What is the purpose of the test? The purpose is to see if the microbe can use corn oil, a lipid, as a source of carbon and energy for growth. Use of corn oil is accomplished by a class of enzymes called lipases .
How is lipase activity determined? A medium containing lipids (in this case corn oil ) and an indicator is used. When lipids are digested, the indicator changes from blue to clear. Halos surrounding colonies is indicative of their ability to digest the lipid in the medium due to the presence of lipase .
What medium is used? The medium used is spirit blue agar plate. The medium is a nutrient agar to which emulsified corn oil is added after the medium has been sterilized. The indicator spirit blue produces a deep blue medium that changes to a light blue opaque medium after addition of the lipid .
How is the test performed? An inoculum from a pure culture is streaked on a sterile plate of spirit blue agar. The inoculated plate is incubated at 35-37 C for 24 hours. Presence of halos surrounding colonies is positive for their ability to digest the lipids and thus indicates presence of lipase.
What reagents are added? None.
To perform this test in VUMIE Online© Online Lab , complete the following steps:
Inoculation of Medium
1. Select the spirit blue agar plate medium.
2. Using an inoculating loop, complete the process of a tube-to-plate aseptic transfer to inoculate the medium. Forgotten how to do these things? Watch the "Show Me How To" videos.
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. Forgotten how to do these things? Watch the "Show Me How To" videos.
Determination of Test Results
5. Incubate this test for only 24 hours.
6. Retrieve the incubated culture from the incubator.
Determination of Test Results
14. Incubate for the appropriate length of time. For this test, 24 hours is sufficient for determining the result.
15. Retrieve desired incubated culture from the incubator.
16. Observe the test result, noting specifically the color of the medium surrounding colonies in the plate. The culture will show clear halos around colonies capable of breaking down lipids. The color surrounding colonies without lipase remains unchanged.
17. Record test result.
18. Dispose of the culture.