Researchers at the University of Queensland have created a uniquely Brisbane beer, isolating a single strain of wild yeast from a jacaranda tree and used by Newstead Brewing Co to brew a beer.

PhD candidate Edward Kerr, who led the project along with Dr Ben Schulz, told Brews News that the project aimed to isolate individual strains of wild yeast for use in commercial beer production, which is challenging and rarely done.

This focus on a single strain is in contrast to spontaneous or other mixed fermentations which result in a mix of yeast and bacteria adding to the final flavour of the beer which may be different every time depending on the presence of different microbes.

Breweries like Tasmania’s Van Dieman, Future Mountain Brewing and Blending, Wildflower and La Sirene have used spontaneous fermentation to great effect, and the jacaranda yeast project builds on this idea.

“The project involves identifying individual strains of wild yeast and characterising how well they make beer and anything else that makes them interesting and scale up fermentation” explained Kerr.

“We wanted to do something different, something unique, and unique to Brisbane as well.”

“When you make beers with mixed ferment like in a coolship, you end up with interesting beers like lambics, but it’s hard to be consistent. There are likely to be different microbes growing each time, changing the flavours.

“What we’ve done is isolate different yeast species down to single strains, which will give the same flavour over and over again, and you’re able to control that.

“It’s not been done before using a single strain of wild yeast as it’s hard to produce finished beers without the help of brewer’s yeast or a mixed culture” he said.

Isolating these jacaranda yeast strains is a laborious process.

“We have to plate out the yeast and re-streak over and over again, like in high school biology, until you can make sure you have a single strain.”

Kerr has been collecting yeasts for the project since 2017, and has encountered a host of types and species.

“Yeast is like any other microbe, there’s a huge variety of them. I like to think of it like fish – there are hundreds of thousands of species under that umbrella. They all look different and do different things.

“Some are pathogenic, some are general environmental yeast that do nothing, some are great at making beer,” Kerr explained.

“Even then those that make beer act differently under different factors. They ferment to a different gravity, they create different flavours or they even look different under a microscope.”

Domestication of yeast

The difference between wild yeast and the domesticated yeast conventionally used in modern brewing is that the latter has effectively been genetically engineered to be more efficient and useful in brewing, in the creation of alcohol and the ability to survive under brewing conditions.

“Wild yeast doesn’t grow as fast as brewing yeast,” explained Kerr.

“With regular brewing yeast, its domestication took place over hundreds to even thousands of years and in an environment of fermenting over and over again using the same yeast, rather than getting in new strains, which isn’t how breweries work anymore.”

In this way brewers’ yeast has been bred to grow faster, work under specific conditions, and do its best work in specific styles of beer. But at what point does the culturing of yeast make it a domesticated rather than wild species?

“That’s a good question, are we domesticating it? The difference is that after trials or testing different characteristics, we always go back to the original culture. We use -80 freezers to store our different cultures so we can go back to the original every time.

“When we’re testing it we’re not changing it, we’re going back to the original and we’re trying to keep it the same, without putting pressures on that yeast over and over again which may change it.

“If you go through these processes, you can avoid genetic drift and evolution taking hold.”

Commercialising yeast

Part of the aim of the project was to make a commercially viable product from a wild and native yeast.

“Newstead has been great in helping us with these wild yeast. This project was specifically trying to get a wild yeast isolate to production at a commercial scale.”

The brewing industry has some specific criteria that yeast needs to fulfill in order for it to be successful, explained Kerr.

“The main thing we were looking for is for it to create ethanol, ensure it can survive in small amounts of ethanol and will break down important brewing sugars. That’s the start of what we were looking for, and to enable us to get rid of everything that doesn’t grow in those conditions.

“Then we determine whether they flocculate, and create interesting flavours and are worth looking at further.”

The jacaranda yeast from a tree on the University of Queensland campus has already been used in proof of concept beers, but still needs some tweaking, explained Kerr.

“When we first made it we had a few issues, it was for GABS beer and it was on a timeline, so it had to be finished with regular brewing yeast.

“This and many wild yeasts are not good at growing. It takes a lot longer to grow enough wild yeast to inoculate a full-scale commercial fermentation then typical brewing yeast, around a couple of months.

“Commercial brewing yeast will grow faster, a week or two to have enough for a brew and you’d be less worried about contamination as it almost always outcompetes everything.”

In addition to the fundamental characteristics of the yeast which make it amenable for use in brewing, it will have to be able to deal with brewery-specific conditions, said Kerr.

“When you’re brewing in a brewery there are so many variables; oxygen amounts, tank shapes and sizes, pressure on the yeast, temperature, flow rates.

“There are so many things at play, experiments are hard to control especially when we want to do things in triplicate and also simulate major and commercial brewery processes.”

Newstead Brewing Co’s CEO Dr Mark Howes said the jacaranda yeast ale was still being perfected.

“We see it as the first in a series of Brisbane wild yeast dominated beers and, hopefully, we’ll be launching more like this in coming years,” he said.

“This particular isolate was selected from the intriguing and delicate esters that it produces.

“I’ve never experienced anything like it, with flavours like white peach, lychee and fresh-baked sourdough.

“It’s really quite amazing.”

When this yeast might be available for commercial use in the wider industry is up in the air with the COVID-19 crisis preventing extensive lab time, but Kerr indicated it could be available from early 2021.