Immobilization of goat brain aminopeptidase B in calcium alginate beads

Aminopeptidase B, an arginyl aminopeptidase, was purified from goat brain with a purification factor of 280 and a yield of 2.7%. It was entrapped in calcium alginate together with bovine serum albumin. The optimal conditions for immobilization for maximum activity yield were 1% CaCl2 and 2.5% alginate. The immobilized enzyme retained 62% of its initial activity and could be used for five successive batch reactions with retention of 30% of the initial activity. The pH and temperature optima of the free and immobilized enzyme were pH 7.4, 45C and pH 7.8, 50C respectively, while the pH and thermal stability as well as the stability of the enzyme in organic solvents were improved significantly after entrapment. The Km value for the immobilized enzyme was about twofold higher than that of the soluble enzyme. Because of this increased stability, the immobilized enzyme may be useful in the meat processing industry.