Elegantly attired in frock coat, snug pantaloons, and intricately tied cravat, the young man in the four-horse coach could easily be mistaken for an aristocratic dandy, a fashion-conscious fop. Not only does he sport one of the newly fashionable elongated top hats, but two additional “stovepipe” hats also sit ostentatiously on the seat opposite him.
And yet, as the northbound coach pulls into the first transfer station on the outskirts of Munich, we learn that 34-year-old Jacob Christian Jacobsen is an astute visionary on a historic mission, according to a popular biopic that aired recently on Danish TV. While the driver hitches fresh horses to the coach, we see the actor playing Jacobsen lift the two stylish hats from the seat to reveal two tall cylindrical tin pots. Careful not to spill their contents, he carries the containers to a water pump, where he chills them down with well water before returning them to the cool sanctuary of the stovepipe hats. Jacobsen will repeat this procedure at each coach station and train depot until he has completed the more than 600-mile journey from Bavaria to his home in Copenhagen in 1845.
We know Jacobsen today as the founder of the Carlsberg Brewery. And his precious cargo? Two liter slurries of a mixed, but mostly bottom-fermenting, culture of yeast, a present from his mentor, Spaten brewer Gabriel Sedlmayr Jr. The yeast not only survived the journey, but thrived in Jacobsen’s new Copenhagen brewery, which became the first in northern Europe to brew lager.
Nearly a half century later, Carlsberg scientist Emil Christian Hansen isolated the first single-cell, pure-culture yeast: Sacchromyces carlsbergensis (also known as S. pastorianus). Today, this hard-working fungus is responsible for fermenting the world’s most popular type of beer: lager.
Modern beer enthusiasts may deride lager as bland and boring, but in the mid-19th century, boring was good. The alternative—ale made with the top-fermenting yeast S. cerevisiae—was an unpredictable beverage susceptible to spoilage, often compromised by wild yeasts, and possessed of a limited shelf life. Lager, however, rarely spoiled, lasted longer, and tasted the same from batch to batch.
While top-fermenters binge on lukewarm sugary wort, lager yeasts nibble slowly and methodically in cooler, darker realms of the fermentation vessel. Ale yeasts show their appreciation for a good meal as extravagantly as an Italian uncle: Though instead of belching, they flocculate madly (clump together) and rise to the top of the tank in showy masses of foam known as barm. Lager yeasts sink to the bottom of the tank, anonymous and unnoticed.
Or at least until the early 1800s, when lager brewing pioneers like Sedlmayr observed that these cold-tolerant, bottom-fermenting yeasts produced a smoother, more stable beer, with fewer undesirable byproducts. More predictable, more docile, and easier to control than ever before, S. cerevisiae had been not just domesticated but transformed into a new species: S. carlsbergensis.
For centuries, brewers in Bavaria had stored (or lagered, in German) their beer deep in hilltop caves during the summer to minimize spoilage. Over time, yeasts evolved that were more tolerant of cooler temperatures and produced fewer of the esters, phenols, and other byproducts that, when carefully modulated, lend ales their expressive personalities.
But recent analysis of the S. carlsbergensis genome tells a more complicated story. More on that next week.