Prevention of Swelling Phenomenon of Alginate Beads To Improve the Stability and Recyclability of Encapsulated Horse Liver Alcohol Dehydrogenase

Abstract

Horse Liver Alcohol Dehydrogenase (HLADH) has been immobilized on calcium‐alginate beads and used for both oxidation and reduction reactions. To avoid swelling of the beads and their subsequent breakage, calcium ions were added to both reaction and storage solutions, allowing the beads to maintain the initial structural features. The techniques used for this purpose revealed that 2 mM Ca2+ is the optimal concentration, which does not significantly change the weight of the beads, the amount of water in them, and their external and internal structure. The optimized experimental procedure has been used to verify the properties of the enzyme in terms of reusability, storage, and thermal stability. The addition of calcium ions allows the enzyme to retain more than 80 % of its initial activity for fourteen cycles and approximately 50 % at the twentieth cycle. Moreover, when the biocatalyst has been stored in a buffer solution containing 2 mM Ca2+, the retention of enzyme activity after 30 days was 100 %, compared to that measured before incubation. The encapsulated enzyme exhibits greater thermal stability than free HLADH up to at least 60 °C, preventing dimer dissociation into the two subunits.