Notes of “horse blanket” and “burnt Band-Aid”: How wild yeasts are bringing offbeat terroir to craft beer

The basic approach involves separating microbes from their source, then diluting and scraping them across an agar plate (a Petri dish with nutrients for cultivating microorganisms) to be identified and isolated. From there, it’s a matter of gradually building up the culture until there’s enough of it to make beer. It’s also possible to start with an already-finished batch of beer, and then work up a yeast culture from its dregs. What you get from this is likely to be a ‘domesticated’ strain, a way of playing with the microbial stock used by the producing brewery. For many crafty brewers, picking up some Petri dishes and sample tubes is hardly a chore—especially if it’s going to add dimension to their brewing process.

“There’s a lot of experimentation going on in the brewing world,” says Heit, who has been brewing for about 23 years. “Everyone’s interested in new hops, new techniques, and I think more new styles have come out in the last five years than in the 17 years before that.”

Though there are simple methods to ensure that even amateurs manage to isolate drinkable yeasts, safety is a concern when working with wild cultures. Yeasts can be found almost anywhere, but so can all sorts of other, less tasty, and even downright deadly microorganisms.

“What’s been described to me is people just go around and sample totally randomly, they take a bit of soil, a bit of grass, chunks of bark, potentially animal feces, who knows,” says Lachance. “I think people who want to be serious about that should try and establish a relationship with somebody who’s equipped to do the identification before they start making beer and drinking it. It’d be a lot safer.”

Yet wild-sourced yeasts and bacteria are nothing new to brewing: Farmhouse, Saison, and Lambic styles in Belgium for example have used ‘spontaneous’ fermentation for centuries, wherein wort is left out overnight in open-air coolships. Ambient yeasts and bacteria—often carried by winds or insects—can then settle in to breed and feed on the wort. In areas where a lot of brewing happens, chances are good that tasty, beer-friendly yeasts have established communities nearby.

Techniques for isolating and controlling yeast cultures largely pushed spontaneous fermentation out of vogue. But the method is being revived by a growing number of breweries around the country, such as Jester King near Austin, Texas. “We’ve always been fans of wild fermentation, so we chose not to brew or ferment with monocultures,” says founder Jeffrey Stuffings. “Brewers are fond of doing that, isolating strains off of wildflowers or fruit. I think the craziest one I ever saw was a brewer’s beard hair.”

Jester King took up wild fermentation in 2013, after a homebrewer cloned one of its beers to near perfection. For a brewery that prioritized the local, the reproducibility of their beer was a wake-up call. “If a brewer several states away can clone our beer so precisely, it made me question how well we were doing [showcasing unique local offerings],” says Stuffings. “So at that point I felt compelled to have us do exclusively wild fermentation.“

Getting reliable results from batch to batch is desirable for obvious reasons. But given how easily yeasts can be sourced from unlikely—and maybe unseemly—places, there’s a lot of opportunity for brewers to produce unique results that stamp their brew with a particular time and place. It doesn’t get more ‘craft’ than that.

Bug business 

The creative case for making beer out of novel yeast strains is easy; the business case, less so.

One of the main challenges to the commercial prospects of wild ‘bugs’—another term of art used by brewers to describe bacteria and wild yeasts—is the fact that they generally produce beers many people won’t want to drink. Sour, funky beers are appealing to a relatively limited set of palates; locality and terroir may lose relevance the further one goes from the source. That’s to say nothing of the difficulty in producing enough beer to make the effort economically viable beyond small batches.

Even an international brewery like Dogfish Head maintains interest in the process and has the customers to buy wild-fermented beers, but sales are confined to a handful of states adjacent to the brewery itself. Given the often offbeat flavor profiles and the limitations of scale for regionally sourced yeasts, the market for wild fermented beverages largely remains local brewers and cultivators.

Wild yeasts represent undiscovered country in biology and brewing alike. Only about 1,500 species have been identified, representing an estimated 5% of the total. As DNA sequencing becomes more common, and techniques for isolating and guiding the mutation of yeasts more widespread, there’s growing room for innovation and, to some extent, propriety.

Nature in general is not a solid basis of intellectual property—one does not simply patent a wild organism. But that changes if you can work out a new way of using that organism, or manage to apply or hybridize strains in a novel way. Indeed, Chicago-based Omega Yeasts, one of the leading ‘boutique’ labs to open in recent years, is in the midst of patenting a strain, the result of in-lab breeding of naturally occurring strains.

“If the hand of man is involved in changing it genetically in some way, you could patent the resulting organism,” explains Omega’s Lance Shaner. Shaner’s business partner Marc Schwarz continues, “If it goes well, we’ll be able to get a patent on that strain, which then means nobody would be able to sell that strain at all except for us, unless they licensed it from us.”

Louis Pasteur patented the idea that you could ferment beer without leaving it open to ambient air, along with the process of isolating yeast strains, though this intellectual property was never commercialized. Techniques like these, as well as traditional strains or mixed cultures, are in the public domain. That leaves trademarking as the avenue most commonly pursued by modern yeast labs looking to stamp their strains.

One example is the increasingly popular range of “Kveik” strains from Norway. Recently these storied strains have been discovered to perform in ways that many brewers find impressive, the result of domestication by generations of Norwegian brewers who kept cultures wrapped in cloth, tucked in drawers, or buried for safekeeping in “Kveik rings,” resembling wooden spines bent into a circle.

Now that these strains are making their way to the States, they create new branding opportunities. Bootleg sells a strain called Oslo; Inland Island sells Norwegian Farmhouse; Imperial Yeast sells Loki. Omega’s strain is called Jovaru Kveik, delivered to Schwarz in person by a Lithuanian woman named Aldona Udriené. The strain had served her family business for generations, but her children weren’t interested in carrying on the brewing business, so she approached Omega in hopes they could find a market for it. These companies don’t own the strains, per se, just the branding associated with them.

As to the commercial future of wild and locally sourced yeast strains, it seems mainly a matter of luck. There’s no telling when or where a yeast wrangler will stumble on an unknown strain that makes a great beer. “When someone finally gets a really good strain that has good commercial properties, that’s probably when you’ll see more interest in it,” says Heit.

For the community of craft and home brewers, the business case often matters less than the pure challenge of finding a novel strain that ties their beer to their region, and more closely to their own efforts. To some, the hunt is more important than the taste.

“When you’re trying to find your own wild yeast, sometimes that’s a secondary concern,” says Jeff Mello. “The achievement of finding the wild yeast is a pretty big one.”

Correction: An earlier version of this post misidentified the Jovaru Kveik strain as a different strain, Hornindal Kveik.