Yeast fusion: the story of JÖTUNN

Selective breeding has led to the creation of many different specialized breeds of animals and plants. One of the most famous animals to be selectively bred is man’s best friend, the dog. Today over 190 different breeds of dogs exist, each one different and able to fit someone’s needs and that doesn’t even include mixed dog breeds. Consider for a moment that 190 purebreeds when combined would result in 36,100 new breeds of dog. Being able to combine the best traits of two dog breeds is something a lot of pet lovers desire. Maybe this is something the beer world could benefit from, although not in hybrid brewing dogs. 


Like yeast, dogs have many different phenotypes despite being genetically similar.

Like yeast, dogs have many different phenotypes despite being genetically similar. 


Imagine being able to take the flocculation behaviour of your favourite English yeast and combining it with the ultra-dry finish of your favourite diastatic yeast. Or to take the amazing fruity flavour component from your favourite Belgian yeast, but combine it with the fast fermentation of kveik.

It seems like something from your wildest brewer’s dream, correct? Well maybe not anymore, during a recent research project done at Escarpment Labs we created multiple customized hybrid yeasts. The first yeast strain to graduate from "hybrid boot camp" is one we are calling JÖTUNN.

How to create yeast hybrids

To create JÖTUNN (and a bunch of other interesting hybrids), we used a yeast breeding technique called rare mating. This method relies on generating yeast mutants which can't make certain types of amino acids. The entire process starts by plating yeast cultures onto two different types of agar plates. One plate containing 5-fluoroctic acid, screening for yeasts which cannot synthesize uracil (ura-),  and the second plate being alpha-aminoadipate, resulting in yeasts which cannot synthesize lysine (lys-). 

These two different yeast cultures would then be introduced to each other via rare mating to create one yeast hybrid which is not lacking in either amino acid. In other words, we put two kinda-crippled yeasts in a tube together, turn the lights down low, and let the magic happen. It's like a slightly dysfunctional, miniature rom-com. 

To initiate mating, we starve the yeasts, which causes them to sporulate. The "rare" part of rare mating relies on the rare but predictable likelihood that spores of the two different strains will combine and mate, forming new hybrids that don't have the nutritional deficiencies we engineered into their parents. We can then select for hybrids using agar deficient in amino acids, since yeasts which are deficient in amino acid synthesis won't grow. 

Following this, we have to run PCR on the newly made hybrids, to ensure what we had were in fact hybrids and not false positives. We use interdelta yeast fingerprinting to compare the delta 2/12 and 12/21 regions of the hybrids to the parental strains and look for evidence of fingerprints from both parents. It's like yeasty Maury Povich.  

Using this we were able to confirm that we in fact did have some hybrid yeast strains, and some false positives. Hybrids created this way tend to have huge genomes with many copies of each chromosome, and over time yeast hybrids tend to lose genetic material and "simplify" their genetic existence. In scientific terms this is called "loss of heterozygosity".

In order to account for this and end up with hybrids that are more stable in brewers' hands, we put the hybrids through six rounds of wort fermentations. After the six rounds, the hybrids got fingerprinted again to ensure there was no cross-contamination. 

Introducing JÖTUNN

In fermentation testing after stabilization, one strain really stood out to us. Not only was it diastatic and flocculent (a rare combo since most saison strains hate flocculating), it also produced a complex mix of fruity esters with none of the aggressive banana and bubblegum esters of typical Belgian strains. Basically, it has the potential to answer the prayers of a bunch of the brewers we work with who make saisons, and we're super excited to share it with them. 

We call this strain JÖTUNN. It is a genetic hybrid of a diastatic Saison yeast and a fruity Kveik yeast, resulting in a best-of-both-worlds farmhouse fusion. We think it's pretty darn great in Saisons, as well as anywhere that a fruity, ultra-dry, slightly peppery outcome is desired. 

There will be more yeasts like JÖTUNN. One of our goals is to improve the efficiency and turnaround time of the yeast breeding process, so that we can respond faster to the needs of brewers and quickly generate new and improved yeast strains. 

Limitations of Yeast Breeding

Unfortunately, not all strains can be bred together. For example, the Cali Ale strain is essentially infertile. This is likely due to a severe amount of aneuploidy (odd numbers of chromosomes). This story rings true for a number of the yeasts in the "Beer 1" family, which includes American, British, and Belgian yeast strains. Luckily, most of the "Beer 2" family of yeasts (mostly Saison and Belgian strains) are very happy to sporulate and breed with other yeasts. 

Yeast breeding could unlock new flavours and abilities, and an unlimited amount of truly unique strains that are yet to be discovered and adopted by brewers. What this means for you, the brewer, is that your dream yeast is pretty close to becoming reality. Right now we regularly work with about 75 yeast strains, which presents the opportunity for creating thousands more. 

What is your dream yeast?

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