Abstract: In this paper, immobilized thermolysin was prepared by using aminopropyltriethoxysilane treated porous silica beads as carrier, and glutaraldehyde as crosslinking agent. The precursor of aspar-tame was synthesized in aqueous medium in good yield by the catalysis of the immobilized thermolysin, and aspartame was then obtained by the catalytic hydrogenolysis of the precursor. In the immobilized thermolysin-catalysed coupling reaction, the factors which affect the yield such as reaction time, temperature, medium pH, amount of the immobilized enzyme, substrate concentration and substrate molar ratio as well as concentration of calcium acetate were studied. Reuse of the immobilized thermolysin was also investigated.

Key words: Thermolysin, Immobilized enzyme, Sweetener, Catalytic synthesis