Kombucha tea is a pleasant, slightly sweet, acidic beverage that is enjoyed all over the world.

It is made from a sugary tea leaf infusion via the fermentation of bacteria and yeast. Black or green tea extract sweetened with 5% to 8% table sugar is the traditional base for kombucha fermentation.

The two sections of kombucha tea are a floating cellulosic pellicle layer, also called a ‘biofilm’, usually on top, and a somewhat acidic liquid broth underneath.

In this picture, the upper thin layer is the tea fungus, whereas the major brownish portion is the sour liquid broth a.k.a the fermented tea .

The history of kombucha

Kombucha is a Germanized version of the Japanese name or this mildly fermented tea beverage. Despite its Japanese name, which literally translates to “kelp tea,” the drink kombucha is known as “kocha kinoko” in Japan.

It was first used for medicinal purposes in East Asia. Kombucha originated in northeast China (Manchuria), where it was valued for its detoxifying and energizing properties during the Tsin Dynasty (“Ling Chi”), about 220 B.C.

The tea fungus was introduced to Japan by the physician Kombu in 414 A.D., and he used it to treat Emperor Inkyo’s digestive problems. As trade routes spread, kombucha made its way into Russian (under the names Cainiigrib, Cainii kvass, Japonskigrib, Kambucha, Jsakvasska) and then into other eastern European countries, eventually making its way to Germany and the rest of Europe around the turn of the century.

“What’s a SCOBY?
It’s not what you think it is”

A SCOBY is an acronym for Symbiotic Culture (or Colony) of Bacteria and Yeasts. So basicly SCOBY refers to all microbes in kombucha. Kombucha is a yeast and bacteria symbiosis i.e., they benefit from each other.

Culturally, though, it has become common for “SCOBY” to refer simply to the pellicle floating on top. K. xylinus has been shown to be responsible for most or all of the physical structure of the “mother”, during fermentation it appears as a thin membrane on the surface of tea to which the bacteria and yeast cell mass is attached.

While its starts thin, it can grow very thick.

The microbiology of kombucha

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.

See how the kombucha pellicle grows

Kombucha is usually maked with black or green tea and table sugar, but kombucha