Explore and Experiment With Yeast Diversity; The Result Could be Amazing!

A Flame-Side Chat, with Prof. Dr Diego Bonatto

Prof. Dr Diego Bonatto

My fellow beer enthusiasts,

Earlier this week, I described an article by Prof. Dr Diego Bonatto. In this post, I will share some discussion Diego and I had behind the scenes. I like to call it a Flame-side chat. I hope you will appreciate his insight and find his advice useful. I certainly did!

Edgar: I was struck by the idea to use an ecological approach to mine a recipe database to learn about yeast. What prompted you to start this work?

Diego: I am a homebrewer and a cellular and molecular biologist (with a twist on bioinformatics also). I am currently working with brewing yeast and hybrid yeast strains in order to understand the molecular mechanisms that allow yeast cells to survive the harsh environment of beer fermentation.

Since I started to make beer, I realized that many of my fellow brewers exclusively use dry yeasts to make beer, and I empirically observed that many recipes for IPAs and APAs also extensively make use of dry yeast strains. As I'm working with brewing yeasts, some professional brewers in my city (Porto Alegre) also previously contact me to help them to solve fermentation problems that happen in their breweries (mostly stuck fermentation problems). Again, I found that these craft breweries industries also use a large quantity of dry yeasts to ferment their beer.

So, all these empirical observations lead me to the question: "is it possible that, despite a large number of liquid yeast available, the brewers prefer to use dry yeast because it is cheap and easy to use, despite the low number of dry strains?" Once the driver question was formulated, I started to collect data from Brewer's Friend (with their permission) and to make all the analyses.

Edgar: What was the biggest challenge whilst carrying out your research?

Diego: It was organizing the data in a comprehensible and in computer-readable format. Recipes can be very confusing, with a lot of misinformation, excessive data description or even the lack of basic data. So, it was necessary to develop a computer pipeline to organize yeast data and then start the analysis.

Edgar: I struggled to separate the terms ”diversity” and ”evenness” of yeast strains in your MS. Could you please elaborate on what each represents?

Diego: In quantitative ecology, diversity is a broad (and more complex) term that encompass a series of "metrics", including richness and evenness. In this sense, richness is the number of species (yeast type) and the total number of individuals found in an area (or in a specific beer category), while evenness is defined as how homogeneous or even an area (or beer category) is in terms of the abundances of its species (yeast strains). A beer category where all yeast strains are equally distributed in a specific number of recipes is considered with a high degree of evenness (but not necessarily with a high diversity).

Edgar: What in your mind was the most surprising result of your study?

Diego: The preference for dried yeasts. They are largely employed by brewers. I think that the brewer's preference for dried yeast has the potential to restrict the brewers’ creativity for designing new beer styles.

Edgar: What do you see as an exciting or necessary follow up to this work?

Diego: It should be important to evaluate if the brewer's yeast preference that we observed with more than 100,000 recipes is the same when we increase the number of recipes to 1,000,000 or more. This can be done by exploring different recipes databases, from different countries.

Edgar: As a molecular biologist, I am quite interested to what extent diversity applies on a genetic level. Do you have any idea as to whether some strains in a given category are genetically related (little diversity or very distinct from each other?)

Diego: Good point. I am also very curious about how diverse are the dry and liquid strains in terms of genomics. I suppose that many commercial dry and liquid strains are genomically more or less similar, but I could be completely wrong. For example, the largely used US-05 dry strain is related to "Chico" strain that, by its turn, is derived from an original strain used in many breweries in England at the beginning of 20th century. The "Chico" strain is still available in liquid form for different companies. How similar they are (US-05 and Chico from different companies)? We know that yeast companies selected their yeast colonies and propagated it indefinitely.

Edgar: How do you think brewers should use the discoveries that you made? What are the opportunities that come from your work?

Diego: Brewers should not be afraid to explore different yeast strains in different beer categories/styles. We know that brewing has a series of "rules" that are in its essence oral traditions that are transmitted from veteran brewers to novices, and the choice of yeast strains for a beer style is part of these traditions. For example, we learned that IPAs and APAs should be fermented with mostly neutral yeast strains (with one or two exceptions); however, these styles can benefit from the use of yeast strains that secret high quantities of beta-glucosidases, a family of enzymes that increase the levels of hop-derived aglycones and improve the flavour of beers. Some non-killer wine strains secrete high amounts of beta-glucosidases (and fruity esters as a bonus) that biotransform hop-derived essential oils in flavour compounds. Why not use a combination of wine and beer yeast strains to synergically increase the flavour and aroma of an IPA?

Edgar: What do you think is the biggest challenge brewers face for which science could provide an answer?

Diego: A good and complex question, indeed! I think that are many challenges in brewing fermentation. For example, the development of ethanol tolerant strains where brewers can reuse it many times without worry about its viability and vitality. Or the development of tailor-made yeast strains, like new lagers/hybrid yeast strains, by using non-GMO techniques. However, the (re)discovery of kveiks strains from Norwegian farmhouse beers can be cited as an example of how science and the recovery of an almost extinct yeast strain can improve brewing. These strains have unique fermentative characters, like high temperature and ester production, and scientists began to study why they are so different. The kveiks could provide us with the information necessary to understand how they can tolerate high inoculation temperatures without the loss of viability and if these characters can be used to improve our traditional yeast strains.

Edgar: What would you advise any brewer who wants to make the most delicious beer?

Diego: Do not be afraid to use different yeasts! Explore the yeast diversity. Combine different yeasts strains. The result could be amazing!

A heartfelt thanks to Diego Bonatto for his help, thoughtful answers and sharing his brewing wisdom!

I hope you enjoyed this episode of “A Flame-side chat”. Next week, we will delve into the genomics and distribution of Brettanomyces, described by a paper from the Carlsberg Research Laboratory! Stay tuned!!