Kombucha is a fermented, slightly alcoholic, lightly effervescent, sweetened black or green tea drink commonly intended as a functional beverage for its supposed health benefits. Kombucha is produced by fermenting tea using a symbiotic culture of bacteria and yeast, or SCOBY, commonly called a "mother" or "mushroom". The microbial populations in a SCOBY vary: the yeast component generally includes Saccharomyces cerevisiae, along with other species; while the bacterial component almost always includes Gluconacetobacter xylinus to oxidize yeast-produced alcohols to acetic acid. Although the SCOBY is commonly called "tea fungus" or "kombucha", the culture is "a symbiotic growth of acetic acid bacteria and osmophilic yeast species in a zoogleal mat [biofilm]". Sometimes the term kombucha tea is used to refer to the beverage to distinguish it from the kombucha culture of bacteria and yeast.