Synthesis of Aspartame

The traditional chemical synthesis method is to convert aspartic acid into acid anhydride, and then condense with phenylalanine methyl ester to form aspartame. The chemical method has poor regioselectivity and produces two isomers: α-aspartame and β-aspartame. α-aspartame is the main product, and β-aspartame has a bitter taste. The separation and removal process is more complicated.

Thermolysin has been successfully used in the synthesis of aspartame precursors in the organic phase. It condenses phenylalanine methyl ester with amino-protected aspartic acid to form aspartame precursors, and then undergoes reduction and desorption. Protecting base, you can get aspartame. The reaction catalyzed by the enzymatic method is enantioselective, and only α-aspartame is synthesized. The racemate phenylalanine methyl ester can be used as the substrate in the reaction, and only L-phenylalanine is used in the enzyme-catalyzed reaction. Acid methyl ester, unreacted D-phenylalanine methyl ester can form a salt, which can be racemized and recycled after acidification.

The catalytic reaction has the following characteristics: ①Using the thermolysin resistant to organic solvents; ②Using the non-aqueous phase system, significantly increasing the concentration of the substrate; ③The effect of thermolysin on the L- in the DL-phenylalanine methyl ester Phenylalanine methyl ester has strict selectivity, and cheap racemates can be used as raw materials; ④The thermolysin and synthetic raw materials are placed in the water phase for enzymatic reaction, and the resulting intermediates are extracted at any time Into the organic phase. Therefore, the enzymatic reaction is not inhibited and can be carried out continuously, and the yield exceeds 95%. To

Synthetic factors (ethanol). Studies have shown that the solubility of aspartame in water is generally small, about 1% (25°C), but as the ethanol content in the solvent continues to increase, the solubility of aspartame is gradually increasing. When the solubility of aspartame in the ethanol aqueous solution reaches its peak, as the ethanol continues to be added, the solubility of aspartame will gradually decrease.

Synthetic influencing factors (temperature), configure the aspartame solution and white sugar solution with the same sweetness at room temperature, seal and heat them at different temperatures for 30 minutes, perform sensory evaluation, and judge whether the heating produces the sweetness of the aspartame solution influences. Average 5 sets of temperatures between 100°C and 120°C were used as the measurement temperature of aspartame. It was found that as the temperature increased, the sweetness of aspartame gradually decreased. The sweetness approaching zero, this result also proves to a certain extent that aspartame is unstable under high temperature conditions, and storage under high temperature conditions should be avoided.