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