| 摘要 |
The aspartame content in aqueous solutions is determined by enzymatic cleavage into aspartic acid and phenylalanine methyl ester using peptidase, followed by a detection reaction cocatalysed by adenine dinucleotide, wherein either the phenylalanine is, after elimination of the ester group by means of chymotrypsin, converted by phenylalanine dehydrogenase in the presence of NAD<+> into phenylpyruvate, and the aspartame concentration is measured via the NADH or NH3 formation taking place during this, or wherein the aspartic acid is converted by means of a cell extract which acts on aspartic acid in the presence of NADP<+>, and the NADPH or NH3 formation is employed to determine the aspartame concentration. In this connection the enzymatic reactions are carried out, in particular, in consecutive enzyme columns with carrier-bound enzymes in the FIA technique. The proportion of hydrolysis products can be measured by analysing another sample omitting the peptidase reaction. The enzymatic cell extract used for the aspartic acid determination is obtained from microorganisms which are isolated from compost samples. The strain DSM 6705 is particularly used for this. The cell extract can be used for the analysis as crude extract without special subsequent purifications. It is generally suitable for detecting aspartic acid. <IMAGE>
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