Effect of the composition, ph and type of drying on enzyme release from dried and wet polyelectrolyte capsules.

SANTAGAPITA, PATRICIO R.; MAZZOBRE, MARÍA F.; BUERA, MARÍA DEL P.

Trieste

Congreso; Frontiers in Water Biophysics; 2010

The encapsulation procedure takes advantages of the immobilization process, which facilitates a wide variety of chemical and biological process. In search of suitable matrices for biomolecule stabilization and delivery, ionically crosslinked hydrogels, such as alginate capsules have been thoroughly investigated. On the other hand, the conservation of labile biomolecules is generally performed in dehydrated or frozen media, being saccharides (especially trehalose) among of the most used excipient. Alginate and pectin are of the most popular anionic polyelectrolytes used for capsule preparation and form gel structures in contact with CaCl2 solution; chitosan, a cationic polyelectrolyte, is frecuently used for coating beads produced after alginate or pectin gelation. As an alternative to the conventional composition for the preparation of capsules, trehalose was added to alginate, alginate chitosan-coated and alginate/ pectin beads in the external calcium gelation media in order to evaluate the release of an enzyme (invertase) on dried and wet capsules. Drying was performed by two different methods: freeze-drying and vacuum-drying. Invertase (â-fructofuranosidase) is an enzyme of high technological impact in the production of invert sugar. The purpose of this work was to evaluate the effect of capsule composition, pH and drying methods on the release of invertase from dried and wet capsules. Capsules were obtained by dropping alginate (1% w/v) or alginate/pectin (1% w/v, 3:1 mass ratio) solution containing invertase (0,06 mg/mL) on a 2.5 % w/v CaCl2 solution with or without trehalose (20% w/v) or with or without chitosan (0.25% w/v) with a syringe, under stirring. Both solutions were adjusted to pH value of 3.8. A peristaltic pump was employed for regulating the flux of the dropping solution. Wet beads were dried by freeze-drying (12 h) and vacuum-drying (4 h at 25°C). Release studies were performed in wet beads in 50 mM acetate buffer. Three different pH values around the isoelectric point of invertase were studied: pH 3.8, 4.5 and 5.5. The remaining enzymatic activity was determined spectrophotometrically. The pH value does not only influence the relative charges of polymers and enzyme but also influences the relaxation of polymers chains which affects enzyme release. The transport mechanism form wet and dried capsules was not affected by their composition but it was mainly affected by pH and drying treatment. Freeze-dried beads showed to be an excellent system for enzyme conservation and also presented release kinetics slower than wet beads. The presence of trehalose in alginate beads improved enzyme conservation and slower the enzyme release. pH and drying methods should be regarded as important factors in order to control the release of enzyme from alginate beads. A second polymer in the beads coating formulation also may change the transport mechanism and the rate of release. pH and drying methods should be regarded as important factors in order to control the release of enzyme from alginate beads. A second polymer in the beads coating formulation also may change the transport mechanism and the rate of release. pH and drying methods should be regarded as important factors in order to control the release of enzyme from alginate beads. A second polymer in the beads coating formulation also may change the transport mechanism and the rate of release. pH and drying methods should be regarded as important factors in order to control the release of enzyme from alginate beads. A second polymer in the beads coating formulation also may change the transport mechanism and the rate of release. pH and drying methods should be regarded as important factors in order to control the release of enzyme from alginate beads. A second polymer in the beads coating formulation also may change the transport mechanism and the rate of release.