Lager beer (the crisp, cold-fermented, fizzy beer) dominates the global beer market. Around 90% of the world’s beer varieties are lager. But lagers are constrained by a surprisingly narrow genetic pool — the genetic pool of yeast.
Expanding the pool
If you’ve ever wondered why lagers taste so similar to one another, it’s because of the yeast. The vast majority of beers use a limited number of yeast strains. Primarily they use Saccharomyces pastorianus, a hybrid of Saccharomyces cerevisiae and Saccharomyces eubayanus. This restricted genetic diversity has confined the range of flavors and aromas in beer. In 2011, that all changed.
“Until a few years ago, it was impossible to create a new lager beer, simply because the maternal species of lager yeast, S. eubayanus, had not yet been discovered,” writes Jennifer Molinet in The Conversation. “But in 2011, this species was found on the bark of trees in Patagonia, Argentina. Since then, hundreds of strains have been isolated from Chilean and Argentinian forests, carrying a stunning amount of genetic diversity.”
A new study co-authored by Molinet leveraged three distinct Patagonian S. eubayanus lineages to expand the repertoire of lager yeast. Researchers combined these wild strains with S. cerevisiae through experimental evolution and selection processes. These enabled them to enhance desirable traits, such as fermentation efficiency and unique aroma profiles, in these novel hybrids.
The initial batches of yeast involved natural, spore-to-spore mating, but this did not initially show significant differences from their parents. To overcome this, the scientists employed experimental evolution — a process that mimics natural selection in a controlled environment. By subjecting the hybrids to different fermentation conditions over 250 generations, they pushed the hybrids beyond their original capacities. The hybrids were then elected based on their ability to thrive in environments with varying sugar content and ethanol levels, mimicking the challenging conditions of beer fermentation.
New yeast, new beer
The results were striking. The hybrids demonstrated enhanced fermentation performance, especially in terms of maltose and maltotriose consumption — two sugars crucial for beer fermentation. This increased sugar consumption led to higher ethanol production and unique aroma profiles that distinguish these hybrids from their commercial counterparts. The researchers also identified the gene mutations that influence this fermentation.
For brewers, the implications of these findings could be a game changer. The ability to craft beers with new flavors and aromas using these novel hybrids could open up a new market segment, appealing to craft beer enthusiasts and traditional lager lovers alike. The evolved hybrids have already shown fermentative capacities on par with, and in some cases exceeding, those of commercial strains. Moreover, their unique aroma profiles — ranging from sweet, fruity notes to more complex, spicy, and phenolic undertones — could diversify the sensory experiences offered by lagers.
In the past, researchers have managed to genetically engineer yeasts to produce variations, but GMO beer didn’t prove too popular with consumers. This research promises to broaden the toolkit of brewers, leading to the development of yeast strains that are not only more efficient but also capable of producing a wider array of flavors and aromas. It represents a significant step forward from the genetically limited strains that have dominated the market for centuries.
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Journal Reference: Jennifer Molinet et al, Wild Patagonian yeast improve the evolutionary potential of novel interspecific hybrid strains for lager brewing, PLOS Genetics (2024). DOI: 10.1371/journal.pgen.1011154