EFFECT OF ORGANIC-SOLVENTS ON ENZYMATIC-SYNTHESIS OF AN ASPARTAME PRECURSOR

Thermolysin-catalyzed enzymatic synthesis of N-(benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methyl ester (ZAPM) which is an aspartame precursor was performed in organic solvent systems. Organic solvents were selected on the basis of the solubility of the substrates and the product; N-(benzyloxycarbonyl)-L-aspartic acid, L-phenylalanine methyl ester and ZAPM. Their solubilities depended upon log P values of solvents. Three reaction systems (system I :organic solvent mono-phasic system, system II :water saturated organic solvent mono-phasic system and system III : water/organic solvent bi-phasic system) were employed for the enzymatic reaction using selected solvents. Methoxyethanol and pyridine were newly found to be useful solvents for system I as well as tert-amyl alcohol and butyl acetate. Ethyl acetate, tert-amyl alcohol, butyl acetate and chloroform were suitable for system II and III. The efficiency of modification of enzyme surface using surfactants was examined in the organic solvent mono-phasic reaction system. An increase of the enzyme activity by the modification was observed in system I using chloroform.