Industrial applications of immobilized enzymes—A review

Immobilization of β-galactosidase from Bacillus licheniformis for application in the dairy industry

The food industry has developed a wide range of products with reduced lactose to allow people with intolerance to consume dairy products. Although β-galactosidase has extensive applications in the food, pharma, and biotechnology industries, the enzymes are high-cost catalysts, and their use makes the process costly. Immobilization is a viable strategy for enzyme retention inside a reactor, allowing its reuse and application in continuous processes. Here, we studied the immobilization of β-galactosidase from Bacillus licheniformis in ion exchange resin. A central composite rotational design (CCRD) was proposed to evaluate the immobilization process in relation to three immobilization solution variables: offered enzyme activity, ionic strength, and pH. The conditions that maximized the response were offered enzyme activity of 953 U, 40 mM ionic strength, and pH 4.0. Subsequently, experiments were performed to provide additional stabilization for biocatalyst, using a buffer solution pH 9.0 at 25 °C for 24 h, and crosslinking with different concentrations of glutaraldehyde. The stabilization step drastically impacted the activity of the immobilized enzyme, and the reticulation with different concentrations of glutaraldehyde showed significant influence on the activity of the immobilized enzyme. In spite of substantially affecting the initial activity of the immobilized enzyme, higher reagent concentrations (3.5 g L^-1) were effective for maintaining stability related to the number of cycles of the enzyme immobilized. The β-galactosidase from Bacillus licheniformis immobilized in Duolite A568 is a promising technique to produce reduced or lactose-free dairy products, as it allows reuse of the biocatalyst, decreasing operational costs.Key Points• Immobilization of β-galactosidase from Bacillus licheniformis in batch reactor• Influence of buffer pH and ionic concentration and offered enzyme activity on immobilization• Influence of glutaraldehyde on operational stability.

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.

Protein immobilization on graphene oxide or reduced graphene oxide surface and their applications: Influence over activity, structural and thermal stability of protein

Due to the essential role of biological macromolecules in our daily life; it is important to control the stability and activity of such macromolecules. Therefore, the most promising route for enhancement in stability and activity is immobilizing proteins on different support materials. Furthermore, large surface area and surface functional groups are the important features that are required for a better support system. These features of graphene oxide (GO) and reduced graphene oxide (RGO) makes them ideal support materials for protein immobilization. Studies show the successful formation of GO/RGO-protein complexes with enhancement in structural/thermal stability due to various interactions at the nano-bio interface and their utilization in various functional applications. The present review focuses on protein immobilization using GO/RGO as solid support materials. Moreover, we also emphasized on basic underlying mechanism and interactions (hydrophilic, hydrophobic, electrostatic, local protein-protein, hydrogen bonding and van der Walls) between protein and GO/RGO which influences structural stability and activity of enzymes/proteins. Furthermore, GO/RGO-protein complexes are utilized in various applications such as biosensors, bioimaging and theranostic agent, targeted drug delivery agents, and nanovectors for drug and protein delivery.

Magnetic Cross-Linked Enzyme Aggregates of a Transpeptidase-Specialized Variant (N450D) of Bacillus licheniformis γ-Glutamyl Transpeptidase: An Efficient and Stable Biocatalyst for l-Theanine Synthesis

γ-Glutamyl transpeptidase (GGT) catalyzes the transfer of glutathione’s γ-glutamyl group and related γ-glutamyl amides to water, amino acids or peptides, and utilizes a conserved Thr residue to process its own polypeptide chain into a large and a small subunit that then assemble to produce a catalytically competent enzyme. In this study, the magnetic cross-linked enzyme aggregates (mCLEAs) of a transpeptidase-specialized variant (N450D) of Bacillus licheniformis GGT were successfully prepared with optimized process parameters viz.1.25:1 (v/v) of isopropanol to N450D (0.3 mg/mL) ratio/0.02:1 (w/w) of enzyme to 3-aminopropyl triethoxysilane (APTES)-coated magnetic nanoparticle ratio/20 mM of glutaraldehyde. The prepared magnetic nanoparticles and immobilized enzyme (N450D-mCLEAs) were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscope integrated with energy dispersive X-ray spectroscopy (FESEM/EDS), and superparamagnetic analysis. As compared with free enzyme, N450D-mCLEAs displayed significantly higher heat resistance at temperatures of 55 and 60 °C, and had a greater stability over a storage period of one month. The immobilized enzyme could also be reused for 10 consecutive biocatalytic cycles with no significant reduction in the percent yield of l-theanine. Conclusively, this immobilization strategy surely provides a meaningful glance of developing N450D-mediated biocatalysis for the production of physiologically important γ-glutamyl compounds.

Nonpungent N-AVAM Capsaicin Analogues and Cancer Therapy

Capsaicin displays robust growth-inhibitory activity in multiple human cancers. However, the feasibility of capsaicin as a clinically relevant anticancer drug is hampered by its adverse side effects. This concern has led to extensive research focused on the isolation and synthesis of second-generation nonpungent capsaicin analogues with potent antineoplastic activity. A major class of nonpungent capsaicin-like compounds belongs to the N-acyl-vanillylamide (N-AVAM) derivatives of capsaicin (hereafter referred as N-AVAM capsaicin analogues). This perspective discusses the isolation of N-AVAM capsaicin analogues from natural sources as well as their synthesis by chemical and enzymatic methods. The perspective describes the pharmacokinetic properties and anticancer activity of N-AVAM capsaicin analogues. The signaling pathways underlying the growth-inhibitory effects of N-AVAM capsaicin analogues have also been highlighted. It is hoped that the insights obtained in this perspective will facilitate the synthesis of a second generation of N-AVAM capsaicin analogues with improved stability and growth-suppressive activity in human cancer.

Nanobiocatalysts for Biodiesel Synthesis through Transesterification—A Review

Converting useless feedstock into biodiesel by utilizing the process of transesterification has been regarded as an alternative approach recently used to address the fuel and energy resources shortage issues. Nanobiocatalysts (NBCs), containing the biological component of lipase enzyme immobilized on nanomaterials (NMs), have also been presented as an advanced catalyst to effectively carry out the process of transesterification with appreciable yields. This study highlights the fundamentals associated with NBCs and the transesterification reaction catalyzed by NBCs for summarizing present academic literature reported in this research domain in recent years. Classification of the NBCs with respect to the nature of NMs and immobilization methods of lipase enzyme is also provided for organizing the recently documented case studies. This review is designed to act as a guideline for the researchers aiming to explore this domain of biodiesel production via NBCs as well as for the scholars looking to expand on this field.

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.

Immobilized GDEst-95, GDEst-lip and GD-95RM lipolytic enzymes for continuous flow hydrolysis and transesterification reactions

In this study lipolytic biocatalysts GD-95RM, GDEst-95 and GDEst-lip were immobilized by encapsulation in calcium alginate beads_. All three immobilized biocatalysts demonstrated significantly increased thermal stability at 60-70 °C temperatures and the activity of GD-95RM lipase increased by 50% at 70-80 °C following the immobilization. Moreover, encapsulated GDEst-95 esterase retained higher than 50% lipolytic activity after 3 months of incubation with butanol (25%) and ethanol (50%); GDEst-lip enzyme possessed 50% activity after 2 months of treatment with ethanol (25%) and methanol (25%); and GD-95RM lipase displayed higher that 50% activity after two-week incubation with methanol (50%). All three immobilized enzymes displayed long-term storage capability (>50% activity) at least until 3 months at 4 °C. It was also detected that immobilized GD-95RM and GDEst-lip can perform flow hydrolysis of both avocado oil and p-NP dodecanoate in prototype packed-bed column reactor. The analysis of continuous transesterification of avocado or sunflower oil with ethanol or methanol as substrates confirmed that encapsulated GD-95RM and GDEst-lip enzymes is a useful approach to produce fatty acid alkyl esters.

A comprehensive review on the application of novel disruption techniques for proteins release from microalgae

There is an emergent demand for sustainable and alternative protein sources such as insects and microorganisms that meet the nutritional requirements. Microalgae possess valuable substances that could satisfy the population's dietary requirement, medicinal purpose, and energy, aligned with effective processing techniques. Several disruption techniques were applied to microalgae species for protein recovery and other compounds. The thick microalgae cell wall makes it difficult to recover all the valuable biomolecules through several downstream processes. Thus, forethought key factors need to be considered when choosing a cell lysis method. The most challenging and crucial issue is selecting a technique that requires consideration of their ability to disrupt all cell types, easy to use, purity degree, reproducible, scalable, and energy efficient. This review aims to provide useful information specifically on mechanical and non-mechanical disruption methods, the status and potential in protein extraction capacities, and constraints. Therefore, further attention in the future on potential technologies, namely explosive decompression, microfluidization, pulsed arc technology, is required to supplement the discussed techniques. This article summarizes recent advances in cell disruption methods and demonstrates insights on new directions of the techniques and future developments.

Functionalization of Porous Cellulose with Glyoxyl Groups as a Carrier for Enzyme Immobilization and Stabilization

The functionalization of the internal surface of macroporous carriers with glyoxyl groups has proven to highly stabilize a large variety of enzymes through multipoint covalent immobilization. In this work, we have translated the surface chemistry developed for the fabrication of glyoxyl-agarose carriers to macroporous cellulose (CEL). To that aim, CEL-based microbeads were functionalized with glyoxyl groups through a stepwise alkoxylation (or alkylation)/oxidation synthetic scheme. This functionalization sequence was analyzed by solid-state NMR, while the scanning electron miscroscopy of CEL microbeads reveals that the mild oxidation conditions negligibly affect the morphological properties of the material. Through the optimal functionalization protocol using rac-glycidol, we introduce up to 200 μmols of aldehyde groups per gram of wet CEL, a similar density to the one obtained for the benchmarked agarose-glyoxyl carrier. This novel CEL-based carrier succeeds to immobilize and stabilize industrially relevant enzymes such as d-amino acid oxidase from Trigonopsis variabilis and xylanases from Trichoderma reseei. Remarkably, the xylanases immobilized on the optimal CEL-based materials present a half-life time of 51 h at 60 °C and convert up to 90% of the xylan after four operation cycles for the synthesis of xylooligosaccharides.

Exploring the synthetic potential of a marine transaminase including discrimination at a remote stereocentre

The marine transaminase, P-ω-TA, can be employed for the transamination from 1-aminotetralins and 1-aminoindanes with differentiation of stereochemistry at both the site of reaction and at a remote stereocentre resulting in formation of ketone products with up to 93% ee. While 4-substituents are tolerated on the tetralin core, the presence of 3- or 8-substituents is not tolerated by the transaminase. In general P-ω-TA shows capacity for remote diastereoselectivity, although both the stereoselectivity and efficiency are dependent on the specific substrate structure. Optimum efficiency and selectivity are seen with 4-haloaryl-1-aminotetralins and 3-haloaryl-1-aminoindanes, which may be associated with the marine origin of this enzyme.

A mild and chemoselective CALB biocatalysed synthesis of sulfoxides exploiting the dual role of AcOEt as solvent and reagent

A mild, chemoselective and sustainable biocatalysed synthesis of sulfoxides has been developed exploiting CALB and using AcOEt with a dual role of more environmentally friendly reaction solvent and enzyme substrate. A series of sulfoxides, including the drug omeprazole, have been synthesised in high yields and with excellent E-factors.

Immobilization strategies of photolyases: Challenges and perspectives for DNA repairing application

Photolyases are enzymes that repair DNA damage caused by solar radiation. Due to their photorepair potential, photolyases added in topical creams and used in medical treatments has allowed to reverse skin damage and prevent the development of different diseases, including actinic keratosis, premature photoaging and cancer. For this reason, research has been oriented to the study of new photolyases performing in extreme environments, where high doses of UV radiation may be a key factor for these enzymes to have perfected their photorepair potential. Generally, the extracted enzymes are first encapsulated and then added to the topical creams to increase their stability. However, other well consolidated immobilization methods are interesting strategies to be studied that may improve the biocatalyst performance. This review aims to go through the different Antarctic organisms that have exhibited photoreactivation activity, explaining the main mechanisms of photolyase DNA photorepair. The challenges of immobilizing these enzymes on porous and nanostructured supports is also discussed. The comparison of the most reported immobilization methods with respect to the structure of photolyases show that both covalent and ionic immobilization methods produced an increase in their stability. Moreover, the use of nanosized materials as photolyase support would permit the incorporation of the biocatalyst into the target cell, which is a technological requirement that photolyase based biocatalysts must fulfill.

Solvent-free esterifications mediated by immobilized lipases: a review from thermodynamic and kinetic perspectives

Esters are a highly relevant class of compounds in the industrial context, and biocatalysis applied to ester syntheses is already a reality for some chemical companies.

Looking Back: A Short History of the Discovery of Enzymes and How They Became Powerful Chemical Tools

Enzymatic approaches to challenges in chemical synthesis are increasingly popular and very attractive to industry given their green nature and high efficiency compared to traditional methods. In this historical review we highlight the developments across several fields that were necessary to create the modern field of biocatalysis, with enzyme engineering and directed evolution at its core. We exemplify the modular, incremental, and highly unpredictable nature of scientific discovery, driven by curiosity, and showcase the resulting examples of cutting-edge enzymatic applications in industry.

Enhancement of laccase immobilization onto wet chitosan microspheres using an iterative protocol and its potential to remove micropollutants

This study was focused on creating a new and effective immobilization method for Trametes versicolor laccase (Lc) by using chitosan (CS) microspheres activated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride. The activation of the support alternated with immobilization of the enzyme, in repetitive procedures, led to obtaining three different products. Also, the physicochemical properties of the new products were investigated and compared with those of free laccase. The discoloration and reusability properties of the immobilized Lc were evaluated using indigo carmine (IC) as a model micropollutant. The ESEM and FT-IR methods demonstrated that the Lc was successfully immobilized. The relative reaction rate and the total amount of immobilized Lc were tripled using the iterative protocol as proved by specific and Bradford assays. The maximum amount of immobilized Lc was 8.4 mg Lc/g CS corresponding to the third immobilization procedure. Compared to the free Lc, the operational stability of the immobilized Lc was significantly improved, presenting a maximum activity plateau over a pH range of 3-5 and a temperature range of 25-50 °C. The thermal inactivation study at 55 °C proved that the immobilized enzyme is three times more stable than the free Lc. The isoconversional and Michaelis-Menten methods showed that the immobilization did not affect the enzyme catalytic properties. After 32 days of storage, the residual activities are 85% for the immobilized laccase and 40% for the free one. In similar conditions, the free and immobilized Lc (2.12 x 10^-6 M) completely decolorized IC (7.15 x 10^-5 M) within 14 min. The immobilized Lc activity remained almost constant (80%) during 10 reusability cycles. All these results highlight the substantial advantages of the new immobilization protocol and demonstrate that immobilized Lc can be used as a promising micropollutant removal from real wastewater.

Flow-through enzymatic reactors using polymer monoliths: From motivation to application

The application of monolithic materials as carriers for enzymes has rapidly expanded to the realization of flow-through analysis and bioconversion processes. This expansion is partly attributed to the absence from diffusion limitation in many monoliths-based enzyme reactors. Particularly, the relatively ease of introducing functional groups renders polymer monoliths attractive as enzyme carriers. After summarizing the motivation to develop enzymatic reactors using polymer monoliths, this review reports the most recent applications of such reactors. Besides, the present review focuses on the crucial characteristics of polymer monoliths affecting the immobilization of enzymes and the processing parameters dictating the performance of the resulting enzymatic reactors. This review is intended to provide a guideline for designing and applying flow-through enzymatic reactors using polymer monoliths.

Current state on the enzymatic synthesis of glycosaminoglycans

Glycosaminoglycans (GAGs) are linear anionic polysaccharides, and most of them show a specific sulfation pattern. GAGs have been studied for decades, and still, new biological functions are discovered. Hyaluronic acid and heparin are sold for medical or cosmetic applications. With increased market and applications, the production of GAGs stays in the focus of research groups and the industry. Common industrial GAG production relies on the extraction of animal tissue. Contamination, high dispersity, and uncontrolled sulfation pattern are still obstacles to this process. Tailored production strategies for the chemoenzymatic synthesis have been developed to address these obstacles. In recent years, enzyme cascades, including uridine-5'-diphosphate sugar syntheses, were established to obtain defined polymer size and dispersity, as well as defined sulfation patterns. Nevertheless, the complex synthesis of GAGs is still a challenging research field.

Kinetic/thermodynamic study of immobilized β-fructofuranosidase from Aspergillus tamarii URM4634 in chitosan beads and application on invert sugar production in packed bed reactor

β-fructofuranosidase (FFase) from Aspergillus tamarii URM4634 was immobilized covalently in chitosan beads. It was characterized biochemically, studied in terms of kinetic and thermodynamic parameters, and applied on conversion of sucrose for invert sugar production in a packed bed reactor (PBR). The optimum reactional conditions were determined and obtained at pH 5.0 and 60 °C. FFase was thermostable at 50-55°C. At 50°C, the enzyme shows longer half-life (t_1/2) (594.13 min) and a higher D-value (1,973.64 min). This indicates that immobilized FFase was stable at temperature commonly used in invert sugar production. The following thermodynamic parameters were obtained: activation energy (E*_d = 301.57 kJ mol^-1), enthalpy (298.76 ≤ ΔH*_d ≤ 298.89 kJ mol^-1), entropy (579.88 ≤ ΔS*_d ≤ 589.27 J K^-1 mol^-1) and Gibbs free energy (100.29 ≤ ΔG*_d ≤ 108.47 kJ mol^-1). The high E*_d, ΔH*_d and ΔG*_d values confirmed FFase thermostability. The high and positive values for ΔS*_d indicate an increase in disorder due opening of the enzyme structure. The sucrose hydrolysis in PBR showed a maximum invert sugar yield (96.0%) at 15 min of operation. The hydrolysis process remained efficient up to 100 min (70.22%). The results obtained in the present study provide a good indication that immobilized FFase on chitosan beads in PBR is efficient to invert sugar production for food industry.

Chemistry, Sustainability and Naturality of Perfumery Biotech Ingredients

White biotechnology has emerged in biochemical manufacturing processes to deliver perfumery ingredients satisfying interests of the society for natural, eco-responsible, and sustainable materials. As a result, an intense R&D activity has taken place on these subjects, resulting in both scientific publications and patent applications reporting combinations of state-of-the-art approaches in biocatalysis, metabolic engineering, synthetic biology, biosynthesis elucidation, gene edition and cloning, and analytical chemistry. In this Minireview, a smelly selection of novel biotechnological processes and ingredients from a scientific articles and patents survey covering the last 6 years is presented and analysed in terms of chemistry, sustainability and naturality. Classification has been made between metabolic engineering on one side, allowing either biotechnological synthesis of essential oil surrogates or single molecule ingredients, and on the other side the optimisation of properties of natural complex substances by specific and selective enzymatic modifications of their chemical composition.

Rhizopus oryzae Lipase, a Promising Industrial Enzyme: Biochemical Characteristics, Production and Biocatalytic Applications

Lipases are biocatalysts with a significant potential to enable a shift from current pollutant manufacturing processes to environmentally sustainable approaches. The main reason of this prospect is their catalytic versatility as they carry out several industrially relevant reactions as hydrolysis of fats in water/lipid interface and synthesis reactions in solvent-free or non-aqueous media such as transesterification, interesterification and esterification. Because of the outstanding traits of Rhizopus oryzae lipase (ROL), 1,3-specificity, high enantioselectivity and stability in organic media, its application in energy, food and pharmaceutical industrial sector has been widely studied. Significant advances have been made in the biochemical characterisation of ROL particularly in how its activity and stability are affected by the presence of its prosequence. In addition, native and heterologous production of ROL, the latter in cell factories like Escherichia coli, Saccharomyces cerevisiae and Komagataella phaffii (Pichia pastoris), have been thoroughly described. Therefore, in this review, we summarise the current knowledge about R. oryzae lipase (i) biochemical characteristics, (ii) production strategies and (iii) potential industrial applications.

Stabilizing enzymes by immobilization on bacterial spores: A review of literature

The ever-increasing applications of enzymes are limited by the relatively poor performance in harsh processing conditions. As a result, there are constant innovations in immobilization protocols for improving biocatalyst activity and stability. Bacterial spores are cheap to generate and highly resistant to environmental stress. The spore core is sheathed by an inner membrane, the germ cell wall, the cortex, outer membrane, spore coat and in some species the exosporium. The spore surface is anion-rich, hydrophobic and contains several reactive groups capable of interacting and stabilizing enzyme molecules through electrostatic forces, hydrophobic interactions and covalent bonding. The probiotic nature of spores obtained from non-toxic bacterial species makes them suitable carriers for the enzyme immobilization, especially food-grade enzymes or those intended for therapeutic use. Immobilization on spores is by direct adsorption, covalent attachment or surface display during the sporulation phase. Hindrances to the immobilization on spore matrix include the production rates, operational instability, and reduced catalytic properties due to conformational changes in enzyme. This paper reviews bacterial spore as a heterofunctional support matrix gives reasons why probiotic bacillus spores are better options and the diverse technologies adopted for spore-enzyme immobilization. It further suggests directions for future use and discusses the commercialization prospects.

Eggshell membrane as feedstock in enzyme immobilization

Eggshell membrane, an eco-compatible, safe and cheap by-product was employed as carrier for the laccase from Trametes versicolor immobilization. In order to evaluate the best protocol to apply for the syringic acid degradation, two different types of laccase loading on eggshell membrane were used by incubation in solution or by enzyme-dropping. Chemicals (covalent) and physicals (adsorption) immobilizations were tested for both procedure using native or periodate-oxidized laccase. It is shown that immobilization of periodate-oxidized laccase on NiCl₂-pretreated eggshell membrane was the best method for the first procedure (immobilized activity 1300 U/Kg, a residual activity of 30 % for 6 reuse). For the enzyme-dropping protocol a covalent method with the bifunctional cross linker (glutaraldehyde) was the best method (immobilized activity 3500 U/Kg, a residual activity of 45 % for 6 reuse).

Application of blocking and immobilization of electrospun fiber in the biomedical field

The fiber obtained by electrospinning technology is a kind of biomaterial with excellent properties, which not only has a unique micro-nanostructure that gives it a large specific surface area and porosity, but also has satisfactory biocompatibility and degradability (if the spinning material used is a degradable polymer). These biomaterials provide a suitable place for cell attachment and proliferation, and can also achieve immobilization. On the other hand, its large porosity and three-dimensional spatial structure show unique blocking properties in drug delivery applications in order to achieve the purpose of slow release or even controlled release. The immobilization effect or blocking effect of these materials is mainly reflected in the hollow or core-shell structure. The purpose of this paper is to understand the application of the electrospun fiber based on biodegradable polymers (aliphatic polyesters) in the biomedical field, especially the immobilization or blocking effect of the electrospun fiber membrane on cells, drugs or enzymes. This paper focuses on the performance of these materials in tissue engineering, wound dressing, drug delivery system, and enzyme immobilization technology. Finally, based on the existing research basis of the electrospun fiber in the biomedical field, a potential research direction in the future is put forward, and few suggestions are also given for the technical problems that urgently need to be solved.

High-level production in a plant system of a thermostable carbonic anhydrase and its immobilization on microcrystalline cellulose beads for CO2 capture

KEY MESSAGE

Plant-produced SazCA and its application to CO2 capture. Technologies that rely on chemical absorption or physical adsorption have been developed to capture CO2 from industrial flue gases and sequester it at storage sites. Carbonic anhydrases (CAs), metalloenzymes, that catalyze the reversible hydration of CO2 have recently received attention as biocatalysts in the capture of CO2 from flue gases, but their cost presents a major obstacle for use at an industrial scale. This cost, however, can be reduced either by producing a long-lasting enzyme suitable for CO2 capture or by lowering production costs. High-level expression, easy purification, and immobilization of CAs from Sulfurihydrogenibium azorense (SazCA) were investigated in a plant system. Fusion of the 60-amino acid-long ectodomain (M-domain) of the human receptor-type tyrosine-protein phosphatase C increased the levels of SazCA accumulation. Fusion of the cellulose-binding module (CBM3) from Clostridium thermocellum resulted in tight binding of recombinant protein to microcrystalline cellulose beads, enabling easy purification. The chimeric fusion protein, BMC-SazCA, which consisted of SazCA with the M and CBM3 domains, was expressed in tobacco (Nicotiana benthamiana), giving a recombinant protein yield in leaf extracts of 350 mg/kg fresh weight. BMC-SazCA produced in planta was active in the presence of various chemicals used in CO2 capture. Immobilization of BMC-SazCA on the surface of microcrystalline cellulose beads extended its heat stability, allowing its reuse in multiple rounds of the CO2 hydration reaction. These results suggest that production of SazCA in plants has great potential for CA-based CO2 sequestration and mineralization.

Production, characterization, and immobilization of protease from the yeast Rhodotorula oryzicola

The protease was produced extracellularly in submerged fermentation by the yeast Rhodotorula oryzicola using different sources of nitrogen and maximum activity (6.54 × 10^-3 U/mg) was obtained in medium containing 2% casein (w/v). Purification of the protease by gel filtration chromatography resulted in a 3.07-fold increase of specific protease activity. The optimal pH and temperature for enzyme activity were 6.51 and 63.04 °C, respectively. Incubation in the presence of some salts enhanced enzyme activity, which peaked under 0.01 M BaCl₂ . The enzyme retained about 90% of enzymatic activity at temperatures 50-60 °C. The commercially available enzyme carriers evaluated, silica gel, Celite 545, and chitosan effectively immobilized the protease. The enzyme immobilized in Celite 545 retained 73.53% of the initial activity after 15 reuse cycles. These results are quite promising for large-scale production and immobilization of protease from R. oryzicola, as the high operational stability of the immobilized enzyme lowers production costs in biotechnological applications that require high enzymatic activity and stability under high temperatures.

Microbial lipases and their industrial applications: a comprehensive review

Lipases are very versatile enzymes, and produced the attention of the several industrial processes. Lipase can be achieved from several sources, animal, vegetable, and microbiological. The uses of microbial lipase market is estimated to be USD 425.0 Million in 2018 and it is projected to reach USD 590.2 Million by 2023, growing at a CAGR of 6.8% from 2018. Microbial lipases (EC 3.1.1.3) catalyze the hydrolysis of long chain triglycerides. The microbial origins of lipase enzymes are logically dynamic and proficient also have an extensive range of industrial uses with the manufacturing of altered molecules. The unique lipase (triacylglycerol acyl hydrolase) enzymes catalyzed the hydrolysis, esterification and alcoholysis reactions. Immobilization has made the use of microbial lipases accomplish its best performance and hence suitable for several reactions and need to enhance aroma to the immobilization processes. Immobilized enzymes depend on the immobilization technique and the carrier type. The choice of the carrier concerns usually the biocompatibility, chemical and thermal stability, and insolubility under reaction conditions, capability of easy rejuvenation and reusability, as well as cost proficiency. Bacillus spp., Achromobacter spp., Alcaligenes spp., Arthrobacter spp., Pseudomonos spp., of bacteria and Penicillium spp., Fusarium spp., Aspergillus spp., of fungi are screened large scale for lipase production. Lipases as multipurpose biological catalyst has given a favorable vision in meeting the needs for several industries such as biodiesel, foods and drinks, leather, textile, detergents, pharmaceuticals and medicals. This review represents a discussion on microbial sources of lipases, immobilization methods increased productivity at market profitability and reduce logistical liability on the environment and user.

Immobilization of Low-Cost Alternative Vegetable Peroxidase (Raphanus sativus L. peroxidase): Choice of Support/Technique and Characterization

In the present work the radish (Raphanus sativus L.) was used as the low-cost alternative source of peroxidase. The enzyme was immobilized in different supports: coconut fiber (CF), calcium alginate microspheres (CAMs) and silica SBA-15/albumin hybrid (HB). Physical adsorption (PA) and covalent binding (CB) as immobilization techniques were evaluated. Immobilized biocatalysts (IBs) obtained were physicochemical and morphologically characterized by SEM, FTIR and TGA. Also, optimum pH/temperature and operational stability were determined. For all supports, the immobilization by covalent binding provided the higher immobilization efficiencies-immobilization yield (IY%) of 89.99 ± 0.38% and 77.74 ± 0.42% for HB and CF, respectively. For CAMs the activity recovery (AR) was of 11.83 ± 0.68%. All IBs showed optimum pH at 6.0. Regarding optimum temperature of the biocatalysts, HB-CB and CAM-CB maintained the original optimum temperature of the free enzyme (40 °C). HB-CB showed higher operational stability, maintaining around 65% of the initial activity after four consecutive cycles. SEM, FTIR and TGA results suggest the enzyme presence on the IBs. Radish peroxidase immobilized on HB support by covalent binding is promising in future biotechnological applications.

Protein-inorganic calcium-phosphate supraparticles as a robust platform for enzyme co-immobilization

Immobilization of enzymes provides many benefits, including facile separation and recovery of enzymes from reaction mixtures, enhanced stability, and co-localization of multiple enzymes. Calcium-phosphate-protein supraparticles imbued with a leucine zipper binding domain (ZR ) serve as a modular immobilization platform for enzymes fused to the complementary leucine zipper domain (ZE ). The zippers provide high-affinity, specific binding, separating enzymatic activity from the binding event. Using fluorescent model proteins (mCherryZE and eGFPZE ), an amine dehydrogenase (AmDHZE ), and a formate dehydrogenase (FDHZE ), the efficacy of supraparticles as a biocatalytic solid support was assessed. Supraparticles demonstrated several benefits as an immobilization support, including predictable loading of multiple proteins, structural integrity in a panel of solvents, and the ability to elute and reload proteins without damaging the support. The dual-enzyme reaction successfully converted ketone to amine on supraparticles, highlighting the efficacy of this system.

Recent advances in β-galactosidase and fructosyltransferase immobilization technology

The highly demanding conditions of industrial processes may lower the stability and affect the activity of enzymes used as biocatalysts. Enzyme immobilization emerged as an approach to promote stabilization and easy removal of enzymes for their reusability. The aim of this review is to go through the principal immobilization strategies addressed to achieve optimal industrial processes with special care on those reported for two types of enzymes: β-galactosidases and fructosyltransferases. The main methods used to immobilize these two enzymes are adsorption, entrapment, covalent coupling and cross-linking or aggregation (no support is used), all of them having pros and cons. Regarding the support, it should be cost-effective, assure the reusability and an easy recovery of the enzyme, increasing its stability and durability. The discussion provided showed that the type of enzyme, its origin, its purity, together with the type of immobilization method and the support will affect the performance during the enzymatic synthesis. Enzymes' immobilization involves interdisciplinary knowledge including enzymology, nanotechnology, molecular dynamics, cellular physiology and process design. The increasing availability of facilities has opened a variety of possibilities to define strategies to optimize the activity and re-usability of β-galactosidases and fructosyltransferases, but there is still great place for innovative developments.

Recent Trends in Biomaterials for Immobilization of Lipases for Application in Non-Conventional Media

The utilization of biomaterials as novel carrier materials for lipase immobilization has been investigated by many research groups over recent years. Biomaterials such as agarose, starch, chitin, chitosan, cellulose, and their derivatives have been extensively studied since they are non-toxic materials, can be obtained from a wide range of sources and are easy to modify, due to the high variety of functional groups on their surfaces. However, although many lipases have been immobilized on biomaterials and have shown potential for application in biocatalysis, special features are required when the biocatalyst is used in non-conventional media, for example, in organic solvents, which are required for most reactions in organic synthesis. In this article, we discuss the use of biomaterials for lipase immobilization, highlighting recent developments in the synthesis and functionalization of biomaterials using different methods. Examples of effective strategies designed to result in improved activity and stability and drawbacks of the different immobilization protocols are discussed. Furthermore, the versatility of different biocatalysts for the production of compounds of interest in organic synthesis is also described.

Melamine-based Covalent Organic Polymers (MCOPs) as Lipase Nanocarrier for Recyclable Esters Hydrolysis and Transesterification

Present study has successfully synthesized melamine-based covalent organic polymers (MCOPs) and applied it as lipase carrier for recyclable esters hydrolysis and transesterification. The synthesized MCOPs are composed of dense nanosheet structures having a thickness of 3.5 nm. Three immobilization methods namely physical adsorption, cross-linking and carrier activation were employed to prepare the MCOPs-immobilized CRL. Cross-linked MCOPs-immobilized CRL (41.30 mg protein/g MCOPs) and carrier activated MCOPs-immobilized CRL (33.20 mg protein/g MCOPs) had higher enzyme loading as compared to physical absorb MCOPs-immobilized CRL (29.30 mg protein/g MCOPs). Nevertheless, physical absorb MCOPs-immobilized CRL demonstrated the highest esters hydrolysis (49.85 U) and transesterification (1.04 U) activities. Despite having the highest enzymatic activity, physical absorb MCOPs-immobilized CRL were not able to maintain its catalytic stability with more than 30% decreased in enzymatic activity during consecutive hydrolysis and transesterification activities. Meanwhile, cross-linked MCOPs-immobilized CRL demonstrated highest catalytic stability with highest enzymatic activities at the end of consecutive reactions. All the MCOPs-immobilized CRL can be easily recovered and reused through centrifugation with more than 85% of recovery rate.

One Pot Use of Combilipases for Full Modification of Oils and Fats: Multifunctional and Heterogeneous Substrates

Lipases are among the most utilized enzymes in biocatalysis. In many instances, the main reason for their use is their high specificity or selectivity. However, when full modification of a multifunctional and heterogeneous substrate is pursued, enzyme selectivity and specificity become a problem. This is the case of hydrolysis of oils and fats to produce free fatty acids or their alcoholysis to produce biodiesel, which can be considered cascade reactions. In these cases, to the original heterogeneity of the substrate, the presence of intermediate products, such as diglycerides or monoglycerides, can be an additional drawback. Using these heterogeneous substrates, enzyme specificity can promote that some substrates (initial substrates or intermediate products) may not be recognized as such (in the worst case scenario they may be acting as inhibitors) by the enzyme, causing yields and reaction rates to drop. To solve this situation, a mixture of lipases with different specificity, selectivity and differently affected by the reaction conditions can offer much better results than the use of a single lipase exhibiting a very high initial activity or even the best global reaction course. This mixture of lipases from different sources has been called “combilipases” and is becoming increasingly popular. They include the use of liquid lipase formulations or immobilized lipases. In some instances, the lipases have been coimmobilized. Some discussion is offered regarding the problems that this coimmobilization may give rise to, and some strategies to solve some of these problems are proposed. The use of combilipases in the future may be extended to other processes and enzymes.