Repeated Yeast Domestication Ups Beer Brewing Another Level

A Flame-Side Chat, with Dr Francisco Cubillos Riffo

Last week, I wrote about an article by Dr Francisco Cubillos Riffo. Francisco is an Associate Researcher at The Millennium Institute for Integrative Biology (iBio). You can learn more about his research here by visiting the Molecular Genetics Lab Website. In short, his group investigates the diversity and genetics of yeasts in brewing. His group uses wild yeasts, found in Chile.

Francisco inspecting a tree during his sampling trip in Tierra del Fuego, Patagonia. Source: Dr Francisco Cubillos Riffo.

His team recently evolved and domesticated a wild yeast in the laboratory. Here, I will share some discussion Francisco, and I had behind the scenes. I am convinced that you will appreciate his insight and find his advice useful. I certainly did!

Francisco sampling a tree while hunting for wild yeast strains in Tierra del Fuego, Patagonia. Source: Dr Francisco Cubillos Riffo.

Edgar: Why did you decide to look at Saccharomyces eubayanus, isolated from Nothofagus trees?

Francisco: This is a nice question. We realized that S. eubayanus was found in Argentina, but no one in Chile looked for it in the Chilean Patagonia. Therefore, we decided to go after it since the Chilean Nothofagus forest is extensive, covering over 2,000 km from the north to the south. We thought it was a fantastic opportunity to look for yeast and understand its diversity. Diversity is what we found indeed! 

Edgar: Could you tell me what your reasons were to start looking into yeast evolution and domestication?

Francisco: When we started evaluating these native S. eubayanus strains’ fermentation capacity, we realized that several aspects could be improved. Among others, fermentations were good (and tasty!), but not as good as commercial strains, and attenuation together with the duration of the overall process were longer. In other words, there was room for improvement.

Edgar: I wondered why you decided to use a pooling approach. In some ways, finding that one strain dominates cultures consistently, suggests that not all yeast isolates are equally able to evolve and adapt to 9% ethanol. How applicable do you think these findings are to other yeast strains/species?

Francisco: Individuals usually compete for nutrients while trying to cope with different environmental perturbations. In the past, during the first stages of yeast domestication, different strains used to compete for wort nutrients. We wanted to recreate this competitive environment while forcing the strains to adapt to stressful conditions, such as high ethanol levels. 

Edgar: What do your results mean for brewing beer? The use of Ethanol is reminiscent of the process to develop turbo yeast. We know that turbo yeasts (generally) perform poorly in homebrewing settings as the flavour profiles can disappoint. Do you have any thoughts on this?

Francisco: This is far from being a turbo yeast. Native strains have never seen wort. This approximation allows them to improve their performance under fermentation conditions by withstanding Ethanol and better using the available sugar sources (rapidly!). Ethanol increases the mutation rate and provides a harsh environment to select for adapted individuals. These individuals may also carry additional mutations that alter other traits. In this way, we found that evolved individuals had different aromatic profiles, which was an intriguing finding. 

Edgar: What did you find were the major problems or bottlenecks that hampered your work?

Francisco: We would’ve liked to analyze many more adapted individuals. However, we were limited by the number of strains we could sequence and the large number of fermentations it would have required. Each individual requires time and proper analysis. 

However, we got a nice evolved strain, and we’re doing dozens of fermentations across the country with different breweries, demonstrating its potential. In general, brewers are very happy with the outcome.

Edgar: What do you think the interesting questions are from this work that you and your lab will pursue?

Francisco: We are pursuing different questions now. Can we improve attenuation even more (and faster)? Can we get other aroma profiles? Can we evolve other strains and obtain a catalogue of strains with different profiles? Can we make commercially attractive hybrids for lager fermentation? 

We are working in all these fields and trying to get as much diversity as possible. In this way, we expect to convince brewers how yeast can diversify their production and differentiate from others.

Francisco carrying out experiments at the VTT in Finland in 2018, in the group of Brian Gibson. Source: Dr Francisco Cubillos Riffo.

Edgar: Are your strains now used for commercial beer production and if so, what characteristics do they like in particular?

Francisco: So far, we got public funding to promote R&D with local producers. In particular, beers are high on ethyl-esters and have intense fruity aromas and some mild phenol leftovers. Overall, producers have tried simple pilsner or Ale worts that enhance the yeast flavours over hops.

Edgar: If the readers are interested in your strains, could they obtain a culture and if so, how?

Francisco: Yes, sure! We have some strains with lots of potentials. Ideally, we like to promote R&D, so we all learn about these yeasts!

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I hope (and I am sure) that work in Francisco’s group, this Flame-Side Chat, and our post will have convinced you of the potential that the diversity of (wild) yeast offers. A heartfelt thanks to Francisco for his help, thoughtful answers and sharing such great insights! Any More questions about this or related work? Get in touch.

Cheers 🍻🍺🍻

Edgar, The Beerologist at ExtrAnalytics.