Evaluating mechanical properties of silica-coated alginate beads for immobilized biocatalysis

For continuous reactions in biochemical engineering, enzymes or whole cells are usually immobilized for structural stabilization and retention in order to ensure repetitive use. One of the most frequently used encapsulation methods is immobilization of biocatalysts in silica-coated alginate beads. The mechanical properties of these beads are of great relevance for biochemical engineering approaches where these beads are applied in stirred tanks or packed bed reactors. In this report, alginate beads prepared in gelation media of different composition and ionic strength were subsequently coated with silica shells of varying chemical composition. The resistance of these coated beads against mechanical stress was then quantitatively compared by measuring the minimal absolute static force necessary to induce breakage of the silica shell. It was found that this force and therefore the structural integrity of the coated beads highly depended not only on the composition of the coating material, but also on the method by which the alginate core was prepared.