Naturally-derived biopolymers: Potential platforms for enzyme immobilization

Recombinant Esterase (BaCEm) Immobilized on Polyethyleneimine-Impregnated Mesoporous Silica SBA-15 Exhibits Outstanding Catalytic Performance

A recombinant esterase, BaCEm, derived from Bacillus aryabhattai and heterologously expressed in Escherichia coli, was successfully immobilized on polyethyleneimine-impregnated mesoporous silica SBA-15. This immobilization utilized glutaraldehyde as a crosslinker. Optimal conditions were established with a PEI/SBA-15 ratio of 25% (w/w), a pH of 7.5, and a glutaraldehyde concentration of 0.5% (w/w), resulting in a loading capacity of 76.4 mg/g, a recovery activity of 43.5%, and a specific activity of 7917 U/g for BaCEm. The immobilized BaCEm demonstrated high enantioselectivity, with an "E" value of 203.92, in the resolution assay of (R,S)-ethyl indoline-2-carboxylate. Notably, the immobilized enzyme, compared to its free counterpart, exhibited enhanced thermostability, maintaining 95.4% of its activity after 3 h at 30 °C. It also showed significant tolerance to organic solvents, retaining 48.4% and 28.7% residual activity in 10% v/v acetonitrile and acetone, respectively. Moreover, its storage stability was confirmed, with 68.5% residual activity preserved after 30 days at 4 °C. Remarkably, the immobilized BaCEm retained 58.1% of its activity after 10 reuse cycles, underscoring the potential of polyethyleneimine-impregnated mesoporous silica SBA-15 as an effective support for enzyme immobilization, promising for industrial applications.

Enzyme immobilization with nanomaterials for hydrolysis of lignocellulosic biomass: Challenges and future Perspectives

Enzyme immobilization has emerged as a prodigious strategy in the enzymatic hydrolysis of lignocellulosic biomass (LCB) promising enhanced efficacy and stability of the enzymes. Further, enzyme immobilization on magnetic nanoparticles (MNPs) facilitates the easy recovery and reuse of biocatalysts. This results in the development of a nanobiocatalytic system, that serves as an eco-friendly and inexpensive LCB deconstruction approach. This review provides an overview of nanomaterials used for immobilization with special emphasis on the nanomaterial-enzyme interactions and strategies of immobilization. After the succinct outline of the immobilization procedures and supporting materials, a comprehensive assessment of the catalysis enabled by nanomaterial-immobilized biocatalysts for the conversion and degradation of lignocellulosic biomasses is provided by gathering state-of-the-art examples. The challenges and future directions associated with this technique providing a potential solution in the present article. Insight on the recent advancements in the process of nanomaterial-based immobilization for the hydrolysis of lignocellulosic biomass has also been highlighted in the article.

Oxidation of Cyclohexane to Cyclohexanol/Cyclohexanone Using Sol-Gel-Encapsulated Unspecific Peroxygenase from Agrocybe aegerita

Unspecific peroxygenase from Agrocybe aegerite (AaeUPO) is a remarkable catalyst for the oxyfunctionalization of non-activated C-H bonds under mild conditions. It exhibits comparable activity to P450 monooxygenase but offers the advantage of using H2O2 instead of a complex electron transport chain to reductively activate O2. Here, we demonstrate the successful oxidation of cyclohexane to cyclohexanol/cyclohexanone (KA-oil) using sol-gel encapsulated AaeUPO. Remarkably, cyclohexane serves both as a solvent and a substrate in this system, which simplifies product isolation. The ratio of cyclohexanone to cyclohexanol using this approach is remarkably higher compared to the oxidation using free AaeUPO in aqueous media using acetonitrile as a cosolvent. The utilization of sol-gel encapsulated AaeUPO offers a promising approach for oxyfunctionalization reactions and improves the chances for this enzyme to be incorporated in the same pot with other chemical transformations.

Polydopamine-functionalized polyethersulfone membrane: A paradigm advancement in the field of α-amylase stability and immobilization

Biocatalytic membranes have great potential in various industrial sectors, with the immobilization of enzymes being a crucial stage. Immobilizing enzymes through covalent bonds is a complex and time-consuming process for large-scale applications. Polydopamine (PDA) offers a more sustainable and eco-friendly alternative for enzyme immobilization. Therefore, surface modification with polydopamine as mussel-inspired antifouling coatings has increased resistance to fouling. In this study, α-amylase enzyme was covalently bound to a bioactive PDA-coated polyethersulfone (PES) membrane surface using cyanuric chloride as a linker. The optimal activity of α-amylase enzyme immobilized on PES/PDA membrane was obtained at temperature and pH of 55°C and 6.5, respectively. The immobilized enzyme can be reused up to five reaction cycles with 55% retention of initial activity. Besides, it maintained 60% of its activity after being stored for five weeks at 4°C. Additionally, the immobilized enzyme demonstrated increased Michaelis constant and maximum velocity values during starch hydrolysis. The results of the biofouling experiment of various membranes in a dead-end cell demonstrated that the PES membrane's water flux increased from 6722.7 Lmh to 7560.2 Lmh after PDA modification. Although α-amylase immobilization reduced the flux to 7458.5 Lmh due to enhanced hydrophilicity, compared to unmodified membrane. The findings of this study demonstrated that the membrane produced through co-deposition exhibited superior hydrophilicity, enhanced coating stability, and strong antifouling properties, positioning it as a promising candidate for industrial applications.

Application of hydrophobic eutectic solvent in efficient biotransformation of total flavonoids of Herba Epimedii

Icaritin, a hydrolysate from total flavonoids of Epimedii (TFE), which has better anti-hepatoma activity than its glycosylated form. In this work, immobilized enzymes 4LP-Tpebgl3@Na-Y and DtRha@ES-107 were used to hydrolyze TFE to prepare icaritin. Five different hydrophobic deep eutectic solvents (HDES) were prepared and the most ideal HDES was successfully selected, which was composed of dodecyl alcohol and thymol with the molar ratio of 2:1. The relative enzyme activity of 4LP-Tpebgl3@Na-Y and DtRha@ES-107 was about 102.4 % and 112.5 %, respectively. In addition, the thermal and binding stability of 4LP-Tpebgl3@Na-Y and DtRha@ES-107 in HDES was not affected negatively. In the biphasic system composed of 50 % (v/v) HDES and Na2HPO4-citric acid buffer (50 mM, pH 5.5), 4LP-Tpebgl3@Na-Y (1.0 U/mL) and TFE (1 g/L) were reacted at 80 °C for 1 h, and then reacted with DtRha@ES-107 (20 U/mL) at 80 °C for 2 h. Finally, TFE was completely converted to 301.8 mg/L icaritin (0.82 mM). After 10 cycles, 4LP-Tpebgl3@Na-Y/DtRha@ES-107 still maintained 84.1 % original activity. In this study, we developed an efficient methodology for icaritin preparation through the integration of enzymatic catalysis and adsorption separation, presenting a viable approach for large-scale, cost-effective production of icaritin.

Advances in aldo-keto reductases immobilization for biocatalytic synthesis of chiral alcohols

Chiral alcohols are essential building blocks of numerous pharmaceuticals and fine chemicals. Aldo-keto reductases (AKRs) constitute a superfamily of oxidoreductases that catalyze the reduction of aldehydes and ketones to their corresponding alcohols using NAD(P)H as a coenzyme. Knowledge about the crucial roles of AKRs immobilization in the biocatalytic synthesis of chiral alcohols is expanding. Herein, we reviewed the characteristics of various AKRs immobilization approaches, the applications of different immobilization materials, and the prospects of continuous flow bioreactor construction by employing these immobilized biocatalysts for synthesizing chiral alcohols. Finally, the opportunities and ongoing challenges for AKR immobilization are discussed and the outlook for this emerging area is analyzed.

Immobilized Urease Vector System Based on the Dynamic Defect Regeneration Strategy for Efficient Urea Removal

The clearance of urea poses a formidable challenge, and its excessive accumulation can cause various renal diseases. Urease demonstrates remarkable efficacy in eliminating urea, but cannot be reused. This study aimed to develop a composite vector system comprising microcrystalline cellulose (MCC) immobilized with urease and metal-organic framework (MOF) UiO-66-NH2, denoted as MCC@UiO/U, through the dynamic defect generation strategy. By utilizing competitive coordination, effective immobilization of urease into MCC@UiO was achieved for efficient urea removal. Within 2 h, the urea removal efficiency could reach up to 1500 mg/g, surpassing an 80% clearance rate. Furthermore, an 80% clearance rate can also be attained in peritoneal dialyzate from patients. MCC@UiO/U also exhibits an exceptional bioactivity even after undergoing 5 cycles of perfusion, demonstrating remarkable stability and biocompatibility. This innovative approach and methodology provide a novel avenue and a wide range of immobilized enzyme vectors for clinical urea removal and treatment of kidney diseases, presenting immense potential for future clinical applications.

Application of Natural Functional Additives for Improving Bioactivity and Structure of Biopolymer-Based Films for Food Packaging: A Review

The global trend towards conscious consumption plays an important role in consumer preferences regarding both the composition and quality of food and packaging materials, including sustainable ones. The development of biodegradable active packaging materials could reduce both the negative impact on the environment due to a decrease in the use of oil-based plastics and the amount of synthetic preservatives. This review discusses relevant functional additives for improving the bioactivity of biopolymer-based films. Addition of plant, microbial, animal and organic nanoparticles into bio-based films is discussed. Changes in mechanical, transparency, water and oxygen barrier properties are reviewed. Since microbial and oxidative deterioration are the main causes of food spoilage, antimicrobial and antioxidant properties of natural additives are discussed, including perspective ones for the development of biodegradable active packaging.

Stabilization of β-D-galactosidase in solution containing chitosan-based membrane: Central composite rotatable design

β-D-galactosidase is a hydrolase enzyme capable of hydrolyzing lactose in milk-based foods. Its free form can be inactivated in solution during the production of low-dosage lactose foods. Then, it is important to study strategies for avoiding the free enzyme inactivation with the aim of circumventing this problem. The stabilization of β-D-galactosidase in aqueous solution after interactions with chitosan/eucalyptus sawdust composite membrane proved to be a potential strategy when optimized by central composite rotatable (CCR) design. In this case, the best experimental conditions for β-D-galactosidase partitioning and stability in an aqueous medium containing the chitosan-based composite membrane reinforced with eucalyptus sawdust were i) enzyme/buffer solution ratio of 0.0057, ii) pH 5.6, iii) membrane mass of 50 mg, and iv) temperature lower than 37 °C. Significance was found for the linear enzyme/buffer solution ratio, linear temperature, and quadratic pH (p < 0.05) in the interval between 0 and 60 min of study. In the interval between 60 and 120 min, there was significance (p < 0.12) for linear temperature, the temperature-enzyme/buffer solution ratio interaction and the interaction between linear pH and linear enzyme/buffer solution ratio. The Pareto charts and response surfaces clearly showed all the effects of the experimental variables on the stabilization of β-D-galactosidase in solution after interactions with the chitosan composite membrane. In this case, industrial food reactors covered with chitosan/eucalyptus sawdust composite membrane could be a strategy for the hydrolysis of lactose during milk-producing processes.

Advances in surface design and biomedical applications of magnetic nanoparticles

Despite significant efforts by scientists in the development of advanced nanotechnology materials for smart diagnosis devices and drug delivery systems, the success of clinical trials remains largely elusive. In order to address this biomedical challenge, magnetic nanoparticles (MNPs) have gained attention as a promising candidate due to their theranostic properties, which allow the simultaneous treatment and diagnosis of a disease. Moreover, MNPs have advantageous characteristics such as a larger surface area, high surface-to-volume ratio, enhanced mobility, mass transference and, more notably, easy manipulation under external magnetic fields. Besides, certain magnetic particle types based on the magnetite (Fe3O4) phase have already been FDA-approved, demonstrating biocompatible and low toxicity. Typically, surface modification and/or functional group conjugation are required to prevent oxidation and particle aggregation. A wide range of inorganic and organic molecules have been utilized to coat the surface of MNPs, including surfactants, antibodies, synthetic and natural polymers, silica, metals, and various other substances. Furthermore, various strategies have been developed for the synthesis and surface functionalization of MNPs to enhance their colloidal stability, biocompatibility, good response to an external magnetic field, etc. Both uncoated MNPs and those coated with inorganic and organic compounds exhibit versatility, making them suitable for a range of applications such as drug delivery systems (DDS), magnetic hyperthermia, fluorescent biological labels, biodetection and magnetic resonance imaging (MRI). Thus, this review provides an update of recently published MNPs works, providing a current discussion regarding their strategies of synthesis and surface modifications, biomedical applications, and perspectives.

Advancements in enzyme immobilization on magnetic nanomaterials: toward sustainable industrial applications

Enzymes are widely used in biofuels, food, and pharmaceuticals. The immobilization of enzymes on solid supports, particularly magnetic nanomaterials, enhances their stability and catalytic activity. Magnetic nanomaterials are chosen for their versatility, large surface area, and superparamagnetic properties, which allow for easy separation and reuse in industrial processes. Researchers focus on the synthesis of appropriate nanomaterials tailored for specific purposes. Immobilization protocols are predefined and adapted to both enzymes and support requirements for optimal efficiency. This review provides a detailed exploration of the application of magnetic nanomaterials in enzyme immobilization protocols. It covers methods, challenges, advantages, and future perspectives, starting with general aspects of magnetic nanomaterials, their synthesis, and applications as matrices for solid enzyme stabilization. The discussion then delves into existing enzymatic immobilization methods on magnetic nanomaterials, highlighting advantages, challenges, and potential applications. Further sections explore the industrial use of various enzymes immobilized on these materials, the development of enzyme-based bioreactors, and prospects for these biocatalysts. In summary, this review provides a concise comparison of the use of magnetic nanomaterials for enzyme stabilization, highlighting potential industrial applications and contributing to manufacturing optimization.

Enhancement of enzyme activity by laser-induced energy propulsion of upconverting nanoparticles under near-infrared light: A comprehensive methodology for in vitro and in vivo applications

If the appropriate immobilization method and carrier support are not selected, partial decreases in the activity of enzymes may occur after immobilization. Herein, to overcome this challenge, an excitation mechanism that enables energy transfer was proposed. Modified upconverting nanoparticles (UCNPs) were constructed and the important role of near-infrared (NIR) excitation in enhancing the catalytic activity of the enzyme was demonstrated. For this purpose, UCNPs were first synthesized via the hydrothermal method, functionalized with isocyanate groups, and then, PEG-L-ASNase was immobilized via covalent binding. UCNPs with and without PEG-L-ASNase were extensively characterized by different methods. These supports had immobilization yield and activity efficiency of >96 % and 78 %, respectively. Moreover, immobilized enzymes exhibited improved pH, thermal, and storage stability. In addition, they retained >65 % of their initial activity even after 20 catalytic cycles. Biochemical and histological findings did not indicate a trend of toxicity in rats due to UCNPs. Most importantly, PEG-L-ASNase activity was triggered approximately 5- and 2-fold under in vitro and in vivo conditions, respectively. Overall, it is anticipated that this pioneering work will shed new light on the realistic and promising usage of NIR-excited UCNPs for the immobilization of enzymes in expensive and extensive applications.

Xanthan: enzymatic degradation and novel perspectives of applications

The extracellular heteropolysaccharide xanthan, synthesized by bacteria of the genus Xanthomonas, is widely used as a thickening and stabilizing agent across the food, cosmetic, and pharmaceutical sectors. Expanding the scope of its application, current efforts target the use of xanthan to develop innovative functional materials and products, such as edible films, eco-friendly oil surfactants, and biocompatible composites for tissue engineering. Xanthan-derived oligosaccharides are useful as nutritional supplements and plant defense elicitors. Development and processing of such new functional materials and products often necessitate tuning of xanthan properties through targeted structural modification. This task can be effectively carried out with the help of xanthan-specific enzymes. However, the complex molecular structure and intricate conformational behavior of xanthan create problems with its enzymatic hydrolysis or modification. This review summarizes and analyzes data concerning xanthan-degrading enzymes originating from microorganisms and microbial consortia, with a particular focus on the dependence of enzymatic activity on the structure and conformation of xanthan. Through a comparative study of xanthan-degrading pathways found within various bacterial classes, different microbial enzyme systems for xanthan utilization have been identified. The characterization of these new enzymes opens new perspectives for modifying xanthan structure and developing innovative xanthan-based applications. KEY POINTS: • The structure and conformation of xanthan affect enzymatic degradation. • Microorganisms use diverse multienzyme systems for xanthan degradation. • Xanthan-specific enzymes can be used to develop xanthan variants for novel applications.

Immobilizing white-rot fungi laccase: Toward bio-derived supports as a circular economy approach in organochlorine removal

Despite their high persistence in the environment, organochlorines (OC) are widely used in the pharmaceutical industry, in plastics, and in the manufacture of pesticides, among other applications. These compounds and the byproducts of their decomposition deserve attention and efficient proposals for their treatment. Among sustainable alternatives, the use of ligninolytic enzymes (LEs) from fungi stands out, as these molecules can catalyze the transformation of a wide range of pollutants. Among LEs, laccases (Lac) are known for their efficiency as biocatalysts in the conversion of organic pollutants. Their application in biotechnological processes is possible, but the enzymes are often unstable and difficult to recover after use, driving up costs. Immobilization of enzymes on a matrix (support or solid carrier) allows recovery and stabilization of this catalytic capacity. Agricultural residual biomass is a passive environmental asset. Although underestimated and still treated as an undesirable component, residual biomass can be used as a low-cost adsorbent and as a support for the immobilization of enzymes. In this review, the adsorption capacity and immobilization of fungal Lac on supports made from residual biomass, including compounds such as biochar, for the removal of OC compounds are analyzed and compared with the use of synthetic supports. A qualitative and quantitative comparison of the reported results was made. In this context, the use of peanut shells is highlighted in view of the increasing peanut production worldwide. The linkage of methods with circular economy approaches that can be applied in practice is discussed.

Temperature-sensitive multifunctional intelligent responsive hydrogel based on carboxymethyl agarose and N-isopropylacrylamide: Controlled drug release and accelerated wound healing

Wound healing remains challenging due to posttraumatic pain. At present, most wound dressings ignore the importance of wound pain. In this study, a temperature-sensitive multifunctional intelligent hydrogel patch (CPAG) containing lidocaine has developed for wound healing. CPAG hydrogel was prepared by grafting N-isopropylacrylamide and acrylamide onto carboxymethyl agarose (CMA) modified by agarose and encapsulating gallic acid and lidocaine. FTIR, 1H NMR spectroscopy, SEM and rheology were used to investigate its structure and temperature-sensitive properties. The contraction force generated by the temperature response characteristics of CPAG at 30 °C can accelerate wound healing. In vitro release assays demonstrated that CPAG directly controlled the same amount of lidocaine release at different temperatures through the competition between polymer-polymer and polymer-water interactions. In addition, MTT, H&E staining and stimulation test further proved its biological safety. The pain behavior study showed that the pain inhibition rates of the lidocaine cataplasms and LID@CPAG were 51.16 % and 67.83 %, respectively. In vitro and in vivo studies have shown that compared with the blank group, the bleeding volume of LID@CPAG decreased by 54.3 %, and the wound healing rate reached 97 %. CPAG hydrogel can play a comprehensive therapeutic role in accelerating wound closure by controlling drug release, analgesia, antioxidation and hemostasis.

Recent update on alginate based promising transdermal drug delivery systems

Alongside oral delivery of therapeutics, transdermal delivery systems have gained increased patient acceptability over past few decades. With increasing popularity, novel techniques were employed for transdermal drug targeting which involves microneedle patches, transdermal films and hydrogel based formulations. Hydrogel forming ability along with other rheological behaviour makes natural polysaccharides an attractive option for transdermal use. Being a marine originated anionic polysaccharide, alginates are widely used in pharmaceutical, cosmetics and food industries. Alginate possesses excellent biodegradability, biocompatibility and mucoadhesive properties. Owing to many favourable properties required for transdermal drug delivery systems (TDDS), the application of alginates are increasing in recent times. This review summarizes the source and properties of alginate along with several transdermal delivery techniques including the application of alginate for respective transdermal systems.

Cellulase immobilization to enhance enzymatic hydrolysis of lignocellulosic biomass: An all-inclusive review

Cellulase-mediated lignocellulosic biorefinery plays a crucial role in the production of high-value biofuels and chemicals, with enzymatic hydrolysis being an essential component. The advent of cellulase immobilization has revolutionized this process, significantly enhancing the efficiency, stability, and reusability of cellulase enzymes. This review offers a thorough analysis of the fundamental principles underlying immobilization, encompassing various immobilization approaches such as physical adsorption, covalent binding, entrapment, and cross-linking. Furthermore, it explores a diverse range of carrier materials, including inorganic, organic, and hybrid/composite materials. The review also focuses on emerging approaches like multi-enzyme co-immobilization, oriented immobilization, immobilized enzyme microreactors, and enzyme engineering for immobilization. Additionally, it delves into novel carrier technologies like 3D printing carriers, stimuli-responsive carriers, artificial cellulosomes, and biomimetic carriers. Moreover, the review addresses recent obstacles in cellulase immobilization, including molecular-level immobilization mechanism, diffusion limitations, loss of cellulase activity, cellulase leaching, and considerations of cost-effectiveness and scalability. The knowledge derived from this review is anticipated to catalyze the evolution of more efficient and sustainable biocatalytic systems for lignocellulosic biomass conversion, representing the current state-of-the-art in cellulase immobilization techniques.

Microencapsulation of Bacillus thuringiensis strains for the control of Aedes aegypti

In this study, we investigated the microencapsulation of two strains of the entomopathogenic bacteria Bacillus thuringiensis (B. thuringiensis) (BtMA-750 and BtMA-1114), which are biopesticides of high toxicity for the mosquito vector Aedes aegypti. The encapsulation of different concentrations of microorganisms in starch microparticles was evaluated, and the inverse suspension polymerization technique was explored. It was possible to observe that the higher amounts of the biopesticide caused a slight decrease in the diameter of the particles; however, even when encapsulated, the biopesticide still presents an average diameter that is able to be consumed by the larvae of Aedes aegypti. Furthermore, it was noticed that the presence of both of the B. thuringiensis strains did not affect the thermal stability of the particles. The microencapsulated bacterial strains presented a high number of viable spores and preserved the expression of proteins with molecular masses corresponding to the insecticidal toxins Cry and Cyt, indicating that the encapsulation process was conducted satisfactorily. Finally, the encapsulated strains were tested against Ae. aegypti larvae and maintained 100% larval mortality even after 35 days. Therefore, microencapsulation of B. thuringiensis not only guarantees the bacterial activity, but also prolongs the action of the biopesticide. Collectively, such findings highlight the great potential of the new biopesticides, which may help to reduce the population indices of the mosquito vector Ae. aegypti via a sustainable and environment-friendly route.

Effect of Chemical Degradation of Sodium Alginate on Capsaicin Encapsulation

Capsaicin is known as an oily extract of paprika that is characterized by pungent taste and bioactivity. It also may cause irritation to the mouth and stomach which is why is so important to immobilize capsaicin on a carrier to prevent it. The usage of alginate oligomers, which has an antioxidant potential compared to alginate, is of benefit because it may be used in the immobilization of bioactive substances that are fragile to oxidation. The purpose of this study was to use sodium alginate oligomers as a coating material in the encapsulation process of paprika oleoresin. Alginate oligomers were produced by chemical degradation with hydrogen peroxide. The characteristics of the samples were obtained by measuring the viscosity, the contact angle of the surface, and the surface tension of solutions. The obtained solution of alginate oligomers served as the carrier material for the immobilization of capsaicin. Capsules were prepared by ionic gelation using a calcium chloride solution as a crosslinking agent. In this way, capsules without and with the core (capsaicin) were prepared and their ability to scavenge free radicals (DPPH) and iron-reducing properties (FRAP) were determined. The stability of the capsules was examined by thermal decomposition and under conditions of the gastric and small intestine, and capsaicin content was detected using high-performance liquid chromatography. It was found that alginate oligomers could be used in the encapsulation of bioactive compounds and the efficiency was above 80%. Capsule production from alginate oligomers affected their thermal stability. The use of alginate derivatives as a carrier increased the antioxidant properties of the finished product, as well as its ability to reduce iron ions. The use of alginate oligomers as a coating material prevented the active substance from being released too early in the conditions of the small intestine, prolonged the stability of the capsules, and supported their durability in gastric conditions.

Identification and statistical optimization of a novel alginate polymer extracted from newly isolated Synechocystis algini MNE ON864447 with antibacterial activity

Cyanobacteria are a potential source of promising secondary metabolites with different biological activities, including antibacterial, antiviral, antifungal, antiprotozoal, and anticancer activities. To combat the emergence of antibiotic resistance, there is an urgent requirement for new drugs, and cyanobacteria metabolites can constitute alternative new antibacterial medication. The chemical complexity of their exopolysaccharides indicates that they have the potential to be bioactive molecules with many biological activities. The present study aimed to produce and optimise a novel alginate polymer from a newly isolated cyanobacterium, S. algini MNE ON864447, in addition to its promising antibacterial activity. We successfully isolated a new cyanobacterium strain, S. algini MNE ON864447 from the Nile River, which produces alginate as an extracellular polymeric substance. The isolated cyanobacterial alginate was identified using a set of tests, including FTIR, TLC, HPLC, GC-MS, and 1H NMR. Plackett-Burman statistical design showed that working volume (X1), the incubation period (X2), and inoculum size (X3) are the most significant variables affecting the production of alginate. The highest alginate production (3.57 g/L) was obtained using 4% inoculum size in 400 mL medium/L conical flask after 20 days of the incubation period. The extracted alginate showed potent antibacterial activity against both Gram-negative and Gram-positive bacteria and Streptococcus mutants (NCTC10449) are the most sensitive tested pathogen for purified cyanobacterial alginate with inhibition zone diameters of 34 ± 0.1 mm at 10 mg/mL of purified alginate while Vibro cholera (NCTC 8021) the lowest sensitive one and showed inhibition zone diameters of 22.5 ± 0.05 mm at the same cyanobacterial alginate concentration. This antibacterial activity is a critical step in the development of antibacterial drugs and presents a new challenge to fight against multi-resistant bacteria.

A critical review of enzymes immobilized on chitosan composites: characterization and applications

Enzymes with industrial significance are typically used in biological processes. However, instability, high sensitivity, and impractical recovery are the major drawbacks of enzymes in practical applications. In recent years, the immobilization technology has attracted wide attention to overcoming these restrictions and improving the efficiency of enzyme applications. Chitosan (CS) is a unique functional substance with biocompatibility, biodegradability, non-toxicity, and antibacterial properties. Chitosan composites are anticipated to be widely used in the near future for a variety of purposes, including as supports for enzyme immobilization, because of their advantages. Therefor this review explores the effects of the chitosan's structure, molecular weight, degree of deacetylation on the enzyme immobilized, effect of key factors, and the enzymes immobilized on chitosan based composites for numerous applications, including the fields of biosensor, biomedical science, food industry, environmental protection, and industrial production. Moreover, this study carefully investigates the advantages and disadvantages of using these composites as well as their potential in the future.

Co-encapsulating Cofactor and Enzymes in Hydrogen-Bonded Organic Frameworks for Multienzyme Cascade Reactions with Cofactor Recycling

Use of hydrogen-bonded organic frameworks (HOFs) for enzyme immobilization faces challenges in the improvement of enzyme activity recovery and the assembly of cofactor-dependent multienzyme systems. Herein, we report a polyelectrolyte-assisted encapsulation approach (PAEA) that enables two cascades with four oxidoreductases and two nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) cofactors co-encapsulated in BioHOF-1 with excellent cargo loading and over 100 % cascade activity. The key role of the polyelectrolyte is to coat enzymes and tether NAD(P)H, thus interacting with HOF monomers in place of enzymes, avoiding the destruction of enzymes by HOF monomers. The versatility and efficiency of PAEA are further illustrated by an HOF-101-based bio-nanoreactor. Moreover, the immobilization by PAEA makes enzymes and NAD(P)H display excellent stability and recyclability. This study has demonstrated a facile and versatile PAEA for fabricating cofactor-dependent multienzyme cascade nanoreactors with HOFs.

Immobilization of commercial horseradish peroxidase in calcium alginate-starch hybrid support and its application in the biodegradation of phenol red dye

In this study, horseradish peroxidase (HRP) was immobilized for the first time on Ca alginate-starch hybrid beads and employed for the biodegradation of phenol red dye. The optimal protein loading was 50 mg/g of support. Immobilized HRP demonstrated improved thermal stability and maximum catalytic activity at 50 °C and pH 6.0, with an increase in half-life (t1/2) and enzymatic deactivation energy (Ed) compared to free HRP. After 30 days of storage at 4 °C, immobilized HRP retained 109% of its initial activity. Compared to free HRP, the immobilized enzyme exhibited higher potential for phenol red dye degradation, as evidenced by the removal of 55.87% of initial phenol red after 90 min, which was 11.5 times greater than free HRP. In sequential batch reactions, the immobilized HRP demonstrated good potential efficiency for the biodegradation of phenol red dye. The immobilized HRP was used for a total of 15 cycles, degrading 18.99% after 10 cycles and 11.69% after 15 cycles, with a residual enzymatic activity of 19.40% and 12.34%, respectively. Overall, the results suggest that HRP immobilized on Ca alginate-starch hybrid supports shows promise as a biocatalyst for industrial and biotechnological applications, particularly for the biodegradation of recalcitrant compounds such as phenol red dye.

Recent advances in cellulose, pectin, carrageenan and alginate-based oral drug delivery systems

Polymers-based drug delivery systems constitute one of the highly explored thrust areas in the field of the medicinal and pharmaceutical industries. In the past years, the properties of polymers have been modified in context to their solubility, release kinetics, targeted action site, absorption, and therapeutic efficacy. Despite the availability of diverse synthetic polymers for the bioavailability enhancement of drugs, the use of natural polymers is still highly recommended due to their easy availability, accessibility, and non-toxicity. The aim of the review is to provide the available literature of the last five years on oral drug delivery systems based on four natural polymers i.e., cellulose, pectin, carrageenan, and alginate in a concise and tabulated manner. In this review, most of the information is in tabulated form to provide easy accessibility to the reader. The data related to active pharmaceutical ingredients and supported components in different formulations of the mentioned polymers have been made available.

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.

Bacteria-Polymer Composite Material for Glycerol Valorization

Bacterial immobilization is regarded as an enabling technology to improve the stability and reusability of biocatalysts. Natural polymers are often used as immobilization matrices but present certain drawbacks, such as biocatalyst leakage and loss of physical integrity upon utilization in bioprocesses. Herein, we prepared a hybrid polymeric matrix that included silica nanoparticles for the unprecedented immobilization of the industrially relevant Gluconobacter frateurii (Gfr). This biocatalyst can valorize glycerol, an abundant by-product of the biodiesel industry, into glyceric acid (GA) and dihydroxyacetone (DHA). Different concentrations of siliceous nanosized materials, such as biomimetic Si nanoparticles (SiNps) and montmorillonite (MT), were added to alginate. These hybrid materials were significantly more resistant by texture analysis and presented a more compact structure as seen by scanning electron microscopy. The preparation including 4% alginate with 4% SiNps proved to be the most resistant material, with a homogeneous distribution of the biocatalyst in the beads as seen by confocal microscopy using a fluorescent mutant of Gfr. It produced the highest amounts of GA and DHA and could be reused for up to eight consecutive 24 h reactions with no loss of physical integrity and negligible bacterial leakage. Overall, our results indicate a new approach to generating biocatalysts using hybrid biopolymer supports.

In situ embedding of glucose oxidase in amorphous ZIF-7 with high catalytic activity and stability and mechanism investigation

Glucose oxidase (GOx) has a great application potential in the determination of glucose concentration. However, its sensitivity to the environment and poor recyclability limited its broader application. Herein, with the assistance of DA-PEG-DA, a novel immobilized GOx based on amorphous Zn-MOFs (DA-PEG-DA/GOx@aZIF-7/PDA) was developed to impart excellent properties to the enzyme. SEM, TEM, XRD, and BET analyses confirmed that GOx was embedded in amorphous ZIF-7 with ~5 wt% loading. Compared with free GOx, DA-PEG-DA/GOx@aZIF-7/PDA exhibited enhanced stability, excellent reusability, and promising potential for glucose detection. After 10 repetitions, the catalytic activity of DA-PEG-DA/GOx@aZIF-7/PDA can maintain 95.53 % ± 3.16 %. In understanding the in situ embedding of GOx in ZIF-7, the interaction of zinc ion and benzimidazole with GOx was studied by using molecular docking and multi-spectral methods. Results showed that zinc ions and benzimidazole had multiple binding sites on the enzyme, which induced the accelerated synthesis of ZIF-7 around the enzyme. During binding, the structure of the enzyme changes, but such changes hardly affect the activity of the enzyme. This study provides not only a preparation strategy of immobilized enzyme with high activity, high stability, and low enzyme leakage rate for glucose detection, but also a more comprehensive understanding of the formation of immobilized enzymes using the in situ embedding strategy.

Grafting of proteins onto polymeric surfaces: A synthesis and characterization challenge

This review aims at answering the following question: how can a researcher be sure to succeed in grafting a protein onto a polymer surface? Even if protein immobilization on solid supports has been used industrially for a long time, hence enabling natural enzymes to serve as a powerful tool, emergence of new supports such as polymeric surfaces for the development of so-called intelligent materials requires new approaches. In this review, we introduce the challenges in grafting protein on synthetic polymers, mainly because compared to hard surfaces, polymers may be sensitive to various aqueous media, depending on the pH or reductive molecules, or may exhibit state transitions with temperature. Then, the specificity of grafting on synthetic polymers due to difference of chemical functions availability or difference of physical properties are summarized. We present next the various available routes to covalently bond the protein onto the polymeric substrates considering the functional groups coming from the monomers used during polymerization reaction or post-modification of the surfaces. We also focus our review on a major concern of grafting protein, which is avoiding the potential loss of function of the immobilized protein. Meanwhile, this review considers the different methods of characterization used to determine the grafting efficiency but also the behavior of enzymes once grafted. We finally dedicate the last part of this review to industrial application and future prospective, considering the sustainable processes based on green chemistry.

Immobilization of Hyperthermostable Carboxylesterase EstD9 from Anoxybacillus geothermalis D9 onto Polymer Material and Its Physicochemical Properties

Carboxylesterase has much to offer in the context of environmentally friendly and sustainable alternatives. However, due to the unstable properties of the enzyme in its free state, its application is severely limited. The present study aimed to immobilize hyperthermostable carboxylesterase from Anoxybacillus geothermalis D9 with improved stability and reusability. In this study, Seplite LX120 was chosen as the matrix for immobilizing EstD9 by adsorption. Fourier-transform infrared (FT-IR) spectroscopy verified the binding of EstD9 to the support. According to SEM imaging, the support surface was densely covered with the enzyme, indicating successful enzyme immobilization. BET analysis of the adsorption isotherm revealed reduction of the total surface area and pore volume of the Seplite LX120 after immobilization. The immobilized EstD9 showed broad thermal stability (10-100 °C) and pH tolerance (pH 6-9), with optimal temperature and pH of 80 °C and pH 7, respectively. Additionally, the immobilized EstD9 demonstrated improved stability towards a variety of 25% (v/v) organic solvents, with acetonitrile exhibiting the highest relative activity (281.04%). The bound enzyme exhibited better storage stability than the free enzyme, with more than 70% of residual activity being maintained over 11 weeks. Through immobilization, EstD9 can be reused for up to seven cycles. This study demonstrates the improvement of the operational stability and properties of the immobilized enzyme for better practical applications.

Nanocellulose-gellan cross-linked scaffolds for vaginal delivery of fluconazole

The objective of this research is to formulate lyophilized fluconazole-loaded nanocellulose-gellan scaffolds cross-linked using trisodium trimetaphosphate as a vaginal drug delivery system. The effect of polymers (nanocellulose and gellan gum) and cross-linking agents on drug release and mucoadhesive strength were determined by approaching a two-factor three-level central composite experimental design. The optimal formulation of the fluconazole-loaded cross-linked rice or wheat nanocellulose-gellan based scaffolds comprised of the concentration of polymers (4.91 % w/v or 4.99 % w/v) and trisodium trimetaphosphate (16.43 % w/v or 15.83 % w/v), respectively. The infrared spectra confirmed the cross-linking of nanocellulose and gellan gum while the thermal graph revealed the higher thermal stability of cross-linked scaffolds. The diffractogram of the scaffolds unveiled their amorphous nature while the electron micrographs depict the porous nature of the fluconazole-loaded nanocellulose-gellan scaffolds. The phosphorylated cross-linked nanocellulose-gellan scaffolds represent more swelling (8-fold higher), porosity (>83 %), tensile strength (>34 MPa), and mucoadhesive strength (>1940 mN), and less enzymatic degradation rate over the non cross-linked scaffolds. The optimal batch of cross-linked nanocellulose-gellan scaffolds provided a sustained release of 99 % of fluconazole over 24 h with 1.19-fold higher ex-vivo vaginal permeation over the native scaffolds. In addition, the phosphorylated nanocellulose-gellan based scaffolds exhibit improved antifungal activity and non-cytotoxicity.

Process optimization for enzymatic production of a valuable biomass-based ester from levulinic acid

The enzymatic production of isoamyl levulinate via esterification of isoamyl alcohol (IA) and levulinic acid (LA), a biomass-based platform chemical with attractive properties, in a solvent system has been performed in this study. For such a purpose, a low-cost liquid lipase (Eversa^® Transform 2.0) immobilized by physical adsorption via hydrophobic interactions (mechanism of interfacial activation) on mesoporous poly(styrenene-divinylbenzene) (PSty-DVB) beads was used as heterogeneous biocatalyst. It was prepared at low ionic strength (5 mmol.L^-1 buffer sodium acetate pH 5.0) and 25 ℃ using an initial protein loading of 40 mg.g^-1 of support. Maximum protein loading of 31.2 ± 2.8 mg.g^-1 of support and an immobilization yield of 83% was achieved. The influence of relevant factors (biocatalyst concentration and reaction temperature) on ester production was investigated using a central composite rotatable design (CCRD). Maximum acid conversion percentage of 65% was achieved after 12 h of reaction at 40 °C, 20% of mass of heterogeneous biocatalyst per mass of reaction mixture (20% m.m^-1), and LA:IA molar ratio of 1:1.5 in a methyl isobutyl ketone (MIBK) medium. The biocatalyst retained around of 30% of its initial activity after five consecutive esterification batches under optimal experimental conditions. The proposed experimental procedure can be considered as an acceptable green process (EcoScale score of 66.5), in addition to the fact that a new strategy is proposed to sustainably produce a valuable industrial ester (isoamyl levulinate) from biomass-based materials using an immobilized and low-cost commercial lipase as catalyst.

Colourimetric Plate Assays Based on Functionalized Gelatine Hydrogel Useful for Various Screening Purposes in Enzymology

Hydrogels are intensively investigated biomaterials due to their useful physicochemical and biological properties in bioengineering. In particular, naturally occurring hydrogels are being deployed as carriers for bio-compounds. We used two approaches to develop a plate colourimetric test by immobilising (1) ABTS or (2) laccase from Trametes versicolor in the gelatine-based hydrogel. The first system (1) was applied to detect laccase in aqueous samples. We investigated the detection level of the enzyme between 0.05 and 100 µg/mL and pH ranging between 3 and 9; the stability of ABTS in the solution and the immobilised form, as well as the retention functional property of the hydrogel in 4 °C for 30 days. The test can detect laccase within 20 min in the concentration range of 2.5−100 µg/mL; is effective at pH 3−6; preserves high stability and functionality under storage and can be also successfully applied for testing samples from a microbial culture. The second system with the immobilised laccase (2) was tested in terms of substrate specificity (ABTS, syringaldazine, guaiacol) and inhibitor (NaN3) screening. ABTS appeared the most proper substrate for laccase with detection sensitivity CABTS > 0.5 mg/mL. The NaN3 tested in the range of 0.5−100 µg/mL showed a distinct inhibition effect in 20 min for 0.5 µg/mL and total inhibition for ≥75 µg/mL.

Development of multifarious carrier materials and impact conditions of immobilised microbial technology for environmental remediation: A review

Microbial technology is the most sustainable and eco-friendly method of environmental remediation. Immobilised microorganisms were introduced to further advance microbial technology. In immobilisation technology, carrier materials distribute a large number of microorganisms evenly on their surface or inside and protect them from external interference to better treat the targets, thus effectively improving their bioavailability. Although many carrier materials have been developed, there have been relatively few comprehensive reviews. Therefore, this paper summarises the types of carrier materials explored in the last ten years from the perspective of structure, microbial activity, and cost. Among these, carbon materials and biofilms, as environmentally friendly functional materials, have been widely applied for immobilisation because of their abundant sources and favorable growth conditions for microorganisms. The novel covalent organic framework (COF) could also be a new immobilisation material, due to its easy preparation and high performance. Different immobilisation methods were used to determine the relationship between carriers and microorganisms. Co-immobilisation is particularly important because it can compensate for the deficiencies of a single immobilisation method. This paper emphasises that impact conditions also affect the immobilisation effect and function. In addition to temperature and pH, the media conditions during the preparation and reaction of materials also play a role. Additionally, this study mainly reviews the applications and mechanisms of immobilised microorganisms in environmental remediation. Future development of immobilisation technology should focus on the discovery of novel and environmentally friendly carrier materials, as well as the establishment of optimal immobilisation conditions for microorganisms. This review intends to provide references for the development of immobilisation technology in environmental applications and to further the improve understanding of immobilisation technology.

Site-Specific Covalent Immobilization of Methylobacterium extorquens Non-Blue Laccse Melac13220 on Fe3O4 Nanoparticles by Aldehyde Tag

In the present study, the non-blue laccase Melac13220 from Methylobacterium extorquens was immobilized using three methods to overcome problems related to the stability and reusability of the free enzyme: entrapment of the enzyme with sodium alginate, crosslinking of the enzyme with glutaraldehyde and chitosan-, and site-specific covalent immobilization of the enzyme on Fe3O4 nanoparticles by an aldehyde tag. The site-specific covalent immobilization method showed the highest immobilization efficiency and vitality recovery. The optimum temperature of Melac13220 was increased from 65 °C to 80 °C. Immobilized Melac13220 showed significant tolerance to some organic solvents and maintained approximately 80% activity after 10 cycles of use. Differential scanning calorimetry (DSC) indicated that the melting temperature of the enzyme was increased (from 57 °C to 79 °C). Immobilization of Melac13220 also led to improvement in dye decolorization such that Congo Red was completely decolorized within 10 h. The immobilized enzyme can be easily prepared without purification, demonstrating the advantages of using the aldehyde tag strategy and providing a reference for the practical application of different immobilized laccase methods in the industrial field.

Alternative design strategies to help build the enzymatic retrosynthesis toolbox

Most of the complex molecules found in nature still cannot be synthesized by current organic chemistry methods. Given the number of enzymes that exist in nature and the incredible potential of directed evolution, the field of synthetic biology contains perhaps all the necessary building blocks to bring about the realization of applied enzymatic retrosynthesis. Current thinking anticipates that enzymatic retrosynthesis will be implemented using conventional cell-based synthetic biology approaches where requisite native, heterologous, designer, and evolved enzymes making up a given multi-enzyme pathway are hosted by chassis organisms to carry out designer synthesis. In this perspective, we suggest that such an effort should not be limited by solely exploiting living cells and enzyme evolution and describe some useful yet less intensive complementary approaches that may prove especially productive in this grand scheme. By decoupling reactions from the environment of a living cell, a significantly larger portion of potential synthetic chemical space becomes available for exploration; most of this area is currently unavailable to cell-based approaches due to toxicity issues. In contrast, in a cell-free reaction a variety of classical enzymatic approaches can be exploited to improve performance and explore and understand a given enzyme's substrate specificity and catalytic profile towards non-natural substrates. We expect these studies will reveal unique enzymatic capabilities that are not accessible in living cells.

Esterases as emerging biocatalysts: Mechanistic insights, genomic and metagenomic, immobilization, and biotechnological applications

Esterase enzymes are a family of hydrolases that catalyze the breakdown and formation of ester bonds. Esterases have gained a prominent position in today's world's industrial enzymes market. Due to their unique biocatalytic attributes, esterases contribute to environmentally sustainable design approaches, including biomass degradation, food and feed industry, dairy, clothing, agrochemical (herbicides, insecticides), bioremediation, biosensor development, anticancer, antitumor, gene therapy, and diagnostic purposes. Esterases can be isolated by a diverse range of mammalian tissues, animals, and microorganisms. The isolation of extremophilic esterases increases the interest of researchers in the extraction and utilization of these enzymes at the industrial level. Genomic, metagenomic, and immobilization techniques have opened innovative ways to extract esterases and utilize them for a longer time to take advantage of their beneficial activities. The current study discusses the types of esterases, metagenomic studies for exploring new esterases, and their biomedical applications in different industrial sectors.

Immobilization of Rhizomucor miehei lipase on magnetic multiwalled carbon nanotubes towards the synthesis of structured lipids rich in sn-2 palmitic acid and sn-1,3 oleic acid (OPO) for infant formula use

Nowadays, breast milk is considered as the ideal food for infants owing to the most common oleic acid-palmitic acid-oleic acid (OA-PA-OA) fatty acid distribution of the human milk fat (HMF). This study reports the synthesis of 1,3-dioleoyl-2-palmotoylglycerol (OPO)-rich human milk fat substitutes in a two-step enzymatic acidolysis reaction with Rhizomucor miehei lipase (RML) immobilized on magnetic multi-walled carbon nanotubes(mMWCNTs). The immobilized RML (RML-mMWCNTs) showed better thermal and pH stability, convenient recovery and reusability than the free soluble form. Under optimized reaction conditions (1:8 tripalmitin (PPP)/OA, 10%wt. enzyme, 50 °C, 5 h), PA content at the sn-2 position and OA incorporation at the sn-1,3 positions reached 93.46% and 59.54%, respectively. Comparison tests have also showed that RML-mMWCNTs has better catalytic activity and reusability than the commercial lipase Lipozyme RM IM. The results suggest that RML-mMWCNTs is a promising biocatalyst for the synthesis of OPO-rich TAGs with potential use in infant formulas.

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

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

Application of magnetic immobilized enzyme of nano dialdehyde starch in deacidification of rice bran oil

Glutaraldehyde is usually used as a cross-linking agent in the immobilization of enzymes, but this will have a negative effect on the enzyme. Dialdehyde starch can effectively replace glutaraldehyde as a cross-linking agent, but the large particle size of dialdehyde starch affects the performance of immobilized enzyme. In this study, dialdehyde starch nanoparticles (DSNP) were combined with modified Fe₃O₄ to obtain magnetic carrier (MDSNP), and Candida Antarctica lipase B (CALB) was crosslinked to the carrier to obtain magnetic immobilized enzyme (MDSNPCALB). The characterization results show that the functional groups of each material have obvious characteristic absorption peaks, strong diffraction peaks and typical crystal structures, high magnetism, no coercivity, relatively good dispersion and nano particle size. MDSNPCALB was added to degummed rice bran oil (RBO) and ethanolamine was used as an acyl receptor for acylation and deacidification. After repeated use for 10 times, MDSNPCALB remained highly active, indicating that MDSNPCALB can be effectively used for the deacidification of RBO.

A Two-Step Cross-Linked Hydrogel Immobilization Strategy for Diacetylchitobiose Deacetylase

Free enzymes often face economic problems due to their non-recyclability, which limits their applications for industrial manufacturing. Organic biopolymers are frequently used to fabricate hydrogel for enzyme immobilization due to their advantages of non-toxicity, biocompatibility, biodegradability, and flexibility. However, for highly thermostable enzymes, simple cross-linking causes either low immobilizing efficiency or low thermal stability. Herein, we developed a novel enzyme immobilization strategy with two-step cross-linked gelatin hydrogel for thermostable enzymes working at high temperature. The hydrogel was firstly “soft cross-linked” to immobilize most enzyme molecules and then “hard cross-linked” to gain strong thermal stability. We selected the enzyme diacetylchitobiose deacetylase (Dac), which was firstly derived from hyperthermophilic bacteria, to demonstrate the advantages of our method. With the optimized fabrication steps, our hydrogel showed ~87% Dac immobilization efficiency and excellent stability against heating, dehydrating, long-time storing, and massive recycling. Importantly, our hydrogel showed ~85.0% relative enzyme activity at 80 °C and retained ~65.8% activity after 10 rounds of catalysis. This strategy showed high immobilizing efficiency and strong thermal stability and we believe it could improve the industrial potential for those enzymes.

Polysaccharide-Based Edible Gels as Functional Ingredients: Characterization, Applicability, and Human Health Benefits

Nowadays, edible materials such as polysaccharides have gained attention due to their valuable attributes, especially gelling property. Polysaccharide-based edible gels (PEGs) can be classified as (i) hydrogels, (ii) oleogels and bigels, (iii) and aerogels, cryogels and xerogels, respectively. PEGs have different characteristics and benefits depending on the functional groups of polysaccharide chains (e.g., carboxylic, sulphonic, amino, methoxyl) and on the preparation method. However, PEGs are found in the incipient phase of research and most studies are related to their preparation, characterization, sustainable raw materials, and applicability. Furthermore, all these aspects are treated separately for each class of PEG, without offering an overview of those already obtained PEGs. The novelty of this manuscript is to offer an overview of the classification, definition, formulation, and characterization of PEGs. Furthermore, the applicability of PEGs in the food sector (e.g., food packaging, improving food profile agent, delivery systems) and in the medical/pharmaceutical sector is also critically discussed. Ultimately, the correlation between PEG consumption and polysaccharides properties for human health (e.g., intestinal microecology, "bridge effect" in obesity, gut microbiota) are critically discussed for the first time. Bigels may be valuable for use as ink for 3D food printing in personalized diets for human health treatment. PEGs have a significant role in developing smart materials as both ingredients and coatings and methods, and techniques for exploring PEGs are essential. PEGs as carriers of bioactive compounds have a demonstrated effect on obesity. All the physical, chemical, and biological interactions among PEGs and other organic and inorganic structures should be investigated.

Corn Cob as a Green Support for Laccase Immobilization-Application on Decolorization of Remazol Brilliant Blue R

The high demand for food and energy imposed by the increased life expectancy of the population has driven agricultural activity, which is reflected in the larger quantities of agro-industrial waste generated, and requires new forms of use. Brazil has the greatest biodiversity in the world, where corn is one of the main agricultural genres, and where over 40% of the waste generated is from cobs without an efficient destination. With the aim of the valorization of these residues, we proposed to study the immobilization of laccase from Aspergillus spp. (L_Asp) in residual corn cob and its application in the degradation of Remazol Brilliant Blue R (RBBR) dye. The highest yields in immobilized protein (75%) and residual activity (40%) were obtained at pH 7.0 and an enzyme concentration of 0.1 g.mL⁻¹, whose expressed enzyme activity was 1854 U.kg⁻¹. At a temperature of 60 °C, more than 90% of the initial activity present in the immobilized biocatalyst was maintained. The immobilized enzyme showed higher efficiency in the degradation (64%) of RBBR dye in 48 h, with improvement in the process in 72 h (75%). The new biocatalyst showed operational efficiency during three cycles, and a higher degradation rate than the free enzyme, making it a competitive biocatalyst and amenable to industrial applications.