Effects of Enzyme Loading and Immobilization Conditions on the Catalytic Features of Lipase From Pseudomonas fluorescens Immobilized on Octyl-Agarose Beads

Novel Immobilized Enzyme System Using Hydrophobic Dendritic Mesoporous Silica Nanospheres for Efficient Flavor Ester Production

Enzymatic synthesis of flavor esters is widely used in the food and flavor industries, but challenges remain in improving the catalytic efficiency and stability of biocatalysts. This study evaluates the performance of a novel biocatalyst, CALB@DMSN-C8, formed by immobilizing Candida antarctica lipase B (CALB) on hydrophobic dendritic mesoporous silica nanospheres (DMSN-C8), for synthesizing flavor esters. The CALB@DMSN-C8 catalyst achieves a caproic acid conversion rate of 98.5 ± 0.5% in just 30 min and demonstrates outstanding thermal stability, retaining a high conversion efficiency over 20 reuse cycles. To our knowledge, this study represents the most efficient synthesis of flavor esters, including ethyl valerate, ethyl caproate, ethyl heptanoate, and ethyl caprylate, compared to studies in the existing literature. Analysis of aroma characteristics and molecular docking simulations revealed the typical flavor profiles and synthesis mechanisms of various mellow esters. This study develops an innovative strategy by using self-made immobilized lipases to catalyze the production of flavor esters with potential applications in food and cosmetics.

A comprehensive review of lipase-catalyzed acidolysis as a method for producing structured glycerides

The production of structured lipids is a current trend in food technology in order to enhance the properties of fats and oils. Lipases have been utilized in many instances for this purpose, in most examples in an immobilized form. In this review, after discussing the different strategies to produce artificial lipids using lipases (esterification, transesterification, interesterification), we have focused on acidolysis. The reaction commences with hydrolysis at one position of the triglyceride molecule and is followed by the esterification between the released hydroxyl group and the target fatty acid (although other carboxylic acids can be used, such as phenolic acid derivatives). This means that water plays a double role, as substrate in the first step and as an undesired by-product in the second one. Therefore, the control of water activity becomes critical in these reactions. This review discusses the advantages, possibilities and drawbacks of this strategy to produce tailor-made designed lipids, summarizing many of the papers related to this strategy. The summarized results show the complexity of this reaction that can make the understanding and reproducibility of the reactions complex if there are no strict controls of all parameters determining the final yields.

Selective synthesis of triacylglycerols by the ADS-17-supported Candida antarctica lipase B through esterification of oleic acid and glycerol

BACKGROUND

Immobilized enzyme possessing both high activity and good selectivity is important in practice. In this study, Candida antarctica lipase B (CALB) was immobilized onto the macroporous resin ADS-17 for triacylglycerol (TAG) synthesis through esterification of oleic acid and glycerol. The reaction conditions were optimized by single-factor study and orthogonal test, and the reusability of the immobilized CALB (CALB@ADS-17) was evaluated. In addition, the mechanism of lipase immobilization was studied and the catalytic mechanism of CALB@ADS-17 was investigated.

RESULTS

Oleic acid conversion up to 99.20% and TAG content at 91.58 wt% could be obtained under optimal conditions. In addition, the CALB@ADS-17 retained 84.28% of its initial activity after 11 cycles of reuse. The mechanism of lipase immobilization was through hydrophobic adsorption. The relationship between temperature and oleic acid conversion was lnV0 = 6.3316 - 4.3321/T, and the activation energy (Ea) was 36.02 kJ mol-1. CALB@ADS-17 did not exhibit an obvious interfacial activation phenomenon. Its kinetic behavior can be described by the Michaelis-Menten model, whose kinetic parameters of vmax, kcat, Km, Ki, and kcat/Km were 0.01265 μmol L-1 s-1, 9310.72 s-1, 0.4907 mmol L-1, 3.997 mmol L-1, and 1.90 × 104 L mmol-1 s-1, respectively.

CONCLUSION

CALB@ADS-17 showed good esterification performance and exhibited good selectivity towards TAG generation. In addition, CALB@ADS-17 exhibited good reusability in esterification reactions and has potential in practical applications. © 2025 Society of Chemical Industry.

An AHL-lactonase mutant featuring a unique "tri-His" motif exhibits enhanced activity, stability and effectively controls plant soft rot

Quorum quenching through AHL-lactonase has been established as a critical approach for managing quorum sensing-mediated bacterial infections. While numerous studies have concentrated on enhancing the activity of AHL lactonases, concurrent improvements in both activity and stability have remained elusive. In this study, we adopted a hybrid strategy involving rational and semirational design to concurrently increase the activity and stability of the marine AHL-lactonase AhlX. The mutant M41 (E77I/D157G/T243Y/H255L) exhibited a significant increase in catalytic efficiency, with an 11-fold increase in kcat/Km, as well as a substantial increase in thermal stability, with a 12 °C increase in the melting temperature and a 0.6-fold longer half-life at 70 °C relative to those of wild-type AhlX. Structural insights from crystallographic analysis revealed a unique "tri-His" motif within the homohexamer that is pivotal for its stability. Removal of the "tri-His" motif from the homohexamer rendered the H158A mutant prone to thermal oligomer disassembly. Incorporation of the D157G mutation disrupted the D157-R122 salt bridge, stabilizing this motif. The T243Y and H255L mutations modify the active site conformation by reshaping surface interactions, enhancing both enzymatic activity and stability. Biocontrol experiments revealed that M41 was highly effective at suppressing potato soft rot caused by Pectobacterium carotovorum, primarily by inhibiting the swimming motility of the bacterium. This work not only deepens our understanding of the structure-activity relationships of AHL-lactonases but also lays a solid theoretical foundation for the engineering of these enzymes for biocontrol applications.

Enzyme loading in the support and medium composition during immobilization alter activity, specificity and stability of octyl agarose-immobilized Eversa Transform

Eversa Transform (ETL) was immobilized on octyl agarose beads at two different enzymes loadings (1 mg/g and 15 mg/g) under 18 different conditions, including different pH values, buffers, additives (different solvents, Ca2+, NaCl). Their activity was analyzed at pH 5 and 7 with p-nitrophenyl butyrate and at pH 5 with triacetin, determining also its stability at pH 5 and 7 (in different media). Ca2+ stabilized ETL biocatalysts while phosphate destabilized them. The overloaded biocatalysts were generally less stable and with a lower specific activity than the lowly loaded biocatalyst. Results show that enzyme activity (even by a 3 fold factor) and stability of the immobilized enzyme may be tailored by controlling the immobilization conditions, but the effects of the immobilization conditions on activity depend on the substrate and conditions of activity determination, the effects on stability depend on the inactivation conditions. Moreover, the enzyme loading of the biocatalysts defines the effects of the immobilization conditions, and there are clear interactions between immobilization conditions (e.g., immobilization pH determines the effect of the presence of NaCl). These suggest that the extrapolation of the results obtained with one substrate under one condition to other conditions can lead to wrong decisions.

Enhanced Biodiesel Production with Eversa Transform 2.0 Lipase on Magnetic Nanoparticles

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

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.

Enhancement of stability and activity of RSD amylase from Paenibacillus lactis OPSA3 for biotechnological applications by covalent immobilization on green silver nanoparticles

The key challenge to the biotechnological applications of amylases is achieving high activity and stability under extreme pH, temperature and often high levels of enzyme denaturants. This study immobilized a novel raw starch-digesting (RSD) amylase from Paenibacillus lactis OPSA3 on glutaraldehyde-activated silver nanoparticles. Effects of time, glutaraldehyde concentration, pH, temperature, and enzyme concentration on immobilization were studied, and the immobilized enzymes were characterized. pH 9.0 was optimum for the enzyme immobilization. The maximum immobilization efficiency of 82.23 ± 7.99 % was achieved at 25 °C for 120 min. After immobilization, the optimum pH and temperature changed from 9.0 to 11.0 and 60 to 70, respectively. Immobilization reduced the amylase's activation energy (KJ/mol) from the initial 58.862 to 45.449 following immobilization. The Km of the amylase decreased after immobilization, while the Vmax increased. The immobilized amylase showed significantly greater storage and thermal stability than the free amylase. At 80, enzyme half-life (min) and D value (min) increased from 12.33 to 179.11 and 40.94 to 594.98, respectively. The immobilized amylase (80-88 %) had more stability to the effects of the studied surfactants than the free enzyme. It also showed improved stability in the presence of commercial detergents compared to the free enzyme. The amylase's enhanced kinetic parameters and stability following successful immobilization on silver nanoparticles indicate its potential for application in the range of biotechnological processes where alkaline- and temperature-stable amylases are employed.

The Immobilization of a Cyclodipeptide Synthase Enables Biocatalysis for Cyclodipeptide Production

Cyclodipeptide synthases (CDPSs) are enzymes that use aminoacylated tRNAs as substrates to produce cyclic dipeptide natural products acting as anticancer and neuroprotective compounds. Many CDPSs, however, suffer from instability and poor recyclability, while enzyme immobilization can enhance catalyst efficiency and reuse. Here, the CDPS enzyme from Parcubacteria bacterium RAAC4_OD1_1 was immobilized using three different supports: biochar from waste materials, calcium-alginate beads, and chitosan beads. Immobilization of active PbCDPS was successful, and production of the cyclodipeptide cyclo (His-Glu) (cHE) was confirmed by HPLC-MS. Biochar from spent coffee activated with glutaraldehyde, alginate beads, and chitosan beads activated with glutaraldehyde led to a 5-fold improvement in cHE production, with the immobilized enzyme remaining active for seven consecutive cycles. Furthermore, we co-immobilized three enzymes participating in the cascade reaction yielding cHE (PbCDPS, histidyl-tRNA synthetase, and glutamyl-tRNA synthetase). The enzymatic cascade successfully produced the cyclic dipeptide, underscoring the potential of immobilizing various enzymes within a single support. Importantly, we demonstrated that tRNAs remained free in solution and were not adsorbed by the beads. We paved the way for the immobilization of enzymes that utilize tRNAs and other complex substrates, thereby expanding the range of reactions that can be exploited by using this technology.

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

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

Preparation of a heterogeneous biocatalyst through Thermomyces lanuginosus lipase immobilization on pore-expanded SBA-15

Heterogeneous biocatalysts were prepared by adsorbing T. lanuginosus lipase (TLL) onto uncalcined (SBAUC-TLL) and calcined (SBAC-TLL) SBA-15, using ammonium fluoride as a pore expander to facilitate TLL immobilization. At an enzyme load of 1 mg/g, high immobilization yields (>90 %) and recovered activities (>80 % for SBAUC-TLL and 70 % for SBAC-TLL) were achieved. When increasing the enzyme load to 5 mg/g, the immobilization yield of SBAUC-TLL was 80 %, and the recovered activity was 50 %, while SBAC-TLL had a yield of 100 % and a recovered activity of 36 %. Crosslinking with glutaraldehyde (GA) was conducted to improve stability (SBAUC-TLL-GA and SBAC-TLL-GA). Although SBAC-TLL-GA lost 25 % of initial activity after GA modifications, it exhibited the highest thermal (t1/2 = 5.7 h at 65 °C), when compared to SBAC-TLL (t1/2 = 12 min) and the soluble enzyme (t1/2 = 36 min), and operational stability (retained 100 % activity after 5 cycles). Both biocatalysts presented high storage stability since they retained 100 % of initial activity for 30 days. These results highlight SBA-15's potential as an enzyme support and the protocol's efficacy in enhancing stability, with implications for industrial applications in the food, chemical, and pharmaceutical sectors.

Functionalized magnetic lipase/Cu3(PO4)2 hybrid nanoflower: Synthesis, characterization, and enzymatic evaluation

This paper reports the synthesis of magnetic lipase/Cu3(PO4)2 hybrid nanoflowers via a rapid ultrasonication method. The enzyme immobilization and nanoflower growth mechanism can be described as the (a) Fe2+, Cu2+, and phosphate "binding", (b) metal phosphate crystals formation, (c) formation and growth of metal phosphate crystals to form plate-like structures, and (d) self-assembly of plate structures that forms a flower-like structure. Some factors contributing to the morphology of the hybrid nanoflowers structure includes the time and concentration of lipase were studied. The effect of temperature, pH, and duration on the enzyme immobilization yield were also studied. In addition, the strong magnetic property (9.73 emu g-1) of the nanoflowers resulted in higher retrievability and reusability after repeated usage. Furthermore, the catalytic activity of lipase/Cu3(PO4)2 hybrid nanoflowers was investigated and the ideal conditions were determined whereby, the maximum activity was calculated to be 1511 ± 44 U g-1, showing a catalytic enhancement of 89% in comparison to free lipase. The reusability study showed that, after 5 cycles, the magnetic lipase/Cu3(PO4)2 nanoflowers successfully retained 60% of its initial activity. From the results obtained, it is worth noting that, the magnetic lipase/Cu3(PO4)2 hybrid nanoflowers are highly efficient in industrial biocatalytic applications.

The effects of the chemical modification on immobilized lipase features are affected by the enzyme crowding in the support

In this article, we have analyzed the interactions between enzyme crowding on a given support and its chemical modification (ethylenediamine modification via the carbodiimide route and picryl sulfonic (TNBS) modification of the primary amino groups) on the enzyme activity and stability. Lipase from Thermomyces lanuginosus (TLL) and lipase B from Candida antarctica (CALB) were immobilized on octyl-agarose beads at two very different enzyme loadings, one of them exceeding the capacity of the support, one well under this capacity. Chemical modifications of the highly loaded and lowly loaded biocatalysts gave very different results in terms of activity and stability, which could increase or decrease enzyme activity depending on the enzyme support loading. For example, both lowly loaded biocatalysts increased their activity after modification while the effect was the opposite for the highly loaded biocatalysts. Additionally, the modification with TNBS of highly loaded CALB biocatalyst increased its stability while decrease the activity.

An application of carbohydrate polymers-based surface-modified gold nanoparticles for improved target delivery to liver cancer therapy - A systemic review

Gold nanoparticles have been broadly investigated as cancer diagnostic and therapeutic agents. Gold nanoparticles are a favorable drug delivery vehicle with their unique subcellular size and good biocompatibility. Chitosan, agarose, fucoidan, porphyran, carrageenan, ulvan and alginate are all examples of biologically active macromolecules. Since they are biocompatible, biodegradable, and irritant-free, they find extensive application in biomedical and macromolecules. The versatility of these compounds is enhanced because they are amenable to modification by functional groups like sulfation, acetylation, and carboxylation. In an eco-friendly preparation process, the biocompatibility and targeting of GNPs can be improved by functionalizing them with polysaccharides. This article provides an update on using carbohydrate-based GNPs in liver cancer treatment, imaging, and drug administration. Selective surface modification of several carbohydrate types and further biological uses of GNPs are focused on.

A Novel Method for γ-Aminobutyric Acid Biosynthesis Using Glutamate Decarboxylase Entrapped in Polyvinyl Alcohol-Sodium Alginate Capsules

γ-aminobutyric acid (GABA) has essential physiological functions in the human body. A novel method using glutamate decarboxylase (GAD) entrapped in polyvinyl alcohol (PVA)-sodium alginate (SA) capsules provides a green biological strategy for GABA synthesis. In this investigation, the stability range of immobilized GAD was effectively broadened, and immobilized GAD could be repeatedly used as a batch and fixed-bed column catalyst. The immobilized enzymes were stable and retained 89% of their activity in a pH range of 4.0-5.6, while there was an approximately 50% decrease in free GAD activity in the pH range of 4.8 ± 0.4. The immobilized GAD affinity to the substrate improved, and this was evidenced by the apparent decrease in Km to 13.3 mmol/L from the 30.9 mmol/L for free GAD. The immobilized GAD retained >90.6% activity after eight cycles and a near-100% enzyme activity retention after 120 h of a continuous fixed-bed column catalyst operation. This study has thus presented an effective PVA-SA-GAD immobilization method that could be used to continuously scale-up GABA biosynthesis.

Glutaraldehyde modification of lipases immobilized on octyl agarose beads: Roles of the support enzyme loading and chemical amination of the enzyme on the final enzyme features

Lipase B from Candida antarctica (CALB) and lipase from Thermomyces lanuginosus (TLL) have been immobilized on octyl agarose at low loading and at a loading exceeding the maximum support capacity. Then, the enzymes have been treated with glutaraldehyde and inactivated at pH 7.0 in Tris-HCl, sodium phosphate and HEPES, giving different stabilities. Stabilization (depending on the buffer) of the highly loaded biocatalysts was found, very likely as a consequence of the detected intermolecular crosslinkings. This did not occur for the lowly loaded biocatalysts. Next, the enzymes were chemically aminated and then treated with glutaraldehyde. In the case of TLL, the intramolecular crosslinkings (visible by the apparent reduction of the protein size) increased enzyme stability of the lowly loaded biocatalysts, an effect that was further increased for the highly loaded biocatalysts due to intermolecular crosslinkings. Using CALB, the intramolecular crosslinkings were less intense, and the stabilization was lower, even though the intermolecular crosslinkings were quite intense for the highly loaded biocatalyst. The stabilization detected depended on the inactivation buffer. The interactions between enzyme loading and inactivating buffer on the effects of the chemical modifications suggest that the modification and inactivation studies must be performed under the target biocatalysts and conditions.

Fabrication of immobilized lipases for efficient preparation of 1,3-dioleoyl-2-palmitoylglycerol

This study aims to fabricate immobilized lipases for efficient preparation of 1,3-dioleoyl-2-palmitoyl-glycerol (OPO) through acidolysis of glycerol tripalmitate (PPP). Twelve (three types) supports and five lipases were studied carefully. Among them, the immobilized Thermomyces lanuginosa lipase (TLL) samples exhibited overall better performance than that of other immobilized lipases. Particularly, organic groups functionalized SBA-15 (R-SBA-15) supported TLL (TLL@R-SBA-15) samples gave PPP conversion from 97.70 to 99.00 % and OPO content from 59.52 to 64.73 %. After optimization, PPP conversion up to 99.07 %, OPO content 73.15 % and sn-2 palmitic acid content 90.09 % were obtained with TLL@C₁₈H₃₇-SBA-15 as catalyst. Moreover, TLL@C₁₈H₃₇-SBA-15 exhibited better acidolysis performance from 50 °C than that from 60 to 80 °C, which helped inhibit acyl migration. In addition, after 5 cycles of reuse, TLL@C₁₈H₃₇-SBA-15 retained 81.04 % (based on OPO content) and 98.88 % (based on sn-2 palmitic acid content) of its initial activity, indicating it had an attractive prospect in future applications.

Renewable, sustainable, and natural lignocellulosic carriers for lipase immobilization: A review

It is well-known that enzymes are molecules particularly susceptible to pH and temperature variations. Immobilization techniques may overcome this weakness besides improving the reusability of the biocatalysts. Given the strong push toward a circular economy, the use of natural lignocellulosic wastes as supports for enzyme immobilization has been increasingly attractive in recent years. This fact is mainly due to their high availability, low costs, and the possibility of reducing the environmental impact that can occur when they are improperly stored. In addition, they have physical and chemical characteristics suitable for enzyme immobilization (large surface area, high rigidity, porosity, reactive functional groups, etc.). This review aims to guide readers and provide them with the tools necessary to select the most suitable methodology for lipase immobilization on lignocellulosic wastes. The importance and the characteristics of an increasingly interesting enzyme, such as lipase, and the advantages and disadvantages of the different immobilization methods will be discussed. The various kinds of lignocellulosic wastes and the processing required to make them suitable as carriers will be also reported.

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

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

β-Glucosidase Immobilized on Magnetic Nanoparticles: Controlling Biomolecule Footprint and Particle Functional Group Density to Navigate the Activity-Stability Tradeoff

In the present work, the immobilized footprint of β-glucosidase (BGL) on silica-coated iron oxide was explored to produce reusable catalysts with flexible active sites for high activity and heightened storage stability. Synthesized iron oxide particles were coated with silica and functionalized with various densities of (3-aminopropyl)triethoxysilane (APTES) to obtain particles with amine densities ranging from 0 to 3 × 10^-5 mol/g particle. The amine-modified particles were activated with glutaraldehyde, and subsequently, BGL was immobilized using either a 0.1 or 1 mg/mL enzyme solution to produce biomolecules with a large or small footprint on the particle surface. The initial activity, activity for subsequent hydrolysis cycles, activity after extended storage, and biomolecule footprint were studied as a function of APTES density and concentration of enzyme used for immobilization. At high immobilization amounts, the specific activity and footprint were reduced, but the immobilized biomolecules were stable during storage. However, at low enzyme immobilizations, the activity of the enzymes was retained, the immobilized enzymes adopted large footprints, and the storage stability increased with APTES density relative to the free enzyme. These results highlight how controlling both the protein load and functional group density can yield immobilized enzymes possessing high activity, which are stable during storage.

Immobilization of Lipase B from Candida antarctica in Octyl-Vinyl Sulfone Agarose: Effect of the Enzyme-Support Interactions on Enzyme Activity, Specificity, Structure and Inactivation Pathway

Lipase B from Candida antarctica was immobilized on heterofunctional support octyl agarose activated with vinyl sulfone to prevent enzyme release under drastic conditions. Covalent attachment was established, but the blocking step using hexylamine, ethylenediamine or the amino acids glycine (Gly) and aspartic acid (Asp) altered the results. The activities were lower than those observed using the octyl biocatalyst, except when using ethylenediamine as blocking reagent and p-nitrophenol butyrate (pNPB) as substrate. The enzyme stability increased using these new biocatalysts at pH 7 and 9 using all blocking agents (much more significantly at pH 9), while it decreased at pH 5 except when using Gly as blocking agent. The stress inactivation of the biocatalysts decreased the enzyme activity versus three different substrates (pNPB, S-methyl mandelate and triacetin) in a relatively similar fashion. The tryptophane (Trp) fluorescence spectra were different for the biocatalysts, suggesting different enzyme conformations. However, the fluorescence spectra changes during the inactivation were not too different except for the biocatalyst blocked with Asp, suggesting that, except for this biocatalyst, the inactivation pathways may not be so different.

Microbial Lipases and Their Potential in the Production of Pharmaceutical Building Blocks

Processes involving lipases in obtaining active pharmaceutical ingredients (APIs) are crucial to increase the sustainability of the industry. Despite their lower production cost, microbial lipases are striking for their versatile catalyzing reactions beyond their physiological role. In the context of taking advantage of microbial lipases in reactions for the synthesis of API building blocks, this review focuses on: (i) the structural origins of the catalytic properties of microbial lipases, including the results of techniques such as single particle monitoring (SPT) and the description of its selectivity beyond the Kazlauskas rule as the "Mirror-Image Packing" or the "Key Region(s) rule influencing enantioselectivity" (KRIE); (ii) immobilization methods given the conferred operative advantages in industrial applications and their modulating capacity of lipase properties; and (iii) a comprehensive description of microbial lipases use as a conventional or promiscuous catalyst in key reactions in the organic synthesis (Knoevenagel condensation, Morita-Baylis-Hillman (MBH) reactions, Markovnikov additions, Baeyer-Villiger oxidation, racemization, among others). Finally, this review will also focus on a research perspective necessary to increase microbial lipases application development towards a greener industry.

Encapsulation of lipases by nucleotide/metal ion coordination polymers: enzymatic properties and their applications in glycerolysis and esterification studies

BACKGROUND

In the present study, lipases of TLL (lipase from Thermomyces lanuginosus), AOL (lipase from Aspergillus oryzae), RML (lipase from Rhizomucor miehei), BCL (lipase from Burkholderia cepacia), CALA (Candida antarctica lipase A) and LU (Lecitase® Ultra) were encapsulated into nucleotide-hybrid metal coordination polymers (CPs). Enzyme concentration was optimized for encapsulation and the enzymatic properties of the obtained lipases were investigated. In addition, their performance in glycerolysis and esterification was evaluated, and glycerolysis conditions (water content, temperature and time) were optimized.

RESULTS

Hydrolysis activity over 10 000 U g^-1 and activity recovery over 90% were observed from AOL@GMP/Tb, TLL@GMP/Tb and RML@GMP/Tb. GMP/Tb encapsulation (of AOL, TLL, RML and LU) improved their thermostability when incubated in air. The encapsulated lipases exhibited moderate [triacylglycerols (TAG) conversion 30-50%] and considerable glycerolysis activity (TAG conversion over 60%). TAG conversions from 69.37% to 82.35% and diacylglycerols (DAG) contents from 58.62% to 64.88% were obtained from CALA@GMP/metal samples (except for CALA@GMP/Cu). Interestingly, none of the encapsulated lipases initiated the esterification reaction. AOL@GMP/Tb, TLL@GMP/Tb, RML@GMP/Tb and CALA@GMP/Tb showed good reusability in glycerolysis, with 88.80%, 94.67%, 89.85% and 78.16% of their initial glycerolysis activity, respectively, remaining after five cycles of reuse. The relationships between temperature and TAG conversion were LnV₀  = 6.5364-3.7943/T and LnV₀  = 13.8820-6.4684/T for AOL@GMP/Tb and CALA@GMP/Tb, respectively; in addition, their activation energies were 31.55 and 53.78 kJ mol^-1 , respectively.

CONCLUSION

Most of the present encapsulated lipases exhibited moderate and considerable glycerolysis activity. In addition, AOL@GMP/Tb, TLL@GMP/Tb, RML@GMP/Tb and CALA@GMP/Tb exhibited good reusability in glycerolysis reactions and potential in practical applications. © 2022 Society of Chemical Industry.

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.

A review on the immobilization of pepsin: A Lys-poor enzyme that is unstable at alkaline pH values

Pepsin is a protease used in many different applications, and in many instances, it is utilized in an immobilized form to prevent contamination of the reaction product. This enzyme has two peculiarities that make its immobilization complex. The first one is related to the poor presence of primary amino groups on its surface (just one Lys and the terminal amino group). The second one is its poor stability at alkaline pH values. Both features make the immobilization of this enzyme to be considered a complicated goal, as most of the immobilization protocols utilize primary amino groups for immobilization. This review presents some of the attempts to get immobilized pepsin biocatalyst and their applications. The high density of anionic groups (Asp and Glu) make the anion exchange of the enzyme simpler, but this makes many of the strategies utilized to immobilize the enzyme (e.g., amino-glutaraldehyde supports) more related to a mixed ion exchange/hydrophobic adsorption than to real covalent immobilization. Finally, we propose some possibilities that can permit not only the covalent immobilization of this enzyme, but also their stabilization via multipoint covalent attachment.

Impact of immobilization strategies on the activity and recyclability of lipases in nanomagnetic supports

The use of enzymes immobilized on nanomagnetic supports has produced surprising results in catalysis, mainly due to the increase in surface area and the potential for recovery and reuse. However, the meticulous control of the process and difficulties in reproducibility have made industrial-scale applications unfeasible. Furthermore, the role of conjugation strategies in the catalytic activity and recycling of catalysts is unclear. Therefore, the objective of this study was to compare the conjugation of enzymes on nanomagnetic supports through physical adsorption (naked) or covalent bonding with mercaptopropyltrimethoxysilane (MPTS) and aminopropyltriethoxysilane (APTS) ligands. The free lipase obtained from Rhizomucor miehei was used as a model enzyme. Total protein and enzyme activity were determined using spectrophotometry (UV-Vis) and the p-nitrophenyl palmitate (p-NPP) hydrolysis method. The results indicated that a more significant enzyme surface loading does not always mean better immobilization success. The physical adsorption binding strategy had higher surface loading and low catalytic activity. On the other hand, covalent coupling with free NH2 had an excellent catalytic activity with very low surface loading. Finally, we show that recyclability can be improved with conjugation mediated by disulfide bonds. The findings presented here are essential for developing nanoconjugates with high enzymatic activity, which can guarantee the success of several industrial applications.

Enzyme Immobilization and Co-Immobilization: Main Framework, Advances and Some Applications

Enzymes are outstanding (bio)catalysts, not solely on account of their ability to increase reaction rates by up to several orders of magnitude but also for the high degree of substrate specificity, regiospecificity and stereospecificity. The use and development of enzymes as robust biocatalysts is one of the main challenges in biotechnology. However, despite the high specificities and turnover of enzymes, there are also drawbacks. At the industrial level, these drawbacks are typically overcome by resorting to immobilized enzymes to enhance stability. Immobilization of biocatalysts allows their reuse, increases stability, facilitates process control, eases product recovery, and enhances product yield and quality. This is especially important for expensive enzymes, for those obtained in low fermentation yield and with relatively low activity. This review provides an integrated perspective on (multi)enzyme immobilization that abridges a critical evaluation of immobilization methods and carriers, biocatalyst metrics, impact of key carrier features on biocatalyst performance, trends towards miniaturization and detailed illustrative examples that are representative of biocatalytic applications promoting sustainability.

The combination of covalent and ionic exchange immobilizations enables the coimmobilization on vinyl sulfone activated supports and the reuse of the most stable immobilized enzyme

The coimmobilization of lipases from Rhizomucor miehei (RML) and Candida antarctica (CALB) has been intended using agarose beads activated with divinyl sulfone. CALB could be immobilized on this support, while RML was not. However, RML was ionically exchanged on this support blocked with ethylendiamine. Therefore, both enzymes could be coimmobilized on the same particle, CALB covalently using the vinyl sulfone groups, and RML via anionic exchange on the aminated blocked support. However, immobilized RML was far less stable than immobilized CALB. To avoid the discarding of CALB (that maintained 90% of the initial activity after RML inactivation), a strategy was developed. Inactivated RML was desorbed from the support using ammonium sulfate and 1% Triton X-100 at pH 7.0. That way, 5 cycles of RML thermal inactivation, discharge of the inactivated enzyme and re-immobilization of a fresh sample of RML could be performed. In the last cycle, immobilized CALB activity was still over 90% of the initial one. Thus, the strategy permits that enzymes can be coimmobilized on vinyl sulfone supports even if one of them cannot be immobilized on it, and also permits the reuse of the most stable enzyme (if it is irreversibly attached to the support).

Characterization of Gentisate 1,2-Dioxygenase from Pseudarthrobacter phenanthrenivorans Sphe3 and Its Stabilization by Immobilization on Nickel-Functionalized Magnetic Nanoparticles

The aim of this study was the biochemical and kinetic characterization of the gentisate 1,2-dioxygenase (GDO) from Pseudarthrobacter phenanthrenivorans Sphe3 and the development of a nanobiocatalyst by its immobilization on Ni2+-functionalized Fe3O4-polydopamine magnetic nanoparticles (Ni2+-PDA-MNPs). This is the first GDO to be immobilized. The gene encoding the GDO was cloned with an N-terminal His-tag and overexpressed in E. coli. The nanoparticles showed a high purification efficiency of GDO from crude cell lysates with a maximum activity recovery of 97%. The immobilized enzyme was characterized by Fourier transform infrared spectroscopy (FTIR). The reaction product was identified by 1H NMR. Both free and immobilized GDO exhibited Michaelis–Menten kinetics with Km values of 25.9 ± 4.4 and 82.5 ± 14.2 μM and Vmax values of 1.2 ± 0.1 and 0.03 ± 0.002 mM*s−1, respectively. The thermal stability of the immobilized GDO was enhanced at 30 °C, 40 °C, and 50 °C, compared to the free GDO. Stored at −20 °C, immobilized GDO retained more than 60% of its initial activity after 30 d, while the free enzyme completely lost its activity after 10 d. Furthermore, the immobilized nanoparticle–enzyme conjugate retained more than 50% enzyme activity up to the fifth cycle.

Ceruloplasmin in flatland: the relationship between enzyme catalytic activity and surface hydrophilicity

The effective immobilization of the enzyme on the substrate surface plays a key role especially in biocatalysis, medicine or industry. Herein, we showed the influence of substrate hydrophilicity on the activity of the physically immobilized ceruloplasmin. To control the hydrophilicity of the substrate, thiols with various terminal groups were used. We have found that the effectiveness of the catalytic process of multimeric protein is the highest in the situation of application of the highly hydrophilic substrate. In the case of physical adsorption, the orientation of the enzyme is random, however the application of the appropriate modifying layer enforces the desired enzyme orientation. The quartz crystal microbalance with dissipation (QCM-D) results showed that the crucial parameter for the highest and most durable catalytic activity of the enzyme is the orientation, not the amount of the physically adsorbed enzyme.

Surface hydrophilicity – the way to control the activity of the immobilized enzyme.

Effect of Different TiO2 Morphologies on the Activity of Immobilized Lipase for Biodiesel Production

Lipase catalytic activity is greatly influenced by immobilization on nanoparticles. In this study, lipase from Aspergillus niger was immobilized on TiO₂ nanoparticles with different morphologies: microspheres, nanotubes, and nanosheets. All TiO₂ samples were prepared by a hydrothermal method. Lipase/TiO₂ nanocomposites were prepared by a physical adsorption method through hydrophobic interactions. The prepared composites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The catalytic activity of free and immobilized lipases was tested using sunflower oil in the presence of methanol to produce biodiesel at 40 °C for 90 min. The lipase immobilized on TiO₂ microspheres showed the highest activity compared to the lipase immobilized on TiO₂ nanotubes and nanosheets. To optimize the lipase-to-microsphere ratio, lipase was immobilized on TiO₂ microspheres in different microspheres/lipase, w/w, (S/L) ratios of 1:1, 1:0.75, 1:0.5, and 1:0.25. It was noticed that the hydrolytic activity follows the order 1:0.25 > 1:0.5 > 1:75 > 1:1. The immobilization yield activities were found to be 113, 123, 125, and 130% for the microspheres/lipase (S/L) ratios of 1:1, 1:0.75, 1:0.5, and 1:0.25, respectively.

Improved cell adhesion to activated vapor silanization-biofunctionalized Ti-6Al-4V surfaces with ECM-derived oligopeptides

Titanium implants are widely used in traumatology and various orthopedic fields. Titanium and other metallic-based implants have limited structural and functional integration into the body, which translates into progressive prosthesis instability and the need for new surgical interventions that have enormous social and economic impacts. To enhance the biocompatibility of titanium implants, numerous biofunctionalization strategies have been developed. However, the problem persists, as more than 70% of implant failures are due to aseptic loosening. In this study we addressed the problem of improving the physiological engraftability and acceptability of titanium-based implants by applying a robust and versatile functionalization method based on the covalent immobilization of extracellular matrix (ECM)-derived oligopeptides on Ti-6Al-4V surfaces treated by activated vapor silanization (AVS). The feasibility of this technique was evaluated with two oligopeptides of different structures and compositions. These oligopeptides were immobilized on Ti-6Al-4V substrates by a combination of AVS and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) crosslinking chemistry. The immobilization was shown to be stable and resistant to chemical denaturing upon sodium dodecyl sulfate treatment. On Ti-6Al-4V surfaces both peptides increased the attachment, spreading, rearrangement and directional growth of mesenchymal stem and progenitor cells (MSC) with chondro- and osteo-regenerative capacities. We also found that this biofunctionalization method (AVS-EDC/NHS) increased the attachment capacity of an immortalized cell line of neural origin with poor adhesive properties, highlighting the versatility and robustness of this method in terms of potential oligopeptides that may be used, and cell lineages whose anchorage to the biomaterial may be enhanced. Collectively, this novel functionalization strategy can accelerate the development of advanced peptide-functionalized metallic surfaces, which, in combination with host or exogenously implanted stem cells, have the potential to positively affect the osteoregenerative and osteointegrative abilities of metallic-based prostheses.

Enzyme-support interactions and inactivation conditions determine Thermomyces lanuginosus lipase inactivation pathways: Functional and florescence studies

Lipase from Thermomyces lanuginosus (TLL) has been covalently immobilized on heterofunctional octyl-vinyl agarose. That way, the covalently immobilized enzymes will have identical orientation. Then, it has blocked using hexyl amine (HEX), ethylenediamine (EDA), Gly and Asp. The initial activity/stability of the different biocatalysts was very different, being the most stable the biocatalyst blocked with Gly. These biocatalysts had been utilized to analyze if the enzyme activity could decrease differently along thermal inactivation courses depending on the utilized substrate (that is, if the enzyme specificity was altered during its inactivation using 4 different substrates to determine the activity), and if this can be altered by the nature of the blocking agent and the inactivation conditions (we use pH 5, 7 and 9). Results show great changes in the enzyme specificity during inactivation (e.g., activity versus triacetin was much more quickly lost than versus the other substrates), and how this was modulated by the immobilization protocol and inactivation conditions. The difference in the changes induced by immobilization and inactivation were confirmed by fluorescence studies. That is, the functional and structural analysis of partially inactivated immobilized enzyme showed that their inactivation pathway is strongly depended on the support features and inactivation conditions.

Effect of the biological functionalization of nanoparticles on magnetic CLEA preparation

Lipase immobilization using adsorption on magnetic nanoparticles, cross-linked enzyme aggregates (CLEA), and a combination of both techniques was investigated. Experimental designs were used for the optimization of the immobilization observing that the pH and ionic strength play a principal role during the lipase immobilization and its activity. For adsorption on magnetic nanoparticles and CLEA synthesis the optimal condition was pH and 100 mM. Besides, during the CLEA synthesis, glutaraldehyde concentration showed to be a significant effect on the enzyme activity. A comparison between a magnetic CLEA prepared with (Lip@mCLEA) and without (mCLEA) biological functionalized magnetic nanoparticles was made observing that the use of functionalized support showed the best performance activity. All biocatalytic systems developed gives to the enzyme thermal stability between 45 and 70 °C, being Lip@mCLEA the more stable biocatalyst. Similar behavior was observed at different pH, where both Lip@mCLEA and mCLEA showed stability at a range of pH 5 to 8. The immobilized biocatalysts showed the same affinity of the subtract that the free enzyme suggested that the enzyme structure not modified the active site. The combination of both types of immobilization show evidenced the importance of the biological functionalization of the support when magnetic CLEA is produced.

Cold-Active Lipase-Based Biocatalysts for Silymarin Valorization through Biocatalytic Acylation of Silybin

Extremophilic biocatalysts represent an enhanced solution in various industrial applications. Integrating enzymes with high catalytic potential at low temperatures into production schemes such as cold-pressed silymarin processing not only brings value to the silymarin recovery from biomass residues, but also improves its solubility properties for biocatalytic modification. Therefore, a cold-active lipase-mediated biocatalytic system has been developed for silybin acylation with methyl fatty acid esters based on the extracellular protein fractions produced by the psychrophilic bacterial strain Psychrobacter SC65A.3 isolated from Scarisoara Ice Cave (Romania). The extracellular production of the lipase fraction was enhanced by 1% olive-oil-enriched culture media. Through multiple immobilization approaches of the cold-active putative lipases (using carbodiimide, aldehyde-hydrazine, or glutaraldehyde coupling), bio-composites (S1–5) with similar or even higher catalytic activity under cold-active conditions (25 °C) have been synthesized by covalent attachment to nano-/micro-sized magnetic or polymeric resin beads. Characterization methods (e.g., FTIR DRIFT, SEM, enzyme activity) strengthen the biocatalysts’ settlement and potential. Thus, the developed immobilized biocatalysts exhibited between 80 and 128% recovery of the catalytic activity for protein loading in the range 90–99% and this led to an immobilization yield up to 89%. The biocatalytic acylation performance reached a maximum of 67% silybin conversion with methyl decanoate acylating agent and nano-support immobilized lipase biocatalyst.

Stabilization of enzymes via immobilization: Multipoint covalent attachment and other stabilization strategies

The use of enzymes in industrial processes requires the improvement of their features in many instances. Enzyme immobilization, a requirement to facilitate the recovery and reuse of these water-soluble catalysts, is one of the tools that researchers may utilize to improve many of their properties. This review is focused on how enzyme immobilization may improve enzyme stability. Starting from the stabilization effects that an enzyme may experience by the mere fact of being inside a solid particle, we detail other possibilities to stabilize enzymes: generation of favorable enzyme environments, prevention of enzyme subunit dissociation in multimeric enzymes, generation of more stable enzyme conformations, or enzyme rigidification via multipoint covalent attachment. In this last point, we will discuss the features of an "ideal" immobilization protocol to maximize the intensity of the enzyme-support interactions. The most interesting active groups in the support (glutaraldehyde, epoxide, glyoxyl and vinyl sulfone) will be also presented, discussing their main properties and uses. Some instances in which the number of enzyme-support bonds is not directly related to a higher stabilization will be also presented. Finally, the possibility of coupling site-directed mutagenesis or chemical modification to get a more intense multipoint covalent immobilization will be discussed.

The Kinetic and Analytical Aspects of Enzyme Competitive Inhibition: Sensing of Tyrosinase Inhibitors

An amperometric biosensor based on tyrosinase, immobilized onto a carbon black paste electrode using glutaraldehyde and BSA was constructed to detect competitive inhibitors. Three inhibitors were used in this study: benzoic acid, sodium azide, and kojic acid, and the obtained values for fifty percent of inhibition (IC50) were 119 µM, 1480 µM, and 30 µM, respectively. The type of inhibition can also be determined from the curve of the degree of inhibition by considering the shift of the inhibition curves. Amperometric experiments were performed with a biosensor polarized at the potential -0.15 V vs. Ag/AgCl and using 0.1 M phosphate buffer (pH 6.8) as an electrolyte. Under optimized conditions, the proposed biosensor showed a linear amperometric response toward catechol detection from 0.5 µM to 38 µM with a detection limit of 0.35 µM (S/N = 3), and its sensitivity was 66.5 mA M-1 cm-2. Moreover, the biosensor exhibited a good storage stability. Conversely, a novel graphical plot for the determination of reversible competitive inhibition was represented for free tyrosinase. The graph consisted of plotting the half-time reaction (t1/2) as a function of the inhibitor concentration at various substrate concentrations. This innovative method relevance was demonstrated in the case of kojic acid using a colorimetric bioassay relying on tyrosinase inhibition. The results showed that the t1/2 provides an extended linear range of tyrosinase inhibitors.

Site directed confinement of laccases in a porous scaffold towards robustness and selectivity

We immobilized a fungal laccase with only two spatially close lysines available for functionalization into macrocellular Si(HIPE) monoliths for the purpose of continuous flow catalysis. Immobilization (30-45 % protein immobilization yields) was obtained using a covalent bond forming reaction between the enzyme and low glutaraldehyde (0.625 % (w/w)) functionalized foams. Testing primarily HBT-mediated RB5 dye decolorization in continuous flow reactors, we show that the activity of the heterogeneous catalyst is comparable to its homogeneous counterpart. More, its operational activity remains as high as 60 % after twelve consecutive decolorization cycles as well as after one-year storage, performances remarkable for such a material. We further immobilized two variants of the laccase containing a unique lysine: one located in the vicinity of the substrate oxidation site (K157) and one at the opposite side of this oxidation site (K71) to study the effect of the proximity of the Si(HIPE) surface on enzyme activity. Comparing activities on different substrates for monoliths with differentially oriented catalysts, we show a twofold discrimination for ABTS relative to ascorbate. This study provides ground for the development of neo-functionalized materials that beyond allowing stability and reusability will become synergic partners in the catalytic process.

Immobilization of Mutant Phosphotriesterase on Fuller’s Earth Enhanced the Stability of the Enzyme

Immobilization is a method for making an enzyme more robust in the environment, especially in terms of its stability and reusability. A mutant phosphotriesterase (YT PTE) isolated from Pseudomonas dimunita has been reported to have high proficiency in hydrolyzing the Sp and Rp-enantiomers of organophosphate chromophoric analogs and therefore has great potential as a decontamination agent and biosensor. This work aims to investigate the feasibility of using Fuller’s earth (FE) as a YT PTE immobilization support and characterize its biochemical features after immobilization. The immobilized YT PTE was found to show improvement in thermal stability with a half-life of 24 h compared to that of the free enzyme, which was only 8 h. The stability of the immobilized YT PTE allowed storage for up to 4 months and reuse for up to 6 times. The immobilized YT PTE showed high tolerance against all tested metal ions, Tween 40 and 80 surfactants and inorganic solvents. These findings showed that the immobilized YT PTE became more robust for use especially with regards to its stability and reusability. These features would enhance the future applicability of this enzyme as a decontamination agent and its use in other suitable industrial applications.

Ethanol as additive enhance the performance of immobilized lipase LipA from Pseudomonas aeruginosa on polypropylene support

Immobilization is practical to upgrade enzymes, increasing their performance and expanding their applications. The recombinant, solvent tolerant lipase LipA PSA01 from Pseudomonas aeruginosa was immobilized on polypropylene Accurel® MP1004 to improve its performance. We investigated the effect of ethanol as an additive during the immobilization process at three concentrations (20%, 25%, and 30%) on the operational behavior of the enzyme. The immobilization efficiency was higher than 92%, and the immobilized enzymes showed hyperactivation and thermal resistance depending on the concentration of ethanol. For example, at 70 °C, the free enzyme lost the activity, while the prepared one with ethanol 25% conserved a residual activity of up to 73.3% (∆ T¹⁵ ₅₀ = 27.1 °C). LipA immobilized had an optimal pH value lower than that of the free enzyme, and the organic solvent tolerance of the immobilized enzymes depended on the ethanol used. Hence, the immobilized enzyme with ethanol 25% showed hyperactivation to more solvents than the soluble enzyme. Remarkable stability towards methanol (up to 8 folds) was evidenced in all the immobilized preparations. The immobilized enzyme changed their chemo preference, and it hydrolyzed oils preferentially with short-chain than those with long-chain. LipA had a notable shelf-life after one year, keeping its activity up to 87%. Ethanol facilitated the access of the enzyme to the hydrophobic support and increased its activity and stability according to the amount of ethanol added.

Immobilization of the Peroxygenase from Agrocybe aegerita. The Effect of the Immobilization pH on the Features of an Ionically Exchanged Dimeric Peroxygenase

This paper outlines the immobilization of the recombinant dimeric unspecific peroxygenase from Agrocybe aegerita (rAaeUPO). The enzyme was quite stable (remaining unaltered its activity after 35 h at 47 °C and pH 7.0). Phosphate destabilized the enzyme, while glycerol stabilized it. The enzyme was not immobilized on glyoxyl-agarose supports, while it was immobilized albeit in inactive form on vinyl-sulfone-activated supports. rAaeUPO immobilization on glutaraldehyde pre-activated supports gave almost quantitative immobilization yield and retained some activity, but the biocatalyst was very unstable. Its immobilization via anion exchange on PEI supports also produced good immobilization yields, but the rAaeUPO stability dropped. However, using aminated agarose, the enzyme retained stability and activity. The stability of the immobilized enzyme strongly depended on the immobilization pH, being much less stable when rAaeUPO was adsorbed at pH 9.0 than when it was immobilized at pH 7.0 or pH 5.0 (residual activity was almost 0 for the former and 80% for the other preparations), presenting stability very similar to that of the free enzyme. This is a very clear example of how the immobilization pH greatly affects the final biocatalyst performance.