Activity and distribution of urease following microencapsulation within polyamide membranes

Urease was microencapsulated by forming a semipermeable polyamide membrane around aqueous microdroplets (266 microns mean diameter) containing the soluble enzyme. The yield of the interfacial polymerization technique, determined spectrophotometrically, was 83% of the original enzyme on a mass basis, resulting in a final intracapsular urease concentration of 62.3 mg ml-1 or 0.1 mM. Similar absorption spectra of broken and intact microcapsules suggested that spectrophotometry may be applied in performing direct studies on the intact microcapsules. The high activity yield of urease microcapsules relative to the mass of entrapped enzyme (92.5%) indicated minimal effects of mass transfer limitation. The mass of active urease incorporated into the nylon membrane represented 6% of the encapsulated enzyme activity. The soluble intracapsular enzyme fraction (94%) was released into solution upon rupture of the membrane. A complete mass and activity balance of the encapsulated enzyme was achieved.