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Nutrient Gelatin

Nutrient Gelatin is used for the differentiation of microorganisms on the basis of gelatinase production in a laboratory setting. Nutrient Gelatin is not intended for use in the diagnosis of disease or other conditions in humans.

Gelatin was the first gelling agent used to solidify culture media. The advantages of solid media over liquid media include isolation of pure cultures and the ability to perform plate counts. The disadvantages of gelatin include incubation at 20°C, a temperature that is lower than optimum for growing many microorganisms, and the fact that many organisms metabolize (liquefy) gelatin. Agar later replaced gelatin as a solidifying agent.

Identifying fermentative and non-fermentative Gram-negative bacilli include testing for gelatin liquefaction. If the proteolytic enzyme gelatinase is present, gelatin is hydrolyzed and loses its gelling characteristic. Edwards and Ewing include this test in the differentiation scheme for Enterobacteriaceae. Procedures for performing the standard tube method for gelatin liquefaction are available.

Formula Liter
Enzymatic Digest of Gelatin 5 g
Beef Extract 3 g
Gelatin 120 g

Final pH: 6.8 ± 0.2 at 25°C
Formula may be adjusted and/or supplemented as required to meet performance specifications.

Directions

  1. Dissolve 128 g of the medium in one liter of purified water.
  2. Heat with frequent agitation to 50°C to completely dissolve the medium.
  3. Autoclave at 121°C for 15 minutes.