Brace yourself, it’s about to get sciency!
Kombucha contains a variety of yeast species in addition to acetic acid bacteria. A wide variety of yeasts have been identified. Saccharomyces, Schizosaccharomyces, Zygosacchomyces, and Brettanomyces are all yeast organisms found in kombucha. Candida species are also found in a variety of kombuchas. The bacterial component of kombucha comprises several species, almost always including Komagataeibacter xylinus (formerly Gluconacetobacter xylinus).
In kombucha, yeasts and bacteria participate in metabolic activities that use sugar in various and complementary ways. Yeasts use something called invertase to change sucrose (table sugar) into simple sugars like glucose and fructose, then use a process called glycolysis to produce alcohol.
How come my kombucha isn’t full of alcohol, you may think?
Well, acetic acid bacteria such as the aformentioned Komagataeibacter xylinus then take this alcohol and creat acetic acid out of it. This is the basic process of making vinegar. They also manufacture gluconic and glucuronic acid from glucose. Due to this formation of organic acids during fermentation, the pH of kombucha tea decreases. It gets more acidic.
In addition, kombucha contains enzymes and amino acids, polyphenols, and various other organic acids which vary between preparations. Other specific components include ethanol, glycerol, lactic acid, usnic acid, and B-vitamins. Kombucha has also been found to contain vitamin C.