None of the bitter isomer of aspartame is
produced.
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
Question
What change(s) do you think are caused
by the use of HCl?
Answer
Hydrolysis of the methyl ester group to carboxylic acid.
Formation of a salt from the amino group of phenylalanine.
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.
