EFFECT OF ORGANIC-SOLVENTS ON ENZYMATIC-S YNTHESIS OF AN ASPARTAME PRECURSOR

Thermolysin-catalyzed enzymatic synthesis of N-(benzyloxycarbonyl)-L-a spartyl-L-phenylalanine methyl ester (ZAPM) which is an aspartame prec ursor was performed in organic solvent systems. Organic solvents were selected on the basis of the solubility of the substrates and the prod uct; N-(benzyloxycarbonyl)-L-aspartic acid, L-phenylalanine methyl est er 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 sy stem III : water/organic solvent bi-phasic system) were employed for t he enzymatic reaction using selected solvents. Methoxyethanol and pyri dine were newly found to be useful solvents for system I as well as te rt-amyl alcohol and butyl acetate. Ethyl acetate, tert-amyl alcohol, b utyl acetate and chloroform were suitable for system II and III. The e fficiency of modification of enzyme surface using surfactants was exam ined in the organic solvent mono-phasic reaction system. An increase o f the enzyme activity by the modification was observed in system I usi ng chloroform.