Magnetic micro-macro biocatalysts applied to industrial bioprocesses

Vinyl sulfone-amino-alkyl supports: heterofunctional matrixes to prevent enzyme release and stabilize lipases via covalent immobilization

New trifunctional supports were prepared (amino-octyl-vinyl sulfone (VS)- and amino-hexyl-VS-agarose) and compared to octyl-VS-agarose. They were utilized to immobilize the lipases A and B from Candida antarctica (CALA and CALB). After incubation to generate some enzyme-support bonds and blocking with different nucleophiles, SDS-PAGE analyses showed that all enzyme molecules become covalently immobilized on the support. In all VS biocatalysts, the blocking reagent presented a great effect in the properties of enzymes. The best blocking agents promoted a significant enzyme stabilization compared to the enzyme stability using the amino-alkyl-agarose supports, higher than that using octyl-VS-agarose supports, although these remained the most stable ones in most cases, as the octyl-biocatalysts were significantly more stable than the enzyme immobilized on amino-alkyl-support. Enzyme activities and specificities could be also greatly tuned by the immobilization in the new trifunctional supports, with enzyme activities in many instances enhancing that of the best non-covalently immobilized enzyme. That way, the results on this paper show that the properties of the enzymes when immobilized on these new trifunctional supports may be significantly tuned by the nature of the acyl chain in the support and the nature of the reagent used to block the reactivity of the remaining VS groups.

Alcalase immobilization in iota-carrageenan-matrix hydrogel beads derived from the macroalga Solieria filiformis

This study aims to immobilize Bacillus licheniformis (Alcalase) protease in iota-carrageenan (ιCAR) matrix hydrogels via adsorption. CAR was extracted from macroalgae Solieria filiformis and used to produce hydrogels using Al3 + as the gelling agent. Subsequently, enzyme immobilization was performed at 25ºC, for 120 min using particles of ∼2.0 mm diameter, varying the medium pH values (7.0, 8.0, and 9.0). The immobilization at pH 8.0 resulted in the biocatalyst with the highest immobilization yield (100 %), expressed activity (88.9 %), and mass activity (10.4 U/g) for 1.0 mg/g of enzyme loading. When using particles with different diameters (1.0, 2.0, and 3.0 mm), the best results were obtained using 1.0 mm particles. This permitted a 100 % immobilization yield, 95.8 % expressed activity, and high mass activity (11.2 U/g). The lyophilized biocatalyst presented varying macro-pore diameters, ranging from 21 to 126 µm. The immobilized biocatalyst was 11 times more stable than the soluble enzyme at 60ºC and pH 8.0 and presented > 80 % retained activity in the pH range 6.0-9.0.

Various Options for Covalent Immobilization of Cysteine Proteases-Ficin, Papain, Bromelain

This study explores various methods for the covalent immobilization of cysteine proteases (ficin, papain, and bromelain). Covalent immobilization involves the formation of covalent bonds between the enzyme and a carrier or between enzyme molecules themselves without a carrier using a crosslinking agent. This process enhances the stability of the enzyme and allows for the creation of preparations with specific and controlled properties. The objective of this study is to evaluate the impact of covalent immobilization under different conditions on the proteolytic activity of the enzymes. The most favorable results were achieved by immobilizing ficin and bromelain through covalent bonding to medium and high molecular weight chitosans, using 5 and 3.33% glutaraldehyde solutions, respectively. For papain, 5 and 6.67% glutaraldehyde solutions proved to be more effective as crosslinking agents. These findings indicate that covalent immobilization can enhance the performance of these enzymes as biocatalysts, with potential applications in various biotechnological fields.

Encapsulation of Immobilized β-Glucosidase with Calcium Metal-Organic Frameworks for Enhanced Stability in Hydrolysis of Cellobiose

β-Glucosidase (β-G) holds promising applications in various fields, such as biomass energy, food, pharmaceuticals, and environmental protection, yet its industrial application is still limited by issues of stability and recycling. Herein, we first immobilized β-G onto the surface of magnetic chitosan nanoparticles (MCS/β-G) through adsorption methods. Subsequently, utilizing the metal-organic framework (MOF), CaBDC, which possesses good stability under acidic conditions, we encapsulated MCS/β-G. The resulting biocatalyst (MCS/β-G@CaBDC) exhibited excellent activity and recyclability. MCS/β-G@CaBDC can convert 91.5% of cellobiose to glucose in 60 min and maintained 81.9% activity after 10 cycles. The apparent Km value of MCS/β-G@CaBDC was 0.148 mM, lower than free β-G (0.166 mM) and MCS/β-G (0.173 mM). The CaBDC layer increased the mass transfer resistance of the reaction but also triggered structural rearrangement of β-G during the encapsulation process. This resulted in the β-sheet content rising to 68.4%, which, in turn, contributed to enhancing the rigidity of β-G. Moreover, the saturated magnetic strength of this biocatalyst could reach 37.3 emu/g, facilitating its magnetic recovery. The biocatalyst prepared in this study exhibits promising application prospects, and the immobilization method can provide valuable insights into the field of enzyme immobilization.

An Overview of Crosslinked Enzyme Aggregates: Concept of Development and Trends of Applications

Enzymes are commonly used as biocatalysts for various biological and chemical processes in industrial applications. However, their limited operational stability, catalytic efficiency, poor reusability, and high-cost hamper further industrial usage. Thus, crosslinked enzyme aggregates (CLEAs) are developed as a better enzyme immobilization tool to extend the enzymes' operational stability. This immobilization method is appealing because it is simpler due to the absence of ballast and permits the collective use of crude enzyme cocktails. CLEAs, so far, have been successfully developed using a variety of enzymes, viz., hydrolases, proteases, amidases, lipases, esterases, and oxidoreductase. Recent years have seen the emergence of novel strategies for preparing better CLEAs, which include the combi- and multi-CLEAs, magnetics CLEAs, and porous CLEAs for various industrial applications, viz., laundry detergents, organic synthesis, food industries, pharmaceutical applications, oils, and biodiesel production. To better understand the different strategies for CLEAs' development, this review explores these strategies and highlights the relevant concerns in designing innovative CLEAs. This article also details the challenges faced during CLEAs preparation and solutions for overcoming them. Finally, the trending strategies to improve the preparation of CLEAs alongside their industrial application trends are also discussed.

Green nanobiocatalysts: enhancing enzyme immobilization for industrial and biomedical applications

Nanobiocatalysts (NBCs), which merge enzymes with nanomaterials, provide a potent method for improving enzyme durability, efficiency, and recyclability. This review highlights the use of eco-friendly synthesis methods to create sustainable nanomaterials for enzyme transport. We investigate different methods of immobilization, such as adsorption, ionic and covalent bonding, entrapment, and cross-linking, examining their pros and cons. The decreased environmental impact of green-synthesized nanomaterials from plants, bacteria, and fungi is emphasized. The review exhibits the various uses of NBCs in food industry, biofuel production, and bioremediation, showing how they can enhance effectiveness and eco-friendliness. Furthermore, we explore the potential impact of NBCs in biomedicine. In general, green nanobiocatalysts are a notable progression in enzyme technology, leading to environmentally-friendly and effective biocatalytic methods that have important impacts on industrial and biomedical fields.

Enzymatic Transglycosylation Features in Synthesis of 8-Aza-7-Deazapurine Fleximer Nucleosides by Recombinant E. coli PNP: Synthesis and Structure Determination of Minor Products

Enzymatic transglycosylation of the fleximer base 4-(4-aminopyridine-3-yl)-1H-pyrazole using recombinant E. coli purine nucleoside phosphorylase (PNP) resulted in the formation of "non-typical" minor products of the reaction. In addition to "typical" N1-pyrazole nucleosides, a 4-imino-pyridinium riboside and a N1-pyridinium-N1-pyrazole bis-ribose derivative were formed. N1-Pyrazole 2'-deoxyribonucleosides and a N1-pyridinium-N1-pyrazole bis-2'-deoxyriboside were formed. But 4-imino-pyridinium deoxyriboside was not formed in the reaction mixture. The role of thermodynamic parameters of key intermediates in the formation of reaction products was elucidated. To determine the mechanism of binding and activation of heterocyclic substrates in the E. coli PNP active site, molecular modeling of the fleximer base and reaction products in the enzyme active site was carried out. As for N1-pyridinium riboside, there are two possible locations for it in the PNP active site. The presence of a relatively large space in the area of amino acid residues Phe159, Val178, and Asp204 allows the ribose residue to fit into that space, and the heterocyclic base can occupy a position that is suitable for subsequent glycosylation. Perhaps it is this "upside down" arrangement that promotes secondary glycosylation and the formation of minor bis-riboside products.

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.

Recent applications and future prospects of magnetic biocatalysts

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

Peptides with biological and technofunctional properties produced by bromelain hydrolysis of proteins from different sources: A review

Bromelains are cysteine peptidases with endopeptidase action (a subfamily of papains), obtained from different parts of vegetable belonging to the Bromeliaceae family. They have some intrinsic medical activity, but this review is focused on their application (individually or mixed with other proteases) to produce bioactive peptides. When compared to other proteases, perhaps due to the fact that they are commercialized as an extract containing several proteases, the hydrolysates produced by this enzyme tends to have higher bioactivities than other common proteases. The peptides and the intensity of their final properties depend on the substrate protein and reaction conditions, being the degree of hydrolysis a determining parameter (but not always positive or negative). The produced peptides may have diverse activities such as antioxidant, antitumoral, antihypertensive or antimicrobial ones, among others or they may be utilized to improve the organoleptic properties of foods and feeds. Evolution of the use of this enzyme in this application is proposed to be based on a more intense direct application of Bromeliaceae extract, without the cost associated to enzyme purification, and the use of immobilized biocatalysts of the enzyme by simplifying the enzyme recovery and reuse, and also making the sequential hydrolysis using diverse proteases possible.

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.

Biocatalytic production of biolubricants: Strategies, problems and future trends

The increasing worries by the inadequate use of energy and the preservation of nature are promoting an increasing interest in the production of biolubricants. After discussing the necessity of producing biolubricants, this review focuses on the production of these interesting molecules through the use of lipases, discussing the different possibilities (esterification of free fatty acids, hydroesterification or transesterification of oils and fats, transesterification of biodiesel with more adequate alcohols, estolides production, modification of fatty acids). The utilization of discarded substrates has special interest due to the double positive ecological impact (e.g., oil distillated, overused oils). Pros and cons of all these possibilities, together with general considerations to optimize the different processes will be outlined. Some possibilities to overcome some of the problems detected in the production of these interesting compounds will be also discussed.

Enzyme immobilization technology as a tool to innovate in the production of biofuels: A special review of the Cross-Linked Enzyme Aggregates (CLEAs) strategy

This review emphasizes the crucial role of enzyme immobilization technology in advancing the production of two main biofuels, ethanol and biodiesel, with a specific focus on the Cross-linked Enzyme Aggregates (CLEAs) strategy. This method of immobilization has gained attention due to its simplicity and affordability, as it does not initially require a solid support. CLEAs synthesis protocol includes two steps: enzyme precipitation and cross-linking of aggregates using bifunctional agents. We conducted a thorough search for papers detailing the synthesis of CLEAs utilizing amylases, cellulases, and hemicellulases. These key enzymes are involved in breaking down starch or lignocellulosic materials to produce ethanol, both in first and second-generation processes. CLEAs of lipases were included as these enzymes play a crucial role in the enzymatic process of biodiesel production. However, when dealing with large or diverse substrates such as lignocellulosic materials for ethanol production and oils/fats for biodiesel production, the use of individual enzymes may not be the most efficient method. Instead, a system that utilizes a blend of enzymes may prove to be more effective. To innovate in the production of biofuels (ethanol and biodiesel), enzyme co-immobilization using different enzyme species to produce Combi-CLEAs is a promising trend.

An Up-to-Date Review on the Remediation of Dyes and Phenolic Compounds from Wastewaters Using Enzymes Immobilized on Emerging and Nanostructured Materials: Promises and Challenges

Addressing the critical issue of water pollution, this review article emphasizes the need to remove hazardous dyes and phenolic compounds from wastewater. These pollutants pose severe risks due to their toxic, mutagenic, and carcinogenic properties. The study explores various techniques for the remediation of organic contaminants from wastewater, including an enzymatic approach. A significant challenge in enzymatic wastewater treatment is the loss of enzyme activity and difficulty in recovery post-treatment. To mitigate these issues, this review examines the strategy of immobilizing enzymes on newly developed nanostructured materials like graphene, carbon nanotubes (CNTs), and metal-organic frameworks (MOFs). These materials offer high surface areas, excellent porosity, and ample anchoring sites for effective enzyme immobilization. The review evaluates recent research on enzyme immobilization on these supports and their applications in biocatalytic nanoparticles. It also analyzes the impact of operational factors (e.g., time, pH, and temperature) on dye and phenolic compound removal from wastewater using these enzymes. Despite promising outcomes, this review acknowledges the challenges for large-scale implementation and offers recommendations for future research to tackle these obstacles. This review concludes by suggesting that enzyme immobilization on these emerging materials could present a sustainable, environmentally friendly solution to the escalating water pollution crisis.

Co-Immobilization of Lipases with Different Specificities for Efficient and Recyclable Biodiesel Production from Waste Oils: Optimization Using Response Surface Methodology

Lipase-catalyzed transesterification is a promising and sustainable approach to producing biodiesel. To achieve highly efficient conversion of heterogeneous oils, combining the specificities and advantages of different lipases is an attractive strategy. To this end, highly active Thermomyces lanuginosus lipase (1,3-specific) and stable Burkholderia cepacia lipase (non-specific) were covalently co-immobilized on 3-glycidyloxypropyltrimethoxysilane (3-GPTMS) modified Fe₃O₄ magnetic nanoparticles (co-BCL-TLL@Fe₃O₄). The co-immobilization process was optimized using response surface methodology (RSM). The obtained co-BCL-TLL@Fe₃O₄ exhibited a significant improvement in activity and reaction rate compared with mono and combined-use lipases, achieving 92.9% yield after 6 h under optimal conditions, while individually immobilized TLL, immobilized BCL and their combinations exhibited yields of 63.3%, 74.2% and 70.6%, respectively. Notably, co-BCL-TLL@Fe₃O₄ achieved 90-98% biodiesel yields after 12 h using six different feedstocks, demonstrating the perfect synergistic effect of BCL and TLL remarkably motivated in co-immobilization. Furthermore, co-BCL-TLL@Fe₃O₄ could maintain 77% of initial activity after nine cycles by removing methanol and glycerol from catalyst surface, accomplished by washing with t-butanol. The high catalytic efficiency, wide substrate adaptability and favorable reusability of co-BCL-TLL@Fe₃O₄ suggest that it will be an economical and effective biocatalyst for further applications.

(Magnetic) Cross-Linked Enzyme Aggregates of Cellulase from T. reesei: A Stable and Efficient Biocatalyst

Cross-linked enzyme aggregates (CLEAs) represent an effective tool for carrier-free immobilization of enzymes. The present study promotes a successful application of functionalized magnetic nanoparticles (MNPs) for stabilization of cellulase CLEAs. Catalytically active CLEAs and magnetic cross-linked enzyme aggregates (mCLEAs) of cellulase from Trichoderma reesei were prepared using glutaraldehyde (GA) as a cross-linking agent and the catalytic activity and stability of the CLEAs/mCLEAs were investigated. The influence of precipitation agents, cross-linker concentration, concentration of enzyme, addition of bovine serum albumin (BSA), and addition of sodium cyanoborohydride (NaBH₃CN) on expressed activity and immobilization yield of CLEAs/mCLEAs was studied. Particularly, reducing the unsaturated Schiff's base to form irreversible linkages is important and improved the activity of CLEAs (86%) and mCLEAs (91%). For increased applicability of CLEAs/mCLEAs, we enhanced the activity and stability at mild biochemical process conditions. The reusability after 10 cycles of both CLEAs and mCLEAs was investigated, which retained 72% and 65% of the initial activity, respectively. The thermal stability of CLEAs and mCLEAs in comparison with the non-immobilized enzyme was obtained at 30 °C (145.65% and 188.7%, respectively) and 50 °C (185.1% and 141.4%, respectively). Kinetic parameters were determined for CLEAs and mCLEAs, and the K_M constant was found at 0.055 ± 0.0102 mM and 0.037 ± 0.0012 mM, respectively. The maximum velocity rate (V_max) was calculated as 1.12 ± 0.0012 µmol/min for CLEA and 1.17 ± 0.0023 µmol/min for mCLEA. Structural characterization was studied using XRD, SEM, and FT-IR. Catalytical properties of immobilized enzyme were improved with the addition of reducent NaBH₃CN by enhancing the activity of CLEAs and with addition of functionalized aminosilane MNPs by enhancing the activity of mCLEAs.

The application of conventional or magnetic materials to support immobilization of amylolytic enzymes for batch and continuous operation of starch hydrolysis processes

In the production of ethanol, starches are converted into reducing sugars by liquefaction and saccharification processes, which mainly use soluble amylases. These processes are considered wasteful operations as operations to recover the enzymes are not practical economically so immobilizations of amylases to perform both processes appear to be a promising way to obtain more stable and reusable enzymes, to lower costs of enzymatic conversions, and to reduce enzymes degradation/contamination. Although many reviews on enzyme immobilizations are found, they only discuss immobilizations of α-amylase immobilizations on nanoparticles, but other amylases and support types are not well informed or poorly stated. As the knowledge of the developed supports for most amylase immobilizations being used in starch hydrolysis is important, a review describing about their preparations, characteristics, and applications is herewith presented. Based on the results, two major groups were discovered in the last 20 years, which include conventional and magnetic-based supports. Furthermore, several strategies for preparation and immobilization processes, which are more advanced than the previous generation, were also revealed. Although most of the starch hydrolysis processes were conducted in batches, opportunities to develop continuous reactors are offered. However, the continuous operations are difficult to be employed by magnetic-based amylases.

Magnetic Multi-Enzymatic System for Cladribine Manufacturing

Enzyme-mediated processes have proven to be a valuable and sustainable alternative to traditional chemical methods. In this regard, the use of multi-enzymatic systems enables the realization of complex synthetic schemes, while also introducing a number of additional advantages, including the conversion of reversible reactions into irreversible processes, the partial or complete elimination of product inhibition problems, and the minimization of undesirable by-products. In addition, the immobilization of biocatalysts on magnetic supports allows for easy reusability and streamlines the downstream process. Herein we have developed a cascade system for cladribine synthesis based on the sequential action of two magnetic biocatalysts. For that purpose, purine 2′-deoxyribosyltransferase from Leishmania mexicana (LmPDT) and Escherichia coli hypoxanthine phosphoribosyltransferase (EcHPRT) were immobilized onto Ni2+-prechelated magnetic microspheres (MagReSyn®NTA). Among the resulting derivatives, MLmPDT3 (activity: 11,935 IU/gsupport, 63% retained activity, operational conditions: 40 °C and pH 5–7) and MEcHPRT3 (12,840 IU/gsupport, 45% retained activity, operational conditions: pH 5–8 and 40–60 °C) emerge as optimal catalysts for further synthetic application. Moreover, the MLmPDT3/MEcHPRT3 system was biochemically characterized and successfully applied to the one-pot synthesis of cladribine under various conditions. This methodology not only displayed a 1.67-fold improvement in cladribine synthesis (compared to MLmPDT3), but it also implied a practically complete transformation of the undesired by-product into a high-added-value product (90% conversion of Hyp into IMP). Finally, MLmPDT3/MEcHPRT3 was reused for 16 cycles, which displayed a 75% retained activity.

Rational Design of a Thermostable 2'-Deoxyribosyltransferase for Nelarabine Production by Prediction of Disulfide Bond Engineering Sites

One of the major drawbacks of the industrial implementation of enzymatic processes is the low operational stability of the enzymes under tough industrial conditions. In this respect, the use of thermostable enzymes in the industry is gaining ground during the last decades. Herein, we report a structure-guided approach for the development of novel and thermostable 2′-deoxyribosyltransferases (NDTs) based on the computational design of disulfide bonds on hot spot positions. To this end, a small library of NDT variants from Lactobacillus delbrueckii (LdNDT) with introduced cysteine pairs was created. Among them, LdNDTS104C (100% retained activity) was chosen as the most thermostable variant, displaying a six- and two-fold enhanced long-term stability when stored at 55 °C (t1/255 °C ≈ 24 h) and 60 °C (t1/260 °C ≈ 4 h), respectively. Moreover, the biochemical characterization revealed that LdNDTS104C showed >60% relative activity across a broad range of temperature (30−90 °C) and pH (5−7). Finally, to study the potential application of LdNDTS104C as an industrial catalyst, the enzymatic synthesis of nelarabine was successfully carried out under different substrate conditions (1:1 and 3:1) at different reaction times. Under these experimental conditions, the production of nelarabine was increased up to 2.8-fold (72% conversion) compared with wild-type LdNDT.

Nano-fibrillated cellulose-based scaffolds for enzyme (co)-immobilization: Application to natural product glycosylation by Leloir glycosyltransferases

Polysaccharide-based scaffolds are promising carriers for enzyme immobilization. Here, we demonstrate a porous scaffold prepared by direct-ink-writing 3D printing of an ink consisting of nanofibrillated cellulose, carboxymethyl cellulose and citric acid for immobilization application. Negative surface charge introduced by the components made the scaffold amenable for an affinity-like immobilization via the cationic protein module Z_basic2. Z_basic2 fusions of two sugar nucleotide-dependent glycosyltransferases (C-glycosyltransferase, Z-CGT; sucrose synthase, Z-SuSy) were immobilized individually, or co-immobilized, and applied to synthesize the natural C-glycoside nothofagin. The cascade reaction involved β-C-glycosylation of phloretin (10 mM, ~90 % conversion) from UDP-glucose, provided from sucrose and catalytic amounts of UDP (1.0 mM). Enzymes were co-immobilized at ~65 mg protein/g carrier to receive activities of 9.5 U/g (Z-CGT) and 4.5 U/g (Z-SuSy) in 22-33 % yield (protein) and an effectiveness of 23 % (Z-CGT) and 13 % (Z-SuSy). The scaffold-bound enzymes were recyclable for 5 consecutive reactions.

Is enzyme immobilization a mature discipline? Some critical considerations to capitalize on the benefits of immobilization

Enzyme immobilization has been developing since the 1960s and although many industrial biocatalytic processes use the technology to improve enzyme performance, still today we are far from full exploitation of the field. One clear reason is that many evaluate immobilization based on only a few experiments that are not always well-designed. In contrast to many other reviews on the subject, here we highlight the pitfalls of using incorrectly designed immobilization protocols and explain why in many cases sub-optimal results are obtained. We also describe solutions to overcome these challenges and come to the conclusion that recent developments in material science, bioprocess engineering and protein science continue to open new opportunities for the future. In this way, enzyme immobilization, far from being a mature discipline, remains as a subject of high interest and where intense research is still necessary to take full advantage of the possibilities.

Tuning Immobilized Commercial Lipase Preparations Features by Simple Treatment with Metallic Phosphate Salts

Four commercial immobilized lipases biocatalysts have been submitted to modifications with different metal (zinc, cobalt or copper) phosphates to check the effects of this modification on enzyme features. The lipase preparations were Lipozyme^®TL (TLL-IM) (lipase from Thermomyces lanuginose), Lipozyme^®435 (L435) (lipase B from Candida antarctica), Lipozyme^®RM (RML-IM), and LipuraSelect (LS-IM) (both from lipase from Rhizomucor miehei). The modifications greatly altered enzyme specificity, increasing the activity versus some substrates (e.g., TLL-IM modified with zinc phosphate in hydrolysis of triacetin) while decreasing the activity versus other substrates (the same preparation in activity versus R- or S- methyl mandelate). Enantiospecificity was also drastically altered after these modifications, e.g., LS-IM increased the activity versus the R isomer while decreasing the activity versus the S isomer when treated with copper phosphate. Regarding the enzyme stability, it was significantly improved using octyl-agarose-lipases. Using all these commercial biocatalysts, no significant positive effects were found; in fact, a decrease in enzyme stability was usually detected. The results point towards the possibility of a battery of biocatalysts, including many different metal phosphates and immobilization protocols, being a good opportunity to tune enzyme features, increasing the possibilities of having biocatalysts that may be suitable for a specific process.

Lipase immobilization via cross-linked enzyme aggregates: Problems and prospects - A review

In this review we have focused on the preparation of cross-linked enzyme aggregates (CLEAs) from lipases, as these are among the most used enzyme in bioprocesses. This immobilization method is considered very attractive due to preparation simplicity, non-use of supports and the possibility of using crude enzyme extracts. CLEAs provide lipase stabilization under extreme temperature or pH conditions or in the presence of organic solvents, in addition to preventing enzyme leaching in aqueous medium. However, it presents some problems in the preparation and limitations in their use. The problems in preparation refer mainly to the crosslinking step, and may be solved using an aminated feeder. The problems in handling have been tackled designing magnetic-CLEAs or trapping the CLEAs in particles with better mechanical properties, the substrate diffusion problems has been reduced by producing more porous-CLEAs, etc. The enzyme co-immobilization using combi-CLEAs is also a new tendency. Therefore, this review explores the CLEAs methodology aimed at lipase immobilization and its applications.

Surface-coated magnetic nanostructured materials for robust bio-catalysis and biomedical applications-A review

BACKGROUND

Enzymes based bio-catalysis has wide range of applications in various chemical and biological processes. Thus, the process of enzymes immobilization on suitable support to obtain highly active and stable bio-catalysts has great potential in industrial applications. Particularly, surface-modified magnetic nanomaterials have garnered a special interest as versatile platforms for biomolecules/enzyme immobilization.

AIM OF REVIEW

This review spotlights recent progress in the immobilization of various enzymes onto surface-coated multifunctional magnetic nanostructured materials and their derived nano-constructs for multiple applications. Conclusive remarks, technical challenges, and insightful opinions on this field of research which are helpful to expand the application prospects of these materials are also given with suitable examples.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Nanostructured materials, including surface-coated magnetic nanoparticles have recently gained immense significance as suitable support materials for enzyme immobilization, due to their large surface area, unique functionalities, and high chemical and mechanical stability. Besides, magnetic nanoparticles are less expensive and offers great potential in industrial applications due to their easy recovery and separation form their enzyme conjugates with an external magnetic field. Magnetic nanoparticles based biocatalytic systems offer a wide-working temperature, pH range, increased storage and thermal stabilities. So far, several studies have documented the application of a variety of surface modification and functionalization techniques to circumvent the aggregation and oxidation of magnetic nanoparticles. Surface engineering of magnetic nanoparticles (MNPs) helps to improve the dispersion stability, enhance mechanical and physicochemical properties, upgrade the surface activity and also increases enzyme immobilization capabilities and biocompatibility of the materials. However, several challenges still need to be addressed, such as controlled synthesis of MNPs and clinical aspects of these materials require consistent research from multidisciplinary scientists to realize its practical applications.

Facile preparation of amorphous cobalt phosphate as inorganic carrier for direct separation and immobilization of his-tagged β-glucosidase from cell lysate

The present work was aimed to develop a facile method to fabricate solid support for the separation and immobilization of his-tagged enzymes directly from cell lysate without pre-purification of the enzymes.

β-Galactosidase from Kluyveromyces lactis: Characterization, production, immobilization and applications - A review

A review on the enzyme β-galactosidase from Kluyveromyces lactis is presented, from the perspective of its structure and mechanisms of action, the main catalyzed reactions, the key factors influencing its activity, and selectivity, as well as the main techniques used for improving the biocatalyst functionality. Particular attention was given to the discussion of hydrolysis, transglycosylation, and galactosylation reactions, which are commonly mediated by this enzyme. In addition, the products generated from these processes were highlighted. Finally, biocatalyst improvement techniques are also discussed, such as enzyme immobilization and protein engineering. On these topics, the most recent immobilization strategies are presented, emphasizing processes that not only allow the recovery of the biocatalyst but also deliver enzymes that show better resistance to high temperatures, chemicals, and inhibitors. In addition, genetic engineering techniques to improve the catalytic properties of the β-galactosidases were reported. This review gathers information to allow the development of biocatalysts based on the β-galactosidase enzyme from K. lactis, aiming to improve existing bioprocesses or develop new ones.

Enhancing stability and by-product tolerance of β-glucuronidase based on magnetic cross-linked enzyme aggregates

β-glucuronidase is an important catalyst which is highly specific for β-glucuronides. Here, we constructed magnetic cross-linking β-glucuronidase aggregates (MCLEAs) to for the production of glycyrrhetinic acid (GA). Before crosslinking via glutaraldehyde, we used carbodiimide to enhance the interaction between enzymes and carboxyl-functionalized Fe₃O₄, efficiently improving the activity recovery. Compared to free enzymes, both k_cat and k_cat/K_m enhanced, indicating that crosslinking and aggregation brought higher catalytic efficiency to enzymes. MCLEAs enhanced pH and thermal stabilities and retained 63.3% of catalytic activity after 6 cycles. More importantly, it was first found that the glucuronic acid tolerance of β-glucuronidase after the formation of MCLEAs enhanced 221.5% in 10 mM of glucuronic acid. According to the Raman spectroscopy, the ordered structure of β-glucuronidase increased from 43.9% to 50.6% after immobilization, which explained the increased stability and tolerance. To sum up, MCLEAs provided an efficient strategy for immobilization of enzymes, which enhanced stability and glucuronic acid tolerance of enzymes. It might be an effective solution to the serious inhibition caused by by-products during the preparation of aglycone from natural glycosides, having a significant applied prospect in industry.

Taylor-made production of pyrimidine nucleoside-5'-monophosphate analogues by highly stabilized mutant uracil phosphoribosyltransferase from Toxoplasma gondii

Nowadays, enzymatic synthesis of nucleotides is an efficient and sustainable alternative to chemical methodologies. In this regard, after the biochemical characterization of wild-type and mutant uracil phosphoribosyltransferases from Toxoplasma gondii (TgUPRT, TgUPRT_2, and TgUPRT₃), TgUPRT₂ was selected as the optimal candidate (69.5 IU mg^-1, UMP synthesis) for structure-guided immobilization onto Ni²⁺ chelate (M_NiUPRT₂) and onto glutaraldehyde-activated microparticles (M_GlUPRT₂). Among resulting derivatives, M_NiUPRT₂3 (6127 IU g^-1_biocat; 92% retained activity; 3-5 fold enhanced stability at 50-60 °C) and M_GlUPRT₂N (3711 IU g^-1_biocat; 27% retained activity; 8-20 fold enhanced stability at 50-60 °C) displayed the best operability. Moreover, the enzymatic synthesis of different pyrimidine NMPs was performed. Finally, the reusability of both derivatives in 5-FUMP synthesis (M_NiUPRT₂3, 80% retained activity after 7 cycles, 5 min; M_GlUPRT₂N, 70% retained activity after 10 cycles, 20 min) was carried out at short times.

Nanobiocatalysts: Advancements and applications in enzyme technology

Nanobiocatalysts are one of the most promising biomaterials produced by synergistically integrating advanced biotechnology and nanotechnology. These have a lot of potential to improve enzyme stability, function, efficiencyand engineering performance in bioprocessing. Functional nanostructures have been used to create nanobiocatalystsbecause of their specific physicochemical characteristics and supramolecular nature. This review covers a wide range of nanobiocatalysts including polymeric, metallic, silica and carbon nanocarriers as well as their recent developments in controlling enzyme activity. The enormous potential of nanobiocatalysts in bioprocessing in designing effective laboratory trials forapplications in various fields such as food, pharmaceuticals, biofuel, and bioremediation is also discussed extensively.

Immobilization of papain: A review

Papain is a cysteine protease from papaya, with many applications due to its broad specificity. This paper reviews for first time the immobilization of papain on different supports (organic, inorganic or hybrid supports) presenting some of the features of the utilized immobilization strategies (e.g., epoxide, glutaraldehyde, genipin, glyoxyl for covalent immobilization). Special focus is placed on the preparation of magnetic biocatalysts, which will permit the simple recovery of the biocatalyst even if the medium is a suspension. Problems specific to the immobilization of proteases (e.g., steric problems when hydrolyzing large proteins) are also defined. The benefits of a proper immobilization (enzyme stabilization, widening of the operation window) are discussed, together with some artifacts that may suggest an enzyme stabilization that may be unrelated to enzyme rigidification.

Second- and third-generation biodiesel production with immobilised recombinant Rhizopus oryzae lipase: Influence of the support, substrate acidity and bioprocess scale-up

Rhizopus oryzae lipase immobilised onto differently functionalised polymethacrylate (Purolite®) and magnetite superparamagnetic supports was assessed as a catalyst for biodiesel production with pomace oil. The presence of surface hydrocarbon chains increased the operational stability of the biocatalysts supported on Purolite® and superparamagnetic particles up to 9 and 2 times, respectively. By contrast, the presence of functional groups had no effect on the initial transesterification rate, which was twice higher with the lipase immobilised onto Purolite®. Also, functionalising Purolite® with epoxide and octadecyl groups led to the highest biodiesel and volumetric productivity. This biocatalyst with other substrates including makauba, jatropha, waste cooking oil, and microbial oil, led to similar initial reaction rates. However, simply raising substrate acidity from 0.5 to 2% increased the operational stability of the biocatalysts 15 times. A synergistic effect between acyl-acceptor concentration and substrate acidity was observed. The transesterification reaction was successfully scaled up to 50 mL.

Bioactive peptides from fisheries residues: A review of use of papain in proteolysis reactions

Papain is a cysteine endopeptidase of vegetal origin (papaya (Carica papaya L.) with diverse applications in food technology. In this review we have focused our attention on its application in the production of bio-peptides by hydrolysis of proteins from fish residues. This way, a residual material, that can become a contaminant if dumped without control, is converted into highly interesting products. The main bioactivity of the produced peptides is their antioxidant activity, followed by their nutritional and functional activities, but peptides with many other bioactivities have been produced. Thera are also examples of production of hydrolysates with several bioactivities. The enzyme may be used alone, or in combination with other enzymes to increase the degree of hydrolysis.

Trends in the development of innovative nanobiocatalysts and their application in biocatalytic transformations

The ever-growing demand for cost-effective and innocuous biocatalytic transformations has prompted the rational design and development of robust biocatalytic tools. Enzyme immobilization technology lies in the formation of cooperative interactions between the tailored surface of the support and the enzyme of choice, which result in the fabrication of tremendous biocatalytic tools with desirable properties, complying with the current demands even on an industrial level. Different nanoscale materials (organic, inorganic, and green) have attracted great attention as immobilization matrices for single or multi-enzymatic systems. Aiming to unveil the potentialities of nanobiocatalytic systems, we present distinct immobilization strategies and give a thorough insight into the effect of nanosupports specific properties on the biocatalysts' structure and catalytic performance. We also highlight the development of nanobiocatalysts for their incorporation in cascade enzymatic processes and various types of batch and continuous-flow reactor systems. Remarkable emphasis is given on the application of such nanobiocatalytic tools in several biocatalytic transformations including bioremediation processes, biofuel production, and synthesis of bioactive compounds and fine chemicals for the food and pharmaceutical industry.

Multi-Enzyme Systems in Flow Chemistry

Recent years have witnessed a growing interest in the use of biocatalysts in flow reactors. This merging combines the high selectivity and mild operation conditions typical of biocatalysis with enhanced mass transfer and resource efficiency associated to flow chemistry. Additionally, it provides a sound environment to emulate Nature by mimicking metabolic pathways in living cells and to produce goods through the systematic organization of enzymes towards efficient cascade reactions. Moreover, by enabling the combination of enzymes from different hosts, this approach paves the way for novel pathways. The present review aims to present recent developments within the scope of flow chemistry involving multi-enzymatic cascade reactions. The types of reactors used are briefly addressed. Immobilization methodologies and strategies for the application of the immobilized biocatalysts are presented and discussed. Key aspects related to the use of whole cells in flow chemistry are presented. The combination of chemocatalysis and biocatalysis is also addressed and relevant aspects are highlighted. Challenges faced in the transition from microscale to industrial scale are presented and discussed.