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Lager yeast: history, science, and origins of Saccharomyces pastorianus

Lager yeast is one of the most fascinating ingredients in beer. Its history is made up of accidental hybridizations, scientific discoveries, and a journey that starts in Patagonia and reaches the Bavarian cellars of the 17th century.

1. Lager yeast is a hybrid

Saccharomyces pastorianus, commonly called lager yeast, was born from the crossbreeding of:

• Saccharomyces cerevisiae — top-fermenting yeast, used for ales
• Saccharomyces eubayanus — wild yeast, cold-tolerant

2. Where and when did the crossbreeding happen?

A 2023 study suggests that this hybridization took place in 1602 at the Munich Court Brewery (Hofbräuhaus), during the period when both top and bottom fermentation beers were produced in the same place. Before that, low-temperature fermentation was already practiced, but probably with unstable mixed strains.

3. The adaptation and success of lager strains

• Before the hybridization: winter fermentation in the cold Bavarian cellars favored cold-tolerant strains.
• After the hybridization: S. pastorianus combined the fermentative capacity of S. cerevisiae with the cold tolerance of S. eubayanus — perfect for low-temperature beers.

4. The search for the missing yeast

In 2011 in Patagonia, wild strains of S. eubayanus were discovered, reinforcing theories about the origin of the wild parent of lager yeast. A discovery that confirmed how global microbial biodiversity is the foundation of the beer we drink every day.

5. Pure yeast and industrial development

In 1883, microbiologist Emil Christian Hansen isolated a single pure yeast cell for the first time at the Carlsberg laboratories. This yeast, called Saccharomyces carlsbergensis, became the basis for the lager strains used industrially worldwide.

Craft lager beers today

Craft lager beers represent a category often underestimated in the craft world, but they are gaining growing appreciation thanks to their cleanliness, balance, and hidden complexity. Craft breweries respect the fundamental characteristics of the style but with an innovative approach: fresh noble hops, local malts, extended lagering.

Want to explore all lager styles? Read the complete guide →

Discover the selection of craft lagers on Maltese — shipping throughout Italy. 🍺