Traditional fermentation technology usually uses naturally occurring substances for fermentation.

Impure microorganisms. Traditional fermentation engineering is the natural fermentation of impure microorganisms, or the industrial fermentation of pure microorganisms is called traditional fermentation engineering. In the production of alcoholic beverages, grains or fruits (grapes, litchi, etc. ) is usually fermented by different microorganisms (yeast, Aspergillus, etc.). ) and processed into different wines. The yogurt that children like to eat is also fermented by adding lactic acid bacteria to fresh milk. Vinegar and sauce are also traditional condiments in China.