Bioprospecting for new yeasts with novel characteristics

The word ‘domestication’ conjures images of dogs, cats, cows, and other pets and farmyard animals, descendants of wild ancestors from thousands of years ago. Surprisingly, the humble yeast that ferments your beer and leavens your bread is also a domesticated organism: a little critter by the name of Saccharomyces cerevisiae, also known as Brewer’s or Baker’s yeast.

Beer, bread, & biofuel

Brewing yeast is a useful microbe with many applications in food, beverage, and biofuel production. Different strains of yeastshow different characteristics stemming from hundreds of years of repeated cultivation on different substrates (bread dough, wort, must, etc.). This process of artificial selection has resulted in thousands of distinct S. cerevisiae strains, each having desirable properties such as flavour and aroma production and fermentation characteristics in specific applications such as bread, beer, or wine.

For example, the image below is a darkfield microscopy image of a type of beer yeast strain originating in Norway called kviek. It has the usual property of being able to produce excellent tasting beer at high temperatures. This differs from the usual ale and lager yeast strains used in beer production which require cooler temperatures to avoid production of unpleasant flavors and aromas.

Kviek brewing yeast under darkfield microscopy.

The use of a specific yeast strain in a given application is essential to obtaining the desired characteristics in the finished product, so use of yeast with known fermentation characteristics is a hallmark of the brewing and winemaking industries.

Diverse uses, but not diverse genetics

Although thousands of S. cerevisiae strains are in current industrial use, there is actually very little genetic diversity among them. The process of S. cerevisiae domestication has resulted in the loss of nearly half of the organism’s genetic information among domesticated strains when compared to wild S. cerevisiae.

Over time, as an organism adapts to a more comfortable and consistent lifestyle it becomes adapted to that environment. Genetic traits needed for survival in other environments are gradually lost and this genetic bottleneck leaves the innovation of new fermented products – for example, beer styles – with a quandary: where to get new yeasts with new properties; new flavours, aromas, and behaviors.

Yeast wrangling

In amateur and home brewing circles, the practice of ‘yeast wrangling’ by exposing pre-fermented beer to environmental yeasts has yielded limited success (around 4%) in capturing wild yeasts that can make palatable beer. This method essentially amounts to purposeful contamination of wort with wild microbes and hoping for the best.

While this method has produced drinkable beer – sometimes even excellent beer – it is clearly inadequate for professional brewing on either a small or large scale. Aside from potential health concerns attendant with serving a product containing unidentified microorganisms, the method is unreliable and unsuited for production of a consistent product.

Proxima Co-founder Iain Wallace is a passionate and experienced home brewer, and he brings that energy and expertise to this project. Below he is seen checking the refractive index of a wort sample prior to inoculating it with a culture of brewing yeast as part of an experimental brewing run.

Checking refactive index of a wort sample.

Bioprospecting for novel yeast strains and genetics

Enter the latest project from Proxima Research and Development! We’re using bioprospecting and the modern tools of genomics and microbiology to discover wild yeasts from the environment with novel brewing properties.  Bioprospecting means turning our eye to nature and living organisms to find solutions to industrial problems.

In this case, we’ll be culturing samples from known yeast-rich environments such as soil, tree bark, and fruit to obtain wild yeasts and yeast-like organisms that have useful and interesting brewing characteristics. Microbiological methods such as culture on media selective for yeasts enables us to isolate pure cultures of these organisms. For example, the image below shows yeasts obtained from a dandilion flower growing on rose bengal chloroamphenicol agar. This medium permits growth of yeasts but suppresses the growth of bacteria and other unwanted contaminants.

Yeast colonies on RBC agar.

Finally, our genomics and genetics expertise will be used to identify these organisms by DNA barcoding analysis and develop methods to test for specific brewing characteristics in novel organisms and strains through rapid genetic analysis.

A truly all-Saskatchewan brew

Saskatchewan produces some of the world’s best malt. What may be a surprise is that we are also a producer of excellent hops. All that is missing is a Saskatchewan-native yeast strain to round out the full beer triad and produce a truly ‘all-Saskatchewan’ brew.

One of the less scientific, though close to our heart, outcomes of this project will be partnering with local breweries to one day brew this truly all-Saskatchewan beer at an industrial scale.

More than just great beer

While enhancing the diversity of yeast strains available for brewing of beer is the focus of this project, we anticipate isolation of many other yeasts and yeast-like organisms. Even though these may not make great beer, they may still have many characteristics useful in biofuel and biopharmaceutical production, providing additional returns from our bioprospecting efforts.

Proxima Co-Founder Iain Wallace will lead this project, and, in collaboration with Professor Chris Eskiw at the University of Saskatchewan and through generous MITACS funding, will complete his Ph.D. based on this project.

Stay tuned! We’re excited to keep you updated on what microbes we discover out in the wilds of Saskatchewan, and how they may help to make the next excellent brew.

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