Magnetic IDA-modified hydrophilic methacrylate-based polymer microspheres for IMAC protein separation

Preparation of hyaluronan oligosaccharides by a prokaryotic beta-glucuronidase: Characterization of free and immobilized forms of the enzyme

Popularity of hyaluronan (HA) in the cosmetics and pharmaceutical industries, led to the investigation and development of new HA-based materials, with enzymes playing a key role. Beta-D-glucuronidases catalyze the hydrolysis of a beta-D-glucuronic acid residue from the non-reducing end of various substrates. However, lack of specificity towards HA for most beta-D-glucuronidases, in addition to the high cost and low purity of those active on HA, have prevented their widespread application. In this study, we investigated a recombinant beta-glucuronidase from Bacteroides fragilis (rBfGUS). We demonstrated the rBfGUS's activity on native, modified, and derivatized HA oligosaccharides (oHAs). Using chromogenic beta-glucuronidase substrate and oHAs, we characterized the enzyme's optimal conditions and kinetic parameters. Additionally, we evaluated rBfGUS's activity towards oHAs of various sizes and types. To increase reusability and ensure the preparation of enzyme-free oHA products, rBfGUS was immobilized on two types of magnetic macroporous bead cellulose particles. Both immobilized forms of rBfGUS demonstrated suitable operational and storage stabilities, and their activity parameters were comparable to the free form. Our findings suggest that native and derivatized oHAs can be prepared using this bacterial beta-glucuronidase, and a novel biocatalyst with enhanced operational parameters has been developed with a potential for industrial use.

Carboxyl-Functionalized Polymeric Microspheres Prepared by One-Stage Photoinitiated RAFT Dispersion Polymerization

Herein, we report a photoinitiated reversible addition-fragmentation chain transfer (RAFT) dispersion copolymerization of methyl methacrylate (MMA) and methyl methacrylic (MAA) for the preparation of highly monodisperse carboxyl-functionalized polymeric microspheres. High rates of polymerization were observed, with more than 90% particle yields being achieved within 3 h of UV irradiation. Effects of reaction parameters (e.g., MAA concentration, RAFT agent concentration, photoinitiator concentration, and solvent composition) were studied in detail, and highly monodisperse polymeric microspheres were obtained in most cases. Finally, silver (Ag) composite microspheres were prepared by in situ reduction of AgNO₃ using the carboxyl-functionalized polymeric microspheres as the template. The obtained Ag composite microspheres were able to catalyze the reduction of methylene blue (MB) with NaBH₄ as a reductant.

Fast and facile one-step synthesis of monodisperse thermo-responsive core–shell microspheres and applications

Highly monodisperse PMMA microspheres covered with a thermo-responsive shell were synthesized in a single step by means of photoinitiated RAFT dispersion polymerization at room temperature.

Properties of Rhodotorula gracilis D-amino acid oxidase immobilized on magnetic beads through his-tag

D-amino acid oxidase catalyzes one of the key steps in the production of semisynthetic cephalosporins. We expressed and purified recombinant Rhodotorula gracilis D-amino acid oxidase with C-terminal his-tags. This engineered enzyme was immobilized onto Ni(2+)-chelated nitrilotriacetic acid magnetic beads through the interaction between his-tag and Ni(2+). The kinetic constants, storage properties, and the reusability of the immobilized d-amino acid oxidase were determined. The effects of temperature, pH, and hydrogen peroxide on the activity of immobilized d-amino acid oxidase were also studied. The highest activity recovery was 75%. Thermal stability was improved after immobilization; the relative activity of the immobilized enzyme was 56% whereas the free enzyme was completely inactivated after incubation at 50 degrees C for 1 h. In the presence of 10 mM hydrogen peroxide, the immobilized enzyme did not show a rapid loss of activity during the first 2 h of incubation, which was observed in the case of the free enzyme; the residual activity of the immobilized enzyme after 9 h was 72% compared with 22% of the free form. The long-term storage stability was improved; the residual activity of the immobilized enzyme was 74% compared with 20% of the free enzyme when stored at room temperature for 10 d. The immobilized form retained 37% of its initial activity after 20 consecutive reaction cycles.

Lysozyme purification with dye-affinity beads under magnetic field

Magnetic poly(2-hydroxyethyl methacrylate) mPHEMA beads carrying Cibacron Blue F3GA were prepared by suspension polymerization of HEMA in the presence of Fe3O4 nano-powder. Average size of spherical beads was 80-120 microm. The beads had a specific surface area of 56.0m(2)/g. The characteristic functional groups of dye-attached mPHEMA beads were analyzed by Fourier transform infrared spectrometer (FTIR) and Raman spectrometer. mPHEMA with a swelling ratio of 68% and carrying 28.5 micromol CibacronBlueF3GA/g were used for the purification of lysozyme. Adsorption studies were performed under different conditions in a magnetically stabilized fluidized bed (i.e., pH, protein concentration, flow-rate, temperature, and ionic strength). Lysozyme adsorption capacity of mPHEMA and mPHEMA/Cibacron Blue F3GA beads were 0.8 mg/g and 342 mg/g, respectively. It was observed that after 20 adsorption-desorption cycle, mPHEMA beads can be used without significant loss in lysozyme adsorption capacity. Purification of lysozyme from egg white was also investigated. Purification of lysozyme was monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. The purity of the desorbed lysozyme was about 87.4% with recovery about 79.6%. The specific activity of the desorbed lysozyme was high as 41.586 U/mg.

Use of magnetic poly(glycidyl methacrylate) monosize beads for the purification of lysozyme in batch system

The hydrophobic affinity ligand L-tryptophan immobilized magnetic poly(glycidyl methacrylate) [m-poly(GMA)] beads in monosize form (1.6 microm in diameter) were used for the affinity purification of lysozyme from chicken egg white. The m-poly(GMA) beads were prepared by dispersion polymerization in the presence of Fe3O4 nano-powder. The epoxy groups of the m-poly(GMA) beads were converted into amino groups with 1,6 diaminohexane (i.e., spacer arm). l-tryptophan was then covalently immobilized on spacer arm attached m-poly(GMA) beads. Elemental analysis of immobilised L-tryptophan for nitrogen was estimated as 42.5 micromol/g polymer. Adsorption studies were performed under different conditions in a batch system (i.e., medium pH, protein concentration and temperature). Maximum lysozyme adsorption amount of m-poly(GMA) and m-poly(GMA)-L-tryptophan beads were 1.78 and 259.6 mg/g, respectively. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium adsorption capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the adsorption process. It was observed that after 10 adsorption-elution cycle, m-poly(GMA)-L-tryptophan beads can be used without significant loss in lysozyme adsorption capacity. Purification of lysozyme from egg white was also investigated. Purification of lysozyme was monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. It was found to be successful in achieving purification of lysozyme in a high yield of 76% with a purification fold of 71 in a single step. The specific activity of the eluted lysozyme (62,580 U/mg) was higher than that obtained with a commercially available pure lysozyme (Sigma (60,000 U/mg).