Enzyme immobilization: Implementation of nanoparticles and an insight into polystyrene as the contemporary immobilization matrix

Immobilization of cholesterol oxidases on functionalized Silica Nanoparticles for biotransformation of cholesterol and 7-ketocholesterol

Cholesterol oxidation leads to the development of several oxysterols such as 7-ketocholesterol (7KC), which are linked to various age-related conditions. An approach to reduce their toxicity is proposed using enzymes from microbial sources to degrade them. Our earlier studies identified Pseudomonas aeruginosa PseA and Rhodococcus erythropolis MTCC 3951 as potential strains capable of using 7KC as their sole carbon source. These strains produced cholesterol oxidase as the primary enzyme in the degradation pathway. To enhance applicability, cholesterol oxidase (ChOx) enzymes from P. aeruginosa PseA (ChOxP), R. erythropolis MTCC 3951 (ChOxR), and a commercial variant from Streptomyces sp. (ChOxS) were immobilized on silane functionalized silica nanoparticles (SNP) using covalent-coupling methods. The immobilization efficiency was 68 %, 86 %, and 83 % for ChOxP, ChOxR, and ChOxS respectively. The catalytic efficiency of the immobilized enzyme was nearly twice that of the free enzyme, with increased stability across a wide range of temperatures (10-70°C) and pH levels (4.0-9.0), although the optimum pH (7.5) and temperature (30°C) remained unchanged. The nano-immobilized cholesterol oxidases were reusable up to 10 cycles. Further, enzyme immobilization on nanoparticles was confirmed by FTIR, SEM, and TEM. Biotransformation of cholesterol and 7KC using the nanobioconjugates produced pharmaceutically important molecules 4-cholesten-3-one and 4-cholesten-3,7-dione respectively.

The application of chitin materials in enzymatic catalysis: A review

Enzymatic catalysis offers notable advantages, including exceptional catalytic efficiency, selectivity, and the ability to operate under mild conditions. However, its widespread application is hindered by the high costs associated with enzymes and cofactors. Materials-mediated immobilization technology has proven effective in the recycling of enzymes and cofactors. An optimal carrier material for protein immobilization must be non-toxic, biocompatible, and should not compromise the biological activity or structure of the enzymes. Compared to synthetic polymers, chitin is a promising carrier given its low cost, renewability, abundance of functional groups, and notable biocompatibility and biodegradability. Although numerous reviews on chitosan and other polymers for immobilization have been published, few have addressed using chitin as supports. In this review, chitin-based materials mediated enzyme immobilization, the one-step purification and immobilization of enzymes, as well as co-immobilization of enzymes and cofactors were summarized. Particularly, the significance of chitin materials in the field of enzymatic catalysis was emphasized. This study has the potential to open new avenues for immobilized biocatalysts.

Engineering thermostability of industrial enzymes for enhanced application performance

Thermostability is a key factor for the industrial application of enzymes. This review categorizes enzymes by their applications and discusses the importance of engineering thermostability for practical use. It summarizes fundamental theories and recent advancements in enzyme thermostability modification, including directed evolution, semi-rational design, and rational design. Directed evolution uses high-throughput screening to generate random mutations, while semi-rational design combines hotspot identification with screening. Rational design focuses on key residues to enhance stability by improving rigidity, foldability, and reducing aggregation. The review also covers rational strategies like engineering folding energy, surface charge, machine learning methods, and consensus design, along with tools that support these approaches. Practical examples are critically assessed to highlight the benefits and limitations of these strategies. Finally, the challenges and potential contributions of artificial intelligence in enzyme thermostability engineering are discussed.

Recent advances in phytase thermostability engineering towards potential application in the food and feed sectors

This review comprehensively examines the advancements in engineering thermostable phytase through genetic modification and immobilization techniques, focusing on developments from the last seven years. Genetic modifications, especially protein engineering, have enhanced enzyme's thermostability and functionality. Immobilization on various supports has further increased thermostability, with 50-60 % activity retention at higher temperature (more than 50 °C). In the food industry, phytase is used in flour processing and bread making, reducing phytate content by around 70 %, thereby improving nutritional value and mineral bioavailability. In the feed industry, it serves as a poultry feed additive, breaking down phytates to enhance nutrient availability and feed efficiency. The enzyme's robustness at high temperatures makes it valuable in feed processing. The integration of microbial production of phytase with genetically engineered strains followed by carrier free immobilization represents a synergistic approach to fortify enzyme structure and improve thermal stability. These advancement in the development of phytase enzyme capable of withstanding high temperatures, thereby pivotal for industrial utilization.

Enhanced Biodiesel Production with Eversa Transform 2.0 Lipase on Magnetic Nanoparticles

This research investigated the usefulness of magnetic iron oxide nanoparticles (Fe3O4) as a support to immobilize the lipase Eversa Transform 2.0 (ET 2.0) to obtain an active and stable biocatalyst, easily recoverable from the reaction medium for applications in the production of biodiesel. Biodiesel was an alternative fuel composed mainly of fatty acid esters with strong transesterification and esterification capabilities. The study focused on the esterification of oleic acid with ethanol to synthesize ethyl oleate. Magnetic nanoparticles were prepared by coprecipitation, then activated with glutaraldehyde and functionalized with γ-aminopropyltriethoxysilane (APTES). The optimal conditions for immobilizing ET 2.0 were pH 10, 25 mM sodium carbonate buffer, an enzymatic load of 200 U/g, and 1 h of contact time, obtaining 78% yield and enzymatic activity of 205.9 U/g. Postimmobilization evaluation showed that the immobilized enzyme performed better than its free form. Kinetic studies were conducted under these optimized conditions (2-96 h at 150 rpm and 37 °C). The biocatalyst was tested for the synthesis of ethyl oleate using oleic acid as the substrate and ethanol, achieving a conversion of 88.1%. Subsequent recirculation tests maintained approximately 80% conversion until the fourth cycle, confirming the sustainability of ester production. Molecular docking studies revealed that the binding affinity for the enzyme-docked oil composition was estimated at -5.8 kcal/mol, suggesting that the combination of the substrate and lipase was stable and suitable for esterification.

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.

Co-immobilization of crosslinked enzyme aggregates on lysozyme functionalized magnetic nanoparticles for enhancing stability and activity

Surface chemistry of carriers plays a key role in enzyme loading capacity, structure rigidity, and thus catalyze activity of immobilized enzymes. In this work, the two model enzymes of horseradish peroxidase (HRP) and glucose oxidase (GOx) are co-immobilized on the lysozyme functionalized magnetic core-shell nanocomposites (LYZ@MCSNCs) to enhance their stability and activity. Briefly, the HRP and GOx aggregates are firstly formed under the crosslinker of trimesic acid, in which the loading amount and the rigidity of the enzyme can be further increased. Additionally, LYZ easily forms a robust anti-biofouling nanofilm on the surface of SiO2@Fe3O4 magnetic nanoparticles with abundant functional groups, which facilitate chemical crosslinking of HRP and GOx aggregates with minimized inactivation. The immobilized enzyme of HRP-GOx@LYZ@MCSNCs exhibited excellent recovery activity (95.6 %) higher than that of the free enzyme (HRP&GOx). Specifically, 85 % of relative activity was retained after seven cycles, while 73.5 % of initial activity was also remained after storage for 33 days at 4 °C. The thermal stability and pH adaptability of HRP-GOx@LYZ@MCSNCs were better than those of free enzyme of HRP&GOx. This study provides a mild and ecofriendly strategy for multienzyme co-immobilization based on LYZ functionalized magnetic nanoparticles using HRP and GOx as model enzymes.

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.

Magnetic Nanoparticle Support with an Ultra-Thin Chitosan Layer Preserves the Catalytic Activity of the Immobilized Glucose Oxidase

Here, we developed magnetically recoverable biocatalysts based on magnetite nanoparticles coated with an ultra-thin layer (about 0.9 nm) of chitosan (CS) ionically cross-linked by sodium tripolyphosphate (TPP). Excessive CS amounts were removed by multiple washings combined with magnetic separation. Glucose oxidase (GOx) was attached to the magnetic support via the interaction with N-hydroxysuccinimide (NHS) in the presence of carbodiimide (EDC) leading to a covalent amide bond. These steps result in the formation of the biocatalyst for D-glucose oxidation to D-gluconic acid to be used in the preparation of pharmaceuticals due to the benign character of the biocatalyst components. To choose the catalyst with the best catalytic performance, the amounts of CS, TPP, NHS, EDC, and GOx were varied. The optimal biocatalyst allowed for 100% relative catalytic activity. The immobilization of GOx and the magnetic character of the support prevents GOx and biocatalyst loss and allows for repeated use.

Quantifying Bound Proteins on Pegylated Gold Nanoparticles Using Infrared Spectroscopy

Protein-nanoparticle (NP) complexes are nanomaterials that have numerous potential uses ranging from biosensing to biomedical applications such as drug delivery and nanomedicine. Despite their extensive use quantifying the number of bound proteins per NP remains a challenging characterization step that is crucial for further developments of the conjugate, particularly for metal NPs that often interfere with standard protein quantification techniques. In this work, we present a method for quantifying the number of proteins bound to pegylated thiol-capped gold nanoparticles (AuNPs) using an infrared (IR) spectrometer, a readily available instrument. This method takes advantage of the strong IR bands present in proteins and the capping ligands to quantify protein-NP ratios and circumvents the need to degrade the NPs prior to analysis. We show that this method is generalizable where calibration curves made using inexpensive and commercially available proteins such as bovine serum albumin (BSA) can be used to quantify protein-NP ratios for proteins of different sizes and structures.

Proteases immobilized on nanomaterials for biocatalytic, environmental and biomedical applications: Advantages and drawbacks

Proteases have gained significant scientific and industrial interest due to their unique biocatalytic characteristics and broad-spectrum applications in different industries. The development of robust nanobiocatalytic systems by attaching proteases onto various nanostructured materials as fascinating and novel nanocarriers has demonstrated exceptional biocatalytic performance, substantial stability, and ease of recyclability over multiple reaction cycles under different chemical and physical conditions. Proteases immobilized on nanocarriers may be much more resistant to denaturation caused by extreme temperatures or pH values, detergents, organic solvents, and other protein denaturants than free enzymes. Immobilized proteases may present a lower inhibition. The use of non-porous materials in the immobilization prevents diffusion and steric hindrances during the binding of the substrate to the active sites of enzymes compared to immobilization onto porous materials; when using very large or solid substrates, orientation of the enzyme must always be adequate. The advantages and problems of the immobilization of proteases on nanoparticles are discussed in this review. The continuous and batch reactor operations of nanocarrier-immobilized proteases have been successfully investigated for a variety of applications in the leather, detergent, biomedical, food, and pharmaceutical industries. Information about immobilized proteases on various nanocarriers and nanomaterials has been systematically compiled here. Furthermore, different industrial applications of immobilized proteases have also been highlighted in this review.

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.

Application of Immobilized Enzymes in Juice Clarification

Immobilized enzymes are currently being rapidly developed and are widely used in juice clarification. Immobilized enzymes have many advantages, and they show great advantages in juice clarification. The commonly used methods for immobilizing enzymes include adsorption, entrapment, covalent bonding, and cross-linking. Different immobilization methods are adopted for different enzymes to accommodate their different characteristics. This article systematically reviews the methods of enzyme immobilization and the use of immobilized supports in juice clarification. In addition, the mechanisms and effects of clarification with immobilized pectinase, immobilized laccase, and immobilized xylanase in fruit juice are elaborated upon. Furthermore, suggestions and prospects are provided for future studies in this area.

A critical review of enzymes immobilized on chitosan composites: characterization and applications

Enzymes with industrial significance are typically used in biological processes. However, instability, high sensitivity, and impractical recovery are the major drawbacks of enzymes in practical applications. In recent years, the immobilization technology has attracted wide attention to overcoming these restrictions and improving the efficiency of enzyme applications. Chitosan (CS) is a unique functional substance with biocompatibility, biodegradability, non-toxicity, and antibacterial properties. Chitosan composites are anticipated to be widely used in the near future for a variety of purposes, including as supports for enzyme immobilization, because of their advantages. Therefor this review explores the effects of the chitosan's structure, molecular weight, degree of deacetylation on the enzyme immobilized, effect of key factors, and the enzymes immobilized on chitosan based composites for numerous applications, including the fields of biosensor, biomedical science, food industry, environmental protection, and industrial production. Moreover, this study carefully investigates the advantages and disadvantages of using these composites as well as their potential in the future.

Extending the Shelf-Life of Immunoassay-Based Microfluidic Chips through Freeze-Drying Sublimation Techniques

Point-of-care testing (POCT) platforms utilizing immunoassay-based microfluidic chips offer a robust and specific method for detecting target antibodies, demonstrating a wide range of applications in various medical and research settings. Despite their versatility and specificity, the adoption of these immunoassay chips in POCT has been limited by their short shelf-life in liquid environments, attributed to the degradation of immobilized antibodies. This technical limitation presents a barrier, particularly for resource-limited settings where long-term storage and functionality are critical. To address this challenge, we introduce a novel freeze-dry sublimation process aimed at extending the shelf-life of these microfluidic chips without compromising their functional integrity. This study elaborates on the mechanisms by which freeze-drying preserves the bioactivity of the immobilized antibodies, thereby maintaining the chip's performance over an extended period. Our findings reveal significant shelf-life extension, making it possible for these POCT platforms to be more widely adopted and practically applied, especially in settings with limited resources. This research paves the way for more accessible, long-lasting, and effective POCT solutions, breaking down previous barriers to adoption and application.

Magnetically separable laccase-biochar composite enable highly efficient adsorption-degradation of quinolone antibiotics: Immobilization, removal performance and mechanisms

The tremendous potential of hybrid technologies for the elimination of quinolone antibiotics has recently attracted considerable attention. This current work prepared a magnetically modified biochar (MBC) immobilized laccase product named LC-MBC through response surface methodology (RSM), and LC-MBC showed an excellent capacity in the removal of norfloxacin (NOR), enrofloxacin (ENR) and moxifloxacin (MFX) from aqueous solution. The superior pH, thermal, storage and operational stability demonstrated by LC-MBC revealed its potential for sustainable application. The removal efficiencies of LC-MBC in the presence of 1 mM 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) for NOR, ENR and MFX were 93.7 %, 65.4 % and 77.0 % at pH 4 and 40 °C after 48 h reaction, respectively, which were 1.2, 1.3 and 1.3 times higher than those of MBC under the same conditions. The synergistic effect of adsorption by MBC and degradation by laccase dominated the removal of quinolone antibiotics by LC-MBC. Pore-filling, electrostatic, hydrophobic, π-π interactions, surface complexation and hydrogen bonding contributed in the adsorption process. The attacks on the quinolone core and piperazine moiety were involved in the degradation process. This study underscored the possibility of immobilization of laccase on biochar for enhanced remediation of quinolone antibiotics-contaminated wastewater. The proposed physical adsorption-biodegradation system (LC-MBC-ABTS) provided a novel perspective for the efficient and sustainable removal of antibiotics in actual wastewater through combined multi-methods.

Zinc sulfide-chitosan hybrid nanoparticles as a robust surface for immobilization of Sillago sihama α-amylase

In the present study, zinc sulfide-chitosan hybrid nanoparticles synthesized by chemical deposition were used as a matrix for the immobilization of purified α-amylase extracted from Sillago sihama (Forsskal, 1775). In this regard, the size and morphological structure of zinc sulfide-chitosan hybrid nanoparticles before and after the stabilization process were evaluated using FT-IR, DLS methods, as well as SEM and TEM electron microscopy, and EDS analyses. Then, the efficiency of the immobilized enzyme was measured in terms of temperature, optimal pH, stability at the critical temperature, and pH values. Immobilization of α-amylase on zinc sulfide -chitosan hybrid nanoparticles increased the long-term stability, as well as its endurance to critical temperatures and pH values; however, the optimal temperature and pH values of the enzyme were not altered following the immobilization process. The kinetic parameters of the enzyme were also changed during immobilization. Enzyme immobilization increased the K_m, whereas decreased the catalytic efficiency (K_cat / K_m) of the immobilized enzyme compared with the free enzyme. These results are very important as, in most cases, enzyme immobilization reduces the activity and catalytic efficiency of enzymes. The nano-enzyme produced in this study, due to its high temperature, and pH stability, could be a good candidate for industrial applications, especially in the food industry.