SAN FRANCISCO

NAOMI MOST, a devoted brewer of a fermented tea called kombucha, keeps her “big momma” in the garage. The big momma in question is a 20-pound pancake of gelatinous and, well, rather gross-looking bacteria and yeast floating atop a vat of kombucha, a drink that enthusiasts tout as a tonic for digestion, hair loss and all manner of bodily ailments.

It’s not for everyone.

“I live with my boyfriend and he finds it really weird,” said Ms. Most, 30, a manager for a nonprofit group in Palo Alto, Calif. “He doesn’t like the smell.”

Looks and aroma notwithstanding, kombucha is gaining popularity among those who favor organic beverages, and it is showing signs of turning into a gold mine for some companies. While the poor economy and worries about health and the environment have diminished the national thirst for soda and bottled water, sales of kombucha and other “functional” juices in the United States topped $295 million last year, up 25 percent over a two-year period, according to SPINS Inc., a market researcher.

In 2009 Americans bought more than a million bottles of GT’s Kombucha, the leading commercial variety made by Millennium Products. The chief executive, G. T. Dave, started the company as a teenager in his parents’ kitchen in Beverly Hills, Calif., but the drink has grown beyond the mom-and-pop scale. Recently major companies like Red Bull and Honest Tea (of which Coca-Cola owns 40 percent) began distributing their own brands.