Kombucha drink under the microscope. Who isn't here...
Kombucha culture is a symbiotic culture of bacteria and yeast (SCOBY), similar to a vinegar mother, containing one or more species of bacteria and yeast that form a zoogloeal mat, known as the "mother". There is a wide range of yeast species spanning several genera present in kombucha culture, including species of Zygosaccharomyces, Candida, Kloeckera/Hanseniaspora, Torulaspora, Pichia, Brettanomyces/Dekkera, Saccharomyces, Lachancea, Saccharomycoides, Schizosaccharomyces, and Kluiveromyces. The bacterial component of kombucha includes several species, almost always including the acetic acid bacteria Komagataeibacter xylinus (formerly Gluconacetobacter xylinus), which ferment the alcohols produced by the yeast into acetic and other acids, increasing acidity and limiting ethanol content. The population of acetic acid-producing bacteria and yeast is reported to increase during the first 4 days of fermentation and then decline. K. xylinus produces bacterial cellulose, and is reported to be responsible for much or all of the physical structure of the "mother culture", which may have been selectively favored by brewers over time to produce stronger (tighter) and more robust cultures. The acetic acid bacteria in kombucha are aerobic, meaning they require oxygen for their growth and activity. Thus, bacteria initially migrate and collect at the air interface, after which, after about 2 days, bacterial cellulose is released.