Stability improvement of invertase via encapsulation in sodium alginate-beads: effect of composition and type of drying

SANTAGAPITA, PATRICIO R.; MAZZOBRE, M. FLORENCIA; BUERA, M. PILAR

Querétaro, México

Simposio; ISOPOW 11; 2010

ISOPOW

Alginate beads have been thoroughly investigated in search of suitable matrices for biomolecule stabilization, controlled release and delivery. On the other hand, trehalose has been found to be optimal to protect labile compounds during drying. Then, as alternatives to the conventional composition for beads preparation, trehalose was added to the external gelation media, chitosan was used as a coating material and pectin was added to the core solution. The stability of an enzyme (invertase) encapsulated was evaluated in dried and wet beads, in relation to their composition and physical characteristics. Beads were obtained by dropping alginate (1%w/v) or alginate/pectin (1%w/v, 3:1 mass ratio) solution containing invertase on a CaCl2 solution with or without trehalose (20%w/v) or chitosan (0.25%w/v) with a syringe. The beads were dried by freeze-drying, vacuum-drying or in a forced air circulation oven. Wet and dried capsules were exposed to thermal treatment (50°C). Beads were characterized by FTIR, DSC and SEM. The enzymatic activity was determined spectrophotometrically. The presence of chitosan and pectin improved enzyme conservation during beads generation. Spherical and smooth-surfaced beads were obtained (1.5 mm of diameter). Drying decreased beads size (between 25-50% of wet beads, depending of the drying method) and drastically affected invertase stability in alginate-calcium beads (< 25% of recovered activity). Trehalose incorporation in the external media greatly improved enzyme stability during drying, especially during freeze-drying. When trehalose was present, enzyme stability was similar in alginate, alginate/pectin or alginate-chitosan beads during both drying and thermal treatment. Chitosan coating or pectin addition were critical to improve beads physical integrity, protecting invertase during bead generation and allowing controlled release. However, of the employed excipients, trehalose provided the highest enzyme protective effect in beads submitted to hydric or thermal stress. Key words: enzyme stability, encapsulation, alginate, trehalose, dehydration. Founding sources: CONICET-PIP468, UBA-X024, ANPCyT-PICT32916 and 20545.