Aspartame Produced By Biosynthesis

Aspartame, α-L-aspartyl-L-phenylalanine methyl ester, is a nutritive substance with intensely sweet taste and low calorie property. It is about 200 times sweeter than sucrose and exhibits a sugar-like taste without bitter or metallic after-taste, therefore, it has been used in many foodstuff, beverages and pharmaceuticals, etc. Aspartame is one of the few artificial sweeteners which were allowed to be used by most of the international organizations and countries , therefore, aspartame has a powerful market potentiality.The methods of synthesis aspartame can be separated of chemical method and biological method. Nowadays, Chemical methods, which are widely used in the synthesis of Aspartame, have advantages in large scale production. However, these methods also present problems, such as protection of amino acid side chains and a requirement for excessive amounts of coupling agents and solvents. Although high yields can be obtained in chemical reaction processes, It will create much by-products due to formation of racemic mixtures. Enzymatic methods ,which have the advantages of low temperature reactions, a reduced number of rection steps ,less protection required for amino acid side chains, has been developed for its selectivity.A strain Dl that can grow well on the aspartame plate was isolated from the nature through simple and efficient methods. A series of treatment has been done to the initial strain Dl, to bread a new mutant ASPD1,which synthesize more aspartame. It was identified as Absidia ramosa. It was not reported to be able to synthesize aspartame so far. The optimal culture conditions for ASPD1 to produce enzyme for synthesizing aspartame were 32℃ inculbating temperature, medium pH5.0, bran 3%, amylum 3%, MgSO₄·7H₂O 0.04%, ZnCl2 0.02%, Na2HPO412H2O 0.05%, KH2PO4 0.2%.in this condition aspartame was 0.03g/L.the synthesis reaction was optimized that the optimum temperature and pH were 40 °C and 4.0, respectively; and the optimum reaction time was 11 hour. The product of aspartame was 0.1 g/L.The synthesizing products was identified by the thin-layer chromatography and HPLC. After analysis we conclude that there are some ester enzyme in the total enzyme series, the amount of aspartame was increased to 0.16g/L by that the reaction was added methanol.