In this post we sit down with Nick Ketchum, Quality Assurance Manager at the Rhinegeist lab. Nick was part of a research team that recently published some important findings on the potential for “killer yeasts” (antifungal proteins naturally produced by Saccharomyces cerevisiae) to safeguard against off-flavors, spontaneous explosions, and other problems that have plagued commercial and non-commercial brewers since the advent of the craft! You can read the entire article on the American Society for Microbiology Journals’ site here, listen to Cincinnati Edition’s episode on the research here, or read on to hear about this exciting discovery directly from one of the scientists!

Short on time? Here’s the nitty gritty:

• Diastatic yeasts can spoil craft beer through hyperattenuation, which boosts the alcohol content and causes bottles to explode.
• Killer toxins, which are produced by other yeast strains, hint at a remedy.
• Researchers found that killer toxins inhibited up to 95% of diastatic yeasts.
• Killer yeasts may help brewers remedy potentially contaminated beers

As many brewers have learned the hard way, secondary fermentation in packaged beer can often result in undesirable consequences, such as off-flavors, unpredictable alcohol levels, hyperattenuation, and even spontaneous explosion! Craft brewing has grown A LOT over the past decade, and new breweries often lack the means for pasteurization, which increases these risks. Luckily for all of us in the craft brewing industry, a group of brewers and microbiologists (including you, of course!) have found a potential solution: using “killer” yeasts in brewing offers a means of remediating product loss by drastically reducing the probability of contamination. What led the team to this discovery? Does everyone on the research team have experience in commercial brewing?

Nick Ketchum: No, I am the only one who has a background in brewing, which is actually quite exciting. The initial research and the original idea started here at Rhinegeist after we had quite a nasty run in with Diastatic yeasts in 2019, which led to us having to dump three different tanks of beer! After this I had an “aha” moment while I was writing a Brewing Microbiology lecture for my side hustle as an adjunct professor. I remember the exact moment I had the idea like it was yesterday.I was typing out a description of how killer yeast toxins are very species-specific, and how they are quite benign to humans, and then *BAM* the dots connected for me! You should be able to use killer yeast toxins to inhibit the growth of diastatic yeasts in beer and leave the beer unadulterated.  I performed the initial experiments over at our Spring Grove site with support from Cole Hackbarth (VP of Brewery Operations) and we saw what we expected to see: killer yeast toxins can in fact kill diastatic yeasts. After this, I gave a poster presentation in 2020 at the World Brewing Congress which  caught the attention of John Bryce over on the MBAA Master Brewers Podcast. From there Dr Paul Rowley, an associate professor at the University of Idaho, who is an expert in killer yeast, reached out to me to see if I would be interested in working together with him. I was ecstatic because he is a leading expert in the world of applied killer yeast toxin research, so it was a natural synergy.

Aside from shoring breweries up against product loss (an obvious benefit), what are some other potential ramifications of your research?

NK: Well, Dr. Rowley is focusing much of his time looking for clinical applications for killer yeast toxins, and combating infectious yeast is actually quite difficult since humans and yeast have very common molecular machinery. So any novel insights we make on this project could potentially be used to combat things like Candida Galbrata infections, which are known to be highly resistant to antibiotics. Additionally, if we can come up with a great product, then hundreds or even thousands of breweries will not need to turn to energy-intensive forms of stabilization like pasteurization or filtration to kill off these pesky diastatic yeasts. This will reduce the size of the craft brewing carbon footprint and the water consumption footprint as well.  

Do you have a favorite yeast pun or joke? We love a good yeast pun. 

Well, I’m a pretty Fun Guy and I always have time for a joke with my best buds, I guess it’s how I was raised…
What do rednecks and yeasts have in common? They are both “in-bread.”

Will you be continuing this research in the future? 

I am working on a STTR grant with Dr. Rowley to get more funding to work on this project, and hopefully turn it into a viable business since I filed a patent on the IP back in 2020.  

What is your favorite yeast? Be honest, we’re all friends here.

 Oh man, that’s a hard one. Umm, Omega Yeast has some really amazing yeast strains. But I am also a sucker for the classics. I would say that the aromas that come from Sake yeasts are amongst my favorites, but I also isolated a yeast from a bee when I first started here and that was a really cool yeast as well.