Gelatine Hydrolysis Test Lab Report

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Gelatine hydrolysis test The tubes containing sterilized gelatine liquefaction medium was stab inoculated with fresh culture of bacterial isolates and incubated at 37±1o C for 24 h. After incubation the tubes were placed in refrigerator at 40 c for 30 min. Then these tubes were kept in ice cubes containing beaker and observed for Gelatine liquefaction by the bacterial isolates. The gelatine liquefied tubes were considered as positive reaction (Aneja, 2001).
Composition of Gelatine liquefaction medium
Peptone 5g
Beef extract 3g
Sodium chloride 5g
Gelatine 120g
Agar 20g
Distilled water 1000ml
PH 7

IV. Casein hydrolysis test The sterilized plates containing skim milk agar medium were point inoculated with fresh bacterial cultures and incubated
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After incubation for MR test tubes 5 drops of methyl red indicator was added and observed for development of red colour which indicates positive test for methyl red. In VP test, after incubation to each test tube 1 ml of barritt’s reagent (Solution A- α-napthol-5g in 95 ml of absolute ethanol: Solution B- 16g of Potassium hydroxide in 100 ml of distilled water, mix solution A and B) was added and the contents shaken gently for 15 minutes. Development of red colour was considered as positive for acetyl methyl carbinol production and hence for VP test.
Composition of MR-VP broth medium
Buffered Peptone 7g
Dextrose 5g
Dipotassium phosphate 5g
Distilled water 1000ml
PH 6.9±2

VII. Citrate utilization test In this test sterilized simmon’s citrate agar medium containing test tube slants were inoculated by streaking fresh bacterial cultures on the surface of the slants and incubated at 37±1o C for 24-48 h (Aneja, 2001). After incubation, if colour changes from green to blue it indicates positive result for citrate utilization.
Composition of Simmon’s citrate agar medium
Magnesium sulphate 0.2g
Ammonium dihydrogen phosphate 1g
Dipotassium phosphate 1g
Sodium citrate 2g
Sodium chloride 5g
Bromothymol blue 0.088g
Agar 15g
Distilled water 1000ml

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