Encapsulation of β-Glucuronidase in Biomimetic Alginate Capsules for Bioconversion of Baicalin to Baicalein

Baicalin was converted into baicalein by β-glucuronidase (GUS) encapsulated in liquid-core alginate capsules, mimicking the natural enzyme existence in lysosome. Taking both the physical properties of the capsule and the activity of the encapsulated enzyme into account, optimal conditions (1.0% w/v sodium alginate; 0.10 mol/L CaCl 2; 30 min gelation time) for GUS encapsulation were determined. The encapsulated GUS retained up to 88% of its free-form activity with an encapsulation efficiency of 77%. Conversion of baicalin by free and encapsulated GUS resulted in the baicalein productivities of 80% and 65%, respectively. The optimal temperature (60 °C) and pH value (pH 7.0) for bioconversion were not changed after encapsulation. In addition, the encapsulated GUS showed no appreciable loss in activity after four repeated cycles, and 90% of its initial activity remained after 26-day storage at 4 °C.