from the reaction system. The formulated nanobiocatalyst was selected for the esterification reaction to synthesize the fruit flavour esters, ethyl acetoacetate and ethyl valerate. The immobilized lipase successfully synthesised flavour compounds in aqueous and n-hexane media having significant higher ester yields compared to free enzyme. The present work successfully combines an industrially prominent biocatalyst, CRL, and a novel magnetic nanocarrier, Fe₃O₄@POT, into an immobilized nanoformulation with upgraded catalytic properties which has excellent potential for practical industrial implications.

Design of GO–Ag-functionalized Fe3O4@CS composite for magnetic adsorption of rhodamine B

In this study, a novel magnetic composite (Fe₃O₄@CS/GO/Ag) modified with chitosan (CS), graphene oxide (GO) and Ag nanoparticles (Ag NPs) was successfully prepared as an efficient adsorbent for detection of rhodamine B (RB) combined with a fluorescence technique. The properties of the magnetic composite were confirmed by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and vibrating sample magnetometry. The components of Fe₃O₄@CS/GO/Ag endowed it with excellent extraction performance and convenient operation. The main parameters affecting extraction and desorption efficiency were all investigated systematically. Under the optimized experimental conditions, the proposed method showed linear ranges (0.2–6.0 μg L⁻¹) with R² = 0.9992. The limits of detection (LODs) and quantification (LOQs) were 0.05 and 0.2 μg L⁻¹ (n = 3), respectively. Fe₃O₄@CS/GO/Ag exhibited outstanding extraction efficiency for RB, compared with CS-coated Fe₃O₄ nanoparticles (Fe₃O₄@CS) and GO-modified Fe₃O₄@CS (Fe₃O₄@CS/GO). The applicability of the proposed method was investigated by analyzing four real samples (waste water, soft drink, shampoo, and red pencil) and the spiked recoveries ranged between 94% and 97% with RSD ranging from 3% to 6%, which showed that the proposed method had satisfactory practicability and operability.

A novel magnetic composite modified with chitosan, graphene oxide and Ag nanoparticles, was successfully prepared as an efficient adsorbent for detection of rhodamine B combining with fluorescence technique.

Magnetic-propelled Fe3O4–chitosan carriers enhancel-asparaginase catalytic activity: a promising strategy for enzyme immobilization

Magnetic-propelled carriers comprising magnetic Fe₃O₄–chitosan nanoparticles were immobilized with l-asparaginase (l-ASNase). The enzyme displayed enhanced catalytic activity in a weak magnetic field, and thermal and pH stabilities. The conjugated l-ASNase presented higher thermostability and wider range of pH stability in comparison with those of free l-ASNase. Moreover, the reusability of conjugated l-ASNase significantly improved after immobilization and it retained 60.5% of its initial activity after undergoing 16 cycles. The conjugated l-ASNase maintained more than 50% and 48% initial activity after 4 weeks of storage at 4 °C and room temperature, respectively. Furthermore, we reveal that the activity of conjugated l-ASNase onto magnetic Fe₃O₄–chitosan particles increased by about 3-fold in the weak magnetic field at certain frequencies and flux density compared with that of free l-ASNase. Considering these excellent attributes, the magnetic-propelled mechanism in the transporting and activation of l-ASNase can be used by enhancing the catalytic activity, stability, and efficiency in vital implications for medicinal biotechnology.

A magnetic-propelled carrier comprising chitosan-coated Fe₃O₄ nanoparticles was prepared to enhance the catalytic activity of immobilized l-asparaginase in a weak magnetic field.