Beer enthusiasts are familiar with the two main categories: lagers and ales. Lagers, known for their crisp taste, are brewed at cool temperatures, while ales, characterized by their spiciness and flavor, are brewed in warmer conditions. Both types derive their unique flavors from fermentation, a process where yeast converts sugars into alcohol and carbon dioxide. Different yeast strains, even when fed the same sugary diet, produce distinct beer flavors.
While ale yeast boasts 358 strains, lager yeast has a significantly smaller pool of only 85 strains. This limited variety has left lager lovers with fewer flavor options. However, a team led by Jennifer Molinet and Francisco Cubillos at the University of Santiago, Chile, is working to change that, potentially ushering in a new era of lager diversity.
Lager yeast are hybrids, a combination of two yeast species: *Saccharomyces cerevisiae* and *Saccharomyces eubayanus*. *S. cerevisiae* is a familiar yeast used in bread, wine, and beer, while *S. eubayanus* is more specialized, thriving in cold environments. These two species crossed paths in Germany over 400 years ago, giving rise to the lager yeast we know today.
Over centuries, lager yeast has been meticulously bred and selected for optimal taste, fermentation speed, and durability. All existing lager strains are descendants of this original hybrid, categorized into two distinct genetic groups: Saaz and Frohberg, named after a Czech town and a German brewery respectively. For a long time, these two groups were thought to be the limits of the lager universe.
However, in a groundbreaking paper published in *PLOS Genetics*, Dr. Molinet, Dr. Cubillos, and their colleagues unveiled new hybrids of *S. cerevisiae* and *S. eubayanus*. These hybrids were impossible to create before 2011, when a different research team discovered new strains of *S. eubayanus* in the bark of Southern beech trees in Patagonia. Dr. Molinet was initially intrigued by the yeast’s ability to survive the harsh, frigid conditions of Tierra del Fuego, the southernmost tip of the region. It was later that she conceived the idea of creating new lager hybrids.
The first hybrid created by Dr. Molinet and her colleagues in 2021 was unsuccessful. It wasn’t any better at converting sugars into alcohol than its parent strains. This wasn’t surprising, as today’s top lager yeasts have benefited from centuries of careful breeding. Undeterred, the researchers opted for an accelerated evolution approach.
Over the next seven months, the team created hundreds of generations of lager yeast, each time selecting those with the most desirable traits for brewing a delicious beer. They observed that yeast inheriting mitochondria (the energy-producing components of cells) from *S. eubayanus* rather than *S. cerevisiae* performed exceptionally well. The researchers believe that these mitochondria, originating from the cold-loving *S. eubayanus*, are better adapted to the brewing conditions required for lager.
After 250 generations, the improvements plateaued. The final hybrid, dubbed H3-E, was a more efficient fermenter than any of its ancestors. It was also more robust and flavorful. Unlike the citrusy taste of commercial lagers, the H3-E hybrid offers a spicy flavor with hints of clove, potentially appealing even to ale enthusiasts.
The researchers presented their work at a microbiology conference in Chile last year, accompanied by 500 liters of their brew. The response was overwhelmingly positive, with the beer running out quickly. Breweries in Chile have since adopted their hybrid for local competitions and limited-edition batches, but widespread availability remains a challenge.
Commercial lager yeast typically ferments in seven days, while the new hybrid requires double that time. This difference would slow down large-scale production. However, Dr. Cubillos and his team are refining their techniques and remain optimistic about the future, suggesting that a new wave of lager flavors is on the horizon.
