The phenol red fermentation test is usually used to differentiate organisms based on their ability to ferment carbohydrates such as from a glucose broth. If the color turns yellow at the end of the test, what does this result imply?

• A. No carbohydrate fermentation took place.
• B. The broth did not contain enough carbohydrates.
• C. There was a contamination during the experiment.
• D. A carbohydrate fermentation occurred.

Answer: (D)