Stabilization and controlled release of invertase through the addition of trehalose in wet and dried alginate-chitosan beads

SANTAGAPITA, PATRICIO R.; MAZZOBRE, MARÍA FLORENCIA; BUERA, MARÍA DEL PILAR

Water Stress in Biological, Chemical, Pharmaceutical and Food Systems

Springer

Año: 2015; p. 353 - 360

Alginate beads have been thoroughly investigated in search of suitable matrices for biomolecule stabilization, controlled release and delivery. As alternatives to the conventional composition for beads preparation, trehalose was added to the external gelation media and chitosan was used as a coating material. The addition of trehalose to the external calcium gelation media and chitosan as a coating agent and the effect of drying method (freeze-drying or vacuum-drying) were evaluated and related to enzyme release kinetics was also evaluated. Beads were prepared by the dropping method, obtaining spherical beads. The size (about 1.5 mm diameter) and morphology of the beads were analyzed by optical microscopy and by scanning electron microscopy. After drying, beads had drastically reduced their size, and showed lower circularity, particularly during freeze drying. The drying method affected the size and shape of the capsules more than the composition change. The wet alginate beads showed diffusional release of the enzyme. The addition of trehalose and chitosan modified the capsule structure, leading to a release mechanism which included the relaxation of the polymerchains, besides fickean diffusion. Enzyme release from vacuum dried beads was much faster than from freeze dried beads, probably due to their higher porous size. Chitosan addition also increased the release rate from freeze dried alginate-trehalose beads. Through the use of a semi-empirical equation, certain characteristics of the enzyme release mechanism could be established. Trehalose and chitosan inclusion, hydration degree and drying method greatly influence the transport mechanism of enzyme release in alginate beads.