Synthesis and characterization of a novel magnetic chitosan microsphere for lactase immobilization

Immobilized enzymes: exploring its potential in food industry applications

The global demand for nutritious, longer-lasting food has spurred the food industry to seek eco-friendly solutions. Enzymes play a vital role in enhancing food quality by improving flavor, texture, and nutritional content. However, challenges like rapid deactivation and non-recoverability of free enzymes are addressed by immobilized enzymes, which enhance efficiency, quality, and sustainability in food processing. Immobilization methods include adsorption, covalent binding, entrapment, encapsulation and cross-liked enzyme aggregates, which enhancing their stability, reusability, and catalytic efficiency. Immobilization of enzyme such as pectinase, amylase, naringinase, cellulase, lactase, glucoamylase, xylanase, invertase, lipase, phytase, and protease have been utilized in fruit, vegetable, baking, dairy, brewing, and feed process due to their high thermostability, improved shelf life, food quality and safety. The catalytic efficiency of immobilized enzymes in detecting and quantifying various food components, contaminants, and quality indicators, also developed functional foods with nutraceuticals benefits, include prebiotic juices, lactose-free dairy products, poly unsaturated fatty acids rich foods, low-calorie sweeteners, fortified food and bioactive peptides.

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Covalently immobilized β-galactosidase onto a novel alginate/lemon peel carrier: Catalytic, kinetic, stability studies, and its application in the production of whey high-protein beverage

β-Galactosidase (βG) was immobilized on novel alginate/lemon peel (Alg/LP) beads, achieving an immobilization yield of 84.7 % and an efficiency of 96.6 %. Both free and immobilized enzymes exhibited optimal activity at 50 °C and pH 5. The immobilized enzyme (Alg/LP/βG) demonstrated significantly improved thermal stability and broader pH tolerance compared to its free form. Immobilization notably altered enzyme kinetics, reducing Km by 57 % and Vmax by 13.4 %. Alg/LP/βG displayed excellent storage stability at 4 °C, retaining 91.3 % activity after 21 days and 79.6 % activity after 35 days. It also maintained 100 % activity after 11 cycles and 75.4 % activity after 15 operational cycles. The enzyme's application was explored in producing high-protein beverages from 13 % whey protein concentrate, enhancing sweetness by hydrolyzing lactose into glucose and galactose, which were further sweetened with 7 % sucrose. Adding lemon peel powder (LPP) improved the beverage's flavor, antioxidant properties, total phenolic content, and viscosity while keeping its chemical composition low. Sensory evaluation identified the beverage with 0.4 % LPP as the most preferred. This study highlights the potential of Alg/LP beads as an effective support matrix for β-galactosidase, offering enhanced stability, reusability, and applicability, particularly for enzymatic processes in the food industry.

Optimization of the degree of deacetylation of chitosan beads for efficient anionic dye adsorption: kinetics, thermodynamics, mechanistic insights via DFT analysis, and regeneration performance

Congo red, a persistent dye widely used in the textile industry, poses significant environmental hazards if not properly treated. In this study, the effectiveness of chitosan beads for removing Congo red from textile wastewater was investigated. A Box-Behnken design was utilized to optimize the degree of deacetylation (DDA) of the chitosan beads, achieving a maximum DDA of 95.79% under the optimal conditions of 100 °C, 300 min reaction time, and 45.91% NaOH concentration. Comprehensive characterization of the synthesized adsorbent was performed using FT-IR, XRD, SEM, and BET analysis, with a BET surface area of 11.5180 m2/g, indicating a substantial surface area for effective adsorption. The adsorption process followed pseudo-second-order kinetics and was best described by the Langmuir model. At pH 6, an adsorbent dose of 0.06 g, and an optimal reaction time of 80 min, a maximum adsorption capacity of 110.37 mg/g was achieved, surpassing the performance of magnetic chitosan (40.12 mg/g) and powdered chitosan (42.48 mg/g). Thermodynamic parameters (ΔH° = 10.91 kJ/mol and ΔG° < 0) indicate that the adsorption process was endothermic and spontaneous. DFT calculations were conducted to elucidate the adsorption mechanism, focusing on the role of benzene rings and oxygen atoms in Congo red as electron donors. These findings demonstrate that chitosan beads are a promising material for the removal of Congo red from contaminated wastewater.

Review of porous microspheres for enzyme immobilization: Strategies, applications, and prospects

Enzymes are natural biocatalysts with the advantages such as high catalytic efficiency, and strong substrate selectivity. However, the features of structure instability and low reusability rates have limited the industrial applications of enzyme. Fortunately, advancements in technology have made enzyme immobilization possible. Porous microspheres possess desirable characteristics, for example a large specific surface area, high porosity, stable mechanical and chemical properties, and cost-effectiveness, making them excellent carriers for immobilized enzymes. This review covered the latest developments in the field and the utilization of porous microsphere nanomaterials for enzyme immobilization. It emphasized the various methods used for carrier immobilization of enzymes and summarized the diverse applications of porous microsphere nanomaterials in enzyme immobilization.

Green and Fast Synthesis of NiCo-MOF for Simultaneous Purification-Immobilization of Bienzyme to Catalyze the Synthesis of Ginsenoside Rh2

Traditional metal-organic frameworks (MOFs) preparation is generally time-consuming, polluting, and lacking specificity for enzyme immobilization. This paper introduced a facile, rapid, and green method to produce three MOFs subsequently employed to purify and coimmobilize recombinant glycosyltransferase (UGT) and recombinant sucrose synthetase (SUSy) using histidine tag (His-tag) for the specific adsorption of Ni2+ and Co2+ from MOFs. This method simplified enzyme purification from crude extracts and enabled enzymes to be reused. The results demonstrated that NiCo-MOF exhibited a higher enzyme load (115.9 mg/g) than monometallic MOFs. Additionally, the NiCo-MOF@UGT&SUSy demonstrated excellent stability and efficiently produced the rare ginsenoside Rh2 by catalyzing a coupling reaction (95.6 μg/mL), solving the problem of the substrate cost of uridine diphosphate glucose (UDPG). The NiCo-MOF@UGT&SUSy retained 68.97% of the initial activity after 10 cycles. Finally, molecular docking studies elucidated the conversion mechanism of the target product Rh2. This technique is important in the industrialization of ginsenoside production and enzyme purification.

Preparation, Structural Characterization, and Enzymatic Properties of Alginate Lyase Immobilized on Magnetic Chitosan Microspheres

Alginate lyase is an enzyme that catalyses the hydrolysis of alginate into alginate oligoalginates. To enhance enzyme stability and recovery, a facile strategy for alginate lyase immobilization was developed. Novel magnetic chitosan microspheres were synthesized and used as carriers to immobilize alginate lyase. The immobilization of alginate lyase on magnetic chitosan microspheres was successful, as proven by Fourier transform infrared spectroscopy and X-ray diffraction spectra. Enzyme immobilization exhibited the best performance at an MCM dosage of 1.5 g/L, adsorption time of 2.0 h, glutaraldehyde concentration of 0.2%, and immobilization time of 2.0 h. The optimal pH of the free alginate lyase was 7.5, and this pH value was shifted to 8.0 after immobilization. No difference was observed at the optimal temperature (45 °C) for the immobilized and free enzymes. The immobilized alginate lyase displayed better thermal stability than the free alginate lyase. The Km values of the free and immobilized enzymes were 0.05 mol/L and 0.09 mol/L, respectively. The immobilized alginate lyase retained 72% of its original activity after 10 batch reactions. This strategy was found to be a promising method for immobilizing alginate lyase.

Role of Clay Substrate Molecular Interactions in Some Dairy Technology Applications

The use of clay materials in dairy technology requires a multidisciplinary approach that allows correlating clay efficiency in the targeted application to its interactions with milk components. For profitability reasons, natural clays and clay minerals can be used as low-cost and harmless food-compatible materials for improving key processes such as fermentation and coagulation. Under chemical stability conditions, clay materials can act as adsorbents, since anionic clay minerals such as hydrotalcite already showed effectiveness in the continuous removal of lactic acid via in situ anion exchange during fermentation and ex situ regeneration by ozone. Raw and modified bentonites and smectites have also been used as adsorbents in aflatoxin retention and as acidic species in milk acidification and coagulation. Aflatoxins and organophilic milk components, particularly non-charged caseins around their isoelectric points, are expected to display high affinity towards high silica regions on the clay surface. Here, clay interactions with milk components are key factors that govern adsorption and surface physicochemical processes. Knowledge about these interactions and changes in clay behavior according to the pH and chemical composition of the liquid media and, more importantly, clay chemical stability is an essential requirement for understanding process improvements in dairy technology, both upstream and downstream of milk production. The present paper provides a comprehensive review with deep analysis and synthesis of the main findings of studies in this area. This may be greatly useful for mastering milk processing efficiency and envisaging new prospects in dairy technology.

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-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.

Design of composite nanosupports and applications thereof in enzyme immobilization: A review

Enzyme immobilization techniques have developed dramatically over the past several decades. Support materials are key in shaping the function of a specific immobilized enzyme. Although they have large specific surface areas and functional active sites, single-component nanomaterials and their surface chemical modification derivatives struggle to meet increasing demand. Thus, composite materials, compounds of two or more materials, have been developed and applied in efficient immobilization through advances in materials science. More methods have been developed and employed to design composite nanomaterials in recent years. These novel composite nanomaterials often show superior physical, chemical, and biological performance as supports in enzyme immobilization, among other applications. In this review, immobilization techniques and their supports are stated first and methods to design and fabricate composite nanomaterials as nanosupports are also shown in the following section. Applications of composite nanosupports in laccase immobilization are discussed as models in the later sections of the paper. This review is intended to help readers gain insight into the design principles of composite nanomaterials for immobilization supports.

Highly effective enzymes immobilization on ceramics: Requirements for supports and enzymes

Enzyme immobilization is a well-known method for the improvement of enzyme reusability and stability. To achieve very high effectiveness of the enzyme immobilization, not only does the method of attachment need to be optimized, but the appropriate support must be chosen. The essential necessities addressed to the support applied for enzyme immobilization can be focused on the material features as well as on the stability and resistances in certain conditions. Ceramic membranes and nanoparticles are the most widespread supports for enzyme immobilization. Hence, the immobilization of enzymes on ceramic membrane and nanoparticles are summarized and discussed. The important properties of the supports are particle size, pore structure, active surface area, volume to surface ratio, type and number of reactive available groups, as well as thermal, mechanical, and chemical stability. The modifiers and the crosslinkers are crucial to the enzyme loading amount, the chemical and physical stability, and the reusability and catalytical activity of the immobilized enzymes. Therefore, the chemical and physical methods of modification of ceramic materials are presented. The most popular and used modifiers (e.g. APTES, CPTES, VTES) as well as activating agents (GA, gelatin, EDC and/or NHS) applied to the grafting process are discussed. Moreover, functional groups of enzymes are presented and discussed since they play important roles in the enzyme immobilization via covalent bonding. The enhanced physical, chemical, and catalytical properties of immobilized enzymes are discussed revealing the positive balance between the effectiveness of the immobilization process, preservation of high enzyme activity, its good stability, and relatively low cost.

pH Shock-promoted lysozyme corona for efficient pathogenic infections treatment: Effects of surface chemistry of mesoporous silica nanoparticles and loading method

The emergence of antibiotic resistant bacteria because of the antibiotics abusement was the motivation to develop the effective alternatives to traditional antibiotics. Hence, various lysozyme corona were prepared through the physical and covalent attachment of lysozyme molecules onto either the bare or carboxyl-functionalized mesoporous silica particles. The prepared samples were characterized by STEM, TGA/DTA, zeta potential, FTIR, UV-vis and CD spectroscopic methods. All the prepared lysozyme-coated particles exhibited an efficient antibacterial activity against Listeria monocytogenes, as a case study, in vitro with no cytotoxicity. The minimal inhibition concentration (MIC) of the lysozyme-physically adsorbed bare and carboxyl-functionalized mesoporous silica nanoparticles (L-MS and L-ads-CMS, respectively) and the lysozyme-covalently attached carboxyl-functionalized MS particles (L-cov-CMS) was 2, 5.3 and 1.7 folds lower than that of the free lysozyme, respectively. Additionally, for the first time, it was reported that the pretreatment of lysozyme corona of L-ads-CMS through inducing a pH-shock can lead to the enhancement of antibacterial properties thereof. This behavior was associated to the controlled release of the immobilized lysozyme molecules and their conformational stability. These natural antibacterial lysozyme-coated silica nanoparticles showing the "pH-shock enhanced activity" could be of utmost interest for design of the highly active enzyme-modified nanoparticles.

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.