Question

• 12. This medium is used to test for hydrolysis: A. starch; B. gelatin; C. lipid. • 13. Which organism shows a positive result for this test? Left or right.

Answer 1

12)option C ,Lipid hydrolysis test.

In lipid hydrolysis test,the test bacteria are grown on agar plate containing tributyrin as the lipid substrate.The result of hydrolysis is demonstrated as transparent clear zones around the colonies and the rest of the areas of the plate remains opaque indicative of unhydrolysed tributyrin region.Fats and oils are hydrolysed by moisture to yield glycerol and 3 fatty acids.This leads to hydrolytic rancidity of food products characterised by an unpleasant odour and aroma.when this hydrolyses occurs the fattyacids are released and the acidity of the reaction mixture will rise.

13)Right shows the positive result,which means the clear zones around the colonies shows the positive test for lipid hydrolysis.This loss of capacity is the result of hydrolytic reaction yielding soluble glycerol and fatty acids and represents a positive reaction.In the absence of lipolytic enzymes the medium retains its opacity.This indicates a negative reaction.Hydrolysis is the breakdown of a substance by addition of water.Fats and oils are hydrolysed by moisture to yield fattyacids and glycerol.This is lipid hydrolysis.