Novel and efficient method for immobilization and stabilization of β-d-galactosidase by covalent attachment onto magnetic Fe3O4–chitosan nanoparticles

Chitosan-based oral hydrogel formulations of β-galactosidase to improve enzyme supplementation therapy for lactose intolerance

β-Galactosidase supplementation plays an important role in the life of people with lactose intolerance. However, these formulations are rendered ineffective by the low pH and pepsin in the stomach and pancreatic proteases in the intestine. Therefore, it is necessary to develop oral transport systems for carrying this enzyme in the active form up to the intestine, where the lactose digestion occurs. In this research, a new hydrogel was developed that could potentially be used for enzyme supplement therapy. In this regard, the chitosan-based β-Gal formulations described in the manuscript are an alternative long-acting preparation to the so far available preparations that allow for enzyme protection and mucosal targeting. These hydrogels were prepared from chitosan and polyethylene glycol and contained a covalently immobilized β-galactosidase from Aspergillus oryzae. The β-galactosidase in the hydrogel was protected from degradation in a gastric medium at a pH of 2.5 and retained 75 % of its original activity under subsequent intestinal conditions. In the case of a simulated gastric fluid with a pH of 1.5, a copolymer containing methacrylic acid functional groups was sufficient to protect the hybrid hydrogel from the extremely acidic pH. In addition, the surface of the hydrogel was chemically modified with thiol and amidine groups, which increased the binding to intestinal mucin by 20 % compared with the unmodified hydrogel. These results represent a promising approach for oral transport as a reservoir for β-galactosidase in the small intestine to reduce the symptoms of hypolactasia.

Recent Advances in Applications of Oxidases and Peroxidases Polymer-Based Enzyme Biocatalysts in Sensing and Wastewater Treatment: A Review

Oxidase and peroxidase enzymes have attracted attention in various biotechnological industries due to their ease of synthesis, wide range of applications, and operation under mild conditions. Their applicability, however, is limited by their poor stability in harsher conditions and their non-reusability. As a result, several approaches such as enzyme engineering, medium engineering, and enzyme immobilization have been used to improve the enzyme properties. Several materials have been used as supports for these enzymes to increase their stability and reusability. This review focusses on the immobilization of oxidase and peroxidase enzymes on metal and metal oxide nanoparticle-polymer composite supports and the different methods used to achieve the immobilization. The application of the enzyme-metal/metal oxide-polymer biocatalysts in biosensing of hydrogen peroxide, glucose, pesticides, and herbicides as well as blood components such as cholesterol, urea, dopamine, and xanthine have been extensively reviewed. The application of the biocatalysts in wastewater treatment through degradation of dyes, pesticides, and other organic compounds has also been discussed.

Design and synthesis of Ag NPs/chitosan-starch nano-biocomposite as a modern anti-human malignant melanoma drug

In recent years, the unprecedented increase in various cancers such as melanoma has caused researchers to focus more on the formulation of newer drugs with less side effects. In this study, we herein indicate the biogenic nanoarchitechtonics of Ag NPs template over chitosan/starch mixed hydrogel having notable reducing potential and anti-malignant melanoma effects. The two biopolymers also could stabilize as-synthesized Ag NPs. Physicochemical features of the material were further characterized over a range of advanced methods like X-ray diffraction (XRD), elemental mapping, dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Fourier transformed infrared spectroscopy (FT-IR). TEM analysis showed the spherical-shaped nanocomposite with the mean diameter in the range of 5-15 nm. Thereafter, the nanocomposite was exploited in the anti-malignant melanoma and cytotoxicity effects studies against various human malignant melanoma cell lines (HT144, RPMI7951, SKMEL2, UACC3074, WM266-4 and MUM2C) in situ. The bio-composite corresponding IC₅₀ values were 193, 102, 227, 250, 301, and 203 μg/mL against MUM2C, WM266-4, UACC3074, SKMEL2, RPMI7951, and HT144 cell lines, respectively. A significantly high IC₅₀ value offered an excellent antioxidant capacity of bio-composite. According to the above results, Ag NPs/CS-Starch nanomaterial can be utilized as an efficient drug to treat malignant melanoma in humans after doing clinical trial studies.

Indoleamine 2,3 dioxygenase 1 immobilization on magnetic nanoparticles for screening inhibitors from coffee

In this study, a ligand fishing method was developed to screen potential indoleamine 2,3-dioxygenase 1 (IDO1) inhibitors from coffee extracts by immobilization of IDO1 enzyme on amino-modified magnetic nanoparticles combined with UHPLC-Q-TOF-MS/MS analysis. Parameters including enzyme concentration, immobilization time, the pH of glutaraldehyde and the amount of magnetic nanoparticles were optimized. The results indicated that immobilized IDO1 could be reused 5 times and was stable during storage for 7 days. Several IDO1 ligands were captured by incubating immobilized IDO1 with coffee extract, of which 10 showed an obvious difference comparing to non-conjugated bare nanoparticles. In vitro inhibitory activity was further performed by CE analysis, in which ferulic acid and chlorogenic acid had better IDO1 inhibitory activity, with IC₅₀ value of 113.7 μM and 307.5 μM. These results demonstrate that this method provides an effective platform for identifying and screening IDO1 inhibitors from natural products.

Ag NPs supported chitosan-agarose modified Fe3O4 nanocomposite catalyzed synthesis of indazolo[2,1-b]phthalazines and anticancer studies against liver and lung cancer cells

In this article we report a novel Ag NPs fabricated chitosan-agarose composite functionalized core-shell type Fe₃O₄ nanoparticle (Ag/CS-Agar@Fe₃O₄). The biogenic material was analyzed over a number of physicochemical methods like, FT-IR, FE-SEM, TEM, EDX, XRD, VSM and ICP-OES. In catalytic exploration we aimed the synthesis of diverse 2H-indazolo0-b]phthalazine-trione derivatives via one-pot three component coupling of phathalalhydrazide, dimedone and different aldehydes. It afforded good to excellent yields under solvent-less conditions. Robustness of the catalyst was justified by catalyst recyclability for consecutive 10 times, hot filtration and leaching tests. Again, biological activity of the material was evaluated by studying the antioxidant and cytotoxicity properties over lung and liver cancer cell lines. Antioxidant potential of Ag/CS-Agar@Fe₃O₄ was assessed by DPPH radical scavenging studies and the corresponding IC50 was found to be 96.57 μg/mL. Liver and lung cancer studies over Ag/CS-Agar@Fe₃O₄ was carried out by MTT assay against HepG2 and A549 cell lines. The corresponding IC50 values were found as 192.35 and 365.28 μg/mL respectively. % Cell viability of the nanomaterial decreased dose dependently over both the cell lines without any cytotoxicity on normal cell line. The results demonstrates Ag/CS-Agar@Fe₃O₄ nanocomposite to be an efficient chemotherapeutic drug against the lung and hepatocellular carcinoma cells.

Immobilization of lipase on β-cyclodextrin grafted and aminopropyl-functionalized chitosan/Fe3O4 magnetic nanocomposites: An innovative approach to fruity flavor esters esterification

The lipase from Bacillus licheniformis NCU CS-5 was immobilized onto β-cyclodextrin (CD) grafted and aminopropyl-functionalized chitosan-coated Fe₃O₄ magnetic nanocomposites (Fe₃O₄-CTS-APTES-GA-β-CD). Fourier transform infrared spectroscopy, thermogravimetry analysis, X-ray diffraction, scanning electron microscopy and transmission electron microscopy showed that not only the functionalized magnetic nanoparticles were synthesized but also the immobilized lipase was successfully produced. The immobilized lipase exhibited higher optimal pH value (10.5) and temperature (60℃) than the free lipase. The pH and thermal stabilities of the immobilized lipase were improved significantly compared to the free lipase. The immobilized lipase remained more than 80% of the relative activity at temperature of 60 ℃ and pH 12.0. The immobilized lipase also remained over 80% of its relative activity after 28 days of storage and 15 cycles of application. The application of the immobilized lipase in esterification of isoamyl acetate and pentyl valerate showed that maximum esterification efficiency was achieved in n-hexane having 68.0% and 89.2% respectively. Therefore, these results indicated that the Fe₃O₄-CTS-APTES-GA-β-CD nanoparticles are novel carriers for immobilizing enzyme, and the immobilized lipase can be used as an innovative green approach to the synthesis of fruity flavor esters in food industry.

Optimizing the immobilization conditions of β-galactosidase on UV-cured epoxy-based polymeric film using response surface methodology

UV-cured epoxy-based polymeric film was prepared from glycidyl methacrylate, trimethylolpropane triacrylate, and poly(ethylene glycol) methylether acrylate. 2-hydroxy-2- methylpropiophenone was used as photo initiator. Covalent binding through epoxy groups was employed to immobilize β-galactosidase from Escherichia coli onto this film, and immobilization conditions were optimized by the response surface methodology. ATR-Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) analysis was carried out to characterize the epoxy-based polymeric film. Immobilization yield of β-galactosidase on the material was calculated as 3.57 mg/g and the highest enzyme activity for the immobilized enzyme recorded at pH 6.5°C and 60°C. The immobilized enzyme preserved 51% of its activity at the end of 12 runs. Free and immobilized enzyme hydrolyzed 163.8 and 172.3 µM lactose from 1% lactose, respectively. Kinetic parameters of both free and immobilized β-galactosidase were also investigated, and K_m values were determined to be 0.647 and 0.7263 mM, respectively. PRACTICAL APPLICATIONS: In our study we prepared a UV-cured epoxy-based polymeric film and optimized the immobilization conditions of β-galactosidase from Escherichia coli onto this polymeric film by using response surface methodology (RSM). For this purpose, three-level and three-factor Box-Behnken design, which is an independent, rotatable or nearly rotatable, quadratic design, was applied. Optimal levels of three variables, namely, the amount of enzyme, immobilization time, and pH were determined using Box-Behnken experimental design. Lactose hydrolysis studies were performed from milk and lactose samples using free and immobilized enzyme. In addition, kinetic parameters, storage stability, and re-usability of immobilized β-galactosidase were examined.

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

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

Cross-linked Enzyme Aggregates of Fibrinolytic Protease BC1 Immobilized on Magnetic Chitosan Nanoparticles (CLEAs-Fib-mChi): Synthesis, Purification, and Characterization

Bacterial fibrinolytic proteases achieved more attention in the prevention and treatment of cardiovascular diseases, so purification, characterization, and activity enhancement are of prime importance. In this study, a fibrinolytic serine metalloprotease was purified from the culture supernatant from Bacillus sp. BC1. It was purified to homogeneity by a two-step procedure with a 24-fold increase in specific activity and a 33.1% yield. It showed 28 kDa molecular weight, while its optimal pH and temperature were obtained 8 and 50-60 °C. The cross-link enzyme aggregates of this fibrinolytic BC1 successfully immobilized on magnetic chitosan nanoparticles. A 52% activity enhancement was obtained by immobilized enzyme at pH 6.0, compared to free protease. K_m values of the free and immobilized proteases were obtained about 0.638 and 0.61 mg/ml, respectively. The free and immobilized enzymes did not show any activity concerning transferrin, γ-globulins, and hemoglobin, as blood plasma proteins. The in vitro blood clot lysis test of the free and immobilized proteases showed a maximum of 42 and 50% clot lysis, which was comparatively higher than that revealed by streptokinase and heparin at the same condition. These results indicated that the free and immobilized proteases have the potential to be effective fibrinolytic agents.

Characterization of TEMPO-oxidized chitin nanofibers with various oxidation times and its application as an enzyme immobilization support

Chitin nanofibers have recently received increased attention and are considered to be a promising material for a wide range of applications because of their excellent characteristics. In this study, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized chitin nanofibers (CNFs) with various oxidation times were prepared and characterized. CNFs with different oxidation times were then utilized for enzyme immobilization, using chymotrypsin as a model enzyme. The effects of oxidation time on enzyme immobilization were explored. Results showed characteristics of chitin nanofibers can be controlled by adjusting oxidation time. CNFs treated with TEMPO for 360 min showed the lowest crystallinity (79.13 ± 1.43%), the shortest length (241.70 ± 74.61 nm), the largest width (12.67 ± 3.43 nm), and the highest transmittance (73.01% at 800 nm). The activity of immobilized enzymes and enzyme loading showed good correlation to the carboxylate content of CNFs. The enzyme efficiency based on CNFs and the content of carboxylate groups peaked at the oxidization time of 60 min. When the additional amount of chymotrypsins (CTs) was 500 or 2000 mg/g carrier, the highest loading amount of CTs was 307.17 ± 4.08 or 726.82 ± 12.05 mg/g carrier, respectively.

Magnetic graphene oxide nanocomposites as an effective support for lactase immobilization with improved stability and enhanced photothermal enzymatic activity

Magnetic graphene oxide-immobilized lactase with high loading capacity, improved stabilities, and photothermal enhancement of activity has been reported.

Large batch production of Galactooligosaccharides using β-glucosidase immobilized on chitosan-functionalized magnetic nanoparticle

β-glucosidase (BglA) immobilization from Thermotoga maritima on magnetic nanoparticles (MNPs) functionalized with chitosan (Cs) were efficiently investigated to improve lactose conversion and galactooligosaccharides (GOS) production. We used a batch method in order to improve the conversion of lactose to GOS. The efficiency and yield of immobilization were 79% and immobilized BglA was effectively recycled via a magnetic separation procedure through a batch-wise GOS with no activity lessening. Furthermore, analyses were done through screening kinetics of enzyme activity, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). Proposed methodology of immobilization shows a potential application as it is stable which was proved through many methods including pH, temperature, heat treatment, storage, and kinetics of the enzyme. GOS and residual enzyme activity showed to be 28.76 and 40.44%, respectively. However, free enzyme synthesis of GOS yield was just 24% after 12 hr. This study proposed applying magnet in the immobilization process of BglA on Cs-MNPs to produce GOS as new method for immobilizing enzyme in a biostable and cost-efficient way. PRACTICAL APPLICATIONS: This paper focus on immobilization of BglA from T. maritima onto MNPs functionalized with CS to investigate their further possibility improving lactose conversion and GOS production. Interestingly, a successful immobilization of Tm-BglA on the substrates were achieved in Cs-MNPs. The obtained results from enzyme activity, SDS-PAGE, FT-IR, and TEM showed that the high binding capacity of BglA to Cs-MNPs was successfully obtained. Furthermore, the binding efficiency calculation indicated that the immobilized BglA-Cs-MNPs conserved 40.44% of its native activity at the end of its 6th repeated use. In addition, magnetic separation technique was successfully employed for reuse of the immobilized BglA for repetitive batch-wise GOS without significant loss of activity.

Enhanced enzymatic activity and stability by in situ entrapment of α-Glucosidase within super porous p(HEMA) cryogels during synthesis

Here, poly(2-hydroxyethyl methacrylate) (p(HEMA)) cryogel were prepared in the presence 0.48, 0.96, and 1.92 mL of α-Glucosidase enzyme (0.06 Units/mL) solutions to obtain enzyme entrapped superporous p(HEMA) cryogels, donated as α-Glucosidase@p(HEMA)-1, α-Glucosidase@p(HEMA)-2, and α-Glucosidase@p(HEMA)-3, respectively. The enzyme entrapped p(HEMA) cryogels revealed no interruption for hemolysis and coagulation of blood rendering viable biomedical application in blood contacting applications. The α-Glucosidase@p(HEMA)-1 was found to preserve its' activity% 92.3 ± 1.4 % and higher activity% against free α-Glucosidase enzymes in 15-60℃ temperature, and 4-9 pH range. The Km and Vmax values of α-Glucosidase@p(HEMA)-1 cryogel was calculated as 3.22 mM, and 0.0048 mM/min, respectively versus 1.97 mM, and 0.0032 mM/min, for free enzymes. The α-Glucosidase@p(HEMA)-1 cryogel was found to maintained enzymatic activity more than 50 % after 10 consecutive uses, and also preserved their activity more than 50 % after 10 days of storage at 25 ℃, whereas free α-Glucosidase enzyme maintained only 1.9 ± 0.9 % activity under the same conditions.

Identification and characterization of proteinase B as an unstable factor for neutral lactase in the enzyme preparation from Kluyveromyces lactis

The stability of the commercial lactase enzyme is important for the dairy industry. A destabilizing factor for neutral lactase in the enzyme preparation from Kluyveromyces lactis was investigated. We found that lactase had lower thermal stability when fragmented bands of lactase were confirmed on SDS-PAGE. After the destabilizing factor of lactase was purified, that was identified by BLAST search as a hypothetical protein in K. lactis similar to proteinase B (PRB) of Saccharomyces cerevisiae. The molecular mass of protease was estimated to be approximately 30 kDa with SDS-PAGE. The purified protease exhibited activity toward lactase and FITC-casein but not toward bovine serum albumin or milk casein. The optimal pH and temperature of the protease were 8.0 and 40 °C, respectively. The protease activity was strongly inhibited by Fe²⁺, Cu²⁺, and a serine protease inhibitor, but activated by Ca²⁺. Based on these properties, the protease was identified as PRB. Lactase fragmentation was accelerated by the addition of purified PRB to the lactase preparation and was suppressed by protease inhibitors. Thus, this is the first report to identify and characterize PRB as the unstable factor of neutral lactase in the K. lactis preparation.

Soluble and Cross-Linked Aggregated Forms of α-Galactosidase from Vigna mungo Immobilized on Magnetic Nanocomposites: Improved Stability and Reusability

α-Galactosidases hold immense potential due to their biotechnological applications in various industrial and functional food sectors. In the present study, soluble and covalently cross-linked aggregated forms of a low molecular weight, thermo-labile α-galactosidase from Vigna mungo (VM-αGal) seeds were immobilized onto chitosan-coated magnetic nanoparticles for improved stability and repeated usage by magnetic separation. Parameters like precipitants (type, amount, and ratio), glutaraldehyde concentration, and enzyme load were optimized for the preparation of chitosan-coated magnetic nanocomposites of cross-linked VM-αGal (VM-αGal-MC) and VM-αGal (VM-αGal-M) resulted in 100% immobilization efficiency. Size and morphology of VM-αGal-M were studied through dynamic light scattering (DLS) and scanning electron microscopy (SEM), while Fourier transform infrared spectroscopy (FTIR) was used to study the chemical composition of VM-αGal-MC and VM-αGal-M. VM-αGal-MC and VM-αGal-M were found more active in a broad range of pH (3-8) and displayed optimal temperatures up to 25 °C higher than VM-αGal. Addition of non-ionic detergents (except Tween-40) improved VM-αGal-MC activity by up to 44% but negatively affected VM-αGal-M activity. Both VM-αGal-MC (15% residual activity after 21 min at 85 °C, E_d 92.42 kcal/mol) and VM-αGal-M (69.0% residual activity after 10 min at 75 °C, E_d 39.87 kcal/mol) showed remarkable thermal stability and repeatedly hydrolyzed the substrate for 10 cycles.

Role of carboxylic group pattern on protein surface in the recognition of iron oxide nanoparticles: A key for protein corona formation

The knowledge of protein-nanoparticle interplay is of crucial importance to predict the fate of nanomaterials in biological environments. Indeed, protein corona on nanomaterials is responsible for the physiological response of the organism, influencing cell processes, from transport to accumulation and toxicity. Herein, a comparison using four different proteins reveals the existence of patterned regions of carboxylic groups acting as recognition sites for naked iron oxide nanoparticles. Readily interacting proteins display a distinctive surface distribution of carboxylic groups, recalling the geometric shape of an ellipse. This is morphologically complementary to nanoparticles curvature and compatible with the topography of exposed Fe^III sites laying on the nanomaterial surface. The recognition site, absent in non-interacting proteins, promotes the nanoparticle harboring and allows the formation of functional protein coronas. The present work envisages the possibility of predicting the composition and the biological properties of protein corona on metal oxide nanoparticles.

Recent advances in β-galactosidase and fructosyltransferase immobilization technology

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

Fabrication of Pd NPs on pectin-modified Fe3O4 NPs: A magnetically retrievable nanocatalyst for efficient C-C and C-N cross coupling reactions and an investigation of its cardiovascular protective effects

The present report represents the synthesis of a novel Pd NPs immobilized over a natural polysaccharide (pectin) coated Fe₃O₄ magnetic nanocomposite material (Fe₃O₄@pectin/Pd) for investigating the cardiovascular protective effects. The biomolecular functionalization not only stabilizes the ferrite nanoparticles from agglomeration but also provides an environment for the biogenic reduction of Pd²⁺ ions. This protocol is a promising breakthrough for the synthesis of a quasi-heterogeneous catalyst, a bridge between heterogeneous and homogeneous medium. The structure, morphology and physicochemical properties of the material were characterized utilizing various analytical techniques like FT-IR, FE-SEM, TEM, VSM, EDX-elemental mapping, ICP, EDX and XPS. The catalyst showed excellent reactivity in C-C and C-N cross coupling reactions via Suzuki and Buchwald-Hartwig reactions respectively. An array of different biphenyls and aryl amines were then procured by reactions of various aryl halides with phenylboronic acid or secondary amines over the catalyst affording good to excellent yields. The catalyst was easily recoverable using an external magnet and thereafter recycled for several trials with insignificant palladium leaching or loss in catalytic performance. To investigate the cardiovascular protective activities of catalyst, the MTT assay was done on Human Aortic Endothelial Cells (HAEC), Human Coronary Artery Endothelial Cells (HCAEC), and Human Pulmonary Artery Endothelial Cells (HPAEC) cell lines. Nanocatalyst-treated cell cutlers significantly (p ≤ 0.01) decreased the caspase-3 activity, and DNA fragmentation. It raised the cell viability and mitochondrial membrane potential in the high concentration of Mitoxantrone-treated HAEC, HCAEC, and HPAEC cells. According to the above findings, nanocatalyst can be administrated as a cardiovascular protective drug for the treatment of cardiovascular diseases after approving in the clinical trial studies in humans.

Enzyme Immobilization on Maghemite Nanoparticles with Improved Catalytic Activity: An Electrochemical Study for Xanthine

Generally, enzyme immobilization on nanoparticles leads to nano-conjugates presenting partially preserved, or even absent, biological properties. Notwithstanding, recent research demonstrated that the coupling to nanomaterials can improve the activity of immobilized enzymes. Herein, xanthine oxidase (XO) was immobilized by self-assembly on peculiar naked iron oxide nanoparticles (surface active maghemite nanoparticles, SAMNs). The catalytic activity of the nanostructured conjugate (SAMN@XO) was assessed by optical spectroscopy and compared to the parent enzyme. SAMN@XO revealed improved catalytic features with respect to the parent enzyme and was applied for the electrochemical studies of xanthine. The present example supports the nascent knowledge concerning protein conjugation to nanoparticle as a means for the modulation of biological activity.

Immobilization of β-Glucosidase from Thermatoga maritima on Chitin-functionalized Magnetic Nanoparticle via a Novel Thermostable Chitin-binding Domain

Enzyme immobilization is a powerful tool not only as a protective agent against harsh reaction conditions but also for the enhancement of enzyme activity, stability, reusability, and for the improvement of enzyme properties as well. Herein, immobilization of β-glucosidase from Thermotoga maritima (Tm-β-Glu) on magnetic nanoparticles (MNPs) functionalized with chitin (Ch) was investigated. This technology showed a novel thermostable chitin-binding domain (Tt-ChBD), which is more desirable in a wide range of large-scale applications. This exclusive approach was fabricated to improve the Galacto-oligosaccharide (GOS) production from a cheap and abundant by-product such as lactose through a novel green synthesis route. Additionally, SDS-PAGE, enzyme activity kinetics, transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) revealed that among the immobilization strategies for Thermotoga maritime-β-Glucosidase thermostable chitin-binding domain (Tm-β-Glu-Tt-ChBD) on the attractive substrate; Ch-MNPs had the highest enzyme binding capacity and GOS production ratio when compared to the native enzyme. More interestingly, a magnetic separation technique was successfully employed in recycling the immobilized Tm-β-Glu for repetitive batch-wise GOS without significant loss or reduction of enzyme activity. This immobilization system displayed an operative stability status under various parameters, for instance, temperature, pH, thermal conditions, storage stabilities, and enzyme kinetics when compared with the native enzyme. Conclusively, the GOS yield and residual activity of the immobilized enzyme after the 10^th cycles were 31.23% and 66%, respectively. Whereas the GOS yield from native enzyme synthesis was just 25% after 12 h in the first batch. This study recommends applying Tt-ChBD in the immobilization process of Tm-β-Glu on Ch-MNPs to produce a low-cost GOS as a new eco-friendly process besides increasing the biostability and efficiency of the immobilized enzyme.

Nanoparticles decorated carbon nanotubes as novel matrix: A comparative study of influences of immobilization on the catalytic properties of Lensculinarisβ-galactosidase (Lcβ-gal)

In the present study, Multiwalled carbon nanotubes (MWCNT) decorated with two different nanoparticles namely tungsten disulfide (WS₂) and tin oxide (SnO₂), nanocomposites (NCs) were synthesized via hydrothermal method. Spectroscopic studies showed that both synthesized NCs possess nearly same functional groups but MWCNT-SnO₂ NCs are rich in O-functional group. Microscopic studies revealed that both NCs have different morphological microstructure. Lens culinaris β-galactosidase (Lcβ-gal) was immobilized using glutaraldehyde cross-linker resulted in immobilization efficiency of 91.5% and 88% with MWCNT-WS₂ and MWCNT-SnO₂ NCs, respectively. Remarkable increase in rate of hydrolysis of whey lactose has been observed with both NCs i.e. Lcβ-gal immobilized MWCNT-WS₂ hydrolyzes the 97% whey lactose in 1.5 h while MWCNT-SnO₂ showed maximum 92% of whey hydrolysis in 2 h at optimum conditions. Both nanobiocatalyst could serve as a promising candidates for dairy industries and would offer a potential platform for enzyme based biosensor fabrication.

Immobilization of bromelain on cobalt-iron magnetic nanoparticles (CoFe2O4) for casein hydrolysis

By means of recycling an enzyme, bromelain was used in casein hydrolysis facilitated by a nanobiocatalyst consisting of bromelain, CoFe2O4 magnetic nanoparticles, chitosan, and glutaraldehyde. Bromelain was immobilized on the chitosan cobalt-magnetite nanoparticle surface via covalent bonds to form the nanobiocatalyst. Immobilized bromelain showed 77% immobilization binding, retaining 85 ± 2% of the initial catalytic activity. Nanoparticles and immobilized bromelain were characterized using UV-Vis and IR spectroscopies, X-ray, square wave voltammetry (SWV), cyclic voltammetry (CV), vibrating-sample magnetization (VSM), and transmission electron microscope (TEM). The Michaelis-Menten constant (KM) and VMAX of the free and immobilized enzyme were calculated: KM = 2.1 ± 0.18 mM and 1.8 mM, respectively and VMAX = 6.08 x 10-2 ± 2.1 x 10-2 U/min and 6.46 ± 0.91 U/min, respectively. The thermal stability of the free enzyme was higher than the immobilized enzyme: 95-98% and 83-87%, respectively. An optimum pH of 6 and a temperature of 20 °C were determined in both cases. Immobilized bromelain maintained 50% of the initial catalytic activity after the fifth use. The immobilized bromelain proved to be effective and reusable for casein hydrolysis. As novel contribution the characterization by VOC and CV was carried out.