Wild yeast and lactic acid bacteria (LAB) are microorganisms that occur naturally on the surfaces of grains, fruits, and vegetables, as well as in soil and air. When given the right conditions — moisture, warmth, and a food source — they multiply and ferment sugars into carbon dioxide, alcohol, and lactic acid.
This microbial community is the basis of sourdough bread, traditional fermented vegetables, and many other foods that predate the use of commercial yeast. A sourdough starter, for example, is simply a stable culture of wild yeast and LAB maintained by regular feeding with flour and water.
The specific species present vary by geography, flour type, and environment, which is part of why sourdough bread tastes different from place to place. Common genera include Saccharomyces, Kazachstania, and Candida among the yeasts, and Lactobacillus, Leuconostoc, and Pediococcus among the bacteria.
How it's produced
Wild yeast and LAB are not farmed in a conventional sense. They are collected or cultivated by creating conditions that encourage their growth. The most common method is maintaining a sourdough starter: mixing flour and water and allowing ambient microorganisms to colonise the mixture over several days, then feeding it regularly to sustain the culture.
In commercial settings, specific strains of wild yeast and LAB may be isolated and propagated in laboratories, then sold as starter cultures for baking, cheesemaking, or fermented beverages. However, the term “wild” generally refers to the naturally occurring, unselected communities rather than these isolated strains.
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