Kombucha

Kombucha is a fermented, slightly alcoholic, lightly effervescent, beverage made from sweetened black or green tea. This sour (acetic acid) drink is often mixed with juice, spices, fruit or other flavorings. The fermentation process involves a symbiotic culture of bacteria and yeast referred to as a SCOBY or "mother." Health benefits from consumption are associated with the microbial content as well as microbial metabolites. The yeast involved includes Saccharomyces cerevisiae and the bacterial component includes Gluconacetobacter xylinus, a member of the acetic acid bacteria.

Kombucha Chemistry

The sugar, most likely sucrose, fructose, and/or glucose added to the tea is metabolized by the yeast (fermentation) in the absence of oxygen (anaerobically) into carbon dioxide and ethanol.

C₆H₁₂O₆ (glucose or fructose) → 2 C₂H₅OH + 2 CO₂

For each molecule of glucose or fructose fermented, 2 molecules of ethanol and 2 molecules of carbon dioxide are formed. The ratio of products to reactants is a general chemistry topic referred to as stoichiometry.

As you can see in the table below, sucrose is a dimer (2) of fructose and glucose. During fermentation an enzyme (biological catalysis) is release resulting in the "inversion" of sucrose into fructose and glucose:

C₁₂H₂₂O₁₁ + H₂O → 2 C₆H₁₂O₆

As noted above, the SCOBY contains both yeast and bacteria. If only yeast was present the final product would be ethanol and carbon dioxide, but since the acetic acid bacteria are also present, the ethanol is subsequently converted to acetic acid:

C₂H₅OH + O₂ → CH₃COOH + H₂O

	Molecular Formula	Chemical Structure
Sucrose	C12H22O11
Glucose	C6H12O6
Fructose	C6H12O6
Ethanol	C2H5OH
Carbon dioxide	CO2

References

A Review on Kombucha Tea—Microbiology, Composition, Fermentation, Beneficial Effects, Toxicity, and Tea Fungus

to oxidize yeast-produced alcohols to acetic acid (and other acids).[4] Although the SCOBY is commonly called "tea fungus" or "mushroom", it is actually "a symbiotic growth of acetic acid bacteria and osmophilic yeast species in a zoogleal mat [biofilm]".[1] The living bacteria are said to be probiotic, one of the reasons for the popularity of the drink.[5][6]

drink commonly consumed for its supposed health benefits. Sometimes the beverage is called kombucha tea to distinguish it from the culture of bacteria and yeast.[2]