About this test
What is the purpose of the test?
This test determines whether the microbe produces 2,3-butanediol as a fermentation product from glucose .
How is 2,3-butanediol production determined?
2,3-butanediol is the end product of a long fermentation pathway, but it is not easily detected. So, the test detects one of the pathway intermediates instead: acetylmethylcarbinol (acetoin) . The production of 2,3-butanediol is thus indirectly detected when the pathway intermediate acetoin reacts with reagents to turn red.
What medium is used?
The medium used is MRVP broth, a nutrient broth medium with 0.5% glucose added. This medium is also used for the methyl red test, which determines whether acidic fermentation products result from growth.
How is the test performed?
An inoculum from a pure culture is transferred aseptically to a sterile tube of MRVP broth. The inoculated tube is incubated at 35-37 C for 24 hours.
What reagents are added?
After incubation, five drops of Barritt’s A are added and the tube is shaken gently to mix the ingredients. Then, five drops of Barritt’s B are added. The tube is then slanted to allow maximum oxygen exposure to the reaction mixture and allowed to stand for up to 30 minutes. Development of a red color indicates a positive test.
Performing this test in the VUMIE Online lab
Inoculation of Medium
1. Select the MRVP broth medium.
2. Complete the process of a tube-to-tube aseptic transfer to inoculate the medium.
Incubation of the Inoculated Medium
3. Place the inoculated tube into the 35-37 C incubator.
4. Press the New Day button to move forward 24 hours.
Addition of Reagents
5. Incubate this test for only 24 hours.
6. Retrieve the incubated culture from the incubator.
7. This is a test that requires addition of reagents to bring about the change in appearance of a positive test.
Select the dropper tool and the appropriate reagent needed from the chemical shelf. Remove the cap. For this test, select Barritt’s A add it, and then add Barritt’s B.
Determination of Test Results
8. Observe test result. For this test, addition of the appropriate reagents makes the culture turn red if the test is positive. If negative, no color change is observed.