Immobilization and characterization of a thermostable β-xylosidase to generate a reusable biocatalyst

Enzymatic glycosylation of bioactive acceptors catalyzed by an immobilized fungal β-xylosidase and its multi-glycoligase variant

A recombinant β-xylosidase (rBxTW1) from the ascomycete Talaromyces amestolkiae and a mutant derived from it, with mostly synthetic activity, have been immobilized as magnetic cross-linked enzyme aggregates (mCLEAs). The mCLEAs of rBxTW1 kept the excellent hydrolytic and O-transxylosylating activities of the free enzyme and had improved thermal and pH stability. The mCLEAs of the mutant also maintained or improved the catalytic properties of the soluble enzyme, synthetizing the O-xylosides of vanillin and (-)-epigallocatechin gallate, and the N- and S-xyloside of 3,5-dibromo-1,2,4-triazole and thiophenol, respectively. The mCLEAs were recyclable across 4 cycles of synthesis of the O-xylosides through a green and highly selective process. The magnetic properties of the scaffold used for immobilization may allow the easy recovery and reuse of the biocatalyst even from reactions containing insoluble lignocellulosic biomass.

Xylan degradation improved by a combination of monolithic columns bearing immobilized recombinant β-xylosidase from Aspergillus awamori X-100 and Grindamyl H121 β-xylanase

Synergistic action of exo- and endohydrolazes is preferred for effective destruction of biopolymers. The main purpose of the present work was to develop an efficient tool for degradation of xylan. Macroporous lab-made monolithic columns and commercial CIM-Epoxy disk were used to immobilize the recombinant β-xylosidase from Aspergillus awamori and Grindamyl β-xylanase. The efficiency of xylan degradation using the low-loaded β-xylosidase column appeared to be four times higher than for the in-solution process and about six times higher than for the high-loaded bioreactor. Disk bioreactor with the Grindamil β-xylanase operated in a recirculation mode has shown noticeable advantages over the column design. Additionally, a system comprised of two immobilized enzyme reactors (IMERs) was tested to accelerate the biopolymer hydrolysis, yielding total xylan conversion into xylose within 20 min. Fast online monitoring HPLC procedure was developed where an analytical DEAE CIM disk was added to the two-enzyme system in a conjoint mode. A loss of activity of immobilized enzymes did not exceed 7% after 5 months of the bioreactor usage. We can therefore conclude that the bioreactors developed exhibit high efficiency and remarkable long-term stability.

Optimization and Immobilization of Purified Labeo rohita Visceral Protease by Entrapment Method

The purified fish visceral protease enzyme was immobilized by using various concentrations of sodium alginate and calcium chloride to optimize the best concentration for the formation of the beads. Then it was characterized by assaying the optimal pH, temperature, storage stability and reusability. The results on immobilization with sodium alginate and calcium chloride showed that a combination of 2% sodium alginate and 0.3 M calcium chloride weas found to be the optimum concentration for the formation of spherical and stable beads, this gave a maximal entrapped activity of 48.31%, and there was no change in the optimum pH 8.0 and temperature 40°C of protease before and after entrapment. The results on stability and reusability indicated that it was stable at 4°C retaining 100% residual activity after 5 days of storage and 67% loss of activity after ten days of storage and it retained 100% residual activity on the first reuse, 75% residual activity on the second reuse, 25% residual activity on the third use and complete loss in the activity on the fourth reuse.

Multifunctional nanoadditives for the thermodynamic and kinetic stabilization of enzymes

Stabilization of enzymes has become a major focus in the quest to improve the activity, sustainability and recyclability of enzymes for their successful integration into both industry and medicine. Here, we describe the kinetic and thermodynamic stabilization of a variety of enzymes in the presence of cationic multifunctional polymeric nanoparticles.

Biocatalytic conversion of wheat bran hydrolysate using an immobilized GH43 beta-xylosidase

To investigate the concept of a xylosidase-based process for the continuous production of xylose from arabinoxylan-containing feedstocks, a beta-xylosidase from Bacillus halodurans C-125 was immobilized and deployed in packed bed reactor (PBR). Among the several immobilization methods tested, glutaraldehyde-mediated immobilization on chitosan was the best both in terms of immobilization and activity yields (91% and 72.9%, respectively). In batch experiments the immobilized enzyme hydrolyzed wheat bran hydrolysates quite efficiently, consuming nearly all xylobiose and xylotriose after 6h. Its reusability showed only a 50% decrease of its activity after 92h. Using the chitosan-immobilized beta-xylosidase in a PBR, xylose productivity was 7.2g xylose l(-1)h(-1) and the conversion factor was 0.55 (derived from initial xylose in the substrate). The operational stability of the PBR was good, because only 25% of productivity was lost after the treatment of three batches of substrate over a 72-h period.

Stable and continuous long-term enzymatic reaction using an enzyme–nanofiber composite

This study shows the preparation and application of enzyme-nanofiber composites for long-term stable operation. The enzyme-nanofiber composite was prepared by coating an enzyme aggregate, the esterase from Rhizopus oryzae, on the surface of the nanofibers. After immobilization on the nanofiber, the apparent K ( m ) for the immobilized esterase was 1.48-fold higher than that of the free esterase, with values of 0.98 and 1.35 mM for the free and immobilized enzymes, respectively. It was found that enzyme-nanofiber was very stable, even when the fibers were shaken in glass vials, preserving 80% of the initial activity for 100 days. In addition, the enzyme-nanofiber composite was used repeatedly in 30 cycles of substrate hydrolysis and still remained active. Consequently, the esterase-nanofiber composite was employed within a continuous reactor system to evaluate its use in a long-term and stable continuous substrate hydrolysis reaction. It was found that the production of p-nitrophenol was stable for at least 400 h. This study demonstrates that the enzyme-nanofiber composite can be used in both repeated-batch mode and a continuous mode for a long-term stable operation.