Yeast hunting in South America and Europe

Yeast, a fascinating microorganism

Please tell us something about yourself and how you got into yeast research.

Dr Juan Ignacio Eizaguirre

My name is Juan Ignacio Eizaguirre, I am a Biotechnologist and I have a PhD in Biology. I specialize in wild yeasts for brewing beer. I started in the beer world as a homebrewer in 2011. When I was in my last year of my Bachelor's degree in Biotechnology and Molecular Biology at the National University of La Plata in Argentina, a professor proposed us as a practical work to do one of the oldest biotechnologies of the world: Brewing beer.  I remembered that the first beer we brewed at the University was a Porter with more than 5 different types of malt: it was incredible!

At that time, with my friends we bought the equipment to make a batch of 50 liters and we started in the garage of my parents' house, without so much knowledge but with a lot of desire. The first beers were consumed among friends, then people started to buy them and by the year of 2012 we had our own brewery in La Plata, Argentina, and we produced about 100 liters per batch. At that time, we were all at the end of our degrees, and each one of us had our own personal goals. Three of my friends began to pursue doctorates but I was not very convinced, I was already tied to brewing beer. So it was then shortly after I contacted a researcher in Patagonia Argentina who had discovered a native yeast that was the origin of Lager beer (at that time I had no idea of the difference between an Ale or Lager beer, but well with some time and a few beers I finally understood the concept).

Well, when I started my career, my goal was to focus on the wine industry, a very strong industry in Argentina. I was always interested in the winemaking process, from grape growing, pressing, fermentation and maturation. Since I was very young, I used to go with my family to visit many wineries and it was something I enjoyed very much. Maybe if I had not learned how to brew beer in that last subject of my career, today I would be working in the wine industry. But at the end, when I understood the world of possibilities I had unlocked by learning how to transform a source of energy, such as barley seed, into such a tasty beverage to share, then there was no turning back.

What are you currently working on and how did you end up at the Weihenstephan Research Centre for Brewing and Food Quality?

Dr Juan Ignacio Eizaguirre

I am currently working at the Forschungszentrum Weihenstephan für Brau- und Lebensmittelqualität as a research assistant. The main project I am working on is on the role of fatty acids in brewing, a project led by Dr. Martin Zarnkow. I am also working on the Yeast Hunting project from Dr. Mathias Hutzler, where we are dedicated to search, isolate and identify new yeasts for the brewing industry. While those are the main lines, we are also trying to form a group of genomic analysis of brewing yeasts, among other very interesting innovation projects.

I came to Weihenstephan as a result of a collaboration between my research group in Argentina and the Weihenstephan group in Germany. A collaboration that Dr. Diego Libkind (my doctoral thesis director) and Dr. Hutzler started some time ago. Within the framework of this collaboration, I received an invitation to participate in a sampling in Georgia, in the Caucasus, and I spent three months in Europe between the sampling and then all the analyses carried out to identify the yeasts. We finally managed to isolate and identify more than 100 yeasts, 35 of which belonged to the Saccharomyces, which is closely related to brewing beer. The following year I received another invitation, and this time it was to stay for a while.

Tell us a little bit about the Patagonian yeast and what it changed in the brewing world?

Dr Juan Ignacio Eizaguirre

The “Patagonian yeast” refers to Saccharomyces eubayanus, a species described by Dr. Libkind and Dr. Hittinger in 2011, isolated in Patagonia, Argentina. This discovery caused a worldwide stir in brewing science, since by studying its complete genome, researchers found the origin of lager yeasts. The

explanation is perhaps a bit more complex, but let's understand this: the type of fermentation of a beer defines its profile, and to some extent even its style. There are two types of fermentations, broadly speaking, Ale-type fermentations and Lager-type fermentations.

The former are carried out by yeasts of the S. cerevisiae species, which has the speed to ferment the sugars in the wort and tolerate the stress conditions that exist in beer, such as ethanol, pH, acidity, among others.

The latter are carried out by S. pastorianus, a yeast hybrid species between an ale yeast (with the previously mentioned fermentative capabilities) and another yeast that allowed the hybrid to ferment at low temperatures. Let's remember that the big difference between an Ale-type fermentation and a Lager-type fermentation is the fermentation temperature, and that is given by the yeast used. When Dr. Libkind sequenced the genome of S. eubayanus (which, by the way, was the first complete genome of a yeast in Argentina), he found that this species was the other parent of the Lager hybrid.

This mystery has been keeping beer microbiologists in suspense but now that has been solved, many more doubts have arisen. How can it be that the origin of the Lager yeast, which elaboration began in Central Europe, is in Patagonia? How did these yeasts arrive in Europe? How did it hybridize with S. cerevisiae? Can this Patagonian yeast be used to brew beer? What types of beer can be produced with it? These were some of the questions that arose.

Today, almost 15 years later, we can answer many of them. It turned out that S. eubayanus was also found in Chile, United States, China, New Zealand, and two years ago in Ireland. However, we still do not understand how these microorganisms migrated, let alone where this hybrid, which was isolated by Chris Emil Hansen in 1883, was actually generated, and which currently produces more than 90% of the world's beers.

Tell us a little bit about the yeast hunters? What does this project is about? And what are your current researches?

Dr Juan Ignacio Eizaguirre

The truth is that this is an extremely interesting project, not only for the brewing world but also in terms of biodiversity, environment, conservation of natural resources, and the biotechnological potential it generates is incalculable.

The project consists in general terms in the isolation and identification of yeasts from natural and anthropic environments, with the aim of using them in the brewing industry. From Hansen's discovery to the present day, beer fermentation has become a monoculture with Lager and Ale yeasts. In the past, however, fermentations were mixed cultures, although probably dominated by a yeast Saccharomyces. These traditions are maintained in very few places, such as Belgium for example, where we know that other yeasts are essential to achieve the characteristic aroma and flavor profiles. So by going out into the wild, or looking at historical sites where beer was brewed or stored, we may come across new yeasts to brew new beers.

First, the sampling site is defined, either by a historical reference or an unexplored natural environment. Then the samples are taken, selective culture media are used to isolate the yeasts we are looking for, and then it is time to identify and characterize these microorganisms. At the end it means, a lot of work, a lot of learning, of all kinds, whether it is the use or development of new and more effective techniques, or the cultural enrichment that comes from being in the middle of the Caucasus, sharing a beer brewed in the mountains at over 2000 meters above sea level.

What developments are you observing in the field of yeast research?

Dr Juan Ignacio Eizaguirre

In recent years, developments in the brewing yeast sector have focused on the production of non-alcoholic beers, a market that is growing by leaps and bounds. While historically the production of those non-alcoholic beers (which, depending on the country, can allow up to 1% alcohol) was generated by interrupted fermentation or by mechanical-physical methods that removed the alcohol from a regular beer, today the focus is on the use of yeasts that cannot consume maltose. A beer wort has glucose, maltose and maltotriose as its main sugars; if a yeast is maltose negative (and therefore, due to the transporters, maltotriose negative), it will only be able to consume the glucose in the wort. So if I generate a low density wort (around 6 or 7 °P) and ferment all the available glucose, I will not reach the alcohol limit levels and that is why it is considered a non-alcoholic beer. From this introduction it is clear that what we are looking for when adding new yeasts to the non-alcoholic beer market is that they can only consume the glucose in the wort. This test is very simple in the laboratory, and allows us the evaluation of many yeasts at the same time, but then comes the more complex part where the fermentative aptitude, the aroma and flavor complexes generated, as well as their ease of reproduction are evaluated. What is striking about this measure is that it opens the range of possibilities and we stop working with Saccharomyces, being able to implement and rediscover new genera such as Torulaspora, Lachancea, Pichia, Cyberlindera, among others.

As for the generation of lager hybrids, the development is more limited and is mostly focused on generating new aroma and flavor profiles, but maintaining the same logic of lager-type yeasts, which are good at fermenting at low temperatures and robust for handling in the factory.

Machine translated