Multi-enzyme co-immobilized nano-assemblies: Bringing enzymes together for expanding bio-catalysis scope to meet biotechnological challenges

A Self-Assembling γPFD-SpyCatcher Hydrogel Scaffold for the Coimmobilization of SpyTag-Enzymes to Facilitate the Catalysis of Regulated Enzymes

In this study, a γPFD-SpyCatcher hydrogel scaffold with the capacity for spontaneous assembly was established. With a maximum loading capacity of a 1:1 molar ratio with SpyTag-enzymes, the immobilized proteins can not only rapidly provide pure enzymes but also exhibit improved thermal and pH stability. The results of the transmission electron microscopic analysis and the traits they present indicated that SpyCatcher promotes the aggregation of γPFD and the formation of hydrogels. In the cell-free pyruvate synthesis system, the γPFD-SpyCatcher coimmobilized SpyTag-hexokinase (HK), SpyTag-phosphofructokinase (PFK) and SpyTag-pyruvate kinase (PK) were employed, and the production of pyruvate increased by 43, 78 and 47% respectively. In in vitro experiments, the oxidative deamination activity of glutamate dehydrogenase (GDH) coimmobilized with γPFD-SpyCatcher was 38% higher than that of purified enzymes. These findings indicate that the γPFD-SpyCatcher-based hydrogels play an important role in breaking the barrier of regulatory enzymes and will provide more strategies for the development of synthetic biology.

Magnetic nanoflowers: a hybrid platform for enzyme immobilization

The use of organic-inorganic hybrid nanoflowers as a support material for enzyme immobilization has gained significant attention in recent years due to their high stability, ease of preparation, and enhanced catalytic activity. However, a major challenge in utilizing these hybrid nanoflowers for enzyme immobilization is the difficulty in handling and separating them due to their low density and high dispersion. To address this issue, magnetic nanoflowers have emerged as a promising alternative enzyme immobilization platform due to their easy separation, structural stability, and ability to enhance catalytic efficiency. This review focuses on different methods for designing magnetic nanoflowers, as well as future research directions. Additionally, it provides examples of enzymes immobilized in the form of magnetic nanoflowers and their applications in environmental remediation, biosensors, and food industries. Finally, the review discusses possible ways to improve the material for enhanced catalytic activity, structural stability, and scalability.

State-of-the-art strategies and research advances for the biosynthesis of D-amino acids

D-amino acids (D-AAs) are the enantiomeric counterparts of L-amino acids (L-AAs) and important functional factors with a wide variety of physiological activities and applications in the food manufacture industry. Some D-AAs, such as D-Ala, D-Leu, and D-Phe, have been favored by consumers as sweeteners and fragrances because of their unique flavor. The biosynthesis of D-AAs has attracted much attention in recent years due to their unique advantages. In this review, we comprehensively analyze the structure-function relationships, biosynthesis pathways, multi-enzyme cascade and whole-cell catalysis for the production of D-AAs. The state-of-the-art strategies, including immobilization, protein engineering, and high-throughput screening, are summarized. Future challenges and perspectives of strategies-driven by bioinformatics technologies and smart computing technologies, as well as enzyme immobilization, are also discussed. These new approaches will promote the commercial production and application of D-AAs in the food industry by optimizing the key enzymes for industrial biocatalysts.

A Multienzyme Cascade Pathway Immobilized in a Hydrogen-Bonded Organic Framework for the Conversion of CO2

The reduction of carbon dioxide to valuable chemicals through enzymatic processes is regarded as a promising approach for the reduction of carbon dioxide emissions. In this study, an in vitro multi-enzyme cascade pathway is constructed for the conversion of CO2 into dihydroxyacetone (DHA). This pathway, known as FFFP, comprises formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH), formolase (FLS), and phosphite dehydrogenase (PTDH), with PTDH serving as the critical catalyst for regenerating the coenzyme NADH. Subsequently, the immobilization of the FFFP pathway within the hydrogen-bonded organic framework (HOF-101) is accomplished in situ. A 1.8-fold increase in DHA yield is observed in FFFP@HOF-101 compared to the free FFFP pathway. This enhancement can be explained by the fact that within FFFP@HOF-101, enzymes are positioned sufficiently close to one another, leading to the elevation of the local concentration of intermediates and an improvement in mass transfer efficiency. Moreover, FFFP@HOF-101 displays a high degree of stability. In addition to the establishment of an effective DHA production method, innovative concepts for the tailored synthesis of fine compounds from CO2 through the utilization of various multi-enzyme cascade developments are generated by this work.

Recent insight into the advances and prospects of microbial lipases and their potential applications in industry

Enzymes play a crucial role in various industrial sectors. These biocatalysts not only ensure sustainability and safety but also enhance process efficiency through their unique specificity. Lipases possess versatility as biocatalysts and find utilization in diverse bioconversion reactions. Presently, microbial lipases are gaining significant focus owing to the rapid progress in enzyme technology and their widespread implementation in multiple industrial procedures. This updated review presents new knowledge about various origins of microbial lipases, such as fungi, bacteria, and yeast. It highlights both the traditional and modern purification methods, including precipitation and chromatographic separation, the immunopurification technique, the reversed micellar system, the aqueous two-phase system (ATPS), and aqueous two-phase flotation (ATPF), moreover, delves into the diverse applications of microbial lipases across several industries, such as food, vitamin esters, textile, detergent, biodiesel, and bioremediation. Furthermore, the present research unveils the obstacles encountered in employing lipase, the patterns observed in lipase engineering, and the application of CRISPR/Cas genome editing technology for altering the genes responsible for lipase production. Additionally, the immobilization of microorganisms' lipases onto various carriers also contributes to enhancing the effectiveness and efficiencies of lipases in terms of their catalytic activities. This is achieved by boosting their resilience to heat and ionic conditions (such as inorganic solvents, high-level pH, and temperature). The process also facilitates the ease of recycling them and enables a more concentrated deposition of the enzyme onto the supporting material. Consequently, these characteristics have demonstrated their suitability for application as biocatalysts in diverse industries.

Combined cross-linking of Rhizomucor miehei lipase and Candida antarctica lipase B for the effective enrichment of omega-3 fatty acids in fish oil

The incorporation of a non-specific lipase and a sn-1,3 specific one in a single immobilized system can be a promising approach for the exploitation of both lipases. A one-step immobilization platform mediated by an isocyanide-based multi-component reaction was applied to create co-cross-linked enzymes (co-CLEs) of lipases from Rhizomucor miehei (sn-1,3 specific) and Candida antarctica (non-specific). Glutaraldehyde was found to be effective cross-linker by producing specific activity of 16.9 U/mg and immobilization yield of 99 %. High activity recovery of up to 404 % was obtained for immobilized derivatives. Leaking experiment showed covalent nature of the cross-linking processes. BSA had considerable effect on the immobilization process, providing 87-100 % immobilization yields and up to 10 times improvement in the specific activity of the immobilized derivatives. Scanning electron microscopy images showed flower-like and rod-like structures for the CLEs prepared by glutaraldehyde and undecanedicarboxylic acid, respectively. The prepared co-CLEs were examined in non-selective enrichment of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil, showing capability of releasing up to 100 % of both omega-3 fatty acids within 8 h of the reaction. The reusability of co-CLEs in five successive cycles presented retaining 63-72 % of their initial activities after the fifth reuse cycle in the hydrolysis reaction.

Fabrication of lignin-based sub-micro hybrid particle as a novel support for adenylate cyclase immobilization

This study developed a surface functionalized lignin-based sub-microsphere as an innovative support for enzyme immobilization. Lignin was first modified with a silane reagent leading to lignin/SiO2 (LS) organic/inorganic hybrid particles, displayed as regular sub-micro spheres with a SiO2 shell as demonstrated in SEM images. The LS particles were further modified to introduce nickel ions, as evidenced in XPS spectra, facilitating affinity adsorption with a his-tagged enzyme. The immobilization of adenylate cyclase from Haloactinopolyspora alba (HaAC), expressed in Escherichia coli, was conducted on the surface functionalized LS (LS-G-NTA-Ni). The immobilization conditions were optimized to achieve the highest relative activity, which were determined to be using a Ni2+ concentration of 62.5 mM, at pH=9.5 and 25 °C, with an enzyme-to-support ratio of 4.0 for a duration of 2 h. The immobilized HaAC shows maximum relative activity at pH=9.5 and 40 °C, and exhibits significantly improved thermal stability compared to the free enzyme. After undergoing five reusing cycles, the immobilized HaAC maintains a satisfactory activity (54.15%), which is due to the surface chemistry and the structural stability of the functionalized LS. This work provides a valuable exploration for high-value application of industrial lignin.

Chitosan-Based metal-organic framework for Stabilization of β-glucosidase: Reusability and storage stability

Enzyme immobilization is a powerful tool for protecting enzymes from harsh reaction conditions and improving enzyme activity, stability, and reusability. In this study, metal organic frameworks (MIL-Fe composites) were synthesized via solvothermal reactions and then modified with chitosan (CS). β-Glucosidase was immobilized on the chitosan-metal organic framework (CS-MIL-Fe), and the resulting composites were characterized with various analytical techniques. The β-glucosidase immobilized on a CS-MIL-Fe composite had an immobilization yield of 85 % and a recovered activity of 74 %. The immobilized enzyme retained 81 % of its initial activity after ten successive cycles and preserved 69 % of its original activity after 30 days of storage at 4 °C. In contrast, the free enzyme had only preserved 32 % of its original activity after 30 days. Under various temperature and pH conditions, the immobilized enzyme showed greater stability than the free enzyme, and the optimal temperature and pH were 60 °C and 6.0 for the immobilized enzyme and 50 °C and 5.0 for the free enzyme. The kinetic parameters were also determined, with the Km values of 13.4 and 6.98 mM for the immobilized and free β-glucosidase, respectively, and Vmax values of 3.96 and 1.72 U/mL, respectively. Overall, these results demonstrate that the CS-MIL-Fe@β-glucosidase is a promising matrix showing high catalytic efficiency and enhanced stability.

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.

Construction of co-immobilized multienzyme systems using DNA-directed immobilization technology and multifunctionalized nanoparticles

The multienzyme co-immobilization systems with high cascade catalytic efficiency and selectivity have attracted considerable attention. In this study, through DNA-directed immobilization (DDI) technology, two model enzymes, glucose oxidase (GOD) and horseradish peroxide (HRP) were co-immobilized on the multifunctional silica nanoparticles (DDI enzyme). In addition to the directional distribution promoted by DNA complementary chains, the multienzyme system allowed the control of the stoichiometric ratio of the enzymes by adjusting the ratio of amino/carboxyl groups. The optimal mole ratio of GOD/HRP was 1:2, while the protein loading amount could reach 8.06 mg·g-1. Compared with the conventional direct adsorption, the catalytic activity of the DDI enzyme was 2.49 times higher. Moreover, with the enhancement of thermal and mechanical stability, the DDI enzyme could still retain at least 50% of its initial activity after 12 cycles. Accompanied by an excellent response and good selectivity, the constructed multienzyme systems simultaneously showed the potential as a glucose detector. Therefore, based on the DDI technology, the highly efficient multienzyme co-immobilization system could be further extended for a wider range of research fields.

Review of covalent organic frameworks for enzyme immobilization: Strategies, applications, and prospects

Efficient enzyme immobilization systems offer a promising approach for improving enzyme stability and recyclability, reducing enzyme contamination in products, and expanding the applications of enzymes in the biomedical field. Covalent organic frameworks (COFs) possess high surface areas, ordered channels, optional building blocks, highly tunable porosity, stable mechanical properties, and abundant functional groups, making them ideal candidates for enzyme immobilization. Various COF-enzyme composites have been successfully synthesized, with performances that surpass those of free enzymes in numerous ways. This review aims to provide an overview of current enzyme immobilization strategies using COFs, highlighting the characteristics of each method and recent research applications. The future opportunities and challenges of enzyme immobilization technology using COFs are also discussed.

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

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

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

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

Co-Immobilization of D-Amino Acid Oxidase, Catalase, and Transketolase for One-Pot, Two-Step Synthesis of L-Erythrulose

Here, we present an immobilized enzyme cascade in a basket-type reactor allowing a one-pot, two-step enzymatic synthesis of L-erythrulose from D-serine and glycolaldehyde. Three enzymes, D-amino acid oxidase from Rhodotorula gracilis (DAAORg), catalase from bovine liver (CAT), and transketolase from Geobacillus stearothermophilus (TKgst) were covalently immobilized on silica monolithic pellets, characterized by an open structure of interconnected macropores and a specific surface area of up to 300 m2/g. Three strategies were considered: (i) separate immobilization of enzymes on silica supports ([DAAO][CAT][TK]), (ii) co-immobilization of two of the three enzymes followed by the third ([DAAO+CAT][TK]), and (iii) co-immobilization of all three enzymes ([DAAO+CAT+TK]). The highest L-erythrulose concentrations were observed for the co-immobilization protocols (ii) and (iii) (30.7 mM and 29.1 mM, respectively). The reusability study showed that the best combination was [DAAO + CAT][TK], which led to the same level of L-erythrulose formation after two reuse cycles. The described process paves the way for the effective synthesis of a wide range of α-hydroxyketones from D-serine and suitable aldehydes.

Industrial applications of fungal lipases: a review

Fungal lipases (triacylglycerol acyl hydrolases EC 3.1.1.3) are significant industrial enzymes and have several applications in a number of industries and fields. Fungal lipases are found in several species of fungi and yeast. These enzymes are carboxylic acid esterases, categorized under the serine hydrolase family, and do not require any cofactor during the catalyzing of the reactions. It was also noticed that processes including the extraction and purification of lipases from fungi are comparatively easier and cheaper than other sources of lipases. In addition, fungal lipases have been classified into three chief classes, namely, GX, GGGX, and Y. Fungal lipases have applications not only in the hydrolysis of fats and oils (triglycerides) but are also involved in synthetic reactions such as esterification, acidolysis, alcoholysis, interesterification, and aminolysis. The production and activity of fungal lipases are highly affected by the carbon source, nitrogen source, temperature, pH, metal ions, surfactants, and moisture content. Therefore, fungal lipases have several industrial and biotechnological applications in many fields such as biodiesel production, ester synthesis, production of biodegradable biopolymers, formulations of cosmetics and personal care products, detergent manufacturing, degreasing of leather, pulp and paper production, textile industry, biosensor development, and drug formulations and as a diagnostic tool in the medical sector, biodegradation of esters, and bioremediation of wastewater. The immobilization of fungal lipases onto different carriers also helps in improving the catalytic activities and efficiencies of lipases by increasing thermal and ionic stability (in organic solvents, high pH, and temperature), being easy to recycle, and inducing the volume-specific loading of the enzyme onto the support, and thus, these features have proved to be appropriate for use as biocatalysts in different sectors.

Co-Immobilization of Lactase and Glucose Isomerase on the Novel g-C3N4/CF Composite Carrier for Lactulose Production

The g-C₃N₄/CF composite carrier was prepared by ultrasound-assisted maceration and high-temperature calcination. The enzyme immobilization using the g-C₃N₄/CF as the novel carrier to immobilize lactase and glucose isomerase was enhanced for lactulose production. The carbon fiber (CF) was mixed with melamine powder in the mass ratio of 1:8. The g-C₃N₄/CF composite carrier was obtained by calcination at 550 °C for 3 h. After the analysis of characteristics, the g-C₃N₄/CF was successfully composited with the carbon nitride and CF, displaying the improvement of co-immobilization efficiency with the positive effects on the stability of the enzyme. The immobilization efficiency of the co-immobilized enzyme was 37% by the novel carrier of g-C₃N₄/CF, with the enzyme activity of 13.89 U g^-1 at 60 °C. The relative activities of co-immobilized enzymes maintained much more steadily at the wider pH and higher temperature than those of the free dual enzymes, respectively. In the multi-batches of lactulose production, the relative conversion rates in enzymes co-immobilized by the composite carrier were higher than that of the free enzymes during the first four batches, as well as maintaining about a 90% relative conversation rate after the sixth batch. This study provides a novel method for the application of g-C₃N₄/CF in the field of immobilizing enzymes for the production of lactulose.

Recent advances in the utilization of immobilized laccase for the degradation of phenolic compounds in aqueous solutions: A review

Phenolic compounds such as phenol, bisphenol A, 2,4-dichlorophenol, 2,4-dinitrophenol, 4-chlorophenol and 4-nitrophenol are well known to be highly detrimental to both human and living beings. Thus, it is of critical importance that suitable remediation technologies are developed to effectively remove phenolic compounds from aqueous solutions. Biodegradation utilizing enzymatic technologies is a promising biotechnological solution to sustainably address the pollution in the aquatic environment as caused by phenolic compounds under a defined environmentally optimized strategy and thus should be investigated in great detail. This review aims to present the latest developments in the employment of immobilized laccase for the degradation of phenolic compounds in water. The review first succinctly delineates the fundamentals of biological enzyme degradation along with a critical discussion on the myriad types of laccase immobilization techniques, which include physical adsorption, ionic adsorption, covalent binding, entrapment, and self-immobilization. Then, this review presents the major properties of immobilized laccase, namely pH stability, thermal stability, reusability, and storage stability, as well as the degradation efficiencies and associated kinetic parameters. In addition, the optimization of the immobilized enzyme, specifically on laccase immobilization methods and multi-enzyme system are critically discussed. Finally, pertinent future perspectives are elucidated in order to significantly advance the developments of this research field to a higher level.

Coimmobilized enzymes as versatile biocatalytic tools for biomass valorization and remediation of environmental contaminants - A review

Due to stringent regulatory norms, waste processing faces confrontations and challenges in adapting technology for effective management through a convenient and economical system. At the global level, attempts are underway to achieve a green and sustainable treatment for the valorization of lignocellulosic biomass as well as organic contaminants in wastewater. Enzymatic treatment in the environmental aspect thrived on being the promising rapid strategy that appeased the aforementioned predicament. On that account, coimmobilization of various enzymes on single support enhances the catalytic activity ensuing operational stability with industrial applications. This review pivoted towards the coimmobilization of enzymes on diverse supports and their applications in biomass conversion to industrial value-added products and removal of contaminants in wastewater. The limelight of this study chronicles the unique breakthroughs in biotechnology for the production of reusable biocatalysts, which inculcating various enzymes towards the scope of environment application.

DNA-directed coimmobilization of multiple enzymes on organic-inorganic hybrid DNA flowers

The artificial multienzyme systems developed by mimicking nature has attracted much interest. However, precisely controlled compositions and ratios of multienzymatic co-immobilization systems are still limited by the indistinguishable nature of enzymes. Herein, a strategy for fabricating DNA-directed immobilization of horseradish peroxidase (HRP) and glucose oxidase (GOx) on hybrid DNA nanoflowers (GOx-HRP@hDFs) is presented. The preparation of micron-sized hybrid DNA flowers (hDFs) begins with the predetermined repeatable polymer-like DNA sequences which contained two strands. The hDFs structure is generated through one-pot rolling circle amplification (RCA) and self-assembly with magnesium pyrophosphate inorganic crystals. Based on the rigid-base pairing, GOx and HRP conjugated with sequences complementary to strands would be anchored to the predesigned locations, respectively. By adjusting the loading amount/ratio of enzymes properly, the maximal catalytic efficiency can be precisely regulated. The reaction activity of GOx-HRP@hDFs was 7.4 times higher than that of the free GOx-HRP under the optimal mole ratio (GOx/HRP 4:1). In addition, this multienzyme catalyst system exhibits excellent precision, specificity, reproducibility, and long-term storage stability when applied to real human blood samples. The preceding results validate that GOx-HRP@hDFs are promising candidates for personal diabetes detection.

Lignocellulosic residues as supports for enzyme immobilization, and biocatalysts with potential applications

Growing demand for agricultural production means a higher quantity of residues produced. The reuse and recycling of agro-industrial wastes reduce worldwide greenhouse emissions. New opportunities are derived from this kind of residuals in the biotechnological field generating valuable products in growing sectors such as transportation, bioenergy, food, and feedstock. The use of natural macromolecules towards biocatalysts offers numerous advantages over free enzymes and friendliness with the environment. Enzyme immobilization improves enzyme properties (stability and reusability), and three types of supports are discussed: inorganic, organic, and hybrid. Several examples of agro-industrial wastes such as coconut wastes, rice husks, corn residues and brewers spent grains (BSG), their properties and potential as supports for enzyme immobilization are described in this work. Before the immobilization, biological and non-biological pretreatments could be performed to enhance the waste potential as a carrier. Additionally, immobilization methods such as covalent binding, adsorption, cross-linking and entrapment are compared to provide high efficiency. Enzymes and biocatalysts for industrial applications offer advantages over traditional chemical processes with respect to sustainability and process efficiency in food, energy, and bioremediation fields. The wastes reviewed in this work demonstrated a high affinity for lipases and laccases and might be used in biodiesel production and textile wastewater treatment, among other applications.

Encapsulation of peroxidase on hydrogel sodium polyacrylate spheres incorporated by silver and gold nanoparticles: A comparative study

The selectivity of biocatalysts based on enzymes, eco-friendly reaction systems, and strong catalyst performance is exceptionally compelling. For improving enzyme recyclability and stability, a good option that has been proved is immobilization. For enzyme immobilization, hydrogel sodium polyacrylate combined with nanoparticles is an interesting class of support matrices as compared to others. This study synthesizes and uses the cross-linked hydrogel sodium polyacrylate-decorated gold or silver nanoparticles (HSP/AuNPs or AgNPs) as immobilized support for peroxidase and FTIR characterizes it. The novel supports immobilized system properties enhanced biocompatibility. They have attained a greater immobilization yield (91% with HSP/AuNPs and 84% with HSP/AgNPs). The rest of the immobilized peroxidase activity, after 10 recurring cycles of HSP/AuNPs was 61% and HSP/AgNPs was 54% . The remaining activity of the immobilized enzyme onto HSP/AgNPs, after storing at 4°C for 6 weeks, was 73% and HSP/AuNPs was 75% of its initial activity. It was revealed that the optimum temperature for the free enzyme and the immobilized enzyme was 50°C and 50–60°C, respectively. For the immobilized enzyme, the optimum pH is 7–7.5, as compared to the optimum pH of free enzyme pH 6.5.

Enzymatic membrane reactor in xylose bioconversion with simultaneous cofactor regeneration

In this study, we present the concept of co-immobilization of xylose dehydrogenase and alcohol dehydrogenase from Saccharomyces cerevisiae on an XN45 nanofiltration membrane for application in the process of xylose bioconversion to xylonic acid with simultaneous cofactor regeneration and membrane separation of reaction products. During the research, the effectiveness of the co-immobilization of enzymes was confirmed, and changes in the properties of the membrane after the processes were determined. Using the obtained biocatalytic system it was possible to obtain 99% xylonic acid production efficiency under optimal conditions, which were 5 mM xylose, 5 mM formaldehyde, ratio of NAD+:NADH 1:1, and 60 min of reaction. Additionally, the co-immobilization of enzymes made it possible to improve stability of the co-immobilized enzymes and to carry out xylose conversion in six consecutive cycles and after 7 days of storage at 4 °C with over 90% efficiency. The presented data confirm the effectiveness of the co-immobilization, improvement of the stability and reusability of the biocatalysts, and show that the obtained enzymatic system is promising for use in xylose bioconversion and simultaneous regeneration of nicotinamide cofactor.

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

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

Coimmobilization of lipases exhibiting three very different stability ranges. Reuse of the active enzymes and selective discarding of the inactivated ones

Lipase B from Candida antarctica (CALB) and lipases from Candida rugosa (CRL) and Rhizomucor miehei (RML) have been coimmobilized on octyl and octyl-Asp agarose beads. CALB was much more stable than CRL, that was significantly more stable than RML. This forces the user to discard immobilized CALB and CRL when only RML has been inactivated, or immobilized CALB when CRL have been inactivated. To solve this problem, a new strategy has been proposed using three different immobilization protocols. CALB was covalently immobilized on octyl-vinyl sulfone agarose and blocked with Asp. Then, CRL was immobilized via interfacial activation. After coating both immobilized enzymes with polyethylenimine, RML could be immobilized via ion exchange. That way, by incubating in ammonium sulfate solutions, inactivated RML could be released enabling the reuse of coimmobilized CRL and CALB to build a new combi-lipase. Incubating in triton and ammonium sulfate solutions, it was possible to release inactivated CRL and RML, enabling the reuse of immobilized CALB when CRL was inactivated. These cycles could be repeated for 3 full cycles, maintaining the activity of the active and immobilized enzymes.

Metal Nanoparticles@Covalent Organic Framework@Enzymes: A Universal Platform for Fabricating a Metal-Enzyme Integrated Nanocatalyst

Cascade catalysis that combines chemical catalysis and biocatalysis has received extensive attention in recent years, especially the integration of metal nanoparticles (MNPs) with enzymes. However, the compatibility between MNPs and enzymes, and the stability of the integrated nanocatalyst should be improved to promote the application. Therefore, in this study, we proposed a strategy to space-separately co-immobilize MNPs and enzymes to the pores and surface of a highly stable covalent organic framework (COF), respectively. Typically, Pd NPs that were prepared by in situ reduction with triazinyl as the nucleation site were distributed in COF (Tz-Da), and organophosphorus hydrolase (OPH) was immobilized on the surface of Tz-Da by a covalent method to improve its stability. The obtained integrated nanocatalyst Pd@Tz-Da@OPH showed high catalytic efficiency and reusability in the cascade degradation of organophosphate nerve agents. Furthermore, the versatility of the preparation strategy of COF-based integrated nanocatalyst has been preliminarily expanded: (1) Pd NPs and OPH were immobilized in the triazinyl COF (TTB-DHBD) with different pore sizes for cascade degradation of organophosphate nerve agent and the particle size of MNPs can be regulated. (2) Pt NPs and glucose oxidase were immobilized in COF (Tz-Da) to obtain an integrated nanocatalyst for efficient colorimetric detection of phenol.

Multienzyme nanoassemblies: from rational design to biomedical applications

Multienzyme nanoassemblies (MENAs) that combine the functions of several enzymes into one entity have attracted widespread research interest due to their improved enzymatic performance and great potential for multiple applications. Considerable progress has been made to design and fabricate MENAs in recent years. This review begins with an introduction of the up-to-date strategies in designing MENAs, mainly including substrate channeling, compartmentalization and control of enzyme stoichiometry. The desirable properties that endow MENAs with important applications are also discussed in detail. Then, the recent advances in utilizing MENAs in the biomedical field are reviewed, with a particular focus on biosensing, tumor therapy, antioxidant and drug delivery. Finally, the challenges and perspectives for development of versatile MENAs are summarized.

Expanding the Biocatalytic Scope of Enzyme-Loaded Polymeric Hydrogels

In recent years, polymeric hydrogels have appeared promising matrices for enzyme immobilization to design, signify and expand bio-catalysis engineering. Therefore, the development and deployment of polymeric supports in the form of hydrogels and other robust geometries are continuously growing to green the twenty-first-century bio-catalysis. Furthermore, adequately fabricated polymeric hydrogel materials offer numerous advantages that shield pristine enzymes from denaturation under harsh reaction environments. For instance, cross-linking modulation of hydrogels, distinct rheological behavior, tunable surface entities along with elasticity and mesh size, larger surface-volume area, and hydrogels' mechanical cushioning attributes are of supreme interest makes them the ideal candidate for enzyme immobilization. Furthermore, suitable coordination of polymeric hydrogels with requisite enzyme fraction enables pronounced loading, elevated biocatalytic activity, and exceptional stability. Additionally, the unique catalytic harmony of enzyme-loaded polymeric hydrogels offers numerous applications, such as hydrogels as immobilization matrix, bio-catalysis, sensing, detection and monitoring, tissue engineering, wound healing, and drug delivery applications. In this review, we spotlight the applied perspective of enzyme-loaded polymeric hydrogels with recent and relevant examples. The work also signifies the combined use of multienzyme systems and the future directions that should be attempted in this field.

Smart chemistry of enzyme immobilization using various support matrices - A review

The surface chemistry, pendent functional entities, and ease in tunability of various materials play a central role in properly coordinating with enzymes for immobilization purposes. Due to the interplay between the new wave of support matrices and enzymes, the development of robust biocatalytic constructs via protein engineering expands the practical scope and tunable catalysis functions. The concept of stabilization via functional entities manipulation, the surface that comprises functional groups, such as thiol, aldehyde, carboxylic, amine, and epoxy have been the important driving force for immobilizing purposes. Enzyme immobilization using multi-functional supports has become a powerful norm and presents noteworthy characteristics, such as selectivity, specificity, stability, resistivity, induce activity, reaction efficacy, multi-usability, high catalytic turnover, optimal yield, ease in recovery, and cost-effectiveness. There is a plethora of literature on traditional immobilization approaches, e.g., intramolecular chemical (covalent) attachment, adsorption, encapsulation, entrapment, and cross-linking. However, the existing literature is lacking state-of-the-art smart chemistry of immobilization. This review is a focused attempt to cover the literature gap of surface functional entities that interplay between support materials at large and enzyme of interest, in particular, to tailor robust biocatalysts to fulfill the growing and contemporary needs of several industrial sectors.

Enzyme (Single and Multiple) and Nanozyme Biosensors: Recent Developments and Their Novel Applications in the Water-Food-Health Nexus

The use of sensors in critical areas for human development such as water, food, and health has increased in recent decades. When the sensor uses biological recognition, it is known as a biosensor. Nowadays, the development of biosensors has been increased due to the need for reliable, fast, and sensitive techniques for the detection of multiple analytes. In recent years, with the advancement in nanotechnology within biocatalysis, enzyme-based biosensors have been emerging as reliable, sensitive, and selectively tools. A wide variety of enzyme biosensors has been developed by detecting multiple analytes. In this way, together with technological advances in areas such as biotechnology and materials sciences, different modalities of biosensors have been developed, such as bi-enzymatic biosensors and nanozyme biosensors. Furthermore, the use of more than one enzyme within the same detection system leads to bi-enzymatic biosensors or multi-enzyme sensors. The development and synthesis of new materials with enzyme-like properties have been growing, giving rise to nanozymes, considered a promising tool in the biosensor field due to their multiple advantages. In this review, general views and a comparison describing the advantages and disadvantages of each enzyme-based biosensor modality, their possible trends and the principal reported applications will be presented.

Immobilization of Enzymes by Polymeric Materials

Enzymes are the highly efficient biocatalyst in modern biotechnological industries. Due to the fragile property exposed to the external stimulus, the application of enzymes is highly limited. The immobilized enzyme by polymer has become a research hotspot to empower enzymes with more extraordinary properties and broader usage. Compared with free enzyme, polymer immobilized enzymes improve thermal and operational stability in harsh environments, such as extreme pH, temperature and concentration. Furthermore, good reusability is also highly expected. The first part of this study reviews the three primary immobilization methods: physical adsorption, covalent binding and entrapment, with their advantages and drawbacks. The second part of this paper includes some polymer applications and their derivatives in the immobilization of enzymes.

Expanding the bio-catalysis scope and applied perspectives of nanocarrier immobilized asparaginases

l-asparaginase is an essential enzyme in medicine and a well-known chemotherapeutic agent. This enzyme's importance is not limited to its use as an anti-cancer agent; it also has a wide variety of medicinal applications. Antimicrobial properties, prevention of infectious disorders, autoimmune diseases, and canine and feline cancer are among the applications. Apart from the healthcare industry, its importance has been identified in the food industry as a food manufacturing agent to lower acrylamide levels. When isolated from their natural habitats, they are especially susceptible to different denaturing conditions due to their protein composition. The use of an immobilization technique is one of the most common approaches suggested to address these limitations. Immobilization is a technique that involves fixing enzymes to or inside stable supports, resulting in a heterogeneous immobilized enzyme framework. Strong support structures usually stabilize the enzymes' configuration, and their functions are maintained as a result. In recent years, there has been a lot of curiosity and focus on the ability of immobilized enzymes. The nanomaterials with ideal properties can be used to immobilize enzymes to regulate key factors that determine the efficacy of bio-catalysis. With applications in biotechnology, immunosensing, biomedicine, and nanotechnology sectors have opened a realm of opportunities for enzyme immobilization.