Kefir
Japanese: ケフィア
A fermented milk drink made by adding kefir grains (a symbiotic cluster of lactic acid bacteria and yeast) to milk. It contains a more diverse microbiome than yogurt.
Kefir is a fermented milk drink originating in the Caucasus. Cauliflower-like kefir grains are placed in milk and fermented at room temperature. These grains host dozens of species of lactic acid bacteria and yeast in a complex microbial ecosystem distinct from yogurt. Slight alcohol fermentation alongside lactic fermentation gives kefir a lightly carbonated, refreshing acidity. The grains multiply with continued use and have traditionally been shared from person to person. The origin of kefir grains is unknown, and they cannot be artificially created. As a natural microbial community shared between people, kefir is a prime example of fermentation sustained as commons.