Spelling: Saccharomyces eubayanus – the discovered yeast
Spelling: Saccharomyces cerevisiae – the original ale yeast
Christopher Todd Hittinger, Assistant Professor
Department of Genetics
UW-Madison College of Agricultural and Life Sciences
The tale of the lost larger beer yeast
4:28 – Total Time
0:20 – The importance of the larger beer yeast discovery
1:00 – Unique nature of the yeast
1:23 – How the yeast traveled
1:51 – What the discovery may mean
2:23 – How the yeast adapted
3:29 – What it felt like to make the discovery
4:18 – Lead out
The history of a beer making yeast is now uncovered. We’re visiting today with Chris Todd Hittinger, Department of Genetics, University of Wisconsin, in the College of Agricultural and Life Sciences, Madison, Wisconsin and I’m Sevie Kenyon.
Sevie Kenyon: Chris, welcome to our microphone. Chris, why was the investigation in the history of this particular yeast so important?
Chris Todd Hittinger: Well, people have been looking for the missing component of lager yeast for a long time and this has been something of an historical curiosity. We’ve known that it is a hybrid of the ale yeast, Saccharomyces cerevisiae, with some missing component that nobody had been able to find in either natural or industrial environments in Europe. We and [our] collaborators have set about sampling Saccharomyces, the genus, from all over the world. And we’ve sampled five different continents and it turns out in Patagonia we finally found a wild species that matches the genome that matches the genetic code of lager yeast.
Sevie Kenyon: What’s so unique about the yeast you’ve uncovered?
Chris Todd Hittinger: Traditional ale strains prefer much warmer temperatures, and so when Bavarians began the lagering process in the 1400s, of brewing and storing their beer in cellars and caves this created a situation where the ale yeasts were not optimal to brewing at these colder temperatures.
Sevie Kenyon: Can you give us a sense for how this yeast got from Argentina to Bavaria?
Chris Todd Hittinger: We know that Saccharomyces yeasts like rotting fruit. With the rise of trans-Atlantic trade in the 1500s there would have been a lot of fruit and other agricultural products, and indeed, fermented beverages going back and forth and Saccharomyces eubayanus would have been happy on any one of these substrates. It’s really any number of ways that trans-Atlantic trade could have provided a fairly efficient route from Patagonia into Europe.
Sevie Kenyon: Chris, can you give us a sense as to what comes after this discovery?
Chris Todd Hittinger: Well there are a few exciting possibilities; one is the original motivation for this study, is to sketch out the biodiversity of this important genus. And these are exactly the kind of tools that you’re going to use in your doctor’s office five, ten and twenty years from now as you go in to understand what makes one human different from another. And, the other application is perhaps a little more fun and that is the understanding the genetic basis of the yeast strains that people use for different brewing strains. You can imagine the brewing industry going through and possibly selecting and making designer yeast.
Sevie Kenyon: Chris, some change took place when this yeast traveled between continents. Can you give us an idea what that looked like?
Chris Todd Hittinger: So as soon as eubayanus came on the scene in Europe and produced spoors, it would have been able to very quickly hybridize with the existing ale strains. Once that hybrid forms, it’s sterile, much like a mule, a cross between a donkey and a horse. So, it can’t then reproduce with any of the other wild yeasts, but it is able to reproduce indefinitely, asexually, especially when it’s in this sugar-rich environment and being actively passaged by brewers from one batch to the next. During that time, this also created a situation where new mutations could be selected for and we actually map out a few differences between this hybrid that would have occurred after this hybridization event and these are genetic changes that occurred during the domestication process and were selected for either by the competitive brewing environment itself or possibly by brewers interested in particular outcomes.
Sevie Kenyon: Can you describe for me what it felt like when you knew you had something unique here?
Chris Todd Hittinger: Yeah, so I remember the first time we got a peek at the genome of this strain. My post-doctoral adviser and Jim Dover who did some of the technical aspects of the sequencing and I, actually did gather over lagers and ales to go over the initial raw data. And, it turned out to be a surprisingly clear and lucid presentation, because the data was so clear. Post-doctoral advisor Mark Johnston and I have had a long-standing, friendly disagreement about the relative merits of ales and lagers and neither of us has changed our opinions on that. He is an ale man and I am a lager man. And I think as data started to come in, we certainly both have a much greater appreciation for the complex processes that have given rise to the lager beers that many of us enjoy today
Sevie Kenyon: We’ve been visiting today with Chris Todd Hittinger, Department of Genetics, University of Wisconsin, in the College of Agricultural and Life Sciences, Madison, Wisconsin and I’m Sevie Kenyon.