Preparation of Chitosan Beads for Trypsin Immobilization

Efficiency Assessment between Entrapment and Covalent Bond Immobilization of Mutant β-Xylosidase onto Chitosan Support

The Y509E mutant of β-xylosidase from Geobacillus stearothermophilus (XynB2Y509E) (which also bears xylanase activity) has been immobilized in chitosan spheres through either entrapment or covalent bond formation methods. The maximum immobilization yield by entrapment was achieved by chitosan beads developed using a 2% chitosan solution after 1 h of maturation time in CFG buffer with ethanol. On the other hand, the highest value in covalent bond immobilization was observed when employing chitosan beads that were prepared from a 2% chitosan solution after 4 h of activation in 1% glutaraldehyde solution at pH 8. The activity expressed after immobilization by covalent bonding was 23% higher compared to the activity expressed following entrapment immobilization, with values of 122.3 and 99.4 IU.g-1, respectively. Kinetic data revealed that catalytic turnover values were decreased as compared to a free counterpart. Both biocatalysts showed increased thermal and pH stability, along with an improved storage capacity, as they retained 88% and 40% of their activity after being stored at 4 °C for two months. Moreover, XynB2Y509E immobilized by covalent binding also exhibited outstanding reusability, retaining 92% of activity after 10 cycles of reuse. In conclusion, our results suggest that the covalent bond method appears to be the best choice for XynB2Y509E immobilization.

The bonding nature of the chemical interaction between trypsin and chitosan based carriers in immobilization process depend on entrapped method: A review

The review article is dedicated to a comprehensive study of the chemical bond formed during the immobilization of the proteolytic enzyme pancreatic trypsin in chitosan-based polymer matrixes and its derivatives. The main focus of the study is to describe the chemical bond that causes immobilization between chitosan based carriers and trypsin. Because the nature of the chemical bond between the carrier and trypsin is a key factor in determining the area of application of the conjugate. It has been found out that after the chemical nature of functional groups, their degree of ionization, the structure of the chemical cross-linking, the medium pH and ionic strength of chitosan are modified, the mechanism of trypsin immobilization is affected. As a result, the attraction enzyme to the matrix occurs due to polar covalent and hydrogen bonds, as well as electrostatic, hydrophobic, Van der Waals forces. The collected research works on the immobilization of trypsin on chitosan-based carriers have been systematized in the paper and shown schematically in subsystems according to the type of chemical interaction. It has been shown that the immobilization of trypsin on chitosan based matrixes occur more often due to the covalent and hydrogen bonds between the protein and the carrier.

Effective phosphorus removal using chitosan/Ca-organically modified montmorillonite beads in batch and fixed-bed column studies

In this study, phosphorus removal from aqueous solution was investigated using chitosan/Ca-organically modified montmorillonite (chitosan/Ca-OMMT) beads in batch and fixed-bed column systems. The XPS spectra confirmed that the calcium ions on the surface of the beads play a dominant role in capturing phosphate ions through surface complexation. The batch adsorption experimental data were fitted with pseudo-second-order kinetics and the Langmuir isotherm. The maximum adsorption capacity of the chitosan/Ca-OMMT beads was found to be 76.15 mg/g at an initial phosphate concentration of 100 mg/L at 25 °C. High phosphate uptake is achieved over the wide pH range 3-11, as well as in the presence of competing anions such as Cl^-, NO₃^-, SO₄^2-, and HCO₃^-. Furthermore, the chitosan/Ca-OMMT beads can be easily regenerated using 0.1 mol/L NaOH as a desorption agent with more than 83.97% adsorption capacity remaining after five adsorption/desorption cycles. The Thomas, Yoon-Nelson, and Adams-Bohart models were applied to the experimental data to predict the breakthrough curves using non-linear regression; the Yoon-Nelson model showing the best agreement with the breakthrough curves. These findings demonstrate that chitosan/Ca-OMMT beads can be used as a cost-effective and environment-friendly adsorbent for the removal of phosphate from wastewater.

Enzyme Immobilization on Metal-Organic Framework (MOF): Effects on Thermostability and Function

MOFs are porous materials with adjustable porosity ensuing a tenable surface area and stability. MOFs consist of metal containing joint where organic ligands are linked with coordination bonding rendering a unique architecture favouring the diverse applications in attachment of enzymes, Chemical catalysis, Gases storage and separation, biomedicals. In the past few years immobilization of soluble enzymes on/in MOF has been the topic of interest for scientists working in diverse field. The activity of enzyme, reusability, storage, chemical and thermal stability, affinity with substrate can be greatly improved by immobilizing of enzyme on MOFs. Along with improvement in enzymes properties, the high loading of enzyme is also observed while using MOFs as immobilization support. In this review a detail study of immobilization on/in Metalorganic Frameworks (MOFs) have been described. Furthermore, strategies for the enzyme immobilization on MOFs and resulting in improved catalytic performance of immobilized enzymes have been reported.

Limited proteolysis in porous membrane reactors containing immobilized trypsin

Trypsin-containing membranes effect limited digestion to identify facile digestion sites in protein structures.

Immobilization of acid phosphatase from Vigna aconitifolia seeds on chitosan beads and its characterization

Acid phosphatase isolated from Vigna aconitifolia seeds was immobilized onto glutaraldehyde activated chitosan beads by crosslinking method. Chitosan beads activated with 2% of glutaraldehyde have demonstrated maximum immobilization yield (∼ 83%). The immobilized enzyme showed optimum activity at pH 7.0, while soluble form was maximally active in acidic range (pH 5.0). With respect to free form, immobilized acid phosphatase showed better activity in alkaline range. On the other side, immobilization does not affect the optimum temperature range i.e., both, soluble and immobilized acid phosphatase exhibited maximum activity at 60 °C. The Km and Vmax values for the immobilized enzyme were calculated to be 0.37 mM and 13.5 U/mg. The immobilization on chitosan beads enhanced the shelf life of acid phosphatase. The immobilized enzyme retained its more than 50% hydrolytic activity for approximately two months. The immobilized acid phosphatase was reusable for more than 40 cycles of reaction.