Lactose Fermentation Test What is the purpose of the test? The purpose is to see if the microbe can ferment the carbohydrate (sugar) lactose as a carbon source. How is lactose fermentation determined?. If lactose is fermented to produce acid end products, the p H of the medium will drop. A p H indicator in the medium changes color to indicate acid production.
The term fermentation is often used to describe the breaking down or catabolism of a carbohydrate under anaerobic conditions. Therefore, bacteria capable of fermenting a carbohydrate are usually facultative anaerobes. Uses of Carbohydrate Fermentation Test
The making of yogurt and some medical tests have the process of lactose fermentation in common. With the help of bacteria, lactose fermentation -- the breaking down of the sugar lactose into an acid -- is used to make fermented dairy foods and to test for food poisoning.
Identification of Bacteria. Lactose Fermentation Test: Bacterial Growth on MacConkey, EMB and Carman© Agars Introduction Various bacteria ferment lactose as you observed in the Methyl Red Test experiment. Besides utilizing methyl red medium to determine the presence of lactose fermenting bacteria, one may also utilize MacConkey (MAC), EMB (eosin-
Phenol red lactose broth is thus used to determine whether the microbe can use the sugar lactose for carbon and energy. How is lactose fermentation determined? If lactose can be used, the microbe will accumulate acidic byproducts. In a positive test, the p H indicator in the medium changes color from its normal red to yellow, indicating acid ...
MacConkey agar is an indicator, a selective and differential culture medium for bacteria designed to selectively isolate Gram-negative and enteric (normally found in the intestinal tract) bacilli and differentiate them based on lactose fermentation.
The sugar fermentation pattern may be unique to a particular species or strain (Figure 2). Figure 2: Sugar fermentation pattern of different bacteria Phenol Red Carbohydrate Fermentation Broth: Phenol red broth is a general purpose fermentation media comprising of trypticase, sodium chloride, phenol red and a carbohydrate.
Lactose fermentation will continue to produce acidic byproducts and the media will remain yellow (picture on the far left below). If gas is produced as a result of glucose or lactose fermentation, then fissures will appear in the agar or the agar will be lifted off the bottom of the tube.
Phenol Red Broth. Phenol Red Broth is a general-purpose differential test medium typically used to differentiate gram negative enteric bacteria. It contains peptone, phenol red (a pH indicator), a Durham tube, and one carbohydrate. We use three different kinds of phenol red broths.
The carbohydrate fermentation test is used to determine whether or not a bacteria can utilize a certain carbohydrate. It tests for the presence of acid or gas produced from carbohydrate fermentation. The media in each tube contains a single carbohydrate – in this case glucose, lactose, and sucrose.