Lactic Bacteria Differential Agar, 2.5 kg

Lactic Bacteria Differential Agar is formulated as per McDonald et al (1) for differentiation of homofermentative lactobacilli and heterofermentative streptococci. Lactobacilli and Streptococci are used as starter cultures in food and dairy industry. Streptococci grow first and produce metabolites, lowering the redox potential which enables Lactobacilli to grow. Lactobacilli synthesize products, which stimulate growth of Streptococci. Medium constituents like casein enzymic hydrolysate, papaic digest of soyabean meal and yeast extract supply all the necessary nutrients for the growth of lactic bacteria. Fructose is the fermentable carbohydrate in the medium. Bromo cresol green is the pH indicator. Heterofermentative lactic acid bacteria produce CO₂, lactic acid, acetic acid, ethanol and mannitol. Homofermentative lactic acid bacteria produce only lactic acid. Homofermentative lactic acid bacteria produce lactic acid from fructose and is indicated by yellow color formation. Heterofermentative lactic acid bacteria induce lesser acidification and thus vary in the color formation by the indicator in the medium. Homofermentative bacteria cultivated on this medium form bluish-green colony on agar while heterofermentative bacteria do not form much-colored colony on agar surface. Storage and Shelf-life: Store at 30°C in tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label. Reference: 1. McDonald L.C., McFecters R.F., Daeschel M.A. and Fleming H.P., 1987, Appl. Environ. Microbiol., 53:1382.