Propionibacter shermani

Propionibacter shermani is a bacterium used in the production of cheese. During cheese-making the bacteria are added to certain cheeses such as Emmental (also known as Swiss) and Leerdammer, and when warmed bubbles of carbon dioxide form in the cheese. These bubbles then become the distinctive holes (or eyes) in the finished product.

Cheesemakers control the size of the holes by changing the acidity, temperature, and curing time of the mixture.

Propionibacter shermani cheeses include Swiss, Leerdammer, and Emmental.