Which bacterium is used to make Swiss-type cheese holes through carbon dioxide production?

Propionibacterium freudenreichii is used to make Swiss-type cheese holes through carbon dioxide production.

This Gram-positive bacterium grows during the warm phase of Swiss cheese production. It converts lactate into propionic acid, acetic acid, and carbon dioxide. The carbon dioxide collects in the developing cheese and forms the familiar holes, while the acids contribute to its characteristic flavor.

The species is also known as a propionic acid bacterium and is associated especially with Emmental-style cheeses. Cheese-making usually involves several microbial partners: starter bacteria first produce lactic acid, and propionibacteria continue the ripening process later.

The holes are not simply bubbles trapped during manufacture. They are biological gas pockets created by microbial metabolism. The size and number of holes depend on factors such as bacterial activity, temperature, acidity, and the physical structure of the curd.