Calcium pectate gel beads for cell entrapment. 3. Physical properties of calcium pectate and calcium alginate gel beads
1991
Gemeiner, P. | Kurillova, L. | Markovic, O. | Malovikova, A. | Uhrin, D. | Ilavsky, M. | Stefuca, V. | Polakovic, M. | Bales, V.
Calcium pectate gel beads were found to have remarkable mechanical properties. These, particularly deformability and penetration modulus, were extremely dependent on the mode of deesterification of pectin. Deesterification catalyzed by pectinesterase is advantageous because the undesired depolymerization of pectin, occurring in alkaline deesterification, is much reduced. The relative high water solubility (less than or equal to 10%) of pectates prepared by enzymatic deesterification of apple and citrus pectin permits the preparation of calcium pectate beads of a high polysaccharide concentration (less than or equal to 7.8%). Stress-strain dependence of single beads in compression showed an elastic behavior typical for swollen beads of cellulose or carboxylic cation exchangers. in the entire range of polysaccharide concentration (1.5-10%) the beads of the enzymatically deesterified apple and citrus pectin showed a several times higher penetration modulus (calculated from stress-strain dependences) than calcium alginate beads. Not even the highest pectate concentration in the beads could substantially influence the diffusion rate of the low-molecular-weight solute (glucose) in the gel. The storage stability of calcium pectate gel beads was studied. In the presence of 0.1 M phosphate buffer (pH 7.5) the beads were destroyed within 1-2 days. The storage stability in water and 50 mM acetate buffer (pH 4.65) was high, over 1 month.
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