Comparative characteristic of sorbents for immobilization of α-amilase
Abstract
A comparative evaluation of the immobilization of the hydrolytic enzyme α-amylase on aminocarboxyl granular ANKB-2, ANKB-50 and fibrous K-3, AK-22-1, X-1 ion exchangers, granular MN-500 and fibrous K-1 sulfocation exchangers, nonionic sorbent Styrosorb was carried out. Methods of sorption analysis and photometry have been used to study the sorption capacity of carriers with respect to the enzyme depending on the concentration of hydrogen ions and protein in solution. It is shown that the best protein sorption is observed at pH 4.5-5.0, in the field of the isoelectric point of the protein. At a given pH, the catalytic activity of enzyme preparations was also of the greatest value.
During the adsorption immobilization of protein on the ion exchangers under study, supramolecular complexes can be realized due to hydrogen, electrostatic, van der Waals, hydrophobic interactions. During the immobilization of α-amylase on super-crosslinked sorbents (MN-500, Stirosorb), the leading role is played by hydrophobic interactions that lead to the appearance of π-π-electron interaction between the sorbat and the sorbent. The maximum catalytic activity of the obtained heterogeneous biocatalysts is 89% for the amylase-AK-22-1 complex and 92% for the amylase-Stirosorb complex from the activity of the native enzyme. It was noted that during the immobilization of α-amylase, the sorbent-water and sorbat-water interaction processes to some extent compete with the parallel sorbent-sorbat interaction process.
Using the IR method, the absorption spectra of a free and immobilized enzyme are compared. The ratio of the types of the secondary structure (a-helix, β-layers, disordered structure) is calculated according to the Bouguer-Lambert-Beer law, using the Amid II band, the oscillation type is nII. It was stated that when the protein is bound to the carriers, the structure of the enzyme changes insignificantly. It was found that heterogeneous biocatalysts immobilized on non-ionogenic Stirosorb sorbent can be used for 14 cycles in the starch hydrolysis reaction. As a result of the studies, the prospective application of the studied non-ionic super-crosslinked polymer Stirosorb and the fibrous aminocarboxylic polyelectrolyte AK-22-1 for the immobilization of α-amylase has been proved.
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References
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