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39: Gelatin Hydrolysis

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    Learning Objectives

    • Learn the method for determining gelatin hydrolysis and the reactions produced


    Gelatin is a protein that is solid at room temperature. If the bacterium makes the enzyme gelatinase (which optimally is produced at 25º C, not 37º C), the gelatin is hydrolyzed and becomes a liquid. There is no indicator or reagent added, simply solidification or liquefaction.


    • 1 nutrient gelatin deep for unknown


    1. Stab the gelatin deep with a needle all the way to the bottom (being careful NOT to get the metal holder into the agar).
    2. Incubate at 25º C for a couple days, up to a week. Keep the medium for a week if negative.
    3. Record the results of your bacterial unknown in your journal.


    The tube is placed on ice for about 15 minutes, or in the fridge for about 30 minutes, to determine liquefaction. If the tube has been incubated at 37º C it will be liquid when taken out of the incubator, so remember to place it on ice before calling the reaction. The liquefaction can be complete throughout the tube or perhaps partial.


    If negative, keep the medium at 25º C for a week to make a final call of negative.


    1. Why place this medium on ice to test for a positive reaction?
    2. This gelatinase enzyme is temperature - sensitive, and preferably works best at what temperature?

    This page titled 39: Gelatin Hydrolysis is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Jackie Reynolds.

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