Magnetic Polymeric Beads Functionalized with Different Mixed-Mode Ligands for Reversible Immobilization of Trypsin

Biomass-derived magnetic nanocomposites modified by choline chloride/citric acid based natural deep eutectic solvents for the magnetic solid phase extraction of trypsin

A novel biomass-derived magnetic nanocomposite of Fe₃O₄-Chitin@NADES-CC composed of a natural deep eutectic solvent (NADES), biological polysaccharide (Chitin) and magnetic Fe₃O₄ was synthesized. After being systematically characterized by Fourier transform infrared spectrometry, thermogravimetry, vibrating sample magnetometry, X-ray diffraction, transmission electron microscopy and dynamic light scattering, Fe₃O₄-Chitin@NADES-CC was used as an extractant to separate trypsin (Tryp) on the basis of magnetic solid phase extraction. Simultaneously, the extraction conditions of Fe₃O₄-Chitin@NADES-CC for Tryp were investigated in turn by single-factor experiments, including screening the types of extractants, the initial concentration of Tryp, the pH value of the solution, the influence of ionic strength, extraction time and temperature, etc. Under the optimal conditions, the extraction capacity of Fe₃O₄-Chitin@NADES-CC for Tryp could reach up to 1082.67 mg g^-1. Adsorption isotherm tests certified that the Langmuir adsorption equilibrium fitted well with the extraction model in this study, which showed that the extraction of Fe₃O₄-Chitin@NADES-CC for Tryp was monolayer adsorption. In addition, in the sections on the regeneration-reuse, selectivity and methodological studies, all the results exhibited the superiority of the Fe₃O₄-Chitin@NADES-CC and Tryp separation strategy which has been established in this work. Finally, Fe₃O₄-Chitin@NADES-CC was ultimately applied to the separation of Tryp from a real bovine pancreas crude extract by the analysis of SDS-PAGE. All the above results highlight that the proposed Fe₃O₄-Chitin@NADES-CC biomass-derived magnetic nanocomposite can be applied in the field of protein purification.

Excellent performance separation of trypsin by novel ternary magnetic composite adsorbent based on betaine-urea- glycerol natural deep eutectic solvent modified MnFe2O4-MWCNTs

The effective trypsin purification methods should be established since trypsin plays a crucial role in biosome. In this work, a novel ternary magnetic composite adsorbent (MnFe₂O₄-MWCNTs@B-U-G) with the features of strong specific selectivity, good adsorption effect, simple and efficient separation process, no secondary pollution brought in was prepared by integrating the superior physicochemical properties of ternary based natural deep eutectic solvent, multi-walled carbon nanotubes and MnFe₂O₄. The property, composition and microtopography structure of MnFe₂O₄-MWCNTs@B-U-G were characterized in detail. Combined with magnetic solid-phase extraction, MnFe₂O₄-MWCNTs@B-U-G was utilized to adsorb trypsin. Response surface methodology experiment was prepared under Box-Behnken design to optimize the adsorption conditions and the results showed that the practical maximum adsorption capacity for trypsin was 1020.1 mg g^-1. Besides, the adsorption isotherms, adsorption kinetics, regeneration studies and method validation studies were investigated systematically to evaluate the established adsorption separation system. Mechanism exploration proved that electrostatic interaction, hydrogen bonding interaction and chelation interaction were the dominant forces for the high-performance adsorption of trypsin. The activity of trypsin after elution had been analyzed by UV-vis spectrophotometer and CD spectrometer with three methods, which illustrated that the enzyme activity, conformation and secondary structure of trypsin did not change significantly during the adsorption-desorption process. In addition, the proposed method was successful and practical applicability to isolation trypsin from crude bovine pancreas. As a result, due to the superiority of the MnFe₂O₄-MWCNTs@B-U-G, the proposed method not only exhibites high-performance adsorption of trypsin, but also provides a green and sustainable potential value in the adsorption of biomacromolecule.

Zinc oxide nanoparticles-impregnated chitosan surfaces for covalent immobilization of trypsin: Stability & kinetic studies

Trypsin (Try, EC. 3.4.21.4) was effectively immobilized on the surface of glutaraldehyde(GA)-activated ZnO/Chitosan nanocomposite through covalent attachment via Schiff-base linkages. Size, structure, surface morphology, & percentage elemental composition of the prepared ZnO nanoparticles and chitosan-coated ZnO nanocomposite were studied by UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction analysis (XRD), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and Energy-Dispersive X-Ray Microanalysis (EDAX) techniques. Optimal immobilization conditions (incubation time (16 h), enzyme concentration (1.8 mg/ml), and pH (7.8)) were investigated to obtain the maximum expressed activity of the immobilized trypsin. Immobilized & solubilized trypsin exhibited the optimum catalytic activity at pH 8.5, 60 °C, and pH 7.8, 45 °C respectively. Kinetic parameters (K_m, V_max) of immobilized (27.12 μM, 8.82 μM/min) & free trypsin (25.76 μM, 4.16 μM/min) were determined, indicating that efficiency of trypsin improves after immobilization. Immobilized trypsin preserved 67% of initial activity at 50 °C during 2 h of incubation & sustained nearly 50% of catalytic activity until the 9th repeated cycle of utilization. Moreover, immobilized trypsin retained 50% of enzymatic activity after 90 days of storage at 4 °C. Hence, the current findings suggest that ZnO/Chitosan-GA-Trypsin would be a promising biocatalyst for large-scale biotechnological applications.

Deviation of Trypsin Activity Using Peptide Conformational Imprints

In this study, a methodology utilizing peptide conformational imprints (PCIs) as a tool to specifically immobilize porcine pancreatic alpha-trypsin (PPT) at a targeted position is demonstrated. Owing to the fabrication of segment-mediated PCIs on the magnetic particles (PCIMPs), elegant cavities complementary to the PPT structure are constructed. Based on the sequence on targeted PPT, the individual region of the enzyme is trapped with different template-derived PCIMPs to show certain types of inhibition. Upon hydrolysis, N-benzoyl-L-arginine ethyl ester (BAEE) is employed to assess the hydrolytic activity of PCIMPs bound to the trypsin using high-performance liquid chromatography (HPLC) analysis. Further, the kinetic data of four different PCIMPs are compared. As a result, the PCIMPs presented non-competitive inhibition toward trypsin, according to the Lineweaver-Burk plot. Further, the kinetic analysis confirmed that the best parameters of PPT/PCIMPs 233-245+G were Vmax = 1.47 × 10-3 mM s-1, Km = 0.42 mM, kcat = 1.16 s-1, and kcat/Km = 2.79 mM-1 s-1. As PPT is bound tightly to the correct position, its catalytic activities could be sustained. Additionally, our findings stated that the immobilized PPT could maintain stable activity even after four successive cycles.

Alcalase Microarray Base on Metal Ion Modified Hollow Mesoporous Silica Spheres as a Sustainable and Efficient Catalysis Platform for Proteolysis

The industrial exploitation of protease is limited owing to its sensitivity to environmental factors and autolysis during biocatalytic processes. In the present study, the alcalase microarray (Bacillus licheniformis, alcalase@HMSS-NH₂-Metal) based on different metal ions modified hollow mesoporous silica spheres (HMSS-NH₂-Metal) was successfully developed via a facile approach. Among the alcalase@HMSS-NH₂-Metal (Ca²⁺, Zn²⁺, Fe³⁺, Cu²⁺), the alcalase@HMSS-NH₂-Fe³⁺ revealed the best immobilization efficiency and enzymatic properties. This tailor-made nanocomposite immobilized alcalase on a surface-bound network of amino-metal complex bearing protein-modifiable sites via metal-protein affinity. The coordination interaction between metal ion and alcalase advantageously changed the secondary structure of enzyme, thus significantly enhanced the bioactivities and thermostability of alcalase. The as-prepared alcalase@HMSS-NH₂-Fe³⁺ exhibited excellent loading capacity (227.8 ± 23.7 mg/g) and proteolytic activity. Compared to free form, the amidase activity of alcalase microarray increased by 5.3-fold, the apparent kinetic constant V_max/K_m of alcalase@HMSS-NH₂-Fe³⁺ (15.6 min⁻¹) was 1.9-fold higher than that of free alcalase, and the biocatalysis efficiency increased by 2.1-fold for bovine serum albumin (BSA) digestion. Moreover, this particular immobilization strategy efficiently reduced the bioactivities losses of alcalase caused by enzyme leaking and autolysis during the catalytic process. The alcalase microarray still retained 70.7 ± 3.7% of the initial activity after 10 cycles of successive reuse. Overall, this study established a promising strategy to overcome disadvantages posed by free alcalase, which provided new expectations for the application of alcalase in sustainable and efficient proteolysis.

Hydrolysis of casein from different sources by immobilized trypsin on biochar: Effect of immobilization method

The present study aimed to evaluate the effect of the immobilization method of trypsin on biochar on the hydrolysis of casein from different sources, when compared to the process using trypsin in native form, to obtain bioactive peptides. The modification of the surface of biochar with glutaraldehyde was effective, as shown by the results of FTIR assay and the texture profile of the materials. Both activated and functionalized biochar showed high immobilization efficiency (greater than 87%) and high binding capacity (greater than 91 mg/g). During hydrolysis, the biocatalyst obtained by enzyme immobilization on the functionalized biochar presented a higher hydrolysis capacity for the different caseins when compared to the enzyme immobilized by adsorption, with values of 3.05 and 2.73 U/mg for goat casein, 2.36 and 1.85 U/mg for bovine casein, and 2.60 and 2.37 U/mg for buffalo, casein, respectively, with 60 min of reaction. The results of inhibitory activity in this study ranged from 93.5% and 25.5% for trypsin in its free form and immobilized on functionalized activated carbon, respectively, under the same reaction conditions. The immobilization methods were efficient, presenting high immobilization capacity. The proteolytic activity of trypsin immobilized via covalent binding was higher when compared the immobilization by adsorption. Thus, the functionalized biochar has proven to be potential support for enzyme immobilization, and the biocatalyst can be reused for more than 4 cycles. Despite lower ACE inhibition values of hydrolyzed obtained with the immobilized enzymes compared to free enzymes, biocatalysts present advantage due to the possibility of reuse.

Fabrication of Microporous Metal-Organic Frameworks in Uninterrupted Mesoporous Tunnels: Hierarchical Structure for Efficient Trypsin Immobilization and Stabilization

Hierarchically porous metal-organic frameworks (HP-MOFs) are promising in various applications. Most reported HP-MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as-prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor-induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record-high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites.

Covalent immobilization of trypsin on polyvinyl alcohol-coated magnetic nanoparticles activated with glutaraldehyde

Magnetic nanoparticles were coated with polyvinyl alcohol and activated with glutaraldehyde for trypsin immobilization. The prepared magnetic nanoparticles were characterized by transmission electron microscopy, fourier transform infrared spectroscopy, thermal gravimetric analysis, zeta potential meter and vibrating sample magnetometer. Free and immobilized trypsin showed optimum activity at pH 6.0, 30 °C and pH 7.0, 40 °C, respectively. Immobilized trypsin was more stable than the free enzyme at 40 °C. After immobilization, K_m of the immobilized trypsin increased, however, V_max value was almost the same with free trypsin. According to the results, the immobilized trypsin retained 50 % of its initial activity, whereas free trypsin retained 19 % of its initial activity after 12-days at 4 °C. Immobilized trypsin sustained 56 % of its initial activity after eight times of successive reuse. The performance of the immobilized trypsin was evaluated by digestion of cytochrome c. The peptide fragments in digest solution were determined by using MALDI-TOF mass spectrometry. Immobilized trypsin showed effective proteolytic activity in shorter time (15 min) than free trypsin (24 h). Hence, immobilized trypsin on the polyvinyl alcohol coated magnetic nanoparticles could be promising biocatalyst for large-scale proteomics studies and practical applications.

Covalent Immobilization of Cellulase Using Magnetic Poly(ionic liquid) Support: Improvement of the Enzyme Activity and Stability

A magnetic nanocomposite was prepared by entrapment of Fe₃O₄ nanoparticles into the cross-linked ionic liquid/epoxy type polymer. The resulting support was used for covalent immobilization of cellulase through the reaction with epoxy groups. The ionic surface of the support improved the adsorption of enzyme, and a large amount of enzyme (106.1 mg/g) was loaded onto the support surface. The effect of the presence of ionic monomer and covalent binding of enzyme was also investigated. The structure of support was characterized by various instruments such as FT-IR, TGA, VSM, XRD, TEM, SEM, and DLS. The activity and stability of immobilized cellulase were investigated in the prepared support. The results showed that the ionic surface and covalent binding of enzyme onto the support improved the activity, thermal stability, and reusability of cellulase compared to free cellulase.

Spheres-on-sphere silica microspheres as matrix for horseradish peroxidase immobilization and detection of hydrogen peroxide

Spheres-on-sphere (SOS) silica microspheres are employed as a matrix for horseradish peroxidase (HRP) immobilization. The SOS-COOH-HRP shows excellent catalytic performance and stability.