Yeast Shepherding Part 2: Beer from thin air

In our never-ending quest for interesting and new beers, we’ve set out on a path that takes us in a very biological direction, focusing on yeasts and other microbes that contribute to beer flavor. This is a path that we’re betting will lead us to a Shangri-La of beer, where new and untold sensations greet us at every sip.  If you read our manifesto on why we collect new yeast strains (part 1 of this series), we hope you’ll agree that this is a worthy and noble mission. In this post, I will explain our approach to collecting yeast and how we begin to tame these wild microbes.


For all of those non-microbiologists out there, it may be difficult to imagine going outside and wrangling a wild yeast, especially since they’re invisible.  Obviously we need a microscope to find these critters.  Of course, just trying to search the landscape one micron at a time would be a tedious task, so we have to get clever. A good starting point is to think about habitat: where do yeast like to hang their microscopic hats when they’re not in bread, wine or beer? It turns out that’s not entirely clear.

One might think, if yeast are so great at fermenting, then we can just find a good sugar source and the yeast should be there, fermenting. Indeed this is what wine- and cider-makers (and some brewers) have been doing for a long time. By just crushing the fruits and letting nature take over, they are encouraging the growth of naturally occurring yeasts and the subsequent production of alcohol. One might think that this implies that yeast are abundant on fruits. However why, then, aren’t copious amounts of alcohol available in nature? Why do we even need breweries and wineries? The answer, at least in part, is that yeast only tend to grow to large numbers in manmade environments. 

In nature, there is an unseen battle among untold varieties of microbes to get at any available energy.  Importantly, though, in a manmade system, we can set up this game so that the winner is predetermined. For vintners, when lots of fruits are mashed up and put together in a giant container where oxygen has trouble getting in, the yeast start to grow and dominate, creating alcohol and ultimately, wine. The specific way that yeast choose their sugars and create acids and alcohol in a certain order allows them to outcompete a large number of other microbes and come out on top. Winemakers (and certain Belgian brewers) have been taking advantage of this for centuries by sticking to strict traditions. The specific steps taken to prepare the ingredients and the fermentation vessels create conditions that favor the dominance of certain yeasts. By being rigorously methodical in their techniques, these artisans have managed to obtain reproducible results from a seemingly chaotic ecosystem without even being aware (until recently) of the microbiological underpinnings of their strategies.

blog-post_Poker-01It is important to note that conditions set up by traditional vintners or brewers, with lots of sugar available in a vast container, do not occur in nature. This man-made setup is the very determinant of what microbes will grow in a spontaneous fermentation.  Is it possible, then, that by creating such a winner-take-all setup that favors certain yeasts, we are forgoing an opportunity to taste the products of other microbes that may have been outcompeted in this scenario?

At this point, I should mention that I’ve been focusing on winemakers because many of them still rely on “spontaneous” fermentation, which is simply fermentation that takes place using ambient microbes, rather than inoculation with specific strains. With a few exceptions, most modern brewers rely on domesticated commercial yeast strains and seldom provide an opportunity for other microbes to even make an appearance. These commercial/industrial yeast strains have been passed down for generations and most likely originated from a winner-take-all spontaneous ferment that occurred centuries ago. A recent article from the Verstrepen lab in Belgium suggested that most modern industrial beer yeasts originate from just a few domestication events. In their words, “the thousands of industrial yeasts that are available today seem to stem from only a few ancestral strains that made their way into food fermentations and subsequently evolved into separate lineages.” Wouldn’t it stand to reason, then, that the vast diversity of genes in wild yeast populations is a largely untapped resource for flavor?

With the tools of microbiology, we should be able to collect specific, purified wild microbes in controlled conditions and culture them so that they have exclusive access to our wort. Our hypothesis is that there are some yeasts out there that make delicious flavors, but because they don’t have Type A personalities, they never make an appearance in commercial beers, even spontaneously fermented ones. If we can simply create a nurturing environment for these creatures, they might thrive and really express themselves. If we can isolate these unusual yeast strains, we believe that we will find flavors that dazzle the senses.

To collect these new strains, we’ve been looking everywhere. The surfaces of fruits, plant leaves, and even the wind have been sources for our prospecting missions. Despite their known tendency to be found on the skins of grapes and such, some researchers have suggested that yeast are nomads, with no obvious niche. They are opportunists, waiting for the right moment to get at that sugar. It is possible that our association of yeasts with fruit skins has more to do with our own preference for fermented fruits than any yeast preference. Therefore, it seems just as reasonable to isolate a new yeast from a banana as from a stop sign.  Indeed, one of our most successful new wild strains was isolated from the wind atop a fire tower in Middlesex Fells. More on that yeast strain and how we go from wild untamed microbe to industrial workhorse in our next and final post of this series.

-Ronn Friedlander

Illustrations by Becka Schuelke