Oxidation/ Fermentation

The OF tube is used to determine whether or not the organism utilized carbohydrates aerobically or anaerobically. A pH indicator bromothymol blue is added to the tube in order to see the acidity produced or not produced. If the organism shows production of acid in both tubes this indicates the occurrence of fermentation. Yellowing in both the OF tube with oil, and that without oil, indicated that the L. casei is able to use fermentation as a primary metabolic pathway.