Discovery

Yakult's Unique Probiotic Strain

Yakult’s probiotic, Lactobacillus casei strain Shirota (L. casei strain Shirota) was specially developed by our founder, Dr. Minoru Shirota.  

In 1930, Dr. Shirota, a doctor from Kyoto Imperial University School of Medicine, succeeded in isolating and biotechnologically strengthening a Lactobacillus strain. The fortified bacteria strain was later named after him as L. casei strain Shirota. The robust L. casei strain Shirota shows good viability in the intestines by withstanding the gastric juice and bile and has excellent beneficial effects on the digestive tracts.

Dr. Shirota’s discovery, L. casei strain Shirota was made into a cultured milk drink, Yakult in 1935 so that as many people as possible could enjoy its benefits.

Strengthening of L. casei strain Shirota

STAGE 1

Original L.casei go through synthetic digestive fluid test

Original L.casei go through synthetic digestive fluid test

STAGE 2

Synthetic digestive fluid (similar to gastric acid and bile) is used at increasing concentration to select stronger L.casei

Synthetic digestive fluid (similar to gastric acid and bile) is used at increasing concentration to select stronger L.casei

STAGE 3

Finally the strongest L.casei that survives is selected and renamed as L.casei strain Shirota

Finally the strongest L.casei that survives is selected and renamed as L.casei strain Shirota

Profile of L. casei strain Shirota

NameLactobacillus casei strain Shitora (L. casei strain Shirota)
MorphologyRod-shaped gram-positive bacteria
(1-2 μm long, 0.4 – 0.8 μm wide)
Conditions for growthProliferate under both anaerobic and aerobic condition, at 15 – 41°C (optimum temperature is 37°C)
MetabolitesProduce lactic acid from sugar (Does not produce any harmful substances such as ammonia, hydrogen sulfide, indole, phenol and amines)
Site of actionSmall intestine
StrengthStrong acid tolerance, able to reach small intestine alive

Scientifically Proven
Health Benefits of
L. casei strain Shirota