Kombucha is any of a variety of fermented, lightly effervescent sweetened black or green tea drinks that are commonly intended as functional beverages for their supposed health benefits. Kombucha is produced by fermenting tea using a "symbiotic 'colony' of bacteria and yeast" (SCOBY). Actual contributing microbial populations in SCOBY cultures vary, but the yeast component generally includes Saccharomyces (a probiotic fungus) and other species, and the bacterial component almost always includes Gluconacetobacter xylinus to oxidize yeast-produced alcohols to acetic and other acids.