Did we domesticate yeast, or did yeast domesticate us?

Either way, it’s a cozy relationship: We feed these talented one-celled organisms a diet of sugar and keep the temperature just so, and they reward us by, among other things, turning barley broth into beer.

Most brewers use a domesticated strain of Saccharomyces cerevisiae (ale yeast) or Saccharomyces pastorianus (lager yeast). But floating in the air around us, clinging to leaves and fruit, hiding in crevices of wood, there might be tens of thousands of wild yeast strains, says researcher Jasper Akerboom. Some are naturally occurring variants of Saccharomyces (Greek for “sugar fungus”); some belong to radically different species.

Akerboom is a brewing scientist with Lost Rhino Brewing in Ashburn, Va., and founder of his own company, JasperYeast LLC. He has been on a talent hunt for the few wild yeasts that will produce a tasty brew. He has found them in unlikely places. Bone Dusters, an amber ale, was fermented by a yeast that Akerboom collected by running a sterile swab over fossilized bones millions of years old. The bones belonged to a proto-cetacean (an ancestor of today’s whales) that a paleontologist friend dredged from Virginia’s Great Dismal Swamp.

This isn’t some exotic Jurassic strain suddenly released from suspended animation. It’s a close cousin of ordinary ale yeast, but it has a funny quirk, says Akerboom. It broke down one-third of the available sugars, stopped for a few weeks, then resumed fermentation. Akerboom speculates that it first gobbled up glucose, then needed to adjust its metabolism to handle more complex, harder-to-digest sugars. (Apparently, some yeasts believe in enjoying dessert first.)

The beer turned out “fruity and Belgiany,” he says.

Most wild strains, adds Rhino founder and co-owner Favio Garcia, “produce beer that tastes like a saison; they tend to ferment very dry.”


Growlers containing pure strains of wild yeast sit on a shelf at Lost Rhino. (Jasper Akerboom)

But not all of them. Native Son is another Lost Rhino release, crafted entirely from Virginia-sourced ingredients. The brewery ferments it with a yeast that Akerboom isolated in 2007, when he worked at the Janelia Research Campus in Ashburn, while home-brewing as a hobby. “It’s very aromatic. It has a great estery profile,” he says. (Esters are byproducts of fermentation that we perceive as fruity in flavor.) However, it doesn’t attenuate well, notes Akerboom. That means that instead of turning all those sugar molecules into alcohol and carbon dioxide, the yeast leaves a lot of that sugar behind, adding sweetness and body to the beer. (Basically, it’s a picky eater.) 

Farther outside the mainstream is Lost Rhino’s Birth of Ace, an India pale ale fermented entirely with a species called Brettanomyces bruxellensis. “Brett” yeasts belong to a genus that’s known for its strong flavors, ranging from acidic to tropical fruit to “horsy.” Akerboom describes Birth of Ace as “very pineappley.” Brett strains work more slowly than Saccharomyces, but they have a voracious appetite for more-complex carbohydrates, often producing a bone-dry beer.

Bluejacket, near the Washington Navy Yard, is the scene of some very complex fermentations. Its saison Mothra, for instance, is fermented by a tag team consisting of two strains of Saccharomyces, two strains of Brettanomyces and a lactobacillus. It has a whiff of barnyard funk, that apple-and-pear fruitiness common to many Belgian ales, and an immensely dry, sour, citrusy finish.

Bluejacket has been conducting an experiment in spontaneous fermentation, letting Mother Nature inoculate the brew without the brewer’s pitching in additional yeast.

On the brewery-restaurant’s second floor is a large, shallow steel pan measuring about 18 1/2 feet long, four feet wide and two feet deep. The vessel is called a “coolship” because the large surface area allows the wort (the unfermented, sugar-rich brewing liquid) to shed heat quickly. One day last November, brewer Josh Chapman opened a valve that allowed the contents of his brew kettle to flow, steaming and spattering, into the coolship. The windows were opened, and overnight the temperature of the wort dropped from near boiling to 45 degrees. Whatever wild yeasts and bacteria exist in the Washington air, wafting over the monuments and government buildings, settled into the liquid.

Within 24 hours, the beer was transferred to four 60-gallon French oak barrels, where it was exposed to whatever microbes were lurking in the wood. It’s now undergoing a long and complicated fermentation typical of Belgian lambics, sour (sometimes mouth-puckeringly so) wheat ales brewed by a handful of breweries in the area around Brussels.

Lambics can spend anywhere from a few months to a few years in the barrel. Brewers will often mix a well-aged lambic with a freshly fermenting version; the result is a highly effervescent beverage called a gueuze. They might age those beers over fruit to create variants, such as a kriek (a cherry lambic) or a framboise (raspberry lambic).

At best, lambics have a dry, sparkling, champagnelike quality. However, different batches and different barrels will yield different results; the only way to achieve a consistent house character is by blending the contents of many casks.

That’s the plan of Bluejacket’s beer director, Greg Engert. A second batch from the coolship yielded six more barrels, for a total of 10 so far. Engert said he would like to see that number eventually grow into the hundreds. But he acknowledges that he’ll have to find a place offsite to store that many barrels.

Not quite two months in the wood, the beer was progressing nicely. “It’s in its acid phase,” Engert said in mid-January, as he sipped a sample of the tart, hazy liquid freshly drawn from the barrel. “There are also some cool tannins coming through.” An earthy note in the aroma could be the first harbinger of Brett.

Other Mid-Atlantic breweries are experimenting with lambic-style beers. Down in Virginia Beach, Justin MacDonald, president and head brewer of Beach Brewing, built an addition to his plant he calls the Cool-Shack, where he’s dabbling in spontaneous fermentation. Flying Dog’s planned satellite brewery, a farmhouse-style operation outside Leesburg, will include a coolship for brewing wild ales. At Lost Rhino, Akerboom exposed a beaker of wort to the outside air, then used it to spike a barrel of now-fermenting ale.

Will these experiments yield anything drinkable? Allagash Brewing in Portland, Maine, has been brewing spontaneously fermented beers since 2007. Resurgam is a gueuze-style blend with lively carbonation, piercing acidity and a dry, peppery finish. Allagash ages the Resurgam on cherries to produce a beer called Cerise and on raspberries to make an ale called Red. All are available in corked bottles — but only at the brewery.

Allagash brew master Jason Perkins cautions that brewing lambic-style brews (he prefers the name “coolship beers”) is a long-term project and many a barrel probably will be dumped along the way. “It was a big leap of faith for us,” he says.

Kitsock is the editor of Mid-Atlantic Brewing News.