Fat, Lipid Hydrolysis Test - Principle, Procedure, Result, Interpretation, Introduction

Introduction to Fat, Lipid Hydrolysis Test

The fat, lipid hydrolysis test is a biochemical test used in the laboratory to determine if the test organism is able to produce lipase (esterase) that cleaves its ester bonds to produce glycerol and fatty acids. Such organisms are called lipolytic organisms.

The fat, lipid hydrolysis test's importance also lies in the food industry where the rancidity of certain foods such as margarine must be measured.

Principle to Fat, Lipid Hydrolysis Test

Lipids (fats) are complex molecules with high molecular weight which are too large to enter the microbial cell to be used as an energy source. Some microorganisms produce the exoenzyme lipase (esterase) which cleaves its ester bonds to produce glycerol and fatty acids. The newly formed glycerol and fatty acids can now be transported into the microbial cells to be further processed.

To test fat/lipid hydrolysis by microorganisms, tributyrin agar (Nutrient agar supplemented with triglyceride tributyrin) is used. The medium is opaque due to tributyrin's characteristic of forming an emulsion when dispersed in the agar.

Procedure of Fat, Lipid Hydrolysis Test

The procedure for fat, lipid hydrolysis test include:

1. Take a sterile tributyrin agar and following aseptic guidelines, draw a single streak. (each plate can have a single streak of multiple test organisms)

2. Incubate the inoculated plate at 35-37°C for 18-24 hours in an inverted position.

3. Observe for a zone of lipolysis

Result, Interpretation of Fat, Lipid Hydrolysis Test

The result and interpretation of fat, lipid hydrolysis tests can be positive or negative.

Positive

Loss of opacity (clear zone) is seen near colonies where lipid hydrolysis has occurred.

Negative

No clear zone is seen.