Negative: Complete solidification of the inoculated tube even after exposure to the cold temperature of an ice bath or refrigerator (4☌)Ĭommon bacteria and their reactions to the gelatin hydrolysis test performed on nutrient gelatin. Positive: Partial or total liquefaction of the inoculated tube (uninoculated control medium must be completely solidified) even after exposure to the cold temperature of ice bath or refrigerator (4☌). Gelatin Hydrolysis Test: Above tube: Positive Reincubate a negative test for up to 2 weeks if indicated by the nature of the organism, and examine at regular intervals.After 30 minutes of refrigeration, tilt the tubes gently to observe liquefaction by the test organism.

(Gelatin normally liquefies at 28☌ and above, so to confirm that liquefaction was due to gelatinase activity, the tubes are immersed in an ice bath or kept in a refrigerator at 4☌). Gently remove the tubes daily from the incubator and place them in an ice bath or refrigerator (4☌) for 30 minutes or until the control tube solidifies.Incubate the inoculated tube along with an uninoculated medium at 35☌, or at the test bacterium’s optimal growth temperature, for 48 hours.Inoculate a heavy inoculum of test bacteria (18- to 24-hour-old) by stabbing 4-5 times (half an inch) on the tube containing nutrient gelatin medium.The standard and most commonly employed method is the nutrient gelatin stab method. There are several methods for determining gelatinase production, all of which make use of gelatin as the substrate. Escherichia coli ATCC 25922-no liquefaction (negative) Procedure of Gelatin hydrolysis test.Pseudomonas aeruginosa ATCC 10145-liquefaction (positive).Use an uninoculated control with each use.Perform QC on each new lot of media prior to using them.

Inspect gelatin agar tubes for contamination, dehydration, and lack of liquefaction at refrigeration temperatures before storage and before use.

The bacterial cells can then take up these amino acids and use them in their metabolic processes. This process takes place in two sequential reactions. In the first reaction, gelatinases degrade gelatin to polypeptides. Then, the polypeptides are further converted into amino acids.

Limitations Principle of Gelatin hydrolysis testĪ gelatin hydrolysis test is used to detect the ability of an organism to produce gelatinases that liquefy gelatin.