Voges–Proskauer Reagent B (40% KOH), 25 mL Tube, 1/Pk

This product provides 25 mL of Voges–Proskauer (VP) Reagent B, consisting of a concentrated 40% Potassium Hydroxide KOH solution. This is the second catalytic component required for the Voges–Proskauer test, a cornerstone of the IMViC series used to differentiate members of the Enterobacteriaceae family.

The "Developer" Mechanism:

The VP test detects bacteria that ferment glucose via the 2,3-butanediol pathway, producing a neutral intermediate called acetoin (acetylmethylcarbinol).

1. The Sequence: The test requires two reagents added in specific order. Reagent A (5% Alpha-Naphthol) is added first to the culture broth.

2. The Role of Reagent B: When this 40% KOH is added, it creates a strongly alkaline environment. It absorbs carbon dioxide and acts as an oxidizing agent.

3. The Reaction: The KOH accelerates the oxidation of acetoin into diacetyl. The diacetyl then reacts with the guanidine nuclei (from the peptone in the broth) and the Alpha-Naphthol to produce a vivid Red Color complex.

   • Positive Result: A red layer forms at the top of the broth (typically within 15–20 minutes).

   • Negative Result: No color change, or a copper/brown color (indicative of unreacted reagents).

The "Shake" Factor:

Unlike many other biochemical tests, the VP reaction requires oxygen. After adding Reagent B, the tube must be shaken vigorously or aerated. The KOH aids in the absorption of atmospheric oxygen, which is necessary to oxidize the acetoin to diacetyl. Without the caustic power of Reagent B and oxygenation, the color will not develop.

Common Applications:

• Enteric ID: Distinguishing Klebsiella pneumoniae and Enterobacter aerogenes (VP Positive) from Escherichia coli (VP Negative).

• Food Microbiology: Differentiating various coliforms in water and food quality testing.

• Listeria ID: Used alongside other tests to confirm Listeria species.

Key Features:

• Standard Concentration: 40% Potassium Hydroxide solution.

• Rapid Reaction: Optimized for quick color development when used with Reagent A.

• Essential Component: The obligatory partner to VP Reagent A (Alpha-Naphthol).

• High Contrast: Produces a distinct cherry-red positive result.

• Format: Liquid reagent in a convenient dispensing tube (1/Pk).

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