By Jennifer MOLINET, Stockholm University

ONE of my favourite summer pastimes is enjoying a cold beer in a bar with friends after work. But not just any beer – it has to be a lager. And I am not alone. With its crisp and refreshing profile, lager accounts for more than 90 per cent of the global beer market.

However, all lager beers taste quite similar, and the diversity of flavours and aromas is limited. This is mainly due to the small numbers of commercial yeast available for production. But what if we could break free from these constraints and create completely new and exciting flavours?

Our recent study, published in PLOS Genetics, takes an approach that does just that, using wild yeast from Patagonia to create new lager yeast.

The problem with traditional lager yeast

Yeast are unicellular fungi that ferment sugar into alcohol and carbon dioxide. For centuries, humans have used yeast, consciously or unconsciously, to produce fermented foods, such as wine, beer and bread.

The traditional lager yeast, Saccharomyces pastorianus, is a hybrid cross between two yeast species: S. cerevisiae (used for producing wine and ale beer) and S.eubayanus (a wild species found on trees).

The hybrid lager yeast was domesticated hundreds of years ago and has since been optimised for brewing under cold conditions.

However, this long history of selective breeding, similar to what we see in our livestock, crops and pets has also narrowed the genetic diversity of lager yeast, resulting in a strongly limited range of available flavours and aromas – leaving little room for innovation.

Enter wild Patagonian yeast

Until a few years ago, it was impossible to create new lager beer, simply because the maternal species of lager yeast, S. eubayanus, had not yet been discovered.

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.

Our research used this genetic diversity to expand the flavour and aroma profiles for lager. We specifically focused on three S. eubayanus lineages from southern Chile that had distinct characteristics, very promising for beer brewing. They are tolerant to cold temperatures, which is necessary for lager production which normally happens at temperatures between 8-15°C. They were also efficient at turning maltose into alcohol and carbon dioxide as well as producing unique aroma profiles.

By creating hybrids of this wild lineage with the ale-yeast S. cerevisiae, we produced a brand new lager yeast that not only retained the robust fermentation characteristics needed for commercial brewing, but also offered novel flavour profiles never before smelled or tasted in lagers.

Brewing the future

That said, our first attempts to generate new hybrids did not create strains with the characteristics we wanted – they were not adapted to the conditions of fermentation. But that can happen.

However, we could improve this process in the lab; we call it experimental evolution. We grew the new hybrids in a medium similar to beer wort for six months, to enhance their brewing performance. This created several new strains thanks to the natural process of evolution.

Then, we selected those strains that demonstrated superior fermentation capacity and the ability to produce higher alcohol levels. We also found that those hybrids that inherited mitochondria (the “engine” of the cell) from their S. eubayanus parent showed larger evolutionary potential and became more efficient in converting sugar into alcohol, able to create a higher alcohol content.

But the most exciting thing for us was that the new lager strains we made showed a much broader spectrum of aroma profiles, towards a more herbal, spicy and clove-like character.

Implications for the beer industry

We believe our new hybrid yeast has the potential to revolutionise lager brewing. Craft brewers in particular, could use these strains to develop new unique lager styles, making their products stand out in a crowded market and even attract those who prefer the more fruity and hoppy ale beers (such as New England, Indian and Belgian Pale).

We have already used the new hybrid strains to produce lager beer on a small scale (500 litres) in association with local breweries in Chile.

Our study not only opens up new possibilities for the lager beer industry but also underscores the importance of biodiversity in brewing. By tapping into the natural genetic diversity of wild yeasts, we can create innovative products that meet consumers’ ever-evolving taste.

As the beer industry continues to grow and diversify, these new hybrids could play a crucial role in shaping the future of brewing.

Jennifer Molinet, Postdoctoral Researcher in Microbiology, Stockholm University

This article is republished from The Conversation under a Creative Commons license. Read the original article.