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Principle
- Phenol red broth base formulated by Vera (1950) is used to study carbohydrate fermentation reactions. It is composed of protease peptone, meat extract, sodium chloride, and phenol red.
- Peptone and meat extract provide carbon, nitrogen sources, and essential growth factors required for the growth of microorganisms. The sodium chloride maintains the osmatic equilibrium of the medium.
- Phenol red is a pH indicator dye. The medium contains all the necessary nutrients required for the growth of microorganisms, except carbohydrates. The desired carbohydrate is added into the medium to carbohydrate fermentation reaction. If the organism has the ability to ferment added carbohydrates, with the acid or acid and gas production.
- Due to the acid production the color of the medium changes to yellow. Whereas the production of mixed acid, notably butyric acid result in a pungent or foul smell. The gas production is detected by gas trapped in Durham’s tubes.
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