Application of Highly Concentrated Substrate to Enzymatic Synthesis of Aspartame Precursor

N-(benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methyl ester (ZAPM) was synthesized enzymatically from highly concentrated N-(benzyloxycarbonyl)-L-aspartic acid (ZA) and L-phenylalanine methyl ester (PM). An approximate linear relationship was obtained between the initial reaction rate and the substrate concentration up to 1000 mmol·dm-3. The highest reaction rate obtained at the concentration ratio of ZA and PM was 0.5. When the ratio of 0.5 ([ZA]/[PM]=400 mmol·dm-3/800 mmol·dm-3) was employed, it was found that the high reaction rate and the conversion of ZAPM synthesis could be performed at pH 6.0, 40°C, with 10 g·dm-3 NaCl addition.