DEV Lactose Broth is used especially for the identification of E.coli and coliform bacteria in bacteriological analysis of water according to German standard methods for the examination of water and drinking water. It is not a selective medium but it is used as a presumptive medium for the detection of coliforms in water and food, and is also used for the determination of lactose fermentative bacteria. It is commonly used with Durham fermentation tubes for the examination of gas formation. Meat peptone and beef extract provide nitrogen, vitamins, minerals and amino acids essential for growth. Lactose is the fermentable carbohydrate providing carbon and energy. The fermentation of lactose is shown by the acidification of the medium that causes the pH indicator (bromocresol purple) to turn yellow, as well as by gas production in Durham tubes. E. coli and coliforms can ferment lactose under gas production and therefore the color of the medium changes to yellow.
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