Lactobacillus delbrueckii subsp. bulgaricus

Overview
Lactobacillus bulgaricus (binomial name Lactobacillus delbrueckii subsp. bulgaricus) is one of several bacteria used for the production of yogurt. First identified in 1905 by the Bulgarian doctor Stamen Grigorov, it is named after Bulgaria. Morphologically, it is a Gram-positive rod that may appear long and filamentous. It is also non-motile, and it does not form spores. It has complex nutritional requirements, including the inability to ferment any sugar except for lactose. This bacterium is also regarded as aciduric or acidphilic, due to the fact that it requires a relatively low pH (around 5.4-4.6) in order to grow effectively.

The bacterium feeds on milk and produces lactic acid which also helps to preserve the milk. It breaks down lactose and is often helpful to sufferers of lactose intolerance, whose digestive systems lack the enzymes to break down lactose to simpler sugars. While fermenting milk, Lactobacillus bulgaricus produces acetaldehyde, which perfumes yogurt. Some of the biggest importers of the bacterium are Japan, USA and the EU.