Raising a glass to yeast, hops and the genomic mysteries of beer

Through the ages, beer’s genetic jumps were as much a result of unusual circumstance as they were coerced by human hand.


Piety and warmongering aside, the European monks of the Middle Ages are known for the richness of their artistry, music and food — most notably cheeses, wine, spirits and beer. In their quest for crafting and preserving beer, the monks were among the first, unwitting, scientists of yeast. At least this is what modern studies that pinpoint the origins of the world’s most popular beer suggest.

Two studies, one in 2011 and the second released this month, trace the development of lager to Bavaria in the 15th century. Up until this time, beer, or more specifically, ale, had always been fermented in warm environments, owing to the properties of Saccharomyces cerevisiae, the yeast found in ale, as well as bread and wine. But, the monks discovered that fermentation was also taking place within the casks kept in the cool recesses of the caves in which it was stored. By tinkering with this new yeast, the Bavarian monks were able to develop the signature clean, crisp profile of lager.

But where had this new yeast come from? As adept as the monks were at the early science of brewing, they lacked the technology to understand it. Fortunately, technology has caught up with beer. In 2011, by using genome sequencing, a research team discovered that lager contained the combined genomes of two different types of yeast — that of S. cerevisiae, our familiar ale yeast, and a second yeast for which no known wild source existed in Europe. The puzzle was where that second yeast originated.

Orange-colored galls from the beech tree forests of Patagonia have been found to harbor the yeast that makes lager beer possible. Image: Diego Libkind, Institute for Biodiversity and Environment Research, Bariloche, Argentina

Strange as it might seem, the answer was in the cool beech forests of Patagonia. Though we will never know exactly how the yeast, Saccharomyces eubayanus, made its way from South America to merge with S. cerevisiae and find a home in the monks’ casks, it must have stowed away on a ship, carried across the Atlantic by a plant or animal.

Compounding the mystery was that two types of lager yeast had evolved, each along separate, but similar pathways. This was result of the more recent study, which revealed a more complete picture of lager’s genomic profile.

Lager has two distinct lineages, Saaz and Frohberg, and each, it seems, are the result of two different hybridization events between variants of S. cerevisiae and S. eubayanus. This may not sound unusual to us non-yeast specialists, but for the lead researcher, Chris Todd Hittinger at the University of Wisconsin-Madison, the merger of these two varieties of yeast is akin to a genetic marriage between “humans and birds.”

Through the ages, beer’s genetic jumps were as much a result of unusual circumstance as they were coerced by human hand. After all, we humans have been beermeisters for a very very long time — it’s been theorized that agriculture was developed to fuel the need for more beer.

Beermaking today is as much a science as it is an art. As important as yeast is to the creation of beer (yeast varieties for beer today are much more varied than they were in the 15th century), the current popularity of microbrews has generated a greater awareness and demand for the other key ingredients as well, such as barley or wheat, and hops. Aligned with this interest, the first draft genome of hops was published in late 2014.

Hops, which gives beer its aroma, stability and bitterness and is the subject of wide experimentation among craft brewers, not merely in the myriad of flavours it can impart but in how and where it is grown — the Calgary-based Big Rock brewery, for example, has planted test plots of hops in an effort to secure fresher and locally-grown ingredients for its brews. Creating cold-tolerant hop hybrids as well as pest-resistant and higher yielding plants is a focus of ongoing research that we all can drink to.


Originally published at genomealberta.ca on August 14, 2015. Some minor edits were made to this edition.

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