Strategies for Stabilization of Enzymes in Organic Solvents

Spontaneous Hollow Coacervate Transition of Silk Fibroin via Dilution and Its Transition to Microcapsules

Polymeric microcapsules are useful for drug delivery, microreactors, and cargo transport, but traditional fabrication methods require complex processes and harsh conditions. Coacervates, formed by liquid-liquid phase separation (LLPS), offer a promising alternative for microcapsule fabrication. Recent studies have shown that coacervates can spontaneously form hollow cavities under specific conditions. Here, we investigate the spontaneous hollow coacervate transition of silk fibroin (SF). SF coacervates, induced by mixing SF with dextran, calcium ions, and copper ions, transition to hollow coacervates upon dilution. Adding ethylenediaminetetraacetic acid (EDTA) further transforms them into vesicle-like capsule coacervates, which solidify into microcapsules. As a proof-of-concept, we successfully loaded a high-molecular-weight polymer cargo into the hollow cavity and bioactive enzyme cargo into the capsule layer by simply mixing the cargo with the coacervate solution. Our results demonstrate a facile, organic-solvent-free approach for fabricating SF-based microcapsules and provide insight into the mechanisms driving hollow coacervate formation.

Understanding Metal-Organic Framework Densification: Solvent Effects and the Growth of Colloidal Primary Nanoparticles in Monolithic ZIF-8

To commercialize metal-organic frameworks (MOFs), it is vital they are made easier to handle. There have been many attempts to synthesize them as pellets, tablets, or granules, though they come with innate drawbacks. Only recently have these been overcome, through the advent of self-shaping densified or monolithic MOFs (monoMOFs), which require minimal post-synthetic modification and avoid poor structural integrity, intractability, and pore collapse or blockage. ZIF-8 (zeolitic imidazolate framework-8) has emerged as a prototypical monoMOF in pure and in situ doped forms. Now its formation in solvent mixtures is studied to better understand the early stages of monolith formation and improve the scope of monoliths for hosting solvent-sensitive guests. Solvent-, temperature- and coagulant-dependent control over reaction kinetics induces variations in morphology that are explained by relating the nucleation and growth rates of primary nanocrystallites to the stability of colloidal dispersions during reaction. This yields mesoporous monoZIF-8 with mean pore size 16 nm, SBET >1400 m2 g-1, bulk density 0.76 g cm-3, and resistance to permanent deformation exceeding previous reports. While the study highlights the powerful manipulation of monoMOF characteristics, a new understanding of the growth and stability of primary nanocrystallites has consequences for colloid synthesis generally.

Immobilized enzymes: exploring its potential in food industry applications

The global demand for nutritious, longer-lasting food has spurred the food industry to seek eco-friendly solutions. Enzymes play a vital role in enhancing food quality by improving flavor, texture, and nutritional content. However, challenges like rapid deactivation and non-recoverability of free enzymes are addressed by immobilized enzymes, which enhance efficiency, quality, and sustainability in food processing. Immobilization methods include adsorption, covalent binding, entrapment, encapsulation and cross-liked enzyme aggregates, which enhancing their stability, reusability, and catalytic efficiency. Immobilization of enzyme such as pectinase, amylase, naringinase, cellulase, lactase, glucoamylase, xylanase, invertase, lipase, phytase, and protease have been utilized in fruit, vegetable, baking, dairy, brewing, and feed process due to their high thermostability, improved shelf life, food quality and safety. The catalytic efficiency of immobilized enzymes in detecting and quantifying various food components, contaminants, and quality indicators, also developed functional foods with nutraceuticals benefits, include prebiotic juices, lactose-free dairy products, poly unsaturated fatty acids rich foods, low-calorie sweeteners, fortified food and bioactive peptides.

Graphical abstract

A highly thermostable ethyl carbamate-degrading urethanase from Thermoflavimicrobium dichotomicum

The carcinogen ethyl carbamate (EC) in food is a potential threat to health. Available urethanases cannot efficiently degrade EC because of their instability or low activity under acidic conditions. Here, a novel thermostable urethanase was identified in Thermoflavimicrobium dichotomicum using a database-mining approach. The enzyme displayed exceptional thermotolerance, with an optimum temperature of 75 °C, and exhibited 58.6 % of its maximum activity at 90 °C. After incubation at temperatures below 70 °C for 30 min, 100 % activity was maintained. Following treatment at 4 °C for 6 h, it retained 59-87 % of its activity at pH 4.0-5.0, demonstrating the highest acid stability reported so far. This enzyme showed good ethanol tolerance. 80.4 % of its activity was retained after incubation in 10 % (v/v) ethanol solution at 37 °C for 1 h. The enzyme exhibited the highest EC affinity (Km, 3.545 mM), and catalytic efficiency (kcat/Km, 46.75 ± 2.34 s-1·mM-1) at pH 4.5. After reacting with 200 U/L purified enzyme at 30 °C for 5 h, 62.4 % and 9.7 % of EC were degraded from rice wine samples with pH 6.0 and 4.5, respectively. Furthermore, the enzyme exhibited significant hydrolytic activity against the 2A carcinogen acrylamide. These findings suggest that this urethanase is a promising industrial enzyme.

Computer-assisted enzyme cocktails enhance fermentation by overcoming toxic inhibitors from pretreatment processes

Lignocellulosic biomass is the most abundant form of biomass available for fuel production, serving as the fourth leading energy source globally. However, inhibitors generated during pretreatment processes often hinder fermentation performance and conversion efficiency. In this study, we developed an enhanced computer-assisted enzyme cocktail strategy (ComEC 2.0) to mitigate the inhibitory effects. Through experimental studies and molecular dynamics simulations, eight optimization strategies were developed for enzyme cocktail formulation (comprising CBHI, EG, BG, XYN, LPMO). Notably, Strategy 4b, which accounts for both overall hydration and the synergistic effects between LPMO and CBHI/EG/BG/XYN, increased glucose and xylose yields by 20.7 % and 21 %, respectively, using corn stover, reducing Process Mass Intensity (PMI) by 70.78 % and water use by 80 % during ethanol fermentation. Applying Strategy 4b to industrial corn cob increased glucose and xylose yields by 22.1 % and 21.6 %, surpassing the commercial Ctec3 blend. This scalable approach significantly enhances biomass conversion and resource efficiency, offering broad industrial potential.

2-Propanol Suspension Method to Increase Acetylcholinesterase and Flow Stability on μPADs

Ensuring detection performance and shelf life is crucial for analytical devices. Advances in materials and reaction mechanisms have improved detection performance, yet extending the operational lifetime of microfluidic paper-based analytical devices (μPADs)─especially those reliant on sensitive enzymes─remains a challenge. Here, we present an alternative to air-drying and lyophilization: loading enzymes suspended in 2-propanol (iPrOH). By suspending the enzyme in iPrOH, we circumvent the enzyme activity losses commonly associated with freeze-thawing and freeze-drying. Accelerated aging tests, supported by statistical analyses of long-term activity retention (including comparisons over multiple time points), indicate that while conventional methods do not sustain consistent superiority, the iPrOH suspension method maintains higher enzymatic activity over extended periods. By avoiding stabilizers and circumventing the limitations of other techniques, our method enables μPADs to achieve both longevity and stable fluid flow. Thus, we provide a more robust, on-site analytical platform capable of reliable on-site detection.

Multienzymatic Platform for Coupling a CCU Strategy to Waste Valorization: CO2 from the Iron and Steel Industry and Crude Glycerol from Biodiesel Production

Ongoing climate crisis demands the development of carbon capture and utilization (CCU) technologies that emphasize simplicity, eco-sustainability, and cost-effectiveness. Enzymatic CO2 reduction emerges as an alternative to biotransforming this cheap raw material into high-value products under milder conditions. This work proposes a multienzymatic platform to reduce CO2 to formate by formate dehydrogenase (FDH) and oxidize glycerol to dihydroxyacetone (DHA) by glycerol dehydrogenase (GlyDH), allowing for efficient cofactor regeneration. Through studies such as pH operating range, enzyme stability, FDH/GlyDH ratio, and reaction medium engineering to achieve optimal soluble CO2 concentrations, the reaction with a gas mixture of 24% CO2 yielded 5.7 mM formate and 6 mM DHA after 30 h, achieving a 92.3% CO2 conversion. To evaluate the feasibility under industrially relevant conditions, a synthetic gas mixture mimicking the composition of the iron and steel industry off-gases (24.5% CO2) and crude glycerol (64% v/v) from biodiesel production was tested as substrates. The simultaneous production was successful, yielding 3.1 mM formate and 4.4 mM DHA. Formic acid was subsequently purified using liquid-liquid extraction, employing the green solvent 2-methyltetrahydrofuran (2-MTHF). For the first time to our knowledge, a CCU strategy has been successfully coupled with industrial waste valorization, obtaining two high-value molecules by means of a robust, profitable, and easily manageable multienzymatic system.

Dynamic protein hydration water mediates the aggregation kinetics of amyloid β peptides at interfaces

Protein hydration water is essential for protein misfolding and amyloid formation, but how it directs the course of amyloid formation has yet to be elucidated. Here, we experimentally demonstrated that femtosecond sum frequency generation vibrational spectroscopy (SFG-VS) and the femtosecond IR pump-SFG probe technique can serve as powerful tools for addressing this issue. Using amyloid β(1-42) peptide as a model, we determined the transient misfolding intermediates by probing the amide band spectral features and the local hydration water changes by measuring the ultrafast vibrational dynamics of the amide I band. For the first time, we established a correlation between the dynamic change in protein hydration water and aggregation propensity. The aggregation propensity depends on the dynamic change in the hydration water, rather than the static hydration water content of the initial protein state. Water expulsion enhances the aggregation propensity and promotes amyloid formation, while protein hydration attenuates the aggregation propensity and inhibits amyloid formation. The suppression of water expulsion and protein hydration can prevent protein aggregation and stabilize proteins. These findings contribute to a better understanding of the underlying effect of hydration water on amyloid formation and protein structural stability and provide a strategy for maintaining long-term stabilization of biomolecules.

Combining Photochemical Oxyfunctionalization and Enzymatic Catalysis for the Synthesis of Chiral Pyrrolidines and Azepanes

Chiral heterocyclic alcohols and amines are frequently used building blocks in the synthesis of fine chemicals and pharmaceuticals. Herein, we report a one-pot photoenzymatic synthesis route for N-Boc-3-amino/hydroxy-pyrrolidine and N-Boc-4-amino/hydroxy-azepane with up to 90% conversions and >99% enantiomeric excess. The transformation combines a photochemical oxyfunctionalization favored for distal C-H positions with a stereoselective enzymatic transamination or carbonyl reduction step. Our study demonstrates a mild and operationally simple asymmetric synthesis workflow from easily available starting materials.

Critical Role of Water beyond the Media to Maintain Protein Stability and Activity in Hydrated Deep Eutectic Solvent

Hydrated deep eutectic solvents (DESs) are recognized for their potential in biocatalysis due to their tunability, biocompatibility, greenness, and ability to keep protein stable and active. However, the mechanisms governing enzyme stability and activity in DES remain poorly understood. Herein, using bromelain as the model enzyme and acetamide (0.5)/urea(0.3)/sorbitol(0.2) as the model DES, we provide experimental evidence that modulation of associated water plays a key role in dictating protein stability and activity in hydrated DES. Specifically, rigid associated water at higher DES concentrations (beyond 40% v/v) stabilizes bromelain through entropy but destabilizes it through enthalpy. On the other hand, flexible associated water dynamics at lower DES concentrations result in an opposite thermodynamic outcome. Importantly, the bulk water dynamics cannot explain the stability trend, which emphasizes the critical role of water near the protein surface. Strikingly, associated water dynamics also correlates strongly with bromelain's proteolytic activity. An increasing flexibility of the associated water dynamics leads to the enhancement of the activity. This is the first study to experimentally link associated water dynamics to enzyme behavior in hydrated DES, offering insights that could guide future developments in solvent engineering for enzyme catalysis.

Active Site Studies to Explain Kinetics of Lipases in Organic Solvents Using Molecular Dynamics Simulations

This study investigates the intricate dynamics underlying lipase performance in organic solvents using comprehensive molecular dynamics (MD) simulations, supported by enzyme kinetics data. The study reveals that a single criterion can neither predict nor explain lipase activity in organic solvents, indicating the need for a comprehensive approach. Three lipases were included in this study: Candida antarctica lipase B (CALB), Rhizomucor miehei lipase (RML), and Thermomyces lanuginosus lipase (TLL). The lipases were investigated in acetonitrile, methyl tert-butyl ether, and hexane with increasing water activity. Computational investigations reveal that CALB's activity is negatively correlated to water cluster formations on its surface. In contrast, TLL's and RML's activity profiles show no negative effects of high water activity. However, TLL's and RML's activities are highly correlated to the conformation and stability of their active site regions. This study may pave the way for tailored applications of lipases, highlighting some of the factors that should be considered when lipase-catalyzed reactions are designed.

Molecular dynamics and solvation structures of the β-glucosidase from Humicola insolens (BGHI) in aqueous solutions containing glucose

The β-glucosidase enzyme is a glycosyl hydrolase that breaks down the β-1,4 linkage of cellobiose. It is inhibited by glucose at high concentrations due to competitive inhibition. However, at lower glucose concentrations, the glucose-tolerant β-glucosidase from Humicola insolens (BGHI) undergoes stimulation. Proteins, in aqueous sugar solutions, tend to be preferentially hydrated, which generally promotes their stabilization. Thus, solvation phenomena may contribute to both glucose tolerance and stimulation processes. We have performed atomistic classical Molecular Dynamics (MD) simulations of BGHI at different glucose concentrations to mimic the conditions found in the catalytic experiments. A detailed examination of the solvent environment through the calculation of minimum distance distribution functions (MDDFs) and Kirkwood-Buff (KB) integrals was performed. The enzyme is preferentially hydrated in the presence of glucose at all concentrations. Nevertheless, the hydration does not prevent the glucose from directly interacting with the BGHI surface or from entering the active site. Based on the obtained results, we hypothesize that preferential hydration is beneficial for enzyme activity. At the same time, product inhibition has little effect at lower concentrations of glucose, and at higher glucose concentrations, competition for the active site becomes predominant and the enzyme is primarily inhibited.

In situ characterization of amine-forming enzymes shows altered oligomeric state

Enzyme stability can be measured in a number of ways, including melting temperature, activity retention, and size analysis. However, these measurements are often conducted in an idealized storage buffer and not in the relevant enzymatic reaction media. Particularly for reactions that occur in alkaline, volatile, and high ionic strength media, typical analyses using differential scanning calorimetry, light scattering, and sodium dodecyl-sulfate polyacrylamide gel electrophoresis are not satisfactory to track the stability of these enzymes. In this work, we monitor the stability of engineered and native dehydrogenases that require a high amount of ammonia for their reaction to occur. We demonstrate the benefits of analyzing these enzymes in their reaction buffer, uncovering trends that were not observable in the typical phosphate storage buffer. This work provides a framework for analyzing the stability of many other enzymes whose reaction media is not suitable for traditional techniques. We introduce several strategies for measuring the melting temperature, oligomeric state, and activity of these enzymes in their reaction media. Further, we have identified opportunities for integration of computational tools into this workflow to engineer enzymes more effectively for solvent tolerance and improved stability.

Ancestral Sequence Reconstruction for Designing Biocatalysts and Investigating their Functional Mechanisms

Biocatalysis has emerged as a green approach for efficient and sustainable production in various industries. In recent decades, numerous advancements in computational and predictive approaches, including ancestral sequence reconstruction (ASR) have sparked a new wave for protein engineers to improve and expand biocatalyst capabilities. ASR is an evolution-based strategy that uses phylogenetic relationships among homologous extant sequences to probabilistically infer the most likely ancestral sequences. It has proven to be a powerful tool with applications ranging from creating highly stable enzymes for direct applications to preparing moderately active robust protein scaffolds for further enzyme engineering. Intriguingly, it can also provide insights into fundamental aspects that are challenging to study with extant (current) enzymes. This Perspective discusses a practical strategy for guiding enzyme engineers on how to embrace ASR as a practical or associated protocol for protein engineering and highlights recent examples of using ASR in various applications, including increasing thermostability, expanding promiscuity, fine-tuning selectivity and function, and investigating mechanistic and evolution aspects. We believe that the use of the ASR approach will continue to contribute to the ongoing development of the biocatalysis field. We have been in a "golden era" for biocatalysis in which numerous useful enzymes have been developed through many waves of enzyme engineering via advancements in computational methodologies.

Changes in ficin specificity by different substrate proteins promoted by enzyme immobilization

Ficin extract has been immobilized using different supports: glyoxyl and Aspartic/1,6 hexamethylenediamine (Asp/HA) agarose beads. The latter was later submitted to glutaraldehyde modification to get covalent immobilization. The activities of these 3 kinds of biocatalysts were compared utilizing 4 different substrates, casein, hemoglobin and bovine serum albumin and benzoyl-arginine-p-nitroanilide at pH 7 and 5. Using glyoxyl-agarose, the effect of enzyme-support reaction time on the activity versus the four substrates at both pH values was studied. Reaction time has been shown to distort the enzyme due to an increase in the number of covalent support-enzyme bonds. Surprisingly, for all the substrates and conditions the prolongation of the enzyme-support reaction did not imply a decrease in enzyme activity. Using the Asp/HA supports (with different amount of HA) differences in the effect on enzyme activity versus the different substrates are much more significant, while with some substrates the immobilization produced a decrease in enzyme activity, with in other cases the activity increased. These different effects are even increased after glutaraldehyde treatment. That way, the conformational changes induced by the biocatalyst immobilization or the chemical modification fully altered the enzyme protein specificity. This may also have some implications when following enzyme inactivation.

Immobilized Horseradish Peroxidase on Enriched Diazo-Activated Silica Gel Harnessed High Biocatalytic Performance at a Steady State in Organic Solvent

Dimethyldichlorosilane (DMDCS), an efficient silane coupling reagent appearing between the -OH groups of silica gel (SG) and picric acid, instantaneously produces a derivative enriched with nitro groups. The nitro group acting as an end-cap terminates the reaction and subsequently was converted into diazo to couple tyrosine's phenol ring via its O-carbon, the inert center to immobilize horseradish peroxidase (HRP) in a multipoint mode. It maintains the status quo of the native enzyme's protein folding and the entire protein groups' chemistry. The molecular formula of the synthesized material was verified and appeared as {Si(OSi)4 (H2O)x}n{-O-Si(CH3)2-O-C6H2(N+≡N)3(HRP)}4·yH2O; the parameters were evaluated as x = 0.5, n = 1158, and y = 752. The immobilized biocatalyst's activity in organic solvents was 1.5 times better than that in an aqueous medium; it worked smoothly, wherein the activity in both solvents stabilized at six months and continued up to nine months at 63 ± 3% compared to the initial.

Optimizing the activation of agarose beads with divinyl sulfone for enzyme immobilization and stabilization

The focus of the present work is to find the optimal conditions for the activation of agarose beads with divinyl sulfone (DVS). The reactivity of the vinyl sulfone groups in the support was checked by the support capacity to react with ethylamine; via elemental analysis. In addition, trypsin was used as a model enzyme to test the immobilization and stabilization capabilities of the different supports. The higher the pH, the more vinyl sulfone groups are incorporated into the support, but lower reactivity versus ethylamine is observed. Too long activation times led to similar results. A N/S ratio of 1 means that all vinyl sulfone groups were reactive, and it was always lower than tis figure. The N in the support was 50 % of the amount observed for glyoxyl supports activated with ethylenediamine, suggesting the VS polymerization may be a likely explanation for this result. The higher N/S ratio in the support (modified with ethylamine), the higher the obtained stabilization, very likely by the lower polymerization of the vinyl sulfone on the support. We propose 360 mM divinyl sulfone, at pH 11.5 and 2 h as optimal conditions to reach the highest enzyme stabilization by immobilization in this support.

Precise Immobilization Strategy Combined with Rational Design to Improve β-Agarase Stability

Recently, the orientational immobilization of enzymes has attracted extensive attention. In this study, we report the development of a strategy combined with rational design to achieve precise site-specific covalent immobilization of β-agarase. We first rationally screened six surface sites that can be mutated to cysteine by combining molecular dynamics simulation and energy calculation. Site-specific immobilization was successfully achieved by Michael addition reaction of mutant enzymes and maleimide-modified magnetic nanoparticles (MAL-MNPs). The enzyme activity retention rate of R66C-MAL-MNPs and K588C-MAL-MNPs was greater than 96%. The thermal deactivation kinetics study revealed that the site-specific immobilization strategy significantly improved the thermal stability of Aga50D, resulting in a substantial increase in its antidenaturation activity at elevated temperatures, and the highest t1/2 of the immobilized mutant enzymes was increased by an impressive 21.25-fold at 40 °C. The immobilized mutant enzymes also showed significantly enhanced tolerance to metal ions and organic reagents. For instance, all of the immobilized enzymes maintained over 90% of their enzymatic activity in the 50% (v/v) acetone/water solution. The present work may pave the way for the design of precisely immobilized enzymes, which can help promote green manufacturing.

Water-mediated active conformational transitions of lipase on organic solvent interfaces

When it comes to enzyme stability and their application in organic solvents, enzyme biocatalysis has emerged as a popular substitute for conventional chemical processes. However, the demand for enzymes exhibiting improved stability remains a persistent challenge. Organic solvents can significantly impacts enzyme properties, thereby limiting their practical application. This study focuses on Lipase Thermomyces lanuginose, through molecular dynamics simulations and experiments, we quantified the effect of different solvent-lipase interfaces on the interfacial activation of lipase. Revealed molecular views of the complex solvation processes through the minimum distance distribution function. Solvent-protein interactions were used to interpret the factors influencing changes in lipase conformation and enzyme activity. We found that water content is crucial for enzyme stability, and the optimum water content for lipase activity was 35 % in the presence of benzene-water interface, which is closely related to the increase of its interfacial activation angle from 78° to 102°. Methanol induces interfacial activation in addition to significant competitive inhibition and denaturation at low water content. Our findings shed light on the importance of understanding solvent effects on enzyme function and provide practical insights for enzyme engineering and optimization in various solvent-lipase interfaces.

Fe3O4@silica-thermolysin: A robust, advantageous, and reusable microbial nanobiocatalyst for proteolysis and milk-clotting

Thermolysin (TLN) is a microbial highly-priced thermostable metallo-endoprotease with complementary substrate specificity to those of proteases widely used in science and industry for protein digestion and milk-clotting. This study is the first to immobilize TLN on aminated superparamagnetic nanoparticles (Fe3O4@silica-NH2) aiming for higher stability, recoverability, reusability, and applicability in proteolysis and as a microbial rennet-like milk-clotting enzyme. The nanobiocatalyst developed (Fe3O4@silica-TLN) displays hydrolytic activity on a synthetic TLN substrate and, apparently, was fully recovered from reaction media by magnetic decantation. More importantly, Fe3O4@silica-TLN retains TLN catalytic properties in the presence of calcium ions even after exposure to 60 °C for 48 h, storage at 4 °C for 80 days and room temperature for 42 days, use in proteolyses, and in milk-clotting for up to 11 cycles. Its proteolytic activity on bovine milk casein in 24 h furnished 84 peptides, of which 29 are potentially bioactive. Also, Fe3O4@silica-TLN catalyzed the digestion of bovine serum albumin. In conclusion, Fe3O4@silica-TLN showed to be a new, less autolytic, thermostable, non-toxic, magnetically-separable, and reusable nanobiocatalyst with highly attractive properties for both science (peptide/protein chemistry and structure, proteomic studies, and the search for new bioactive peptides) and food industry (cheese manufacture).

Enhancing monoclonal antibody stability during protein a chromatography using 2-methyl imidazolium dihydrogen phosphate

This study investigates the impact of 2-methyl imidazolium dihydrogen phosphate (2-MIDHP) on monoclonal antibody (mAb) aggregation during the Protein A purification stage, at a low pH (pH 3.0), and the viral inactivation phase. Size-exclusion high-performance liquid chromatography (SE-HPLC) and dynamic light scattering (DLS) were used to assess the mAb aggregation. Additionally, the influence of 2-MIDHP on mAb recovery, host cell protein (HCP) clearance, and Protein A leaching was investigated. Thermal stability of mAb, eluted in buffers containing 5 % to 25 % 2-MIDHP was analysed, using differential scanning calorimetry (DSC). Structural insights were obtained via circular dichroism (CD) and fluorescence spectroscopy. Our findings indicated that 2-MIDHP exerted a concentration-dependent protective effect against mAb aggregation, at the pH of 3.0. As the concentration of 2-MIDHP was increased from 0 % to 25 %, the aggregation was significantly reduced from 3.8 ± 0.01 % to 0.56 ± 0.002 %, as analysed by SE-HPLC. Addition of 2-MIDHP did not significantly impact the mAb recovery, HCP clearance, or Protein A leaching. DSC data supported these results, with higher 2-MIDHP concentrations leading to increased melting temperatures of mAb. CD and fluorescence spectroscopy revealed no significant changes in the secondary structure or aromatic residue environment in 2-MIDHP-treated samples, despite the observed reduction in aggregation. The results suggested that 2-MIDHP mitigated mAb aggregation during Protein A purification, possibly by stabilizing the protein structure under acidic stress conditions. These findings offer valuable insights for improving the robustness of mAb purification processes, enhancing product quality and yield.

Boosting Fructosyl Transferase's Thermostability and Catalytic Performance for Highly Efficient Fructooligosaccharides (FOS) Production

Achieving enzymatic food processing at high substrate concentrations can significantly enhance production efficiency; however, related studies are notably insufficient. This study focused on the enzymatic synthesis of fructooligosaccharides (FOS) at high temperature and high substrate concentration. Results revealed that increased viscosity and limited substrate solubility in high-concentration systems could be alleviated by raising the reaction temperature, provided it aligned with the enzyme's thermostability. Further analysis of enzyme thermostability in real sucrose solutions demonstrates that the enzyme's thermostability was remarkedly improved at higher sucrose concentrations, evidenced by a 10.3 °C increase in melting temperature (Tm) in an 800 g/L sucrose solution. Building upon these findings, we developed a novel method for enzymatic FOS synthesis at elevated temperatures and high sucrose concentrations. Compared to existing commercial methods, the initial transglycosylation rate and volumetric productivity for FOS synthesis increased by 155.9% and 113.5%, respectively, at 65 °C in an 800 g/L sucrose solution. This study underscores the pivotal role of substrate concentration, incubation temperature, and the enzyme's actual status in advancing enzyme-catalyzed processes and demonstrates the potential of enzymatic applications in enhancing food processing technologies, providing innovative strategies for the food industry.

Design Glutamate Dehydrogenase for Nonaqueous System by Motifs Reassembly and Interaction Network Analysis

Glutamate dehydrogenases (GDH) serve as the key regulated enzyme that links protein and carbohydrate metabolism. Combined with motif reassembly and mutation, novel GDHs were designed. Motif reassembly of thermophilic GDH and malate dehydrogenase aims to overcome stability and activity tradeoff in nonaqueous systems. Structural compatibility and dynamic cooperation of the designed AaDHs were studied by molecular dynamics simulation. Furthermore, multipoint mutations improved its catalytic activity for unnatural substrates. Amino acid interaction network analysis indicated that the high density of hydrogen-bonded salt bridges is beneficial to the stability. Finally, the experimental verification determines the kinetics of AaDHs in a nonaqueous system. The activity of Aa05 was increased by 1.78-fold with ionic liquid [EMIM]BF4. This study presents the strategy of a combination of rigid motif assembly and mutations of active sites for robust dehydrogenases with high activity in the nonaqueous system, which overcomes the activity-stability tradeoff effect.

Degradable living plastics programmed by engineered spores

Plastics are widely used materials that pose an ecological challenge because their wastes are difficult to degrade. Embedding enzymes and biomachinery within polymers could enable the biodegradation and disposal of plastics. However, enzymes rarely function under conditions suitable for polymer processing. Here, we report degradable living plastics by harnessing synthetic biology and polymer engineering. We engineered Bacillus subtilis spores harboring the gene circuit for the xylose-inducible secretory expression of Burkholderia cepacia lipase (BC-lipase). The spores that were resilient to stresses during material processing were mixed with poly(caprolactone) to produce living plastics in various formats. Spore incorporation did not compromise the physical properties of the materials. Spore recovery was triggered by eroding the plastic surface, after which the BC-lipase released by the germinated cells caused near-complete depolymerization of the polymer matrix. This study showcases a method for fabricating green plastics that can function when the spores are latent and decay when the spores are activated and sheds light on the development of materials for sustainability.

Engineered Proteins and Materials Utilizing Residue-Specific Noncanonical Amino Acid Incorporation

The incorporation of noncanonical amino acids into proteins and protein-based materials has significantly expanded the repertoire of available protein structures and chemistries. Through residue-specific incorporation, protein properties can be globally modified, resulting in the creation of novel proteins and materials with diverse and tailored characteristics. In this review, we highlight recent advancements in residue-specific incorporation techniques as well as the applications of the engineered proteins and materials. Specifically, we discuss their utility in bio-orthogonal noncanonical amino acid tagging (BONCAT), fluorescent noncanonical amino acid tagging (FUNCAT), threonine-derived noncanonical amino acid tagging (THRONCAT), cross-linking, fluorination, and enzyme engineering. This review underscores the importance of noncanonical amino acid incorporation as a tool for the development of tailored protein properties to meet diverse research and industrial needs.

Advances in aldo-keto reductases immobilization for biocatalytic synthesis of chiral alcohols

Chiral alcohols are essential building blocks of numerous pharmaceuticals and fine chemicals. Aldo-keto reductases (AKRs) constitute a superfamily of oxidoreductases that catalyze the reduction of aldehydes and ketones to their corresponding alcohols using NAD(P)H as a coenzyme. Knowledge about the crucial roles of AKRs immobilization in the biocatalytic synthesis of chiral alcohols is expanding. Herein, we reviewed the characteristics of various AKRs immobilization approaches, the applications of different immobilization materials, and the prospects of continuous flow bioreactor construction by employing these immobilized biocatalysts for synthesizing chiral alcohols. Finally, the opportunities and ongoing challenges for AKR immobilization are discussed and the outlook for this emerging area is analyzed.

Enhancing Enzyme Stability and Functionality: Covalent Immobilization of Trypsin on Magnetic Gum Arabic Modified Fe3O4 Nanoparticles

This study aimed to fabricate gum Arabic (GA)-coated Fe3O4 nanoparticles bearing numerous active aldehyde groups on their surface, followed by an assessment of their capability as a magnetic support for the covalent immobilization of the trypsin enzyme for the first time. FT-IR, XRD, TGA, and SEM results demonstrated the successful synthesis of GA-coated Fe3O4 nanoparticles, along with the covalent immobilization of the enzyme onto the support. Immobilization enhanced the relative enzymatic activity across a range of aqueous solution pH levels (ranging from 4 to 11) and temperatures (ranging from 20 to 80 °C) without altering the optimum pH and temperature for trypsin activity. Kinetic studies using Michaelis-Menten plots revealed changes in kinetic parameters, including a lower Vmax and higher Km for immobilized trypsin compared to the free enzyme. The immobilization onto magnetic gum Arabic nanoparticles resulted in an improved stability of trypsin in the presence of various solvents, maintaining a stability order comparable to that of the free enzyme due to the stabilizing effect of the support. The reusability results showed that the immobilized enzyme can retain over 93% of its activity for up to 15 cycles.

Investigation of Antibody Tolerance in Methanol for Analytical Purposes: Methanol Effect Patterns and Molecular Mechanisms

The extraction of targets from biological samples for immunoassays using organic solvents, such as methanol, is often necessary. However, high concentrations of organic solvents in extracts invariably lead to instability of the employed antibody, resulting in poor performance of the immunoassay. Evaluating the tolerance ability and exploring the molecular mechanisms of antibody tolerance in organic solvents are essential for the development of robust immunoassays. In this work, 25 monoclonal antibodies and methanol are utilized as models to address these questions. A novel protocol is initially established to precisely and rapidly determine antibody tolerance in methanol, identifying two distinct methanol effect patterns. Through a detailed investigation of the structural basis, a novel hypothesis regarding methanol effect patterns is proposed, termed "folding-aggregation," which is subsequently validated through molecular dynamics simulations. Furthermore, the investigation of sequence basis reveals significant differences in residue types within the complementarity-determining regions and ligand-binding residues, distinguishing the two antibody methanol effect patterns. Moreover, the methanol effect patterns of the antibodies are defined by germline antibodies. This work represents the first exploration of antibody methanol effect patterns and associated molecular mechanisms, with potential implications for the discovery and engineering of tolerant antibodies for the development of robust immunoassays.

Programming aliphatic polyester degradation by engineered bacterial spores

Enzymatic degradation of plastics is a sustainable approach to addressing the growing issue of plastic accumulation. The primary challenges for using enzymes as catalysts are issues with their stability and recyclability, further exacerbated by their costly production and delicate structures. Here, we demonstrate an approach that leverages engineered spores that display target enzymes in high density on their surface to catalyze aliphatic polyester degradation and create self-degradable materials. Engineered spores display recombinant enzymes on their surface, eliminating the need for costly purification processes. The intrinsic physical and biological characteristics of spores enable easy separation from the reaction mixture, repeated reuse, and renewal. Engineered spores displaying lipases completely degrade aliphatic polyesters and retain activity through four cycles, with full activity recovered through germination and sporulation. Directly incorporating spores into polyesters results in robust materials that are completely degradable. Our study offers a straightforward and sustainable biocatalytic approach to plastic degradation.

A review on the immobilization of bromelain

This review shows the endeavors performed to prepare immobilized formulations of bromelain extract, usually from pineapple, and their use in diverse applications. This extract has a potent proteolytic component that is based on thiol proteases, which differ depending on the location on the fruit. Stem and fruit are the areas where higher activity is found. The edible origin of this enzyme is one of the features that determines the applications of the immobilized bromelain to a more significant degree. The enzyme has been immobilized on a wide diversity of supports via different strategies (covalent bonds, ion exchange), and also forming ex novo solids (nanoflowers, CLEAs, trapping in alginate beads, etc.). The use of preexisting nanoparticles as immobilization supports is relevant, as this facilitates one of the main applications of the immobilized enzyme, in therapeutic applications (as wound dressing and healing components, antibacterial or anticancer, mucus mobility control, etc.). A curiosity is the immobilization of this enzyme on spores of probiotic microorganisms via adsorption, in order to have a perfect in vivo compatibility. Other outstanding applications of the immobilized enzyme are in the stabilization of wine versus haze during storage, mainly when immobilized on chitosan. Curiously, the immobilized bromelain has been scarcely applied in the production of bioactive peptides.

Solvent concentration at 50% protein unfolding may reform enzyme stability ranking and process window identification

As water miscible organic co-solvents are often required for enzyme reactions to improve e.g., the solubility of the substrate in the aqueous medium, an enzyme is required which displays high stability in the presence of this co-solvent. Consequently, it is of utmost importance to identify the most suitable enzyme or the appropriate reaction conditions. Until now, the melting temperature is used in general as a measure for stability of enzymes. The experiments here show, that the melting temperature does not correlate to the activity observed in the presence of the solvent. As an alternative parameter, the concentration of the co-solvent at the point of 50% protein unfolding at a specific temperature T in shortc U 50 T is introduced. Analyzing a set of ene reductases,c U 50 T is shown to indicate the concentration of the co-solvent where also the activity of the enzyme drops fastest. Comparing possible rankings of enzymes according to melting temperature andc U 50 T reveals a clearly diverging outcome also depending on the specific solvent used. Additionally, plots ofc U 50 versus temperature enable a fast identification of possible reaction windows to deduce tolerated solvent concentrations and temperature.

Solvent Tolerance Improvement of Lipases Enhanced Their Applications: State of the Art

Lipases, crucial catalysts in biochemical synthesis, find extensive applications across industries such as food, medicine, and cosmetics. The efficiency of lipase-catalyzed reactions is significantly influenced by the choice of solvents. Polar organic solvents often result in a decrease, or even loss, of lipase activity. Conversely, nonpolar organic solvents induce excessive rigidity in lipases, thereby affecting their activity. While the advent of new solvents like ionic liquids and deep eutectic solvents has somewhat improved the activity and stability of lipases, it fails to address the fundamental issue of lipases' poor solvent tolerance. Hence, the rational design of lipases for enhanced solvent tolerance can significantly boost their industrial performance. This review provides a comprehensive summary of the structural characteristics and properties of lipases in various solvent systems and emphasizes various strategies of protein engineering for non-aqueous media to improve lipases' solvent tolerance. This study provides a theoretical foundation for further enhancing the solvent tolerance and industrial properties of lipases.

An In Vitro Hybrid Biocatalytic System Enabled by a Combination of Surface-Displayed, Purified, and Cell-Free Expressed Enzymes

Enzymatic cascades have become a green and sustainable approach for the synthesis of valuable chemicals and pharmaceuticals. Using sequential enzymes to construct a multienzyme complex is an effective way to enhance the overall performance of biosynthetic routes. Here we report the design of an efficient in vitro hybrid biocatalytic system by assembling three enzymes that can convert styrene to (S)-1-phenyl-1,2-ethanediol. Specifically, we prepared the three enzymes in different ways, which were cell surface-displayed, purified, and cell-free expressed. To assemble them, we fused two orthogonal peptide-protein pairs (i.e., SpyTag/SpyCatcher and SnoopTag/SnoopCatcher) to the three enzymes, allowing their spatial organization by covalent assembly. By doing this, we constructed a multienzyme complex, which could enhance the production of (S)-1-phenyl-1,2-ethanediol by 3 times compared to the free-floating enzyme system without assembly. After optimization of the reaction system, the final product yield reached 234.6 μM with a substrate conversion rate of 46.9% (based on 0.5 mM styrene). Taken together, our strategy integrates the merits of advanced biochemical engineering techniques, including cellular surface display, spatial enzyme organization, and cell-free expression, which offers a new solution for chemical biosynthesis by enzymatic cascade biotransformation. We, therefore, anticipate that our approach will hold great potential for designing and constructing highly efficient systems to synthesize chemicals of agricultural, industrial, and pharmaceutical significance.

Enhanced triolein and ethyl ferulate interesterification performance by CRL-AuNPs

This study established a Candida rugosa lipase (CRL) system to catalyze triolein and ethyl ferulate interesterification. The products were identified, and the binding mode between the substrates and CRL was predicted through molecular docking. Three methods for preparing CRL-AuNPs were proposed and characterized. It was found that the addition of 40 mL of 15 nm gold nanoparticles increased the CRL activity from 3.05 U/mg to 4.75 U/mg, but the hybridization efficiency was only 32.7 %. By using 4 mL of 0.1 mg/mL chloroauric acid, the hybridization efficiency was improved to 50.7 %, but the enzyme activity was sharply decreased. However, when the molar ratio of Mb to HAuCl4 was 0.2, the hybridization efficiency increased to 71.8 %, and the CRL activity was also enhanced to 5.98 U/mg. Under optimal conditions, the enzyme activity of CRL-AuNPs③ was maintained at 95 % after 6 repetitions and 85.6 % after 30 days at room temperature.

Evaluation of the operational conditions of the glucose oxidase and catalase multienzymatic system through enzyme co-immobilization on amino hierarchical porous silica

Hexaric acids have attracted attention lately because they are platform chemicals for synthesizing pharmaceuticals. In particular, gluconic acid is one of the most studied because it is readily available in nature. In this work, operational conditions like temperature and pH were evaluated for the enzymatic production of gluconic acid. For this purpose, glucose oxidase (GOx) and catalase (CAT) were individually immobilized and co-immobilized using amino-silica as support. The catalytic performance of the enzymes both as separate biocatalysts (GOx or CAT) and as an enzymatic complex (GOx-CAT) was assessed in terms of enzymatic activity and stability at temperatures 45 °C and 50 °C and pH 6 to 8. The results show that CAT is a key enzyme for gluconic acid production as it prevents GOx from being inhibited by H2O2. However, CAT was found to be less stable than GOx. Therefore, different GOx to CAT enzymatic ratios were studied, and a ratio of 1-3 was determined to be the best. The highest glucose conversion conditions were 45 °C and pH 7.0 for 24 h. Regarding the biocatalyst reuse, GOx-CAT retained more than 70% of its activity after 6 reaction cycles. These results contribute to further knowledge and application of oxidases for hexaric acid production and shed greater light on the role of the glucose oxidase/catalase pair in better catalytic performance. Both enzymes were immobilized in one pot, which is relevant for their potential use in industry; an enzyme system was obtained in a single step.

Engineering diaryl alcohol dehydrogenase KpADH reveals importance of retaining hydration shell in organic solvent tolerance

Alcohol dehydrogenases (ADHs) are synthetically important biocatalysts for the asymmetric synthesis of chiral alcohols. The catalytic performance of ADHs in the presence of organic solvents is often important since most prochiral ketones are highly hydrophobic. Here, the organic solvent tolerance of KpADH from Kluyveromyces polyspora was semi-rationally evolved. Using tolerant variants obtained, meticulous experiments and computational studies were conducted to explore properties including stability, activity and kinetics in the presence of various organic solvents. Compared with WT, variant V231D exhibited 1.9-fold improvement in ethanol tolerance, while S237G showed a 6-fold increase in catalytic efficiency, a higherT 50 15 $$ {\mathrm{T}}_{50}^{15} $$ , as well as 15% higher tolerance in 7.5% (v/v) ethanol. Based on 3 × 100 ns MD simulations, the increased tolerance of V231D and S237G against ethanol may be ascribed to their enhanced ability in retaining water molecules and repelling ethanol molecules. Moreover, 6.3-fold decreased KM value of V231D toward hydrophilic ketone substrate confirmed its capability of retaining hydration shell. Our results suggest that retaining hydration shell surrounding KpADH is critical for its tolerance to organic solvents, as well as catalytic performance. This study provides useful guidance for engineering organic solvent tolerance of KpADH and other ADHs.

Structure-based modification of a-amylase by conventional and emerging technologies: Comparative study on the secondary structure, activity, thermal stability and amylolysis efficiency

α-Amylase is an endo-enzyme that catalyzes the hydrolysis of starch into shorter oligosaccharides. α-Amylase plays a crucial role in various industries. Manipulated α-amylases are of particular interest due to their remarkable amylolysis efficiency and thermostability for large-scale biotechnological processes. The retained catalytic activity of enzymes is decreased according to extreme pH, temperature, pressure, and chemical reagents. Broad industrial applications of α-amylases need special properties such as stability against temperature, pH, and chelators, and also attain reusability, desirable enzymatic activity, efficiency, and selectivity. Considering the biotechnological importance of α-amylase, its high stability is the most critical challenge for its economic viability. Therefore, improving its functionality and stability recently gained much interest. To achieve this purpose, various emerging technologies in combination with conventional methods on α-Amylases with different sources have been conducted. The present review is an attempt to summarize the effect of various conventional methods and emerging technologies employed to date on α-amylase secondary structure, thermal stability, and performance.

Do Ionic Liquids Exhibit the Required Characteristics to Dissolve, Extract, Stabilize, and Purify Proteins? Past-Present-Future Assessment

Proteins are highly labile molecules, thus requiring the presence of appropriate solvents and excipients in their liquid milieu to keep their stability and biological activity. In this field, ionic liquids (ILs) have gained momentum in the past years, with a relevant number of works reporting their successful use to dissolve, stabilize, extract, and purify proteins. Different approaches in protein-IL systems have been reported, namely, proteins dissolved in (i) neat ILs, (ii) ILs as co-solvents, (iii) ILs as adjuvants, (iv) ILs as surfactants, (v) ILs as phase-forming components of aqueous biphasic systems, and (vi) IL-polymer-protein/peptide conjugates. Herein, we critically analyze the works published to date and provide a comprehensive understanding of the IL-protein interactions affecting the stability, conformational alteration, unfolding, misfolding, and refolding of proteins while providing directions for future studies in view of imminent applications. Overall, it has been found that the stability or purification of proteins by ILs is bispecific and depends on the structure of both the IL and the protein. The most promising IL-protein systems are identified, which is valuable when foreseeing market applications of ILs, e.g., in "protein packaging" and "detergent applications". Future directions and other possibilities of IL-protein systems in light-harvesting and biotechnology/biomedical applications are discussed.

Targeted Detoxification of Aflatoxin B1 in Edible Oil by an Enzyme-Metal Nanoreactor

Mycotoxin contamination is an important issue for food safety and the environment. Removing mycotoxins from food without losing nutrients and flavor components remains a challenge. In this study, a novel strategy was proposed for the targeted removal of aflatoxin B1 (AFB1) from peanut oil using an amphipathic enzyme-metal hybrid nanoreactor (PL-GOx-Fe3O4@COF) constructed with covalent organic frameworks (COFs) which can selectively adsorb AFB1. Due to the confined space provided by COFs and the proximity effect between GOx and Fe3O4, the detoxification of AFB1 is limited in the nanoreactor without affecting the composition and properties of the oil. The detoxification efficiency of AFB1 in the chemoenzymatic cascade reaction catalyzed by PL-GOx-Fe3O4@COF is six times higher than that of the combination of free GOx and Fe3O4. The AFB1 transformation product has nontoxicity to kidney and liver cells. This study provides a powerful tool for the targeted removal of mycotoxins from edible oils.

Stereoselective synthesis of (R)-(+)-1-(1-naphthyl)ethylamine by ω-amine transaminase immobilized on amino modified multi-walled carbon nanotubes and biocatalyst recycling

Immobilized enzymes exhibit favorable advantages in biocatalysis, such as high operation stability, feasible reusability, and improved organic solvents tolerance. Herein, an immobilized ω-amine transaminase AtATA@MWCNTs-NH2 is successfully prepared using amino modified multi-walled carbon nanotubes as carrier and glutaraldehyde as crosslinker. Under the optimum immobilization conditions, the activity recovery is 78.7%. Compared with purified enzyme AtATA, AtATA@MWCNTs-NH2 possesses superior stability, even in harsh conditions (e.g., high temperature, acidic or alkali environment, and different kind of organic solvents). To simplify the separation and extraction of products, we choose methanol (10%, v/v) as the cosolvent, replacing DMSO (20%, v/v) in our previous work, for the catalytic reaction of AtATA@MWCNTs-NH2. AtATA@MWCNTs-NH2 can be used for stereoselective synthesis (R)-(+)- 1(1-naphthyl)ethylamine ((R)-NEA) for 15 cycles, with the e.e.p (enantiomeric excess) > 99.5%. The catalytic process of AtATA@MWCNTs-NH2 achieves cycle production of (R)-NEA using methanol as cosolvent.

A multistep (semi)-continuous biocatalytic setup for the production of polycaprolactone

Biocatalysis has gained increasing importance as an eco-friendly alternative for the production of bulk and fine chemicals. Within this paradigm, Baeyer Villiger monoxygenases (BVMOs) serve as enzymatic catalysts that provide a safe and sustainable route to the conventional synthesis of lactones, such as caprolactone, which is employed for the production of polycaprolactone (PCL), a biocompatible polymer for medicinal applications. In this work, we present a three-step, semi-continuous production of PCL using an entirely biocatalytic process, highlighting the merits of continuous manufacturing for enhancing biocatalysis. First, caprolactone is produced in batch from cyclohexanol using a coenzymatic cascade involving an alcohol dehydrogenase (ADH) and BVMO. Different process parameters and aeration modes were explored to optimize the cascade's productivity. Secondly, the continuous extraction of caprolactone into an organic solvent, needed for the polymerization step, was optimized. 3D-printed mixers were applied to enhance the mass transfer between the organic and the aqueous phases. Lastly, we investigated the ring-opening polymerization of caprolactone to PCL catalyzed by Candida antarctica lipase B (CAL-B), with a focus on eco-friendly solvents like cyclopentyl-methyl-ether (CPME). Space-time-yields up to 58.5 g L-1 h-1 were achieved with our overall setup. By optimizing the individual process steps, we present an efficient and sustainable pathway for PCL production.

Potential utility of bacterial protein nanoreactor for sustainable in-situ biocatalysis in wide range of bioprocess conditions

Bacterial microcompartments (MCPs) are proteinaceous organelles that natively encapsulates the enzymes, substrates, and cofactors within a protein shell. They optimize the reaction rates by enriching the substrate in the vicinity of enzymes to increase the yields of the product and mitigate the outward diffusion of the toxic or volatile intermediates. The shell protein subunits of MCP shell are selectively permeable and have specialized pores for the selective inward diffusion of substrates and products release. Given their attributes, MCPs have been recently explored as potential candidates as subcellular nano-bioreactor for the enhanced production of industrially important molecules by exercising pathway encapsulation. In the current study, MCPs have been shown to sustain enzyme activity for extended periods, emphasizing their durability against a range of physical challenges such as temperature, pH and organic solvents. The significance of an intact shell in conferring maximum protection is highlighted by analyzing the differences in enzyme activities inside the intact and broken shell. Moreover, a minimal synthetic shell was designed with recruitment of a heterologous enzyme cargo to demonstrate the improved durability of the enzyme. The encapsulated enzyme was shown to be more stable than its free counterpart under the aforementioned conditions. Bacterial MCP-mediated encapsulation can serve as a potential strategy to shield the enzymes used under extreme conditions by maintaining the internal microenvironment and enhancing their cycle life, thereby opening new means for stabilizing, and reutilizing the enzymes in several bioprocess industries.

Chemically Bonded Pepsin via Its Inert Center to Diazo Functionalized Silica Gel through Multipoint Attachment Mode: A Way of Restoring Biocatalytic Sustainability over "Wider pH" Range

Proteolytic enzymes play a pivotal role in the industry. Still, because of denaturation, the extensive applicability at their level of best catalytic efficiency over a more comprehensive pH range, particularly in alkaline conditions over pH 8, has not been fully developed. On the other hand, enzyme immobilization following a suitable protocol is a long pending issue that determines the conformational stability, specificity, selectivity, enantioselectivity, and activity of the native enzymes at long-range pH. As a bridge between these two findings, in an attempt at a freezing temperature 273-278 K at an alkaline pH, the diazo-functionalized silica gel (SG) surface has been used to rapidly diazo couple pepsin through its inert center, the O-carbon of the phenolic -OH of surface-occupied Tyr residues in a multipoint mode: when all the various protein groups, viz., amino, thiol, phenol, imidazole, carboxy, etc., in the molecular sequence including those belonging to the active sites, remain intact, the inherent inbuilt interactions among themselves remain. Thereby, the macromolecule's global conformation and helicity preserve the status quo. The dimension of the SG-enzyme conjugate confirms as {Si(OSi)4 (H2O)1.03}n {-O-Si(CH3)2-O-C6H4-N═N+}4·{pepsin}·yH2O; where the values of n and y have been determined respectively as 347 and 188. The material performs the catalytic activity much better at 7-8.5 than at pH 2-3.5 and continues for up to six months without any appreciable change.

Unravelling the Mechanism of Elastin-like Polypeptide-Enzyme Fusion Stabilization in Organic Solvents

Elastin-like polypeptides (ELP) are a class of materials that are widely used as purification tags and in potential therapeutic applications. We have used the hydrophobic nature of ELP to extract them into organic solvents and precipitate them to obtain highly pure materials. Although many different types of ELP have been rapidly purified in this manner, the underlying mechanism for this process and its ability to retain functional proteins within organic phase-rich media has been unclear. A cleavable ELP-Intein construct fused with the enzyme chorismate mutase (ELP-I-Cm2) was used to better understand the organic solvent extraction process for ELP and the factors impacting the retention of enzyme activity. Our extraction studies indicated that a cell lysis step was essential to stabilize the ELP-I-Cm2 in the organic phase, prevent intein cleavage, and extract the fusion protein with high efficiency and retained activity. Circular dichroism and infrared spectroscopic characterization of ELP-I-Cm2 in organic solvents and aqueous solutions of the extracted and precipitated material indicated that the ELP secondary structure was retained in both environments. Atomic force microscopy and negative stain transmission electron microscopy imaging of ELP-I-Cm2 in organic solvents revealed highly regular circular features that were ∼50 nm in diameter, in contrast to larger (>100 nm) irregular features found in aqueous solutions. Since reverse micelles have often been used in catalytic processes, we evaluated the enzymatic activity of the ELP-I-Cm2 reversed micelles in different organic solvent mixtures and found that Cm2-mediated reactions in organic media were of comparable rate and efficiency to those in aqueous media. Based on these findings, we report an exciting new opportunity for ELP-enzyme fusion applications by exploiting their ability to form catalytically active reverse micelles in organic media.

Atomic-level design of metalloenzyme-like active pockets in metal-organic frameworks for bioinspired catalysis

Natural metalloenzymes with astonishing reaction activity and specificity underpin essential life transformations. Nevertheless, enzymes only operate under mild conditions to keep sophisticated structures active, limiting their potential applications. Artificial metalloenzymes that recapitulate the catalytic activity of enzymes can not only circumvent the enzymatic fragility but also bring versatile functions into practice. Among them, metal-organic frameworks (MOFs) featuring diverse and site-isolated metal sites and supramolecular structures have emerged as promising candidates for metalloenzymes to move toward unparalleled properties and behaviour of enzymes. In this review, we systematically summarize the significant advances in MOF-based metalloenzyme mimics with a special emphasis on active pocket engineering at the atomic level, including primary catalytic sites and secondary coordination spheres. Then, the deep understanding of catalytic mechanisms and their advanced applications are discussed. Finally, a perspective on this emerging frontier research is provided to advance bioinspired catalysis.

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 %.

Understanding the intricacy of protein in hydrated deep eutectic solvent: Solvation dynamics, conformational fluctuation dynamics, and stability

Deep eutectic solvents (DESs) are potential biocatalytic media due to their easy preparation, fine-tuneability, biocompatibility, and most importantly, due to their ability to keep protein stable and active. However, there are many unanswered questions and gaps in our knowledge about how proteins behave in these alternate media. Herein, we investigated solvation dynamics, conformational fluctuation dynamics, and stability of human serum albumin (HSA) in 0.5 Acetamide/0.3 Urea/0.2 Sorbitol (0.5Ac/0.3Ur/0.2Sor) DES of varying concentrations to understand the intricacy of protein behaviour in DES. Our result revealed a gradual decrease in the side-chain flexibility and thermal stability of HSA beyond 30 % DES. On the other hand, the associated water dynamics around domain-I of HSA decelerate only marginally with increasing DES content, although viscosity rises considerably. We propose that even though macroscopic solvent properties are altered, a protein feels only an aqueous type of environment in the presence of DES. This is probably the first experimental study to delineate the role of the associated water structure of the enzyme for maintaining its stability inside DES. Although considerable effort is necessary to generalize such claims, it might serve as the basis for understanding why proteins remain stable and active in DES.

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.

Evolution of Organic Solvent-Resistant DNA Polymerases

The introduction of thermostable polymerases revolutionized the polymerase chain reaction (PCR) and biotechnology. However, many GC-rich genes cannot be PCR-amplified with high efficiency in water, irrespective of temperature. Although polar organic cosolvents can enhance nucleic acid polymerization and amplification by destabilizing duplex DNA and secondary structures, nature has not selected for the evolution of solvent-tolerant polymerase enzymes. Here, we used ultrahigh-throughput droplet-based selection and deep sequencing along with computational free-energy and binding affinity calculations to evolve Taq polymerase to generate enzymes that are both stable and highly active in the presence of organic cosolvents, resulting in up to 10% solvent resistance and over 100-fold increase in stability at 97.5 °C in the presence of 1,4-butanediol, as well as tolerance to up to 10 times higher concentrations of the potent cosolvents sulfolane and 2-pyrrolidone. Using these polymerases, we successfully amplified a broad spectrum of GC-rich templates containing regions with over 90% GC content, including templates recalcitrant to amplification with existing polymerases, even in the presence of cosolvents. We also demonstrated dramatically reduced GC bias in the amplification of genes with widely varying GC content in quantitative polymerase chain reaction (qPCR). By expanding the scope of solvent systems compatible with nucleic acid polymerization, these organic solvent-resistant polymerases enable a dramatic reduction of sequence bias not achievable through thermal resistance alone, with significant implications for a wide range of applications including sequencing and synthetic biology in mixed aqueous-organic media.

Accelerating Biocatalysis Discovery with Machine Learning: A Paradigm Shift in Enzyme Engineering, Discovery, and Design

Emerging computational tools promise to revolutionize protein engineering for biocatalytic applications and accelerate the development timelines previously needed to optimize an enzyme to its more efficient variant. For over a decade, the benefits of predictive algorithms have helped scientists and engineers navigate the complexity of functional protein sequence space. More recently, spurred by dramatic advances in underlying computational tools, the promise of faster, cheaper, and more accurate enzyme identification, characterization, and engineering has catapulted terms such as artificial intelligence and machine learning to the must-have vocabulary in the field. This Perspective aims to showcase the current status of applications in pharmaceutical industry and also to discuss and celebrate the innovative approaches in protein science by highlighting their potential in selected recent developments and offering thoughts on future opportunities for biocatalysis. It also critically assesses the technology's limitations, unanswered questions, and unmet challenges.