In Michigan's remote Keweenaw Peninsula, Emily Geiger observes a science lab table full of beer-fermenting starter yeast. But this is no ordinary beer yeast—the culture was gathered from the shores of Lake Superior, in the Upper Peninsula, over the course of a week, then returned to the lab, stripped of imperfections, and prepared to enter a brewing cycle. Geiger is now gathering yeast from three different areas in the Upper Peninsula, creating six native strands. She currently works as the microbiologist at Keweenaw Brewing Company in tiny South Range, Michigan, but her company, Craft Cultures, distributes the lake yeast to a number of breweries across the state.

Geiger’s lake yeast is a new option in a line of ever-increasing unique yeast sources, from Oregon-based Rogue Ales' beard-yeast beer to California's Fossil Fuels Brewing Company’s retired 45-million-year-old yeast strain, derived from an ancient Lebanese weevil beetle encased in amber. Dogfish Head out in Delaware produces Delaware Native Ale, with yeast collected from the skin of locally grown peaches, in addition to Ta Henket, a beer inspired by ancient Egypt that incorporates yeast trapped from a date grove in Cairo.

... craft brewers around the world are beginning to experiment with collecting wild yeast from nature.

Because many breweries would go belly up if their non-renewable yeast strains were somehow destroyed, craft brewers around the world are beginning to experiment with collecting wild yeast from nature. Brewers are looking for yeast strains that impart not only unique flavors, but are also wild-sourced, ensuring that they don't have to depend on a separate commercial entity’s yeast—even if that yeast provides an always reliable and identical taste.

Setting Yeast Traps

Catching yeast may seem like a far-fetched science experiment, but overall the process is pretty simple. Geiger takes a mason jar filled with wort (a yeast-attracting sugary infusion of mashed grain and water), covers the top with cheesecloth, and buries the jar in sand with the top above ground. Then she waits between a few days and a week, checking on the trap’s progress periodically. When finished, the jar contains a mixture of bacteria, yeast and mold. She uses the pure culture technique, a microbiologist’s method of separating organisms, to isolate the area’s particular yeast strand. From there, she brews small batches of beer with the yeast to see the characteristics of the finished product.

And Geiger isn't set on only catching lakeshore yeast. She says that yeast lives everywhere, just waiting to be caught, and she can set traps up wherever a customer wants—like right now, she’s working on trapping yeast from a grain farm.

Luckily, nobody has ever stolen any of Geiger's traps—but that doesn’t mean collecting the yeast is always easy. "Some of the yeast is undesirable," she explains. "Just like undesirable characteristics in beer. I mean, they’re from nature, so you don’t know what style of beer it’s going to make. Certain beer styles use certain strains in the brewing industry, and so when we’re using something that purposely has never been used before, we don’t know what we’re getting. It can be disappointing for some people. It’s like, ahh ... we got some, but it’s no good, we have to try again."

Whether usable yeast forms is essentially luck of the draw ...

Whether usable yeast forms is essentially luck of the draw—and because of variable air quality on a day to day basis, there’s really no way to control that. But for many of her customers, although producing bad beer is disappointing, customers are generally onboard to start over.

Some of the Michigan breweries with which Geiger works—like New Holland Brewing, Witch’s Hat Brewing Co., and Stormcloud Brewing Company—are specifically interested in brewing all-Michigan beers, brews where every ingredient and flavor is locally sourced. So, brewers usually want her to do everything she can to get a good strain.

A Changing Flavor Profile

Just about every corporate beer brand available (think the Millers and the Buds of the world) uses commercial lab-produced yeast, which ensures that a beer will taste exactly the same every time it's brewed. On the other hand, because Geiger’s yeast strands are wild-caught in the great outdoors, every single one of them is different. Even yeast trapped from the same location can have subtle flavor differences in the finished brew, depending on what’s in the air that day—similar to how honey tastes different based on where the bees have collected pollen. As far as the yeast strands Geiger isolates, they each bring a unique flavor to the finished product.

Craft Cultures' UP Lager Yeast, gathered from a site near Marquette, Michigan, tastes clean and crisp, with low sulfur (which is often produced as a byproduct of the fermentation process), so the beer's other flavors can shine through. Geiger's Keweenaw Ale Yeast, collected in the Keweenaw Peninsula, shows characteristics of a Belgian-style mixed with some farmhouse notes that give the beer a spicy and fruity finish. And the Eagle River Ale Yeast, gathered from the original test site where Eagle River meets Lake Superior, is another fruity and spicy Belgian-style minus the Keweenaw Ale Yeast farmhouse notes. "They’re different but they share some characteristics, which I guess all brewing strains do," Geiger states. Generally, brewers who purchase yeast from Craft Cultures can choose from lager yeast or ale yeast.

Geiger's idea to catch wild yeast stemmed from a casual conversation with a friend, as the two discussed the spot where Eagle River meets Lake Superior in the Upper Peninsula. "He’s like, ‘There’s the one location that smells really yeasty,’ and he wanted to try and isolate yeast from there," Geiger recalls. "So he gave me coordinates and I literally went hunting for this location and set out yeast traps. We successfully isolated two strains from that site."