The Microscopic Alchemist
Hunting the Wild Yeast
Dr. Anne Madden and Lea Shell
In a world festooned with colossal whales, radiant peacocks, and tool-making crows, yeasts are thoroughly unimpressive creatures.
Each yeast is only a single cell, too small to see with the naked eye.
Even when compared to their microscopic kin, yeasts appear feeble species.
They aren’t particularly good at moving from place to place.
They don’t notoriously cause disease, and, unlike other fungi, they can’t even produce colorful mushrooms.
Yet yeasts have one remarkable trait that separates them from other life forms. They embody an alchemist’s secret, which makes them one of the most useful creatures to humans.
They can make alcohol.
In the process of fermentation, while feeding on sugar and transforming it into alcohol, yeasts simultaneously produce a bouquet of chemicals interpreted as flavors and aromas which humans have been enjoying for millennia. Each beer you’ve ever drunk has been the life work of many millions and millions of yeast cells.
Beer is remarkably simple when viewed as a list of ingredients: water, grains, hops, and yeast. But this list over-simplifies the process, just as a prize-winning pumpkin is more than the result of just a seed landing in soil. Like the gardener, the brewer makes decisions that impact the yeast, and in turn the beer they produce. Yet we are not the masters of yeast, but rather their doting caretakers.
Brewers strive to create the right feeding and environmental conditions for yeast that will coax out the best flavors in the final beers, while avoiding the worst. Crisp and biscuity? These yeast were likely luxuriating in cool temperatures. Artificial butter, rotten eggs, or soap herald the woes of stressed yeast. They tell the story of millions of yeast cells dying in crippling heat, suffocating under toxic chemicals, or suffering from a bacterial infection of their own.
For the last 150 years, most of the beer produced in the world has been made using a handful of domesticated yeast species. Brewers trade them with colleagues, or buy them from yeast factory farms. Every species and subspecies with its own flavor profile catalogued for the choosing. Want to brew a dry and crisp lager? “WLP802” is for you. Interested in making a red ale? “1084” is recommended.
This system works well for producing known flavors from known yeasts. But brewers seeking new flavors need new yeasts.
And to come up with new yeasts, you need a wild yeast wrangler.
For organisms that can’t run or fly away, yeasts are remarkably elusive in nature. There are no footprints to follow, calls to hear, or traps to set.
There are two things we do know: yeasts like sugar, and sugar is rare in nature. Some yeast wranglers hike through Patagonian forests, finding wild yeasts clinging to sweet tree sap.
Some wranglers tread through lush orchards, finding yeasts nestled near the stems of rotting fruit. Still others find yeasts swimming in the pools of nectar in flowers, or in the dregs of wine in oak barrels.
I am of a tribe of wranglers that is, like the yeasts themselves, opportunistic. I let sugar-seeking insects do the collecting of yeasts for me.
As a wasp travels from rotten fruit to tree sap to nectar, gulping down sugars, it is also gathering yeasts.
When I return from the field with bags of angry insects, the real work begins. I extract and grow the yeasts, then test and identify them. In doing so I find out which yeasts might be able to make beer, and which ones could be dangerous.
Along with other scientists and brewers, I am now hunting for what conditions are best for wild yeasts, hoping that just one of them will stick around long enough to see the inside of a brewery.
Many yeasts recoil from the domestic life and are unable to flourish in the boiled grains of beer. Still others wreak chemical havoc in beers, adding flavors like wet dog, horse sweat, and vinegar.
Yet sometimes a new yeast is able to produce new beers with wonderful flavors. Beers where every sip seems dipped in honey. Beers that become beautifully tart in record time. Beers that inspire the palate. Here the brewer, the wrangler, and the yeast have worked together to reveal the flavor secrets of the wild world.
But in discovering these new yeasts, we are gaining more than new beers. In uncovering these chemicals that delight the senses we find that yeasts are naturally churning out additional chemicals valuable for the cosmetics, food, and health industries. Some yeast have the ability to make fuels from waste, still others may hold the key to probiotics and our health.
The more we look at these wild yeasts, the more we find they offer chemical solutions to problems beyond bland beer. Their presence and promise on this planet extend far beyond their physicality. They are surprising translators, and alchemists in miniature.
*Dr. Anne A. Madden is a microbiology researcher and yeast wrangler in the Rob Dunn Lab at NC State University. Working with John Sheppard from NC State University, she and Dunn made beer from wasp and bumblebee yeast. She can be found on Twitter as @AnneAMadden
Lea Shell is the Curator of Digital Media for the Rob Dunn Lab at NC State University.
Her side projects include woodworking, beer brewing and raising tiny humans to ask really good questions. You might also know her as @YourWild_Life or @veganbuglady.