SAN FRANCISCO — Naomi Most, a devoted brewer of a fermented tea called kombucha, keeps her “Big Momma” in the garage. Big Momma 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 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 thirst for soda and bottled water, sales of kombucha and other “functional” juices in the U.S. topped $295 million last year, up 25 percent over a two-year period, according to market researcher SPINS Inc.

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.

‘The mother’

In the Bay Area, many fans have taken to making their own kombucha, trading recipes and selling good brews. Craigslist, for example, is full of those selling fermented patties. Several foodie groups organize regular swap meets for fermented cultures.

To make kombucha, brewers rely on what’s called a starter — a bit of already fermented tea — passed between makers and referred to reverentially as “the mother.” Once the mother is added to sweetened tea and allowed to sit in a glass jar unrefrigerated for seven to 14 days, a glop known as a symbiotic colony of bacteria and yeast grows over the surface.

This “mother” will expand and split into smaller patties called “babies,” which brewers often give to friends or sell online. “I have kombucha babies available in several different types of tea (pu-erh, oolong, white tea, some others),” reads a post by Most on the Kombucha Exchange, an online forum.

Risks

The rise in kombucha’s popularity is part of a larger trend in “probiotic” foods containing bacteria, which some studies suggest benefit digestion and boost the immune system.

“It’s become incredibly trendy lately in the 20-to-30-something, foodie, intelligentsia set,” said Dr. Daphne Miller, a family practitioner and professor of nutrition and integrative medicine at the University of California, San Francisco.

Kombucha is said to have originated in ancient China, but various forms of fermented tea exist in many countries, said Miller, who traveled the world researching healthy traditional diets while writing her book, “The Jungle Effect.” Some medical professionals, however, think the drink is dangerous. Dr. Andrew Weil, a doctor and leader in alternative health, writes on his Web site: “I don’t recommend kombucha tea at all. I know of no scientific studies backing up the health claims made for it.” He goes on to warn of homebrews contaminated with aspergillus, a toxin-producing fungus, and cautions pregnant women, the elderly, children and anyone with a compromised immune system against drinking it.

This most recent growth in popularity is actually the tea’s second act in the United States. In the early 1990s, the drink became popular with health food enthusiasts and those with HIV and AIDS who believed it would help compromised immune systems and increase T-cell counts. In 1995, the Centers for Disease Control and Prevention issued a report linking kombucha to the death of an Iowa woman and the illness of another woman. Both experienced severe metabolic acidosis, excessive acid buildup in the body that health officials thought may have been related to their daily use of kombucha.

DIY

But the drink’s standing as the cure-all of the moment was not the attraction for some.

Lev Kilun, 51, was an unemployed telecommunications engineer when he bought his first bottle of kombucha several years ago. He immediately recognized the distinct effervescent tang. “I called it tea kvass,” said Kilun, who emigrated in the late 1980s from what is now Uzbekistan. “In Russia it was very popular. It was like an old women’s drink. My grandmother used to make it.”

Seeing a business opportunity and feeling something akin to a birthright, Kilun started his own company, Lev’s Original Kombucha. He now bottles and sells six flavors brewed with green tea and distributes kegs to restaurants and cafes around the Bay Area. Kilun says the tea is thought to help cure a hangover, which he says makes for brisk sales in liquor stores.

Kombucha’s popularity has also attracted homebrewers. Tim Anderson, founder of a 3-D printer technology company, moved from Boston to Berkeley, Calif., with his “mother” — passed on to him from a friend who got it.

Anderson, an advocate for all things do-it-yourself, made step-by-step kombucha brewing instructions complete with videos for Instructables.com. Nearly 60,000 people have viewed the kombucha guide to date, according to the site’s page-view statistics.

“I’m surprised people would pay to get this stuff,” Anderson said. “The kind you can buy tastes vinegary and dry, whereas the one you can make yourself is so incredibly delicious.”

Recently he put out a call for kombucha culture after he neglected his brew and let the fermented patty dry out. “You can’t go around saying you killed your mother,” he said. “It freaks people out.”