Current status and trends in enzymatic nanoimmobilization

Recent trends in production and potential applications of microbial amylases: A comprehensive review

α-amylases are vital biocatalysts that constitute a billion-dollar industry with a substantial and enduring global demand. Amylases hydrolyze the α-1,4-glycosidic linkages in starch polymers to generate maltose and malto-oligosaccharides subunits. Amylases are key enzymes that have promising applications in various industrial processes ranging from pharmaceutical, pulp and paper, textile food industries to bioremediation and biofuel sectors. Microbial enzymes have been widely used in industrial applications owing to their ease of availability, cost-effectiveness and better stability at extreme temperatures and pH. α-amylases derived from distinct microbial origins exhibit diverse characteristics, which make them suitable for specific applications. The routine application of immobilized enzymes has become a standard practice in the production of numerous industrial products across the pharmaceutical, chemical, and food industries. This review details the structural makeup of microbial α-amylase to understand its thermodynamic characteristics, aiming to identify key areas that could be targeted for improving the thermostability, pH tolerance and catalytic activity of α-amylase through various immobilization techniques or specific enzyme engineering methods. Additionally, the review briefly explores the enzyme production strategies, potential sources of α-amylases, and use of cost-effective and sustainable raw materials for enzyme production to obtain α-amylases with unconventional applications in various industrial sectors. Major hurdles, challenges and future prospects involving microbial α-amylases has been briefly discussed by considering its diverse applications in industrial bioprocessing.

Application of Goat and Lamb Lipases on the Development of New Immobilized Biocatalysts Aiming at Fish Oil Hydrolysis

The use of lipases from animal sources for the synthesis of new biocatalysts is barely studied in the literature. The present work focused on the immobilization of lipases from kid goat's and lamb's epiglottis in different ionic supports. For this, anionic supports (monoaminoethyl-N-aminoethyl-agarose (MANAE) and diethylaminoethyl-agarose (DEAE)) and cationic supports (carboxymethyl-agarose and sulfopropyl-agarose) were used. The immobilization parameters were evaluated, as well as the thermal stability of the immobilized enzymes and their stability at different values of pH. Then, the performance of the biocatalysts was evaluated in hydrolysis reactions for obtaining omega-3 fatty acids from fish oil (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)). Values of 100% of recovered activity were obtained for lipase from goats, indicating that it was possible to maintain all the enzymatic activities of the immobilized enzymes on the supports. The immobilized enzymes were more stable in different pH conditions and at a temperature of 50 °C, reaching values of stabilization factor of 12.17 and t1/2 of 9.86 h-1, for lamb lipase immobilized in sulfopropyl agarose. In general, the anionic supports led to lower Km values and the cationic ones to a higher Vmax. Lamb lipase showed the highest selectivity values for EPA/DHA, reaching values of 6.43 using MANAE. Thus, the high potential for using such biocatalysts from animal sources in the food or pharmaceutical industries is observed.

Enhanced triolein and ethyl ferulate interesterification performance by CRL-AuNPs

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

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

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

Recent applications and future prospects of magnetic biocatalysts

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

Microfluidic based continuous enzyme immobilization: A comprehensive review

Conventional techniques for enzyme immobilization suffer from suboptimal activity recovery due to insufficient enzyme loading and inadequate stability. Furthermore, these techniques are time-consuming and involve multiple steps which limit the applicability of immobilized enzymes. In contrast, the use of microfluidic devices for enzyme immobilization has garnered significant attention due to its ability to precisely control immobilization parameters, resulting in highly active immobilized enzymes. This approach offers several advantages, including reduced time and energy consumption, enhanced mass-heat transfer, and improved control over the mixing process. It maintains the superior structural configuration in immobilized form which ultimately affects the overall efficiency. The present review article comprehensively explains the design, construction, and various methods employed for enzyme immobilization using microfluidic devices. The immobilized enzymes prepared using these techniques demonstrated excellent catalytic activity, remarkable stability, and outstanding recyclability. Moreover, they have found applications in diverse areas such as biosensors, biotransformation, and bioremediation. The review article also discusses potential future developments and foresees significant challenges associated with enzyme immobilization using microfluidics, along with potential remedies. The development of this advanced technology not only paves the way for novel and innovative approaches to enzyme immobilization but also allows for the straightforward scalability of microfluidic-based techniques from an industrial standpoint.

Adsorption of lipases on porous silica-based materials for esterification in a solvent-free system

This study deals with lipase immobilization on micro- and mesoporous silica-based materials. The effects of the type of support (silica MCM-41, zeolite HZSM-5 (SAR 25), zeolite HZSM-5 (SAR 280), and the silica-aluminas Siral 10, Siral 20, and Siral 40) were investigated on the immobilization of lipase B from Candida antarctica (CALB) and lipase from Rhizomucor miehei (RML). The supports that allowed the highest immobilization efficiencies for the CALB were Siral 40 (91.4%), HZSM-5 (SAR 280) (90.6%), and MCM-41 (89.4%). Siral 20 allowed the highest immobilization efficiency for RML (97.6%), followed by HZSM-5 (SAR 25) (77.1%) and HZSM-5 (SAR 280) (62.7%). The effect of protein concentration on lipase immobilization was investigated, and the results adjusted well on the Langmuir isotherm model (R2 > 0.9). The maximum protein adsorption capacity of the support determined by the Langmuir model was equal to 10.64 and 20.97 mgprotein gsupport-1 for CALB and RML, respectively. The effects of pH (pH 7.0 and pH 11.0) and phosphate buffer solution concentration (5 and 100 mmol L-1) were also investigated on lipase immobilization. The immobilization efficiency for both lipases was similar for the different pH values. The use of 100 mmol L-1 phosphate buffer decreased the lipase immobilization efficiency. The biocatalysts (CALB-Siral 40 and RML-Siral 20) were tested in the ethyl oleate synthesis. The conversion of 61.7% was obtained at 60 °C in the reaction catalyzed by CALB-Siral 40. Both heterogeneous biocatalysts showed increased thermal stability compared with their free form. Finally, the reuse of the biocatalysts was studied. CALB-Siral 40 and RML-Siral 20 maintained about 30% of the initial conversion after 3 batches of ethyl oleate synthesis. Silica-aluminas (Siral 20 and 40) proved to be a support that allowed a high efficiency of immobilization of lipases and activity for esterification reaction.

Has the time finally come for green oleochemicals and biodiesel production using large-scale enzyme technologies? Current status and new developments

With the growth of the chemical industry over the last decade, the need for cheaper (and more environmentally friendly) alternatives to petrochemicals of ever-increasing cost has grown steadily. Oleochemicals and biodiesel (OC/BD) are considered as green alternatives to petroleum derivatives, because they come from renewable oils and fats. OC/BD are currently produced by the traditional energy intensive chemical catalyzed methods, which have several economic and environmental drawbacks. For these reasons, the enzymatic production of OC/BD has attracted a growing attention for their greener pathway with respect to the chemically catalyzed processes. Lipase-catalyzed processes have a low energy requirement, since reactions are performed under atmospheric pressure and mild temperature and without the creation of side reactions. Furthermore, utilization of enzyme catalysts offers many advantages such as reducing the initial capital investment due to simplified downstream processing steps. Despite all the previous advantages, however, the high cost of lipases restricted their large-scale utilization. In the past decade, efforts have been made to reduce the cost of the enzymatic-catalyzed synthesis of OC/BD. However, most previous studies have studied only the technical feasibility of the lipase-catalyzed reactions and overlocked the economic viability. This review critically discusses the factors affecting the promotion of the economic feasibility of the enzymatic processes from the lab to large scale. These include reactor configuration, type of feedstock, conditions optimization, immobilization, lipase-producing microorganisms, and substrate diversification. In addition, this review reports the recent advances in lipase-catalyzed production of fatty acids, fatty esters, monoglycerides, and biodiesel in the lab as well as in the large-scales. To the best of authors' knowledge, this is the first review article reports the recent global progress achieved in both lab- and large-scale for the enzymatic production of OC/BD.

Novel biocatalysts based on enzymes in complexes with nano- and micromaterials

In today's world, there is a wide array of materials engineered at the nano- and microscale, with numerous applications attributed to these innovations. This review aims to provide a concise overview of how nano- and micromaterials are utilized for enzyme immobilization. Enzymes act as eco-friendly biocatalysts extensively used in various industries and medicine. However, their widespread adoption faces challenges due to factors such as enzyme instability under different conditions, resulting in reduced effectiveness, high costs, and limited reusability. To address these issues, researchers have explored immobilization techniques using nano- and microscale materials as a potential solution. Such techniques offer the promise of enhancing enzyme stability against varying temperatures, solvents, pH levels, pollutants, and impurities. Consequently, enzyme immobilization remains a subject of great interest within both the scientific community and the industrial sector. As of now, the primary goal of enzyme immobilization is not solely limited to enabling reusability and stability. It has been demonstrated as a powerful tool to enhance various enzyme properties and improve biocatalyst performance and characteristics. The integration of nano- and microscale materials into biomedical devices is seamless, given the similarity in size to most biological systems. Common materials employed in developing these nanotechnology products include synthetic polymers, carbon-based nanomaterials, magnetic micro- and nanoparticles, metal and metal oxide nanoparticles, metal-organic frameworks, nano-sized mesoporous hydrogen-bonded organic frameworks, protein-based nano-delivery systems, lipid-based nano- and micromaterials, and polysaccharide-based nanoparticles.

An Accessible Method to Improve the Stability and Reusability of Porcine Pancreatic α-Amylase via Immobilization in Gellan-Based Hydrogel Particles Obtained by Ionic Cross-Linking with Mg2+ Ions

Amylase is an enzyme used to hydrolyze starch in order to obtain different products that are mainly used in the food industry. The results reported in this article refer to the immobilization of α-amylase in gellan hydrogel particles ionically cross-linked with Mg2+ ions. The obtained hydrogel particles were characterized physicochemically and morphologically. Their enzymatic activity was tested using starch as a substrate in several hydrolytic cycles. The results showed that the properties of the particles are influenced by the degree of cross-linking and the amount of immobilized α-amylase enzyme. The temperature and pH at which the immobilized enzyme activity is maximum were T = 60 °C and pH = 5.6. The enzymatic activity and affinity of the enzyme to the substrate depend on the particle type, and this decreases for particles with a higher cross-linking degree owing to the slow diffusion of the enzyme molecules inside the polymer's network. By immobilization, α-amylase is protected from environmental factors, and the obtained particles can be quickly recovered from the hydrolysis medium, thus being able to be reused in repeated hydrolytic cycles (at least 11 cycles) without a substantial decrease in enzymatic activity. Moreover, α-amylase immobilized in gellan particles can be reactivated via treatment with a more acidic medium.

Developing Enzyme Immobilization with Fibrous Membranes: Longevity and Characterization Considerations

Fibrous membranes offer broad opportunities to deploy immobilized enzymes in new reactor and application designs, including multiphase continuous flow-through reactions. Enzyme immobilization is a technology strategy that simplifies the separation of otherwise soluble catalytic proteins from liquid reaction media and imparts stabilization and performance enhancement. Flexible immobilization matrices made from fibers have versatile physical attributes, such as high surface area, light weight, and controllable porosity, which give them membrane-like characteristics, while simultaneously providing good mechanical properties for creating functional filters, sensors, scaffolds, and other interface-active biocatalytic materials. This review examines immobilization strategies for enzymes on fibrous membrane-like polymeric supports involving all three fundamental mechanisms of post-immobilization, incorporation, and coating. Post-immobilization offers an infinite selection of matrix materials, but may encounter loading and durability issues, while incorporation offers longevity but has more limited material options and may present mass transfer obstacles. Coating techniques on fibrous materials at different geometric scales are a growing trend in making membranes that integrate biocatalytic functionality with versatile physical supports. Biocatalytic performance parameters and characterization techniques for immobilized enzymes are described, including several emerging techniques of special relevance for fibrous immobilized enzymes. Diverse application examples from the literature, focusing on fibrous matrices, are summarized, and biocatalyst longevity is emphasized as a critical performance parameter that needs increased attention to advance concepts from lab scale to broader utilization. This consolidation of fabrication, performance measurement, and characterization techniques, with guiding examples highlighted, is intended to inspire future innovations in enzyme immobilization with fibrous membranes and expand their uses in novel reactors and processes.

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

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

Multienzyme Coimmobilization on Triheterofunctional Supports

Immobilized multienzyme systems are gaining momentum in applied biocatalysis; however, the coimmobilization of several enzymes on one carrier is still challenging. In this work, we exploited a heterofunctional support activated with three different chemical functionalities to immobilize a wide variety of different enzymes. This support is based on agarose microbeads activated with aldehyde, amino, and cobalt chelate moieties that allow a fast and irreversible immobilization of enzymes, enhancing the thermostability of most of the heterogeneous biocatalysts (up to 21-fold higher than the soluble one). Furthermore, this trifunctional support serves to efficiently coimmobilize a multienzyme system composed of an alcohol dehydrogenase, a reduced nicotinamide adenine dinucleotide (NADH) oxidase, and a catalase. The confined multienzymatic system demonstrates higher performance than its free counterpart, achieving a total turnover number (TTN) of 1 × 10⁵ during five batch consecutive cycles. We envision this solid material as a platform for coimmobilizing multienzyme systems with enhanced properties to catalyze stepwise biotransformations.

A comprehensive review on bio-mimicked multimolecular frameworks and supramolecules as scaffolds for enzyme immobilization

Immobilization depicts a propitious route to optimize the catalytic performances, efficient recovery, minimizing autocatalysis, and also augment the stabilities of enzymes, particularly in unnatural environments. In this opinion, supramolecules and multimolecular frameworks have captivated immense attention to achieve profound controllable interactions between enzyme molecules and well-defined natural or synthetic architectures to yield protein bioconjugates with high accessibility for substrate binding and enhanced enantioselectivities. This scholastic review emphasizes the possibilities of associating multimolecular complexes with biological entities via several types of interactions, namely covalent interactions, host-guest complexation, π - π ${\rm{\pi }}-{\rm{\pi }}$ interactions, intra/inter hydrogen bondings, electrostatic interactions, and so forth offers remarkable applications for the modulations of enzymes. The potential synergies between artificial supramolecular structures and biological systems are the primary concern of this pedagogical review. The majority of the research primarily focused on the dynamic biomolecule-responsive supramolecular assemblages and multimolecular architectures as ideal platforms for the recognition and modulation of proteins and cells. Embracing sustainable green demeanors of enzyme immobilizations in a quest to reinforce site-selectivity, catalytic efficiency, and structural integrality of enzymes are the contemporary requirements of the biotechnological sectors that instigate the development of novel biocatalytic systems.

Biological oxidation methods for the removal of organic and inorganic contaminants from wastewater: A comprehensive review

Enzyme-based bioremediation is a simple, cost-effective, and environmentally friendly method for isolating and removing a wide range of environmental pollutants. This study is a comprehensive review of recent studies on the oxidation of pollutants by biological oxidation methods, performed individually or in combination with other methods. The main bio-oxidants capable of removing all types of pollutants, such as organic and inorganic molecules, from fungi, bacteria, algae, and plants, and different types of enzymes, as well as the removal mechanisms, were investigated. The use of mediators and modification methods to improve the performance of microorganisms and their resistance under harsh real wastewater conditions was discussed, and numerous case studies were presented and compared. The advantages and disadvantages of conventional and novel immobilization methods, and the development of enzyme engineering to adjust the content and properties of the desired enzymes, were also explained. The optimal operating parameters such as temperature and pH, which usually lead to the best performance, were presented. A detailed overview of the different combination processes was also given, including bio-oxidation in coincident or consecutive combination with adsorption, advanced oxidation processes, and membrane separation. One of the most important issues that this study has addressed is the removal of both organic and inorganic contaminants, taking into account the actual wastewaters and the economic aspect.

A multi-component reaction for covalent immobilization of lipases on amine-functionalized magnetic nanoparticles: production of biodiesel from waste cooking oil

A new approach was used for the immobilization of Thermomyces lanuginosus lipase (TLL), Candida antarctica lipase B (CALB), and Rhizomucor miehei lipase (RML) on amine-functionalized magnetic nanoparticles (Fe3O4@SiO2-NH2) via a multi-component reaction route (using cyclohexyl isocyanide). The used method offered a single-step and very fast process for covalent attachment of the lipases under extremely mild reaction conditions (25 °C, water, and pH 7.0). Rapid and simple immobilization of 20 mg of RML, TLL, and CALB on 1 g of the support produced 100%, 98.5%, and 99.2% immobilization yields, respectively, after 2 h of incubation. The immobilized derivatives were then used for biodiesel production from waste cooking oil. Response surface methodology (RSM) in combination with central composite rotatable design (CCRD) was employed to evaluate and optimize the biodiesel production. The effect of some parameters such as catalyst amount, reaction temperature, methanol concentration, water content for TLL or water-adsorbent for RML and CALB, and ratio of t-butanol (wt%) were investigated on the fatty acid methyl esters (FAME) yield.

Structural Rearrangements of Carbonic Anhydrase Entrapped in Sol-Gel Magnetite Determined by ATR–FTIR Spectroscopy

Enzymatically active nanocomposites are a perspective class of bioactive materials that finds their application in numerous fields of science and technology ranging from biosensors and therapeutic agents to industrial catalysts. Key properties of such systems are their stability and activity under various conditions, the problems that are addressed in any research devoted to this class of materials. Understanding the principles that govern these properties is critical to the development of the field, especially when it comes to a new class of bioactive systems. Recently, a new class of enzymatically doped magnetite-based sol-gel systems emerged and paved the way for a variety of potent bioactive magnetic materials with improved thermal stability. Such systems already showed themself as perspective industrial and therapeutic agents, but are still under intense investigation and many aspects are still unclear. Here we made a first attempt to describe the interaction of biomolecules with magnetite-based sol-gel materials and to investigate facets of protein structure rearrangements occurring within the pores of magnetite sol-gel matrix using ATR Fourier-transform infrared spectroscopy.

Biocatalytic asymmetric synthesis of secondary allylic alcohols using Burkholderia cepacia lipase immobilized on multiwalled carbon nanotubes

The lipase from Burkholderia cepacia (BCL) was immobilized through physical adsorption on pristine and functionalized multiwalled carbon nanotubes (MWCNTs) with carboxyl or amine groups and used in the stereoselective acylation of (R,S)-1-octen-3-ol (1) and (R,S)-(E)-4-phenyl-3-buten-2-ol (4) with vinyl acetate. All immobilized preparations produced better results than free BCL. For (R,S)-4, 50% conversion and E > 200 were obtained in n-hexane or in solvent-free medium. For (R,S)-1, in solvent-free medium, the conversion was 38% with a slight increase in the E-value (E = 10).

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

BACKGROUND

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

AIM OF REVIEW

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

KEY SCIENTIFIC CONCEPTS OF REVIEW

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

Roles of Surfactants in Oriented Immobilization of Cellulase on Nanocarriers and Multiphase Hydrolysis System

Surfactants, especially non-ionic surfactants, play an important role in the preparation of nanocarriers and can also promote the enzymatic hydrolysis of lignocellulose. A broad overview of the current status of surfactants on the immobilization of cellulase is provided in this review. In addition, the restricting factors in cellulase immobilization in the complex multiphase hydrolysis system are discussed, including the carrier structure characteristics, solid-solid contact obstacles, external diffusion resistance, limited recycling frequency, and nonproductive combination of enzyme active centers. Furthermore, promising prospects of cellulase-oriented immobilization are proposed, including the hydrophilic-hydrophobic interaction of surfactants and cellulase in the oil-water reaction system, the reversed micelle system of surfactants, and the possible oriented immobilization mechanism.

Preparation and characterization of stable core/shell Fe3O4@Au decorated with an amine group for immobilization of lipase by covalent attachment

The self-assembly approach was used for amine decoration of core/shell Fe₃O₄@Au with 4-aminothiophenol. This structure was used for covalent immobilization of lipase using a Ugi 4-component reaction. The amine group on the structure and carboxylic group from lipase can react in the Ugi reaction and a firm and stable covalent bond is created between enzyme and support. The synthesized structure was fully characterized and its activity was explored in different situations. The results showed the pH and temperature stability of immobilized lipase compared to free lipase in a wide range of pH and temperature. Also after 60 days, it showed excellent activity while residual activity for the free enzyme was only 10%. The synthesized structure was conveniently separated using an external magnetic field and reused 6 times without losing the activity of the immobilized enzyme.

The self-assembly approach was used for amine decoration of core/shell Fe₃O₄@Au with 4-aminothiophenol.

Nanoflowers: A New Approach of Enzyme Immobilization

Enzymes are biocatalysts known for versatility, selectivity, and brand operating conditions compared to chemical catalysts. However, there are limitations to their large-scale application, such as the high costs of enzymes and their low stability under extreme reaction conditions. Immobilization techniques can efficiently solve these problems; nevertheless, most current methods lead to a significant loss of enzymatic activity and require several steps of activation and functionalization of the supports. In this context, a new form of immobilization has been studied: forming organic-inorganic hybrids between metal phosphates as inorganic parts and enzymes as organic parts. Compared to traditional immobilization methods, the advantages of these nanomaterials are high surface area, simplicity of synthesis, high stability, and catalytic activity. The current study presents an overview of organic-inorganic hybrid nanoflowers and their applications in enzymatic catalysis.

Effects of Pore Size and Crosslinking Methods on the Immobilization of Myoglobin in SBA-15

A series of stable mesoporous silica sieves (SBA-15) with different pore sizes (9.8, 7.2, and 5.5 nm) were synthesized using a hydrothermal method. The resulting mesoporous material was then utilized for protein immobilization using myoglobin (Mb) as the target protein. The effects of pore size and adsorption methods on the immobilization efficiency of Mb in a mesoporous material were studied. The SBA-15 with a pore size of 7.2 nm showed the best loading capacity, reaching 413.8 mg/g. The SBA-15 with a pore size of 9.8 nm showed the highest retained catalytic ability (92.36%). The immobilized enzyme was more stable than the free enzyme. After seven consecutive assay cycles, Mb adsorbed by SBA-15 (Mb/SBA-15) and Mb adsorbed by SBA-15 and crosslinked with glutaraldehyde (Mb/G/SBA-15) retained 36.41% and 62.37% of their initial activity, respectively.

Immobilization of β-Galactosidase by Encapsulation of Enzyme-Conjugated Polymer Nanoparticles Inside Hydrogel Microparticles

Increasing the shelf life of enzymes and making them reusable is a prominent topic in biotechnology. The encapsulation inside hydrogel microparticles (HMPs) can enhance the enzyme's stability by preserving its native conformation and facilitating continuous biocatalytic processes and enzyme recovery. In this study, we present a method to immobilize β-galactosidase by, first, conjugating the enzyme onto the surface of polymer nanoparticles, and then encapsulating these enzyme-conjugated nanoparticles (ENPs) inside HMPs using microfluidic device paired with UV-LEDs. Polymer nanoparticles act as anchors for enzyme molecules, potentially preventing their leaching through the hydrogel network especially during swelling. The affinity binding (through streptavidin-biotin interaction) was used as an immobilization technique of β-galactosidase on the surface of polymer nanoparticles. The hydrogel microparticles of roughly 400 μm in size (swollen state) containing unbound enzyme and ENPs were produced. The effects of encapsulation and storage in different conditions were evaluated. It was discovered that the encapsulation in acrylamide (AcAm) microparticles caused an almost complete loss of enzymatic activity. Encapsulation in poly(ethylene glycol) (PEG)-diacrylate microparticles, on the other hand, showed a residual activity of 15-25%, presumably due to a protective effect of PEG during polymerization. One of the major factors that affected the enzyme activity was presence of photoinitiator exposed to UV-irradiation. Storage studies were carried out at room temperature, in the fridge and in the freezer throughout 1, 7 and 28 days. The polymer nanoparticles showcased excellent immobilization properties and preserved the activity of the conjugated enzyme at room temperature (115% residual activity after 28 days), while a slight decrease was observed for the unbound enzyme (94% after 28 days). Similar trends were observed for encapsulated ENPs and unbound enzyme. Nevertheless, storage at -26°C resulted in an almost complete loss of enzymatic activity for all samples.

A review of sustainable biodiesel production using biomass derived heterogeneous catalysts

The production of biodiesel through chemical production processes of transesterification reaction depends on suitable catalysts to hasten the chemical reactions. Therefore, the initial selection of catalysts is critical although it is also dependent on the quantity of free fatty acids in a given sample of oil. Earlier forms of biodiesel production processes relied on homogeneous catalysts, which have undesirable effects such as toxicity, high flammability, corrosion, by-products such as soap and glycerol, and high wastewater. Heterogeneous catalysts overcome most of these problems. Recent developments involve novel approaches using biomass and bio-waste resource derived heterogeneous catalysts. These catalysts are renewable, non-toxic, reusable, offer high catalytic activity and stability in both acidic and base conditions, and show high tolerance properties to water. This review work critically reviews biomass-based heterogeneous catalysts, especially those utilized in sustainable production of biofuel and biodiesel. This review examines the sustainability of these catalysts in literature in terms of small-scale laboratory and industrial applications in large-scale biodiesel and biofuel production. Furthermore, this work will critically review natural heterogeneous biomass waste and bio-waste catalysts in relation to upcoming nanotechnologies. Finally, this work will review the gaps identified in the literature for heterogeneous catalysts derived from biomass and other biocatalysts with a view to identifying future prospects for heterogeneous catalysts.

Biological Methods in Biodiesel Production and Their Environmental Impact

This publication presents the technologies of enzymatic biodiesel production in comparison to the conventional methods using acid and base catalysts. Transesterification with conventional catalysts has some disadvantages, and for this reason, alternative methods of biodiesel production have been investigated. These solutions include the replacement of chemical catalysts with biological ones, which show substrate specificity in relation to fats. Replacing chemical with biological catalysts causes elimination of some disadvantages of chemical processes, for instance: high temperatures of reaction, problematic process of glycerol purification, higher alcohol-to-oil molar ratios, and soap formation. Moreover, it causes operational cost reduction and has a positive environmental impact. This is due to the lower temperature of the process, which in turn translates into lower cost of equipment and lower GHG emissions associated with the need to provide less heat to the process. The increase of biofuels’ demand has led to the technology of enzymatic biodiesel production being constantly being developed. This research mainly focuses on the possibility of obtaining cheaper and more effective biocatalysts, as well as increasing the durability of enzyme immobilization on different materials.

Perspectives on new opportunities for nano-enabled strategies for gene delivery to plants using nanoporous materials

Engineered nanocarriers have great potential to deliver different genetic cargos to plant cells and increase the efficiency of plant genetic engineering. Genetic engineering has improved the quality and quantity of crops by introducing desired DNA sequences into the plant genome. Traditional transformation strategies face constraints such as low transformation efficiency, damage to plant tissues, and genotype dependency. Smart nanovehicle-based delivery is a newly emerged method for direct DNA delivery to plant genomes. The basis of this new approach of plant genetic transformation, nanomaterial-mediated gene delivery, is the appropriate protection of transferred DNA from the nucleases present in the cell cytoplasm through the nanocarriers. The conjugation of desired nucleic acids with engineered nanocarriers can solve the problem of genetic manipulation in some valuable recalcitrant plant genotypes. Combining nano-enabled genetic transformation with the new and powerful technique of targeted genome editing, CRISPR (clustered regularly interspaced short palindromic repeats), can create new protocols for efficient improvement of desired plants. Silica-based nanoporous materials, especially mesoporous silica nanoparticles (MSNs), are currently regarded as exciting nanoscale platforms for genetic engineering as they possess several useful properties including ordered and porous structure, biocompatibility, biodegradability, and surface chemistry. These specific features have made MSNs promising candidates for the design of smart, controlled, and targeted delivery systems in agricultural sciences. In the present review, we discuss the usability, challenges, and opportunities for possible application of nano-enabled biomolecule transformation as part of innovative approaches for target delivery of genes of interest into plants.

Robust nanocarriers to engineer nanobiocatalysts for bioprocessing applications

The synergistic integration of bio-catalysis engineering with nanostructured materials, as unique multifunctional carrier matrices, has emerged as a new interface of nanobiocatalysis (NBC). NBC is an emerging innovation that offers significant considerations to expand the designing and fabrication of robust catalysts at the nanoscale with improved catalytic characteristics for multipurpose bioprocessing applications. In addition, nanostructured materials with unique structural, physical, chemical, and functional entities have manifested significant contributions in mimicking the enzyme microenvironment. A fine-tuned enzyme microenvironment with an added-value of NBC offers chemo- regio- and stereo- selectivities and specificities. Furthermore, NBC is growing rapidly and will become a powerful norm in bio-catalysis with much controlled features, such as selectivity, specificity, stability, resistivity, induce activity, reaction efficacy, multi-usability, improved mass transfer efficiency, high catalytic turnover, optimal yield, ease in recovery, and cost-effectiveness. Considering the above critics and unique structural, physicochemical, and functional attributes, herein, we present and discuss advances in NBC and its bioprocessing applications in different fields. Briefly, this review is focused on four parts, i.e., (1) NBC as a drive towards applied nanobiocatalysts (as an introduction with opportunities), (2) promising nanocarriers to develop nanobiocatalysts, (3) applications in the fields of biotransformation, biofuel production, carbohydrate hydrolysis, bio-/nanosensing, detergent formulations, and extraction and purification of value-added compounds, and (4) current challenges, concluding remarks, and future trends.

Non-covalent and covalent immobilization of papain onto Ti3C2 MXene nanosheets

Papain was immobilized onto Ti₃C₂ MXene nanosheets by physical adsorption and physical adsorption combined with covalent crosslinking with glutaraldehyde. Ti₃C₂ MXene nanosheets were prepared by hydrofluoric acid etching method. The resulting products were well characterized by SEM, BET, XRD, FTIR, XPS. The optimized immobilization conditions are pH 6.5, immobilization time of 20 h, immobilization temperature of 10℃, and 10 mL 2 mg mL^-1 papain, the amount of papain immobilized was 156 mg g^-1, the activity of the immobilized papain determined was 1701 U∙g^-1. The immobilized papain exhibited enhanced pH and temperature endurances, immobilized papain also showed improved storage stability (39.25 % and 65.57 % after 20 days of storage at 4 °C). papain reusability was significantly improved after immobilization and it retained more than 50 % of its initial activity after 5 repeated cycles. Interestingly, the results of immobilized enzymes demonstrated that the immobilization of enzymes on Ti₃C₂ MXene is feasible. Such approach could be transferred to other support systems for anchoring enzyme.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

Preparation of regenerable magnetic nanoparticles for cellulase immobilization: Improvement of enzymatic activity and stability

To obtain regenerable magnetic nanoparticles, triethoxy(3-isocyanatopropyl)silane and iminodiacetic acid (IZ) were used as the starting material and immobilized on Fe₃ O₄ nanoparticles. Copper ions (Cu²⁺ ions) were loaded on the Fe-IZ nanoparticles and used for cellulase immobilization. The support was characterized by spectroscopic methods (FTIR, NMR) and thermogravimetric analysis, transmission electron microscopy, scanning electron microscope, X-ray diffraction, energy dispersive X-ray analysis, and vibrating sample magnetometer techniques. As a result of experiments, the amount of protein bound to immobilized cellulase (Fe-IZ-Cu-E) and cellulase activity was found to be 33.1 mg/g and 154 U/g at pH 5, 50°C, for 3 h. The results indicated that the free cellulase had kept only 50% of its activity after 2 h, while the Fe-IZ-Cu-E was observed to be around 77%, at 60°C. It was found that the immobilized cellulase maintained 93% of its initial catalytic activity after its sixth use. Furthermore, the Fe-IZ-Cu-E retained about 75% of its initial activity after 28 days of storage. To reuse the support material (Fe-IZ-Cu), it was regenerated by thorough washing with ammonia or imidazole.

Stabilization of β-Galactosidase on Modified Gold Nanoparticles: A Preliminary Biochemical Study to Obtain Lactose-Free Dairy Products for Lactose-Intolerant Individuals

The unique chemical, optical, and electrical characteristics of nanoparticles make their utilization highly successful in every field of biological sciences as compared to their bulk counterpart. These properties arise as a result of their miniature size, which provides them an excellent surface area-to-volume ratio, inner structure, and shape, and hence increases their surface characteristics. Therefore, this study was undertaken to engineer gold nanoparticles (AuNPs) for improving their catalytic activity and stability in biotechnological processes. The characterization of AuNPs was performed by XRD, UV spectra, and TEM. The synthesized AuNPs were surface-modified by polyvinyl alcohol (PVA) for binding the enzyme in excellent yield. The developed immobilized enzyme system (PVA-AuNPs-β-galactosidase) displayed pH optima at pH 7.0 and temperature optima at 40 °C. Moreover, the stability of PVA-AuNPs-β-galactosidase was significantly enhanced at wider pH and temperature ranges and at higher galactose concentrations, in contrast to the free enzyme. β-galactosidase bound to PVA-modified AuNPs exhibited greater operational activity, even after its sixth reuse. The developed nanosystem may prove useful in producing lactose-free dairy products for lactose-intolerant patients.

Nanoformulation approach for improved stability and efficiency of lactoperoxidase

Lactoperoxidase is a glycosylated protein with a molecular mass of 78 kDa, which being excreted in several mammalian secretions. Lactoperoxidase is included in many biological processes and well-known to have biocidal actions, attending as active antibiotics and antiviral agents. This wide-spectrum of biocidal activities mediates via a definite inhibitory system named lactoperoxidase system which acts a potent role in the innate immune response since its activity is not restricted by the antimicrobial effect, but might act a significant role in the hydrolysis of many toxins like aflatoxin. Hence with the current progresses in technology, nanoparticles can offer chances as an active candidate that might be utilized for stabilizing and potentiating the activity of LPO for use in several applications. Due to the variability functions of LPO, this enzyme considers an active target to be encapsulated or coated to NPs for developing novel nanocombinations with controlled surface characteristics. The development of approaches which might enhance conformational stabilization for several weeks of LPO via nanoformulation could improve the biopharmaceutical applicability of this bioactive ingredient. Nanoformulation of LPO enhances novel functions that can be useful in many biotechnological applications like food industry, cosmetic and pharmaceutical applications or to deliver and encapsulate bioactive components.

Immobilization of alcohol dehydrogenase from Saccharomyces cerevisiae onto carboxymethyl dextran-coated magnetic nanoparticles: a novel route for biocatalyst improvement via epoxy activation

A novel method is described for the immobilization of alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae onto carboxymethyl dextran (CMD) coated magnetic nanoparticles (CMD-MNPs) activated with epoxy groups, using epichlorohydrin (EClH). EClH was used as an activating agent to bind ADH molecules on the surface of CMD-MNPs. Optimal immobilization conditions (activating agent concentration, temperature, rotation speed, medium pH, immobilization time and enzyme concentration) were set to obtain the highest expressed activity of the immobilized enzyme. ADH that was immobilized onto epoxy-activated CMD-MNPs (ADH-CMD-MNPs) maintained 90% of the expressed activity. Thermal stability of ADH-CMD-MNPS after 24 h at 20 °C and 40 °C yielded 79% and 80% of initial activity, respectively, while soluble enzyme activity was only 19% at 20 °C and the enzyme was non-active at 40 °C. Expressed activity of ADH-CMD-MNPs after 21 days of storage at 4 °C was 75%. Kinetic parameters (K_M, v_max) of soluble and immobilized ADH were determined, resulting in 125 mM and 1.2 µmol/min for soluble ADH, and in 73 mM and 4.7 µmol/min for immobilized ADH.

Cytochrome c oxidase oxygen reduction reaction induced by cytochrome c on nickel-coordination surfaces based on graphene oxide in suspension

BACKGROUND

The electrochemical and spectroscopic investigation of bacterial electron-transfer proteins stabilized on solid state electrodes has provided an effective approach for functional respiratory enzyme studies.

METHODS

We assess the biocompatibility of carboxylated graphene oxide (CGO) functionalized with Nickel nitrilotriacetic groups (CGO-NiNTA) ccordinating His-tagged cytochrome c oxidase (CcO) from Rhodobacter sphaeroides.

RESULTS

Kinetic studies employing UV-visible absorption spectroscopy confirmed that the immobilized CcO oxidized horse-heart cytochrome c (Cyt c) albeit at a slower rate than isolated CcO. The oxygen reduction reaction as catalyzed by immobilized CcO could be clearly distinguished from that arising from CGO-NiNTA in the presence of Cyt c and dithiothreitol (DTT) as a sacrificial reducing agent. Our findings indicate that while the protein content is about 3.7‰ by mass with respect to the support, the contribution to the oxygen consumption activity averaged at 56.3%.

CONCLUSIONS

The CGO-based support stabilizes the free enzyme which, while capable of Cyt c oxidation, is unable to carry out oxygen consumption in solution on its own under our conditions. The turnover rate for the immobilized CcO was as high as 240 O₂ molecules per second per CcO unit.

GENERAL SIGNIFICANCE

In vitro investigations of electron flow on isolated components of bacterial electron-transfer enzymes immobilized on the surface of CGO in suspension are expected to shed new light on microbial bioenergetic functions, that could ultimately contribute toward the improvement of performance in living organisms.

Clickable artificial heme-peroxidases for the development of functional nanomaterials

Artificial metalloenzymes as catalysts are promising candidates for their use in different technologies, such as bioremediation, biomass transformation, or biosensing. Despite this, their practical exploitation is still at an early stage. Immobilized natural enzymes have been proposed to enhance their applicability. Immobilization may offer several advantages: (i) catalyst reuse; (ii) easy separation of the enzyme from the reaction medium; (iii) better tolerance to harsh temperature and pH conditions. Here, we report an easy immobilization procedure of an artificial peroxidase on different surfaces, by means of click chemistry. FeMC6*a, a recently developed peroxidase mimic, has been functionalized with a pegylated aza-dibenzocyclooctyne to afford a "clickable" biocatalyst, namely FeMC6*a-PEG₄@DBCO, which easily reacts with azide-functionalized molecules and/or nanomaterials to afford functional bioconjugates. The clicked biocatalyst retains its structural and, to some extent, its functional behaviors, thus housing high potential for biotechnological applications.

Immobilization of Naringinase from Aspergillus Niger on a Magnetic Polysaccharide Carrier

Naringinase is an enzymatic complex used in the deglycosylation of compounds with a high application potential in the food and pharmaceutical industries. The aim of the study was to immobilize naringinase from Aspergillus niger KMS on a magnetic carrier obtained on the basis of carob gum activated by polyethyleneimine. Response surface methodology was used to optimize naringinase immobilization taking into account the following factors: pH, immobilization time, initial concentration of naringinase and immobilization temperature. The adsorption of the enzyme on a magnetic carrier was a reversible process. The binding force of naringinase was increased by crosslinking the enzyme with the carrier using dextran aldehyde. The crosslinked enzyme had better stability in an acidic environment and at a higher temperature compared to the free form. The immobilization and stabilization of naringinase by dextran aldehyde on the magnetic polysaccharide carrier lowered the activation energy, thus increasing the catalytic capacity of the investigated enzyme and increasing the activation energy of the thermal deactivation process, which confirms higher stability of the immobilized enzyme in comparison with free naringinase. The preparation of crosslinked naringinase retained over 80% of its initial activity after 10 runs of naringin hydrolysis from fresh and model grapefruit juice.

A Review on Bio-Based Catalysts (Immobilized Enzymes) Used for Biodiesel Production

The continuous increase of the world’s population results in an increased demand for energy drastically from the industrial and domestic sectors as well. Moreover, the current public awareness regarding issues such as pollution and overuse of petroleum fuel has resulted in the development of research approaches concerning alternative renewable energy sources. Amongst the various options for renewable energies used in transportation systems, biodiesel is considered the most suitable replacement for fossil-based diesel. In what concerns the industrial application for biodiesel production, homogeneous catalysts such as sodium hydroxide, potassium hydroxide, sulfuric acid, and hydrochloric acid are usually selected, but their removal after reaction could prove to be rather complex and sometimes polluting, resulting in increases on the production costs. Therefore, there is an open field for research on new catalysts regarding biodiesel production, which can comprise heterogeneous catalysts. Apart from that, there are other alternatives to these chemical catalysts. Enzymatic catalysts have also been used in biodiesel production by employing lipases as biocatalysts. For economic reasons, and reusability and recycling, the lipases urged to be immobilized on suitable supports, thus the concept of heterogeneous biocatalysis comes in existence. Just like other heterogeneous catalytic materials, this one also presents similar issues with inefficiency and mass-transfer limitations. A solution to overcome the said limitations can be to consider the use of nanostructures to support enzyme immobilization, thus obtaining new heterogeneous biocatalysts. This review mainly focuses on the application of enzymatic catalysts as well as nano(bio)catalysts in transesterification reaction and their multiple methods of synthesis.