How is aspartame made?

    Written by:
    Thomas Solomon

    Fact-checked

    by:

    Nick Milazzo
    Last Updated: May 16, 2025

    Aspartame can be produced through chemical or enzymatic synthesis methods; the latter is preferred because it exclusively yields the sweet isomer (α-aspartame) via the enzyme thermolysin. Chemical synthesis, in contrast, results in both sweet (α-aspartame) and bitter (β-aspartame) isomers, which must then be separated.

    Aspartame was discovered in 1965 by James Schlatter[1] and can be made using either chemical or enzymatic synthesis methods.[2][3][4]

    Chemical synthesis methods couple the two amino acids that aspartame is composed of, L-aspartic acid and L-phenylalanine. However, chemical synthesis has the limitation that it produces a bitter isomer (β-aspartame) as well as the sweet isomer (α-aspartame) used in aspartame products. These isomers then have to be separated.

    Enzymatic methods are preferable because they use Thermolysin, an enzyme derived from a bacterium called Bacillus thermoproteolyticus, which only produces the sweet isomer (α-aspartame).[5][6][7]

    Due to a lack of information on different manufacturers’ websites, it is unclear exactly which methods are used to produce aspartame by different manufacturers (Canderel, Hermesetas Gold, NutraSweet, Pal Sweet, etc.).