History
Lactobacillus delbrueckii subsp. bulgaricus was first identified in 1905 by Stamen Grigorov, who named it Bacillus bulgaricus.
Ilya Metchnikoff, a professor at the Pasteur Institute in Paris, researched the relationship between the longevity of Bulgarians and their consumption of yogurt. He had the idea that aging is caused by putrefactive activity, or proteolysis, by microbes that produce toxic substances in the intestine.
Proteolytic bacteria such as clostridia, which are part of the normal intestinal flora, produce toxic substances including phenols, ammonia and indols by digestion of proteins. These compounds are responsible for what Metchnikoff called intestinal auto-intoxication, which, according to him, was the cause of the physical changes associated with old age. It was already known at that time that fermentation with lactic acid bacteria inhibits the deterioration of milk because of its low pH.
Metchnikoff's research had also noted that, in Europe, Bulgaria and the Russian steppes, some rural populations who had consumed milk fermented with lactic acid bacteria lived relatively long lives. Based on these data Metchnikoff proposed that consumption of fermented milk would seed the intestine with harmless lactic acid bacteria, which would increase intestinal acidity and thus suppress the growth of proteolytic bacteria.
Read more about this topic: Lactobacillus Delbrueckii Subsp. bulgaricus
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