Inspired by the writings of Ilya Ilyich Mechnikov, Shirota developed a stronger strain of lactic acid bacteria which might work to destroy the harmful bacteria living in the intestines, and therefore improve and maintain the health of human beings.[4][5] In 1930, Shirota was working in a microbiology lab at Kyoto Imperial University's School of Medicine when he became the first in the world to succeed in culturing a strain of lactic acid bacteria beneficial to human health. This bacterium was named Lactobacillus casei strain shirota after Shirota.[6]
The result of his efforts was the successful culturing of Lactobacillus casei strain shirota. Shirota then began working together with supporters to make a drink incorporating the strain. This led to the development of Yakult which was introduced to the market in 1935.[1][6]