LONG-TERM CONTINUOUS SYNTHESIS OF ASPARTAME PRECURSOR IN A COLUMN REACTOR WITH AN IMMOBILIZED THERMOLYSIN

N-(Benzyloxycarbonyl)-l-asparty-l-phenylalanine methyl ester, the precursor of the synthetic sweetener aspartame, was continuously synthesized in an immobilized thermolysin plug-flow type reactor at 25° C with the substrates (N-benzyloxycarbonyl-l-aspartic acid and l-phenylalanine methyl ester) dissolved in ethyl acetate. The immobilized enzyme was quite stable in ethyl acetate containing 2.5% 0.01 M 2-(N-morpholino)ethanesulphonic acid-NaOH buffer, pH 6.0, and 20 m M CaCl2 with or without the substrate at 25° C. By periodically washing the column, we could conduct a continuous reaction for over 500 h with an average yield of 95% and a space velocity of 1.85 h -1. © 1990 Springer-Verlag.