What end product of glucose fermentation does the Voges-Proskauer (VP) test detect?

The Voges-Proskauer (VP) test is specifically designed to detect the presence of acetoin, which is a neutral fermentation product of glucose metabolism. During the fermentation process, certain bacteria convert glucose into various byproducts, one of which is acetoin, a compound that can be further oxidized to diacetyl.

In the VP test, two reagents, α-naphthol and potassium hydroxide, are added to a culture medium that has been incubated to allow fermentation. If acetoin is present, the reagents will react to form a red color, indicating a positive result for the test. This reaction is critical for distinguishing certain fermentative bacteria, especially when classifying them based on their metabolic end products. Acetoin is typically produced by organisms such as Enterobacter and Klebsiella, making the VP test particularly useful for identifying these genera.

The other options refer to different metabolic byproducts that are not the focus of the Voges-Proskauer test. For example, nitrite is a product of nitrate reduction, while acetic acid is a type of organic acid that may be produced during fermentation but does not indicate a positive result in the VP test. Hydrogen sulfide is associated with the reduction of sulfur compounds and