For determination of coliform bacteria particularly Enterobacteriaceae on the basis of their ability to ferment lactose
ANDRADE 0.5% LACTOSE PEPTONE WATER is used for determination of coliform bacteria, particularly Enterobacteriaceae, in water and foodstuff on basis of their ability to ferment lactose. Lactose fermentation reaction produces acids which help in differentiation and identification of various bacteria. On metabolism of lactose in the medium, pH of the medium gets lowered due to formation of acid. This causes subsequent colour change of the indicator, from colourless to pink to red. If the carbohydrate is not metabolized, the colour of the medium remains unchanged. Lactose is a fermentable carbohydrate while acidic fuchsin acts as a pH indicator. Peptone, Special serves as a source of nitrogen, amino acids, vitamins, and other essential growth requirements.