The yeast used to brew Guinness is unlike any other found in Ireland or the UK

The yeast used to make your most recent Guinness isn’t like any other found in Ireland or the UK!

The yeast used to brew Guinness is unlike any other found in Ireland or the UK
Kerruish DWM et al. 2024. The origins of the Guinness stout yeast. Nature Comm. DOI: 10.1038/s42003-023-05587-3
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Not surprisingly, beer brewing seems to have gotten its start at the same time as the domestication of rice and cereals.

The fermentation of those grains came soon after and were mostly a family affair with small personalized brews being made in clay pots with the aid of airborne yeast.

The majority of these ancient ‘breweries’ have been found in the middle-east and China dating back as far as 7,000 BCE!

But the modern version of beer that we think of today didn’t arrive on the scene until the 14th and 15th centuries when the process became more common with the addition of hops (Yay Germany!), saving cultures, and the establishment of Pubs and Monasteries that routinely served the beverage.

Beer making really became industrialized in the late 18th century with the invention of the thermometer and hydrometer which allowed for better control of the brewing process.

This also made the process much more scientific!

And science is (mostly) responsible for all of the different types of beer that we have today.

Many of these arose in specific geographic regions with different flavor profiles originating from the malt and hops endemic to the region doing the brewing.

But there’s one other major contributor to the flavor of beer:


While the raw materials that go into the beer making process are important, it’s the yeast that eats those materials to create the ethanol and the metabolites that form much of the flavor profile of our favorite brews.

Guinness is no exception and the researchers behind today’s paper sought to identify the origins of the yeast used to brew this iconic and velvety stout.

The Guinness brewery was established in 1759 and maintains detailed records of its brewing process.

It knows that the yeast it uses today is one that originated from a 1903 Watling Laboratory Guinness yeast.

However, the origin of THAT yeast is unknown, so the researchers used both short-read and long-read whole genome sequencing to both confirm the identity of Guinness yeast and find its next closest ancestor!

What they found was surprising and their analyses revealed that Guinness yeast isn’t related to any Irish or British strains.

Its closest cousins are actually US yeasts!

And its closest ancestor is Beer042, an isolate that was likely obtained from the Carlsberg group yeast collection, and used to brew a Belgian lager style beer.

But, the Guinness yeast strain is special and shows a mosaic ancestry, sharing only about 40% genetic identity with Beer042.

The authors believe this is due to how the Guinness yeast was handled and used in the early days which resulted in distinct genetic adaptations that gave rise to the beer (and yeast) we all know and love today!

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