Spherical alginate granules formulated for quick-release active subtilisin

Novel attrition-resistant and spherical enzyme granules encapsulating active subtilisin were formed by emulsification of 2% alginate sol loaded with active enzyme, instantaneous gelation triggered through in situ release of Ca(2+) (internal gelation), particle separation, and finally acetone extractive drying. Granular subtilisin was highly active, readily dispersible, and mechanically robust. This technique serves as a new and attractive alternative to established enzyme granulation processes, such as fluid bed coating, extrusion followed by marumerization, drum granulation, or prilling, for use in industrial enzyme applications such as detergents, textile manufacturing, and food processing. The formulation and encapsulation conditions were optimized to maximize the resistance of the granule to compression and impact forces, consistent with enzyme release and particle dispersion in detergent solutions. Well characterized alginates, with specified guluronic/mannuronic acid (G/M) content and molecular weight, were used in the formulation. The characteristics of the resulting microspheres, including their size and distribution, morphology, shrinkage, compression resistance, impact strength, solubility and encapsulation yield, were examined. Spherical dry granules were formulated with a mean diameter of 500 microm with particle sizes ranging from 300 to 800 microm. Dry alginate granules were discrete, spherical, and glossy white and exhibited impact strength, compression resistance, and solubility difference dependent on composition. Reduced starch levels, high alginate concentration, low alginate molecular weight, and use of high guluronate alginates resulted in the lowest dust level and highest compression resistance. Subtilisin mass yields were approximately 50%, and specific activity yields ranged from 60% to 100%. A formulation consisting of 3% SG150 alginate, 10% starch, 10% TiO(2), and 1% CaCO(3) provided granules appropriate for use in detergent application.