Waller St. Brewery’s Microbiological Signature

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Patrick Thibeault

Waller Street Brewery is located in the cramped basement of a downtown Ottawa stone heritage building. It’s not easy to find which is perfect for the speakeasy vibe they’re going for. But beyond the space, in a market nearly drowning in great craft beers, how does a such a small microbrewery distinguish itself? One trick, it turns out, has been to hire Dimitri Carrabin, a microbiologist by training and a brewer by choice.

Given Dimitri’s expertise, its founders knew that the Waller Street Brewery would stand out from the crowd if it had its own microbiological signature, its own strains of yeasts and lactobacilli. Armed with petri dishes, test tubes, an incubator and other science lab doohickies, he set out to isolate yeast and lactobacillus strains, which could then be used in Waller Street’s beers. It’s been a recipe for delicious success, giving beers like their Livery Stable Blue, a Brett Farmhouse Ale crafted by head brewer Marc-André Chainey, notes of baked apples.

So how did he do it?

It all started with a trip to a local organic farm; the organic bit is important since Dimitri was looking for living organisms which don’t tend to do very well when they’re doused in pesticides. Since any fruit containing sugar will naturally have wild yeasts on its surface, Dimitri chose strawberries, ground cherries, tomatoes as well as various flowers and barks as his potential yeast sources. Once home, forever making sure that everything was sterile, he prepared his incubating liquid: 10% sterilized dry malt extract (DME), 5% ethanol (to make sure he would only get alcohol resistant microorganisms) and 85% water. He placed pieces of all the things he’d gathered in 10 ml tubes, covered these with a parafilm membrane, popped the whole thing in an incubator at 32 °C and left it there till the solutions started becoming cloudy, a sign of microbial activity.

Once he was sure something microbial was up, he extracted 20 uL from the cloudy solutions and placed this on a petri dish which went into the incubator. During the week long incubation, all the microorganisms started getting busy. Using an image bank of yeast colony morphologies, Dimitri was able to identify in which petri dish patch he had struck gold; it was dome shaped, creamy looking and beige. It came from the ground cherry sample. Careful observation under a microscope also confirmed that he’d found brewer’s yeast.

Still not knowing what exactly he’d managed to find, Dimitri took a sample of his yeast patch and proceeded to propagating his newfound microbial pets in the incubator in a spectrophotometre containing a 10% DME solution. This part of the process takes approximately 16 hours. Making sure he had the right number of yeast cells per volume and density, he then brewed his first 1 gallon test batch. The results were excellent. The yeast Dimitri had isolated on those ground cherries gave the beer notes of baked apples.

Since that initial batch, Dimitri has isolated another wild yeast strain from the walls of the Waller Street Brewery as well as a lactobacillus strain which had contaminated their annual Christmas beer. These microorganisms are what give the Waller Street beers their signature, those original flavours which no other brewery has. They are also expressions of the brewery’s microbiological terroir, a final frontier for any brewer or drinker who cares about locally sourced ingredients and the flavour of place.

In addition to flavour, having Dimitri on board has had an important economic advantage. Since Waller Street brewery has flat bottomed fermenters salvaged from a local winery instead of the usual cylindroconical fermenters, they cannot recuperate and reuse their yeast. Every batch must start with fresh yeast which would obviously cost an arm and a leg if they were to buy it in new every time. Therefore, every Sunday, Dimitri propagates new batches of yeast to be used in the week’s brews. If you ask him, the freshness of the yeast has a great impact on the quality of the finished beer. Sipping on a flight of Waller Street’s beers, it would be hard to find anyone who disagrees