Skip to main content
[ "article:topic", "showtoc:no", "Tryptone Broth", "authorname:smithselby" ]
Biology LibreTexts

3.7: Tryptone Broth

  • Page ID
    14684
  • Bacterial tryptophanase coverts the amino acid tryptophan into pyruvate, ammonia, and indole. The medium used to test for this enzyme is 1% tryptone in water.

    Procedure
    1. Obtain a tube of tryptone broth.
    2. Using an inoculating loop, swish some of your assigned organism in the broth.
    3. Incubate the tube for at least 48 hours.
    4. After the incubation period, add several drops of Kovac's reagent to the tube.
     Interpretation

    The chemicals in Kovac's reagent react with the indole to produce a red color. In a positive test, a red layer will float at the surface of the broth.

    1538176070(1).png

    Indole Positive