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Biology LibreTexts

3.11: Phenylalanine Agar

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  • Bacteria that produce phenylalanine deaminase are able to remove the amino group from the amino acid phenylalanine yielding ammonia and phenylpyruvic acid


    1. Obtain a slant of phenylalanine agar.
    2. Using an inoculating loop, zigzag up the slant with your assigned organism.
    3. Incubate the tube for at least 48 hours.
    4. After the incubation period, add 3-5 drops of FeCl3 (ferric chloride) to the tube, making sure that it touches the slant.


    Phenylpyruvic acid turns green in the presence of ferric chloride indicating the production of phenylalanine deaminase.


    Positive Result