of the Enzyme Route
is completely stereo selective. This means that it is possible to
use either a racemic
mixture or the L-isomer of the substrate.
None of the bitter isomer of aspartame is
The reaction takes place under mild conditions
- pH: 7.0 -7.5
- Temperature: 500c
- In aqueous solution
After the enzyme reaction there is
further chemical processing to remove protecting groups, and to
convert the methyl ester to aspartame itself.
|Reaction Scheme for Aspartame Manufacture
| X is a protecting group
removed at the end
What change(s) do you think are caused
by the use of HCl?
|The enzyme employed is
called thermolysin found in the bacterial strain Bacillus proteolicus/
thermoproteolyticus in the Rokko Hot Spring in Japan. The enzyme
is stable up to temperatures of 60oC. It is extracted
and used in a form soluble in water in a process started in 1988.
The reaction is limited by the equilibrium
position, and so products have to be removed from the mixture
in order to achieve high yields.