Conformational changes of enzymes upon immobilisation

Tuning almond lipase features by the buffer used during immobilization: The apparent biocatalysts stability depends on the immobilization and inactivation buffers and the substrate utilized

The lipase from Prunus dulcis almonds was inactivated under different conditions. At pH 5 and 9, enzyme stability remained similar under the different studied buffers. However, when the inactivation was performed at pH 7, there were some clear differences on enzyme stability depending on the buffer used. The enzyme was more stable in Gly than when Tris was employed for inactivation. Then, the enzyme was immobilized on methacrylate beads coated with octadecyl groups at pH 7 in the presence of Gly, Tris, phosphate and HEPES. Its activity was assayed versus triacetin and S-methyl mandelate. The biocatalyst prepared in phosphate was more active versus S-methyl mandelate, while the other ones were more active versus triacetin. The immobilized enzyme stability at pH 7 depends on the buffer used for enzyme immobilization. The buffer used in the inactivation and the substrate used determined the activity. For example, glycine was the buffer that promoted the lowest or the highest stabilities depending on the substrate used to quantify the activities.

Immobilized chitinase as effective biocatalytic platform for producing bioactive di-N-acetyl chitobiose from recycled chitin food waste

Described is chitinase immobilization on magnetic nanoparticles (MNPs) as biocompatible support for enzymatic production of di-N-acetyl chitobiose from chitin waste. Chitinase immobilization was feasible with an immobilization yield of 88.9 ± 1.6 % with 97.8 ± 1.0 % retention of activity and compared to free enzyme work, immobilization conferred better thermal and storage stability. As practical benefit the attachment to magnetic nanocarriers enabled easy enzyme recovery after repeated application runs and thus sustainable reuse. In fixed state chitinase retained a remarkable 39.7 ± 2.6 % of the starting activity after 16 reaction cycles. Furthermore, immobilized chitinase showed higher catalytic activity than free chitinase in converting shrimp shells and squid-pens chitins into di-N-acetyl chitobiose in a single-step reaction. The final yield of purified compound was 37.0 ± 1.2 % from shrimp shells and 61.1 ± 0.5 % from squid-pens chitin. In conclusion, an efficient MNP-based chitinase immobilization system with the potential for large-scale production was developed.

Recent advances and synergistic effect of bioactive zeolite imidazolate frameworks (ZIFs) for biosensing applications

The rapid developments in the field of zeolitic imidazolate frameworks (ZIFs) in recent years have created unparalleled opportunities for the development of unique bioactive ZIFs for a range of biosensor applications. Integrating bioactive molecules such as DNA, aptamers, and antibodies into ZIFs to create bioactive ZIF composites has attracted great interest. Bioactive ZIF composites have been developed that combine the multiple functions of bioactive molecules with the superior chemical and physical properties of ZIFs. This review thoroughly summarizes the ZIFs as well as the novel strategies for incorporating bioactive molecules into ZIFs. They are used in many different applications, especially in biosensors. Finally, biosensor applications of bioactive ZIFs were investigated in optical (fluorescence and colorimetric) and electrochemical (amperometric, conductometric, and impedance) fields. The surface of ZIFs makes it easier to immobilize bioactive molecules like DNA, enzymes, or antibodies, which in turn enables the construction of cutting-edge, futuristic biosensors.

Unveiling the Detrimental Effect of Glipizide on Structure and Function of Catalase: Spectroscopic, Thermodynamics and Simulation Studies

Free radicals, products of oxidative processes, induce cellular damage linked to diseases like Parkinson's and diabetes due to increased reactive oxygen species (ROS) levels. Catalase, crucial for scavenging ROS, emerges as a therapeutic agent against ailments including atherosclerosis and tumor progression. Its primary function involves breaking down hydrogen peroxide into water and oxygen. Research on catalase-drug interactions reveals structural changes under specific conditions, affecting its activity and cellular antioxidant balance, highlighting its pivotal role in defending against oxidative stress-related diseases. Hence, targeting catalase is considered an effective strategy for controlling ROS-induced cellular damage. This study investigates the interaction between bovine liver catalase and glipizide using spectroscopic and computational methods. It also explores glipizide's effect on catalase activity. More than 20% inhibition of catalase enzymatic activity was recorded in the presence of 50 µM glipizide. To investigate the inhibition of catalase activity by glipizide, we performed a series of binding studies. Glipizide was found to form a complex with catalase with moderate affinity and binding constant in the range of 3.822 to 5.063 × 104 M-1. The binding was spontaneous and entropically favourable. The α-helical content of catalase increased from 24.04 to 29.53% upon glipizide complexation. Glipizide binding does not alter the local environment surrounding the tyrosine residues while a notable decrease in polarity around the tryptophan residues of catalase was recorded. Glipizide interacted with numerous active site residues of catalase including His361, Tyr357, Ala332, Asn147, Arg71, and Thr360. Molecular simulations revealed that the catalase-glipizide complex remained relatively stable in an aqueous environment. The binding of glipizide had a negligible effect on the secondary structure of catalase, and hydrogen bonds persisted consistently throughout the trajectory. These results could aid in the development of glipizide as a potent catalase inhibitor, potentially reducing the impact of reactive oxygen species (ROS) in the human body.

Directed-evolution mutations enhance DNA-binding affinity and protein stability of the adenine base editor ABE8e

Adenine base editors (ABEs), consisting of CRISPR Cas nickase and deaminase, can chemically convert the A:T base pair to G:C. ABE8e, an evolved variant of the base editor ABE7.10, contains eight directed evolution mutations in its deaminase TadA8e that significantly increase its base editing activity. However, the functional implications of these mutations remain unclear. Here, we combined molecular dynamics (MD) simulations and experimental measurements to investigate the role of the directed-evolution mutations in the base editing catalysis. MD simulations showed that the DNA-binding affinity of TadA8e is higher than that of the original deaminase TadA7.10 in ABE7.10 and is mainly driven by electrostatic interactions. The directed-evolution mutations increase the positive charge density in the DNA-binding region, thereby enhancing the electrostatic attraction of TadA8e to DNA. We identified R111, N119 and N167 as the key mutations for the enhanced DNA binding and confirmed them by microscale thermophoresis (MST) and in vivo reversion mutation experiments. Unexpectedly, we also found that the directed mutations improved the thermal stability of TadA8e by ~ 12 °C (Tm, melting temperature) and that of ABE8e by ~ 9 °C, respectively. Our results demonstrate that the directed-evolution mutations improve the substrate-binding ability and protein stability of ABE8e, thus providing a rational basis for further editing optimisation of the system.

Enzyme stability in polymer hydrogel-enzyme hybrid nanocarrier containing phosphorylcholine group

Enzymes are biological catalysts with good biocompatibility and high efficiency and have been widely used in many fields, such as wastewater treatment, biosensors, and the medical industry. However, their inherently low stability under conditions of practical use limits further applications. Zwitterionic polymers possessing a pair of oppositely charged groups in their repeating units can increase protein stability because of their good biocompatibility and high water content. In this study, zwitterionic copolymer nanogels comprising poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-methacrylic acid-N-hydroxy succinimide ester (MNHS)) (PMS) were synthesized via reversible addition-fragmentation chain-transfer polymerization (RAFT). β-Galactosidase (β-gal) was post-modified within zwitterionic polymer nanogels with a covalently-bound spacer and the activity was compared with that of directly immobilized β-gal and free β-gal. Compared with direct immobilization, covalent immobilization with a spacer could reduce the structural change of β-gal, as confirmed by the circular dichroism spectra. Although the activity of β-gal decreased after immobilization, the hybrids of the β-gal immobilized nanogels, termed hybrid nanogel-enzymes, demonstrated superior stability compared to the free enzymes. The hybrid nanogel-enzymes maintained their function against inactivation by organic solvents and proteinases owing to their high water content, anti-biofouling properties, and limited mass transfer. They can also withstand protein aggregation at high temperatures and maintain their activity. Compared to direct immobilization, immobilization with a spacer resulted in a dramatic increase in the enzyme activity and a slight decrease in the stability. These results indicate that polymer nanogels containing phosphorylcholine units are promising materials for enzyme immobilization, expanding the scope of enzyme applications.

Diaminated Cellulose Beads as a Sustainable Support for Industrially Relevant Lipases

Environmentally persistent polystyrene or polyacrylic beads are used as supports in enzyme large-scale bioprocesses, including conversion glucose isomerization for high-fructose corn syrup production, hydrolysis of lactose, and synthesis of active pharmaceutical ingredients. In this paper, we report the development of a novel sustainable and scalable method to produce diaminated cellulose beads (DAB) as highly efficient alternative supports for industrially relevant lipases. Regenerated cellulose beads were grafted with diaminated aliphatic hydrocarbons via periodate oxidation and reductive amination. The oxidation step indicated that aldehyde content can be easily tuned through the reaction time and concentration of reactants. Reductive amination of dialdehyde cellulose was more efficient as the length of the diaminated hydrocarbon compound increased. Morphological analysis of DAB showed that cellulose chemical grafting enabled the preservation of the bead shape and internal structure upon freeze-drying. Enzymatic degradability studies demonstrated that chemical functionalization did not undermine enzyme cellulose hydrolysis. The addition of aminated moieties on cellulose dramatically increased absorption efficiency for all industrially relevant lipases used, reaching 100% for Thermomyces lanuginosus lipase (TLL). Storage and recyclability experiments demonstrated that enzymes were retained and recyclable for at least nine cycles, although the activity gradually declined after each cycle. Medium chain triacylglycerol hydrolysis in a SpinChem reactor using TLL immobilized on 1,6 DAB exhibited higher activity compared to acrylic beads (588 vs 459 U/g) suggesting that biodegradable cellulose-based materials could be a valid and attractive alternative to plastics carriers.

Single-Particle and Single-Molecule Characterization of Immobilized Enzymes: A Multiscale Path toward Optimizing Heterogeneous Biocatalysts

Heterogeneous biocatalysis is highly relevant in biotechnology as it offers several benefits and practical uses. To leverage the full potential of heterogeneous biocatalysts, the establishment of well-crafted protocols, and a deeper comprehension of enzyme immobilization on solid substrates are essential. These endeavors seek to optimize immobilized biocatalysts, ensuring maximal enzyme performance within confined spaces. For this aim, multidimensional characterization of heterogeneous biocatalysts is required. In this context, spectroscopic and microscopic methodologies conducted at different space and temporal scales can inform about the intraparticle enzyme kinetics, the enzyme spatial distribution, and the mass transport issues. In this Minireview, we identify enzyme immobilization, enzyme catalysis, and enzyme inactivation as the three main processes for which advanced characterization tools unveil fundamental information. Recent advances in operando characterization of immobilized enzymes at the single-particle (SP) and single-molecule (SM) levels inform about their functional properties, unlocking the full potential of heterogeneous biocatalysis toward biotechnological applications.

Switchable CO2-Responsive Janus Nanoparticle for Lipase Catalysis in Pickering Emulsion

The use of convertible immobilized enzyme carriers is crucial for biphasic catalytic reactions conducted in Pickering emulsions. However, the intense mechanical forces during the conversion process lead to enzyme leakage, affecting the stability of the immobilized enzymes. In this study, a CO2-responsive switchable Janus (CrSJ) nanoparticle (NP) was developed using silica NP, with one side featuring aldehyde groups and the other side adsorbing N,N-dimethyldodecylamine. A switchable Pickering emulsion catalytic system for biphasic interface reactions was prepared by covalently immobilizing lipase onto the CrSJ NPs. The CO2-responsive nature of the CrSJ NPs allowed for rapid conversion of the Pickering emulsion, and covalent immobilization substantially reduced lipase leakage while enhancing the stability of the immobilization during the conversion process. Impressively, after repeated transformations, the Pickering emulsion still maintains its original structure. Following 10 consecutive cycles of esterification and hydrolysis reactions, the immobilized enzyme's activity remains at 77.7 and 79.5% of its initial activity, respectively. The Km of the CrSJ catalytic system showed no significant change compared to the free enzyme, while its Vmax values were 1.2 and 1.6 times that of the free enzyme in esterification and hydrolysis reactions, respectively.

In Situ Preparation of Tannic Acid-Modified Poly(N-isopropylacrylamide) Hydrogel Coatings for Boosting Cell Response

The improvement of the capability of poly(N-isopropylacrylamide) (PNIPAAm) hydrogel coating in cell adhesion and detachment is critical to efficiently prepare cell sheets applied in cellular therapies and tissue engineering. To enhance cell response on the surface, the amine group-modified PNIPAAm (PNIPAAm-APTES) nanohydrogels were synthesized and deposited spontaneously on tannic acid (TA)-modified polyethylene (PE) plates. Subsequently, TA was introduced onto PNIPAAm-APTES nanohydrogels to fabricate coatings composed of TA-modified PNIPAAm-APTES (PNIPAAm-APTES-TA). Characterization techniques, including TEM, SEM, XPS, and UV-Vis spectroscopy, confirmed the effective deposition of hydrogels of PNIPAAm as well as the morphologies, content of chemical bonding-TA, and stability of various coatings. Importantly, the porous hydrogel coatings exhibited superhydrophilicity at 20 °C and thermo-responsive behavior. The fluorescence measurement demonstrated that the coating's stability effectively regulated protein behavior, influencing cell response. Notably, cell response tests revealed that even without precise control over the chain length/thickness of PNIPAAm during synthesis, the coatings enhanced cell adhesion and detachment, facilitating efficient cell culture. This work represented a novel and facile approach to preparing bioactive PNIPAAm for cell culture.

Enzymatic Nanomotors Surviving Harsh Conditions Enabled by Metal Organic Frameworks Encapsulation

Enzyme-driven micro/nanomotors (MNMs) have demonstrated potentials in the biomedical field because of their excellent biocompatibility, versatility, and fuel bioavailability. However, the fragility of enzymes limits their practical application, because of their susceptibility to denaturation and degradation in realistic scenarios. Herein, a simple yet versatile and effective approach is reported to preserve the enzymatic activity and propulsion capability of enzymatic MNMs under various harsh conditions using metal organic frameworks (MOFs) as a protective shell. Urease can be encapsulated within the exoskeleton of zeolitic imidazolate framework-8 (ZIF-8) via biomimetic mineralization to form ZIF-8@urease (ZU-I) nanomotors that exhibit self-propulsion in the presence of urea. When exposed to harsh conditions, including high temperature, presence of proteases, and organic solvents, the ZU-I nanomotors still maintained their activity and mobility, whereas ZIF-8 with externally modified urease (ZU-O) nanomotors with externally modified urease as a control rapidly lost their motion capabilities owing to the inactivation of urease. Furthermore, ZU-I nanomotors exhibit effectively enhanced diffusion within the small intestine fluid, achieving a fourfold higher mucus penetration than the ZU-O nanomotors. The results highlight the effectiveness of using MOFs as protective shells for enzyme nano-engines, which can greatly advance the practical applications of enzymatic MNMs under realistic conditions, especially for biomedical purpose.

DNA-Directed Assembly of Hierarchical MOF-Cellulose Nanofiber Microbioreactors with "Branch-Fruit" Structures

Assembling metal-organic frameworks (MOFs) into ordered multidimensional porous superstructures promises the encapsulation of enzymes for heterogeneous biocatalysts. However, the full potential of this approach has been limited by the poor stability of enzymes and the uncontrolled assembly of MOF nanoparticles onto suitable supports. In this study, a novel and exceptionally robust Ni-imidazole-based MOF was synthesized in water at room temperature, enabling in situ enzyme encapsulation. Based on this MOF platform, we developed a DNA-directed assembly strategy to achieve the uniform placement of MOF nanoparticles onto bacterial cellulose nanofibers, resulting in a distinctive "branch-fruit" structure. The resulting hybrid materials demonstrated remarkable versatility across various catalytic systems, accommodating natural enzymes, nanoenzymes, and multienzyme cascades, thus showcasing enormous potential as universal microbioreactors. Furthermore, the hierarchical composites facilitated rapid diffusion of the bulky substrate while maintaining the enzyme stability, with ∼3.5-fold higher relative activity compared to the traditional enzyme@MOF immobilized in bacterial cellulose nanofibers.

Biomimetic Mineralization of Large Enzymes Utilizing a Stable Zirconium-Based Metal-Organic Frameworks

Enzymes are natural catalysts for a wide range of metabolic chemical transformations, including selective hydrolysis, oxidation, and phosphorylation. Herein, we demonstrate a strategy for the encapsulation of enzymes within a highly stable zirconium-based metal-organic framework. UiO-66-F4 was synthesized under mild conditions using an enzyme-compatible amino acid modulator, serine, at a modest temperature in an aqueous solution. Enzyme@UiO-66-F4 biocomposites were then formed by an in situ encapsulation route in which UiO-66-F4 grows around the enzymes and, consequently, provides protection for the enzymes. A range of enzymes, namely, lysozyme, horseradish peroxidase, and amano lipase, were successfully encapsulated within UiO-66-F4. We further demonstrate that the resulting biocomposites are stable under conditions that could denature many enzymes. Horseradish peroxidase encapsulated within UiO-66-F4 maintained its biological activity even after being treated with the proteolytic enzyme pepsin and heated at 60 °C. This strategy expands the toolbox of potential metal-organic frameworks with different topologies or functionalities that can be used as enzyme encapsulation hosts. We also demonstrate that this versatile process of in situ encapsulation of enzymes under mild conditions (i.e., submerged in water and at a modest temperature) can be generalized to encapsulate enzymes of various sizes within UiO-66-F4 while protecting them from harsh conditions (i.e., high temperatures, contact with denaturants or organic solvents).

Immobilization of l-asparaginase on chitosan nanoparticles for the purpose of long-term application

Asparaginase holds significant commercial value as an enzyme in the food and pharmaceutical industries. This study examined the optimum and practical use of the l-asparaginase derived from Pseudomonas aeruginosa HR03. Specifically, the study focused on the effectiveness of the stabilized enzyme when applied to chitosan nanoparticles. The structure, size, and morphology of chitosan nanoparticles were evaluated in relation to the immobilization procedure. This assessment involved the use of several analytical techniques, including FT-IR, DLS, SEM, TEM, and EDS analysis. Subsequently, the durability of the enzyme that has been stabilized was assessed by evaluating its effectiveness under extreme temperatures of 60 and 70 °C, as well as at pH values of 3 and 12. The findings indicate that incorporating chitosan nanoparticles led to enhanced immobilization of the l-asparaginase enzyme. This improvement was observed in terms of long-term stability, stability under crucial temperature and pH conditions, as well as thermal stability. In addition, the optimum temperature increased from 40 to 50 °C, and the optimum pH increased from 8 to 9. Enzyme immobilization led to an increase in Km and a decrease in kcat compared to its free counterpart. Because of its enhanced long-term stability, l-asparaginase immobilization on chitosan nanoparticles may be a potential choice for use in industries that rely on l-asparaginase enzymes, particularly the pharmaceutical and food industries.

β-Glucosidase on clay minerals: Structure and function in the synthesis of octyl glucoside

β-Glucosidase is a biological macromolecule that catalyzes the hydrolysis of various glycosides and oligosaccharides. It may also be used to catalyze the synthesis of glycosides under suitable conditions. Carrier-bound β-glucosidase can enhance the enzymatic activity in the synthesis of glycosides in organic solvent solutions, although the molecular mechanism regulating activity is yet unknown. This study investigated the impact of utilizing montmorillonite (Mmt), attapulgite (Attp), and kaolinite (Kao) as carriers on the activity of β-glucosidase from Prunus dulcis (PdBg). When Attp was used as carriers, the molecular dynamic (MD) simulations found the distance between pNPG and the active site residues E183 and E387 was minimally impacted by the adsorptions, hence PdBg maintained about 81.3 ± 0.89 % of its native activity. Out of the three clay minerals, the relative activity of PdBg loaded on Mmt was the lowest because of the highest electrostatic energy. The substrate channel of PdBg on Kao is directed towards the surface, limiting the accessibility of substrates. Secondary structure and conformation studies revealed that the conformational stability of PdBg in solvent solutions was enhanced by coupling to Attp. Unlike dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF) and 1,2-dimethoxyethane (DME), tert-butanol (t-BA) did not penetrate into the active site of PdBg interfering with its binding to the substrate. The maximum yield of n-octyl-β-glucoside (OGP) synthesis catalyzed by Attp-immobilized PdBg reached 48.3 %.

Polydopamine modified cellulose nanocrystals (CNC) for efficient cellulase immobilization towards advanced bamboo fiber flexibility and tissue softness

Herein, a green facile approach to improve the flexibility of unbleached bamboo kraft pulp (UBKP) via an immobilized enzyme technology is proposed. Polydopamine (PDA) acts as versatile modification and coating materials of cellulose nanocrystals (CNC) for assembling versatile bio-carriers (PDA@CNC). Cellulase biomacromolecules are efficiently immobilized on PDA@CNC to form cellulase@PDA@CNC nanocomposites. The relative enzyme activity, temperature/pH tolerance, and storage stability of cellulase were significantly improved after immobilization. The degree of polymerization treated UBKP decreased by 5.42 % (25 U/g pulp) compared to the control sample. The flexibility of treated fibers was 6.61 × 1014/(N·m2), which was 96.93 % higher (25 U/g) compared to the control and 3.88 times higher than that of the blank fibers. Cellulase@PDA@CNC performs excellent accessibility to fiber structure and induces high degree of fibrillation and hydrolysis of UBKP fibers, which contributes high softness of obtained tissue handsheets. The bio-carrier PDA@CNC within paper framework may further enhance tissue tensile strength. This study proposes a practical and environmentally friendly immobilization approach of cellulase@PDA@CNC for improving the hydrolysis efficiency and flexibility of UBKP fibers, which provides the possibility to maintain the strength of tissue paper while improving its softness, thus broadening the high-value application of immobilized enzyme technology in tissue production.

Cellulase immobilization to enhance enzymatic hydrolysis of lignocellulosic biomass: An all-inclusive review

Cellulase-mediated lignocellulosic biorefinery plays a crucial role in the production of high-value biofuels and chemicals, with enzymatic hydrolysis being an essential component. The advent of cellulase immobilization has revolutionized this process, significantly enhancing the efficiency, stability, and reusability of cellulase enzymes. This review offers a thorough analysis of the fundamental principles underlying immobilization, encompassing various immobilization approaches such as physical adsorption, covalent binding, entrapment, and cross-linking. Furthermore, it explores a diverse range of carrier materials, including inorganic, organic, and hybrid/composite materials. The review also focuses on emerging approaches like multi-enzyme co-immobilization, oriented immobilization, immobilized enzyme microreactors, and enzyme engineering for immobilization. Additionally, it delves into novel carrier technologies like 3D printing carriers, stimuli-responsive carriers, artificial cellulosomes, and biomimetic carriers. Moreover, the review addresses recent obstacles in cellulase immobilization, including molecular-level immobilization mechanism, diffusion limitations, loss of cellulase activity, cellulase leaching, and considerations of cost-effectiveness and scalability. The knowledge derived from this review is anticipated to catalyze the evolution of more efficient and sustainable biocatalytic systems for lignocellulosic biomass conversion, representing the current state-of-the-art in cellulase immobilization techniques.

A comprehensive evaluation of arginine and its derivatives as protein formulation stabilizers

Arginine and its derivatives (such as arginine ethyl ester and acetyl arginine) have varying degrees of protein aggregation suppressor effect across different protein solutions. To understand this performance ambiguity, we evaluated the activity of arginine, acetyl arginine, and arginine ethyl ester for aggregation suppressor effect against human intravenous immunoglobulin G (IgG) solution at pH 4.8. Both arginine and its cationic derivative arginine ethyl ester in their hydrochloride salt forms significantly reduced the colloidal and conformational stability (reduced kd and Tm) of IgG. Consequently, the monomer content was decreased with an increase in subvisible particulates after agitation or thermal stress. Furthermore, compared to arginine, arginine ethyl ester with one more cationic charge and hydrochloride salt form readily precipitated IgG at temperatures higher than 25 °C. On the contrary, acetyl arginine, which mostly exists in a neutral state at pH 4.8, efficiently suppressed the formation of subvisible particles retaining a high amount of monomer owing to its higher colloidal and conformational stability. Concisely, the charged state of additives significantly impacts protein stability. This study demonstrated that contrary to popular belief, arginine and its derivatives may either enhance or suppress protein aggregation depending on their net charge and concentration.

Real-Time Optical Tracking of Protein Corona Formation on Single Nanoparticles in Serum

The formation of a protein corona, where proteins spontaneously adhere to the surface of nanomaterials in biological environments, leads to changes in their physicochemical properties and subsequently affects their intended biomedical functionalities. Most current methods to study protein corona formation are ensemble-averaging and either require fluorescent labeling, washing steps, or are only applicable to specific types of particles. Here we introduce real-time all-optical nanoparticle analysis by scattering microscopy (RONAS) to track the formation of protein corona in full serum, at the single-particle level, without any labeling. RONAS uses optical scattering microscopy and enables real-time and in situ tracking of protein adsorption on metallic and dielectric nanoparticles with different geometries directly in blood serum. We analyzed the adsorbed protein mass, the affinity, and the kinetics of the protein adsorption at the single particle level. While there is a high degree of heterogeneity from particle to particle, the predominant factor in protein adsorption is surface chemistry rather than the underlying nanoparticle material or size. RONAS offers an in-depth understanding of the mechanisms related to protein coronas and, thus, enables the development of strategies to engineer efficient bionanomaterials.

Immobilization of Lipases on Chitosan Hydrogels Improves Their Stability in the Presence of the Products of Triglyceride Oxidation

A significant bottleneck for the industrial application of lipases stems from their poor stability in the presence of commercial triglycerides. This is mainly due to the inactivating effect of the products of triglyceride oxidation (PTO), which are usually produced when oils and fats, being imported from far countries, are stored for long periods. In this study, the immobilization of a lipase from Candida rugosa on chitosan hydrogels has been carried out following two alternative approaches based on the enzyme adsorption and entrapment to increase the lipase stability under the operating conditions that are typical of oleochemical transformations. The effect of model compounds representing different classes of PTO on a lipase has been studied to optimize the enzyme immobilization method. Particular attention has been devoted to the characterization of the inactivating effect of PTO in nonaqueous media, which are adopted for most industrial applications of lipases.

Easy and Versatile Technique for the Preparation of Stable and Active Lipase-Based CLEA-like Copolymers by Using Two Homofunctional Cross-Linking Agents: Application to the Preparation of Enantiopure Ibuprofen

An easy and versatile method was designed and applied successfully to obtain access to lipase-based cross-linked-enzyme aggregate-like copolymers (CLEA-LCs) using one-pot, consecutive cross-linking steps using two types of homobifunctional cross-linkers (glutaraldehyde and putrescine), mediated with amine activation through pH alteration (pH jump) as a key step in the process. Six lipases were utilised in order to assess the effectiveness of the technique, in terms of immobilization yields, hydrolytic activities, thermal stability and application in kinetic resolution. A good retention of catalytic properties was found for all cases, together with an important thermal and storage stability improvement. Particularly, the CLEA-LCs derived from Candida rugosa lipase showed an outstanding behaviour in terms of thermostability and capability for catalysing the enantioselective hydrolysis of racemic ibuprofen ethyl ester, furnishing the eutomer (S)-ibuprofen with very high conversion and enantioselectivity.

Grafting Strategies of Oxidation-Prone Coiled-Coil Peptides for Protein Capture in Bioassays: Impact of Orientation and the Oxidation State

Many biomedical and biosensing applications require functionalization of surfaces with proteins. To this end, the E/K coiled-coil peptide heterodimeric system has been shown to be advantageous. First, Kcoil peptides are covalently grafted onto a given surface. Ecoil-tagged proteins can then be non-covalently captured via a specific interaction with their Kcoil partners. Previously, oriented Kcoil grafting was achieved via thiol coupling, using a unique Kcoil with a terminal cysteine residue. However, cysteine-terminated Kcoil peptides are hard to produce, purify, and oxidize during storage. Indeed, they tend to homodimerize and form disulfide bonds via oxidation of their terminal thiol group, making it impossible to later graft them on thiol-reactive surfaces. Kcoil peptides also contain multiple free amine groups, available for covalent coupling through carbodiimide chemistry. Grafting Kcoil peptides on surfaces via amine coupling would thus guarantee their immobilization regardless of their terminal cysteine's oxidation state, at the expense of the control over their orientation. In this work, we compare Kcoil grafting strategies for the subsequent capture of Ecoil-tagged proteins, for applications such as surface plasmon resonance (SPR) biosensing and cell culture onto protein-decorated substrates. We compare the "classic" thiol coupling of cysteine-terminated Kcoil peptides to the amine coupling of (i) monomeric Kcoil and (ii) dimeric Kcoil-Kcoil linked by a disulfide bond. We have observed that SPR biosensing performances relying on captured Ecoil-tagged proteins were similar for amine-coupled dimeric Kcoil-Kcoil and thiol-coupled Kcoil peptides, at the expense of higher Ecoil-tagged protein consumption. For cell culture applications, Ecoil-tagged growth factors captured on amine-coupled monomeric Kcoil signaled through cell receptors similarly to those captured on thiol-coupled Kcoil peptides. Altogether, while oriented thiol coupling of cysteine-terminated Kcoil peptides remains the most reliable and versatile platform for Ecoil-tagged protein capture, amine coupling of Kcoil peptides, either monomeric or dimerized through a cysteine bond, can offer a good alternative when the challenges and costs associated with the production of monomeric cysteine-tagged Kcoil are too dissuasive for the application.

Design of a 3D Amino-Functionalized Rice Husk Ash Nano-Silica/Chitosan/Alginate Composite as Support for Laccase Immobilization

Recycling of agro-industrial waste is one of the major issues addressed in recent years aimed at obtaining products with high added value as a future alternative to traditional ones in the per-spective of a bio-based and circular economy. One of the most produced wastes is rice husk and it is particularly interesting because it is very rich in silica, a material with a high intrinsic value. In the present study, a method to extract silica from rice husk ash (RHA) and to use it as a carrier for the immobilization of laccase from Trametes versicolor was developed. The obtained mesoporous nano-silica was characterized by X-ray diffraction (XRD), ATR-FTIR spectroscopy, Scanning Elec-tron Microscopy (SEM), and Energy Dispersive X-ray spectroscopy (EDS). A nano-silica purity of about 100% was found. Nano-silica was then introduced in a cross-linked chitosan/alginate scaffold to make it more easily recoverable after reuse. To favor laccase immobilization into the composite scaffold, functionalization of the nano-silica with (γ-aminopropyl) triethoxysilane (APTES) was performed. The APTES/RHA nano-silica/chitosan/alginate (ARCA) composite al-lowed to obtain under mild conditions (pH 7, room temperature, 1.5 h reaction time) a robust and easily reusable solid biocatalyst with 3.8 U/g of immobilized enzyme which maintained 50% of its activity after six reuses. The biocatalytic system, tested for syringic acid bioremediation, was able to totally oxidize the contaminant in 24 h.

Advances in immobilization of phytases and their application

The review describes the advances in the phytase immobilization for the past decade and their biotechnological applications. Different approaches for phytase immobilization are described including the process using organic and inorganic matrices and microbial cells, as well as nanostructures of various nature. Moreover, the immobilization of phytase-producing microbial cells and the use of cross-linked phytase aggregates have been under consideration. A detailed classification of various carriers for immobilization of phytases and the possibility of their applications are presented. A particular attention is drawn to a breakthrough approach of biotechnological significance to the design of microencapsulation of bacterial phytase from Obesumbacterium proteus in the recombinant extremophile of Yarrowia lipolytica.

Enzyme immobilization studied through molecular dynamic simulations

In recent years, simulations have been used to great advantage to understand the structural and dynamic aspects of distinct enzyme immobilization strategies, as experimental techniques have limitations in establishing their impact at the molecular level. In this review, we discuss how molecular dynamic simulations have been employed to characterize the surface phenomenon in the enzyme immobilization procedure, in an attempt to decipher its impact on the enzyme features, such as activity and stability. In particular, computational studies on the immobilization of enzymes using i) nanoparticles, ii) self-assembled monolayers, iii) graphene and carbon nanotubes, and iv) other surfaces are covered. Importantly, this thorough literature survey reveals that, while simulations have been primarily performed to rationalize the molecular aspects of the immobilization event, their use to predict adequate protocols that can control its impact on the enzyme properties is, up to date, mostly missing.

Thermally Stable and Reusable Silica and Nano-Fructosome Encapsulated CalB Enzyme Particles for Rapid Enzymatic Hydrolysis and Acylation

This study reports the preparation of silica-coated and nano-fructosome encapsulated Candida antarctica lipase B particles (CalB@NF@SiO₂) and a demonstration of their enzymatic hydrolysis and acylation. CalB@NF@SiO₂ particles were prepared as a function of TEOS concentration (3-100 mM). Their mean particle size was 185 nm by TEM. Enzymatic hydrolysis was performed to compare catalytic efficiencies of CalB@NF and CalB@NF@SiO₂. The catalytic constants (K_m, V_max, and K_cat) of CalB@NF and CalB@NF@SiO₂ were calculated using the Michaelis-Menten equation and Lineweaver-Burk plot. Optimal stability of CalB@NF@SiO₂ was found at pH 8 and a temperature of 35 °C. Moreover, CalB@NF@SiO₂ particles were reused for seven cycles to evaluate their reusability. In addition, enzymatic synthesis of benzyl benzoate was demonstrated via an acylation reaction with benzoic anhydride. The efficiency of CalB@NF@SiO₂ for converting benzoic anhydride to benzyl benzoate by the acylation reaction was 97%, indicating that benzoic anhydride was almost completely converted to benzyl benzoate. Consequently, CalB@NF@SiO₂ particles are better than CalB@NF particles for enzymatic synthesis. In addition, they are reusable with high stability at optimal pH and temperature.

Immobilized biocatalyst engineering: Biocatalytic tool to obtain attractive enzymes for industry

Biocatalysis can improve current bioprocesses by identifying or improving enzymes that withstand harsh and unnatural operating conditions. Immobilized Biocatalyst Engineering (IBE) is a novel strategy integrating protein engineering and enzyme immobilization as a single workflow. Using IBE, it is possible to obtain immobilized biocatalysts whose soluble performance would not be selected. In this work, Bacillus subtilis lipase A (BSLA) variants obtained through IBE were characterized as soluble and immobilized biocatalysts, and how the interactions with the support affect their structure and catalytic performance were analyzed using intrinsic protein fluorescence. Variant P5G3 (Asn89Asp, Gln121Arg) showed a 2.6-fold increased residual activity after incubation at 76 °C compared to immobilized wild-type (wt) BSLA. On the other hand, variant P6C2 (Val149Ile) showed 4.4 times higher activity after incubation in 75 % isopropyl alcohol (36 °C) compared to Wt_BSLA. Furthermore, we studied the advancement of the IBE platform by performing synthesis and immobilizing the BSLA variants using a cell-free protein synthesis (CFPS) approach. The observed differences in immobilization performance, high temperature, and solvent resistance between the in vivo-produced variants and Wt_BSLA were confirmed for the in vitro synthesized enzymes. These results open the door for designing strategies integrating IBE and CFPS to generate and screen improved immobilized enzymes from genetic diversity libraries. Furthermore, it was confirmed that IBE is a platform that can be used to obtain improved biocatalysts, especially those with an unremarkable performance as soluble biocatalysts, which wouldn't be selected for immobilization and further development for specific applications.

Genipin and glutaraldehyde based laccase two-layers immobilization with improved properties: New biocatalysts with high potential for enzymatic removal of trace organic contaminants

This research proposes the preparation of a two-layer laccase biocatalyst using genipin or/and glutaraldehyde as cross-linking agents. The multilayer biocatalysts were prepared using different combinations of genipin and glutaraldehyde in the individual preparation of the first and second laccase layers. First, chitosan was treated with genipin or glutaraldehyde, followed by the immobilization of the first laccase layer to form a single-layer biocatalyst. Then, the immobilized laccases were coated once again with genipin or glutaraldehyde, and a new laccase layer was immobilized onto the system, resulting in the final two-layer biocatalyst. Compared to the single-layer biocatalysts, catalytic activity increased 1.7- and 3.4-fold when glutaraldehyde coating was used to prepare the second laccase layer. However, adding a second layer did not always produce more active biocatalysts, since the two-layer biocatalysts prepared with genipin (GenLacGenLac and GluLacGenLac) presented a decrease in activity of 65% and 28%, respectively. However, these two-layer biocatalysts prepared with genipin maintained 100% of their initial activity after 5 cycles of ABTS oxidation. Nevertheless, the two-layer, genipin-coated biocatalyst resulted in a higher removal of trace organic contaminants, since it removed 100% of mefenamic acid and 66% of acetaminophen, compared with the glutaraldehyde-coated biocatalyst, which removed 20% of mefenamic acid, and 18% of acetaminophen.

A comprehensive review on the potential of microbial enzymes in multipollutant bioremediation: Mechanisms, challenges, and future prospects

Industrialization and other human activity represent significant environmental hazards. Toxic contaminants can harm a comprehensive platform of living organisms in their particular environments. Bioremediation is an effective remediation process in which harmful pollutants are eliminated from the environment using microorganisms or their enzymes. Microorganisms in the environment often create a variety of enzymes that can eliminate hazardous contaminants by using them as a substrate for development and growth. Through their catalytic reaction mechanism, microbial enzymes may degrade and eliminate harmful environmental pollutants and transform them into non-toxic forms. The principal types of microbial enzymes which can degrade most hazardous environmental contaminants include hydrolases, lipases, oxidoreductases, oxygenases, and laccases. Several immobilizations, genetic engineering strategies, and nanotechnology applications have been developed to improve enzyme performance and reduce pollution removal process costs. Until now, the practically applicable microbial enzymes from various microbial sources and their ability to degrade multipollutant effectively or transformation potential and mechanisms are unknown. Hence, more research and further studies are required. Additionally, there is a gap in the suitable approaches considering toxic multipollutants bioremediation using enzymatic applications. This review focused on the enzymatic elimination of harmful contaminants in the environment, such as dyes, polyaromatic hydrocarbons, plastics, heavy metals, and pesticides. Recent trends and future growth for effectively removing harmful contaminants by enzymatic degradation are also thoroughly discussed.

Probing the toxic effect of quinoline to catalase and superoxide dismutase by multispectral method

Quinoline is a common nitrogen heterocyclic aromatic hydrocarbon with high water solubility. Studies have shown that quinoline can be teratogenic, carcinogenic and mutagenic. And Hepatocytes are the target cell of quinoline, which contain a large number of mitochondria and are related to cell function and the balance of reactive oxygen species (ROS). However, the research on the effect of quinoline on hepatocyte damage and anti-oxidation system is still unclear. Through the means of multispectral experiments, it is concluded that quinoline can affect the catalase (CAT) and superoxide dismutase (SOD), change their structure and affect their activity. The binding mode and binding site of quinoline to CAT/SOD were analyzed by isothermal calorimetric titration (ITC) and Molecular Operating Environment (MOE). In molecular docking simulation, the binding site of quinoline-CAT system is close to the active site, and affect the microenvironment of Tyr 357. This may be the reason why quinoline affects CAT activity and synchronous fluorescence (Δλ = 15 nm). This study demonstrated that quinoline has a great effect on CAT, which may affect the intracellular ROS balance and become a potential way to cause hepatocyte damage.

Bioinspired Framework Catalysts: From Enzyme Immobilization to Biomimetic Catalysis

Enzymatic catalysis has fueled considerable interest from chemists due to its high efficiency and selectivity. However, the structural complexity and vulnerability hamper the application potentials of enzymes. Driven by the practical demand for chemical conversion, there is a long-sought quest for bioinspired catalysts reproducing and even surpassing the functions of natural enzymes. As nanoporous materials with high surface areas and crystallinity, metal-organic frameworks (MOFs) represent an exquisite case of how natural enzymes and their active sites are integrated into porous solids, affording bioinspired heterogeneous catalysts with superior stability and customizable structures. In this review, we comprehensively summarize the advances of bioinspired MOFs for catalysis, discuss the design principle of various MOF-based catalysts, such as MOF-enzyme composites and MOFs embedded with active sites, and explore the utility of these catalysts in different reactions. The advantages of MOFs as enzyme mimetics are also highlighted, including confinement, templating effects, and functionality, in comparison with homogeneous supramolecular catalysts. A perspective is provided to discuss potential solutions addressing current challenges in MOF catalysis.

Research Progress and Trends on Utilization of Lignocellulosic Residues as Supports for Enzyme Immobilization via Advanced Bibliometric Analysis

Lignocellulosic biomasses are used in several applications, such as energy production, materials, and biofuels. These applications result in increased consumption and waste generation of these materials. However, alternative uses are being developed to solve the problem of waste generated in the industry. Thus, research is carried out to ensure the use of these biomasses as enzymatic support. These surveys can be accompanied using the advanced bibliometric analysis tool that can help determine the biomasses used and other perspectives on the subject. With this, the present work aims to carry out an advanced bibliometric analysis approaching the main studies related to the use of lignocellulosic biomass as an enzymatic support. This study will be carried out by highlighting the main countries/regions that carry out productions, research areas that involve the theme, and future trends in these areas. It was observed that there is a cooperation between China, USA, and India, where China holds 28.07% of publications in this area, being the country with the greatest impact in the area. Finally, it is possible to define that the use of these new supports is a trend in the field of biotechnology.

Hierarchically-structured laccase@Ni3(PO4)2 hybrid nanoflowers for antibiotic degradation: Application in real wastewater effluent and toxicity evaluation

Laccase@Ni₃(PO₄)₂ hybrid nanoflowers (HNFs) were prepared by the anisotropic growth of biomineralized nickel phosphate. The immobilization yield was 77.5 ± 3.6 %, and the immobilized enzyme retained 50 % of its initial activity after 18 reusability cycles. The immobilized and free enzymes lost 80 % of their activity after 18 and 6 h incubation in municipal wastewater effluent (MWWE), respectively. The increase in α-helix content (8 %) following immobilization led to a more rigid enzyme structure, potentially contributing to its improved stability. The removal of ciprofloxacin from MWWE by laccase@Ni₃(PO₄)₂·HNFs/p-coumaric acid oxidation system was optimized using a Box-Behnken design. Under the optimized conditions [initial laccase activity (0.05 U mL^-1), the concentration of p-coumaric acid (2.9 mM), and treatment time (4.9 h)], the biocatalyst removed 90 % of ciprofloxacin (10 mg L^-1) from MWWE. The toxicity of ciprofloxacin against some G⁺ and G^- bacteria was reduced by 35-70 %, depending on their strain. The EC₅₀ of ciprofloxacin for the alga Raphidocelis subcapitata reduced from 3.08 to 1.07 mg L^-1 (p-value <0.05) after the bioremoval. Also, the acute and chronic toxicity of identified biodegradation products was lower than ciprofloxacin at three trophic levels, as predicted by ECOSAR software.

Shield, Anchor, and Adhesive Roles of Methylene Blue in Tyrosinase Adsorbed on Carbon Felt for a Flow Injection Amperometric Enzyme Biosensor for Phenolic Substrates and Inhibitors

Methylene blue (MB) acted as a stabilizer for preventing surface-induced denaturation of tyrosinase (TYR) adsorbed on a carbon felt (CF) surface, which is based on shield and anchor roles preventing the unfavorable conformational change of TYR on the hydrophobic CF surface. Furthermore, MB acted as an effective adhesive for TYR immobilization on CF. The resulting TYR and MB coadsorbed CF (TYR/MB-CF) worked as an excellent working electrode unit in an electrochemical detector in a flow injection amperometric biosensor, which allowed highly sensitive consecutive determination of not only TYR substrates but also competitive inhibitors. Simultaneous adsorption of TYR and MB from their mixed solution was much useful as compared with step-wise separated adsorption of TYR on the MB-adsorbed CF, which suggests that the binding interaction of MB with TYR in the solution phase is important for this phenomenon. Fluorescence and UV-vis spectroscopy revealed that not only electrostatic forces between the cationic MB and anionic amino acid residues of TYR but also hydrophobic interactions via the phenothiazine ring of MB play a principal binding driving force of MB with TYR at the surface of the TYR molecules. Synchronous fluorescence, three-dimensional fluorescence, and circular dichroism (CD) spectroscopy clarified that the conformation and the secondary structure of TYR slightly changed upon the MB binding, implying that MB binding leads to the modification of the original intramolecular bonding in part.

Conformational changes and location of BSA upon immobilization on zeolitic imidazolate frameworks

The location and the conformational changes of proteins/enzymes immobilized within Metal Organic Frameworks (MOFs) are still poorly investigated and understood. Bovine serum albumin (BSA), used as a model protein, was immobilized within two different zeolitic imidazolate frameworks (ZIF-zni and ZIF-8). Pristine ZIFs and BSA@ZIFs were characterized by X-ray diffraction, small-angle X-ray scattering, scanning electron microscopy, confocal laser scanning microscopy, thermogravimetric analysis, micro-FTIR and confocal Raman spectroscopy to characterize MOFs structure and the protein location in the materials. Moreover, the secondary structure and conformation changes of BSA after immobilization on both ZIFs were studied with FTIR. BSA is located both in the inner and on the outer surface of MOFs, forming domains that span from the micro- to the nanoscale. BSA crystallinity (β-sheets + α-helices) increases up to 25 % and 40 % due to immobilization within ZIF-zni and ZIF-8, respectively, with a consequent reduction of β-turns.

EDTA and IAA Ameliorates Phytoextraction Potential and Growth of Sunflower by Mitigating Cu-Induced Morphological and Biochemical Injuries

As an essential micronutrient, copper is vital for normal growth and development of plants, however, its accumulation in soil exerts a severe negative impact on the agronomic characteristics and yield of the crop plants. Phytoextraction is a low-cost method for restoring soil fertility and avoiding losses due to heavy metal contamination. We found that using EDTA and IAA together improved sunflower hyperaccumulation capacity. Sunflowers were cultivated under various levels of Cu (0 (control), 25, 50, and 75 mg/kg of soil) and treated with EDTA alone or combined with IAA. The results revealed that the amended treatment significantly enhanced the absorption and accumulation of Cu in the sunflowers. Furthermore, the various doses of Cu significantly reduced the root and shoot growth of sunflowers in a concentration-dependent manner by impairing the chlorophyll content, hormones (indole 3-acetic acid, salicylic acid, and gibberellic acid), flavonoids, phenolics, and antioxidant response. The injurious effect of Cu was reduced by the addition of EDTA alone, and the supplementation of IAA led to a significant restoration of shoot growth (~70%) and root growth (~13%) as compared to the plant treated with Cu alone. Moreover, significantly higher levels of chlorophyll content, GA3, endogenous IAA, and flavonoids were recorded, indicating the effectiveness of the treatment in ameliorating plant health. The results also showed considerable restoration of the catalase and ascorbate peroxidase activities in plants treated with EDTA and IAA. These results are suggestive that application of EDTA and IAA enhances the Cu absorption potential of sunflower and increases its tolerance to copper, which may not only serve as a better technique for phytoextraction of Cu, but also to bring Cu contaminated soil under cultivation.

Nanostructured supports for multienzyme co-immobilization for biotechnological applications: Achievements, challenges and prospects

The synergistic combination of current biotechnological and nanotechnological research has turned to multienzyme co-immobilization as a promising concept to design biocatalysis engineering. It has also intensified the development and deployment of multipurpose biocatalysts, for instance, multienzyme co-immobilized constructs, via biocatalysis/protein engineering to scale-up and fulfil the ever-increasing industrial demands. Considering the characteristic features of both the loaded multienzymes and nanostructure carriers, i.e., selectivity, specificity, stability, resistivity, induce activity, reaction efficacy, multi-usability, high catalytic turnover, optimal yield, ease in recovery, and cost-effectiveness, multienzyme-based green biocatalysts have become a powerful norm in biocatalysis/protein engineering sectors. In this context, the current state-of-the-art in enzyme engineering with a synergistic combination of nanotechnology, at large, and nanomaterials, in particular, are significantly contributing and providing robust tools to engineer and/or tailor enzymes to fulfil the growing catalytic and contemporary industrial needs. Considering the above critics and unique structural, physicochemical, and functional attributes, herein, we spotlight important aspects spanning across prospective nano-carriers for multienzyme co-immobilization. Further, this work comprehensively discuss the current advances in deploying multienzyme-based cascade reactions in numerous sectors, including environmental remediation and protection, drug delivery systems (DDS), biofuel cells development and energy production, bio-electroanalytical devices (biosensors), therapeutical, nutraceutical, cosmeceutical, and pharmaceutical oriented applications. In conclusion, the continuous developments in nano-assembling the multienzyme loaded co-immobilized nanostructure carriers would be a unique way that could act as a core of modern biotechnological research.

Construction of Covalent Organic Framework Capsule-Based Nanoreactor for Sensitive Glucose Detection

Enzyme immobilization is critical to boosting its application in various areas. Covalent organic frameworks (COFs) are ideal hosts for enzyme immobilization due to their porous and predesignable structures. Nevertheless, the construction of COFs-based enzyme immobilization systems with high activity via existing immobilization methods (including covalent linkages and channel entrapment) remains a considerable challenge. Herein, a versatile approach was introduced to encapsulate enzymes within hollow COF capsule (named enzyme@COF) using metal-organic frameworks (including ZPF-1(C8H11N4O4.5Zn), ZIF-8(C8H10N4Zn), and ZIF-90(C8H6N4O2Zn)) as sacrificial templates. The obtained porous COF capsule could not only facilitate the efficient mass transfer of enzymatic reactions but also protect enzymes against the incompatible conditions, resulting in enhanced activity and stability of the encapsulated enzymes. Moreover, this approach offered an opportunity to spatially organize multienzymes in COF capsule to construct enzyme cascade system. For instance, glucose oxidase (GOx) and cytochrome c (Cyt c) were coencapsulated within COF capsule to construct GOx-Cyt c cascade. The integration of GOx and Cyt c within COF capsule achieved ∼1.6-fold improvement in catalytic activity than that of free enzymes and the resultant GOx-Cyt c@COF was successfully adopted as a nanoreactor for the sensitive determination of glucose in serum. This work provided a new insight into the design of COFs-based enzyme immobilization systems.

Interactions of Catalytic Enzymes with n-Type Polymers for High-Performance Metabolite Sensors

The tight regulation of the glucose concentration in the body is crucial for balanced physiological function. We developed an electrochemical transistor comprising an n-type conjugated polymer film in contact with a catalytic enzyme for sensitive and selective glucose detection in bodily fluids. Despite the promise of these sensors, the property of the polymer that led to such high performance has remained unknown, with charge transport being the only characteristic under focus. Here, we studied the impact of the polymer chemical structure on film surface properties and enzyme adsorption behavior using a combination of physiochemical characterization methods and correlated our findings with the resulting sensor performance. We developed five n-type polymers bearing the same backbone with side chains differing in polarity and charge. We found that the nature of the side chains modulated the film surface properties, dictating the extent of interactions between the enzyme and the polymer film. Quartz crystal microbalance with dissipation monitoring studies showed that hydrophobic surfaces retained more enzymes in a densely packed arrangement, while hydrophilic surfaces captured fewer enzymes in a flattened conformation. X-ray photoelectron spectroscopy analysis of the surfaces revealed strong interactions of the enzyme with the glycolated side chains of the polymers, which improved for linear side chains compared to those for branched ones. We probed the alterations in the enzyme structure upon adsorption using circular dichroism, which suggested protein denaturation on hydrophobic surfaces. Our study concludes that a negatively charged, smooth, and hydrophilic film surface provides the best environment for enzyme adsorption with desired mass and conformation, maximizing the sensor performance. This knowledge will guide synthetic work aiming to establish close interactions between proteins and electronic materials, which is crucial for developing high-performance enzymatic metabolite biosensors and biocatalytic charge-conversion devices.

Enhanced Activity of Enzyme Immobilized on Hydrophobic ZIF-8 Modified by Ni2+ Ions

The development of efficient enzyme immobilization to promote their recyclability and activity is highly desirable. Zeolitic imidazolate framework-8 (ZIF-8) has been proved to be an effective platform for enzyme immobilization due to its easy preparation and biocompatibility. However, the intrinsic hydrophobic characteristic hinders its further development in this filed. Herein, a facile synthesis approach was developed to immobilize pepsin (PEP) on the ZIF-8 carrier by using Ni²⁺ ions as anchor (ZIF-8@PEP-Ni). By contrast, the direct coating of PEP on the surface of ZIF-8 (ZIF-8@PEP) generated significant conformational changes. Electrochemical oxygen evolution reaction (OER) was employed to study the catalytic activity of immobilized PEP. The ZIF-8@PEP-Ni composite attains remarkable OER performance with an ultralow overpotential of only 127 mV at 10 mA cm^-2 , which is much lower than the 690 and 919 mV overpotential values of ZIF-8@PEP and PEP, respectively.

Hollow Mesoporous Carbon-Based Enzyme Nanoreactor for the Confined and Interfacial Biocatalytic Synthesis of Phytosterol Esters

Rationally designing carriers to obtain efficient and stable immobilized enzymes for the production of food raw materials is always a challenge. In this work, hollow cube carbon (HMC) as a carrier of Candida rugosa lipase (CRL) was prepared to construct a Pickering interfacial biocatalysis system, which was applied to biphasic biocatalysis. For comparison, the nonporous carbon (HC) and porous MoS₂ (HMoS₂) were also designed. On these grounds, p-NPP and linolenic acid were selected as the representative substrates for hydrolysis and esterification reactions. Under the optimal conditions, the protein loading amount, specific activity, and expressed activity of CRL immobilized on HMC (HMC@CRL) were 167.2 mg g^-1, 5.41 U mg^-1, and 32.34 U/mg protein, respectively. In the "oil-water" biphase, the relative hydrolytic activity of HMC@CRL was higher than that of HC@CRL, HMoS₂@CRL, and CRL by 50, 68, and 80%, respectively, as well as itself in one phase. Compared to other reports (1.13%), HMC@CRL demonstrated a satisfactory hydrolysis rate (3.02%) and was the fastest among all other biocatalysts in the biphase. Moreover, compared with the free CRL in one-phase system, the Pickering interfacial biphasic biocatalyst, HMC@CRL, exhibited a higher esterification rate (85%, 2.7-fold enhancement). Therefore, the HMC@CRL nanoreactors had more optimal performance in the field of biomanufacturing and food industry.

Designing multifunctional biocatalytic cascade system by multi-enzyme co-immobilization on biopolymers and nanostructured materials

In recent decades, enzyme-based biocatalytic systems have garnered increasing interest in industrial and applied research for catalysis and organic chemistry. Many enzymatic reactions have been applied to sustainable and environmentally friendly production processes, particularly in the pharmaceutical, fine chemicals, and flavor/fragrance industries. However, only a fraction of the enzymes available has been stepped up towards industrial-scale manufacturing due to low enzyme stability and challenging separation, recovery, and reusability. In this context, immobilization and co-immobilization in robust support materials have emerged as valuable strategies to overcome these inadequacies by facilitating repeated or continuous batch operations and downstream processes. To further reduce separations, it can be advantageous to use multiple enzymes at once in one pot. Enzyme co-immobilization enables biocatalytic synergism and reusability, boosting process efficiency and cost-effectiveness. Several studies on multi-enzyme immobilization and co-localization propose kinetic advantages of the enhanced turnover number for multiple enzymes. This review spotlights recent progress in developing versatile biocatalytic cascade systems by multi-enzyme co-immobilization on environmentally friendly biopolymers and nanostructured materials and their application scope in the chemical and biotechnological industries. After a succinct overview of carrier-based and carrier-free immobilization/co-immobilizations, co-immobilization of enzymes on a range of biopolymer and nanomaterials-based supports is thoroughly compiled with contemporary and state-of-the-art examples. This study provides a new horizon in developing effective and innovative multi-enzymatic systems with new possibilities to fully harness the adventure of biocatalytic systems.

Immobilization of Alcalase on Silica Supports Modified with Carbosilane and PAMAM Dendrimers

Enzyme immobilization is a powerful strategy for enzyme stabilization and recyclability. Materials covered with multipoint molecules are very attractive for this goal, since the number of active moieties to attach the enzyme increases with respect to monofunctional linkers. This work evaluates different dendrimers supported on silica to immobilize a protease enzyme, Alcalase. Five different dendrimers were employed: two carbosilane (CBS) dendrimers of different generations (SiO₂-G₀Si-NH₂ and SiO₂-G₁Si-NH₂), a CBS dendrimer with a polyphenoxo core (SiO₂-G₁O₃-NH₂), and two commercial polyamidoamine (PAMAM) dendrimers of different generations (SiO₂-G₀PAMAM-NH₂ and SiO₂-G₁PAMAM-NH₂). The results were compared with a silica support modified with a monofunctional molecule (2-aminoethanethiol). The effect of the dendrimer generation, the immobilization conditions (immobilization time, Alcalase/SiO₂ ratio, and presence of Ca²⁺ ions), and the digestion conditions (temperature, time, amount of support, and stirring speed) on Alcalase activity has been evaluated. Enzyme immobilization and its activity were highly affected by the kind of dendrimer and its generation, observing the most favorable behavior with SiO₂-G₀PAMAM-NH₂. The enzyme immobilized on this support was used in two consecutive digestions and, unlike CBS supports, it did not retain peptides released in the digestion.

Immobilization of Kluyveromyces lactis β-Galactosidase on Meso-macroporous Silica: Use of Infrared Spectroscopy to Rationalize the Catalytic Efficiency

Enzyme immobilization on adequate carriers is a challenging strategy. Understanding the enzyme-carrier interactions and their effects on enzyme conformation and bioactivity is critical. In this study, a meso-macropores silica (MMS) was used to immobilize β-galactosidase from the yeast Kluyveromyces lactis (β-gal-KL) by physical adsorption. The bioactivity of the immobilized β-gal-KL was altered, evidenced by the increased K_m , decreased V_max and k_cat , and increased activity at alkaline values. By performing infrared spectroscopy analysis and subsequent secondary structure assessment from the amide I band, the immobilized β-gal-KL suffered a β-sheet (∼31-35 %) to α-helix (∼15-19 %) transition with increased turns (∼21-22 %) with respect to the free β-gal-KL having ∼12 % α-helix, ∼42 % β-sheet, and ∼17 % turns. These findings led us to correlate the observed bioactivity performance to structural alterations to a non-native conformation. The presented line of thought can lead to a better understanding of the reasons causing bioactivity alterations upon enzyme immobilization.