Ingredients Gms / Litre :Peptic digest of animal tissue 10.000Sodium chloride 5.000Beef extract 3.000Bromo cresol purple 0.040Final pH ( at 25°C)**Formula adjusted, standardized to suit performance parameters 7.0±0.2Principle & Interpretation :Basal medium (without carbohydrates) are usually used for studying the carbohydrate utilizing behavior of different organisms by the addition of the desired carbohydrate to the basal medium. Various indicator dyes are used in the basal medium which helps in the visualization of these carbohydrate-utilizing reactions. Bromo Cresol Purple Broth Base is one such basal medium, in which bromocresol purple is used as indicator dye. If the test organism ferments the added carbohydrate, the pH of the medium turns acidic due to the production of acids and causes the indicator BCP to change colour from purple to yellow. Air bubbles trapped in the inverted Durhams tubes indicate gas production. Bromo Cresol Purple Broth Base is recommended by APHA (1) for studying fermentation behavior of carbohydrates by pure cultures (2).Bromo Cresol Purple Broth Base consists of a peptone medium supplemented with yeast extract to supply B complex vitamins necessary to support growth. Specific carbohydrates are added to the basal medium in a concentration of 0.5-1%. The pattern of fermentation of different carbohydrates is characteristic of a given species or group of species and may be used for their classification or identification.