The Weihenstephan Strain (WLP300/WY3068) – Saccharomyces or Torulaspora? Part 1

I was flipping through some old ACS “Molecule of the Week” posts today when I came across this post about 4-vinylguaicol (4VG), one of the molecules that yeast can produce to generate a clove-like flavor in beer. This is particularly common in various yeast strains, such as Torulaspora delbrueckii (although the ACS post uses outdated nomenclature – Saccharomyces delbrueckii). This flavor is particularly desirable in wheat beers and is detectable in beers made with classic hefe yeast strains such as WLP300/WY3068. While the role of 4VG in hefeweizen wasn’t exactly news to me – many people have discussed 4VG and the best practices surrounding it’s production – it got me thinking about the strains we typically use for hefeweizens and related beers.

4VG

4VG, 2-methoxy-4-vinylphenol

I’ve always assumed that WLP300 (the Weihenstephan strain, also one of my favorite strains) was S. cerevisae – after all, S. cerevisae has the capability of converting ferulic acid into 4VG.¹ That said, I was unable to find any documentation indicating that this strain was actually S. cerevisae with the exception of this paper (though it appears to lack validation that WLP300 was indeed S. cerevisae)The authors did sequence 4 loci in all of the yeast strains studied, including WLP300, but it’s not unreasonable that they wouldn’t be able to determine the species based on only the limited sequence data from those four regions (which they were expecting to be highly conserved or highly variable between S. cerevisae strains).

On the other hand, Randy Mosher’s “Tasting Beer” claims that Bavarian Weissbier, aka hefeweizen, uses a unique Torulaspora delbrueckii yeast that produces a clove aroma, along with banana and bubble-gum fruitiness.” Even though he doesn’t directly address this specific strain, it’s hard to imagine him not including WLP300/3068 under the umbrella of authentic Bavarian hefeweizen yeast.

I also found some individuals claiming that WLP300 is indeed T. delbrueckii, in the HBD archive, the Mr. Malty yeast database, and at Eureka Brewing (WY3068), but with no backing documentation.² In fact, many references to WLP300/WY3068 being T. delbrueckii all write “Weihenstephan 68 (S. delbrueckii single strain)” leading me to think that most individuals are finding this information in a common location – perhaps the Mr. Malty yeast database.

Saccharomyces or Torulaspora? – from homebrewing.org

Either way, with the information available on the internet, it’s a dead end, with no really convincing or conclusive information. Both White Labs and Wyeast’s descriptions of the respective strains are curiously vague when describing the strains, not mentioning the what the species is. I would imagine if these strains were not S. cerevisae, that they’d make it a point to highlight that fact.³ As indicated by the Eureka Brewing post linked above, there’s no available rRNA data for this strain, making it a bit more difficult to determine the species without access to specialized equipment or services. I could get the rRNA at work but there would be no way to fund the sequencing without digging into my own pockets – not exactly realistic for this grad student! There are other potentially cheaper routes of species ID, but I’ll get into that in another post.

There is a teeny light at the end of the tunnel. I found a study comparing the osmotolerance of S. cerevisae and T. delbrueckii – it turns out that T. delbrueckii is quite a bit more osmotolerant than S. cerevisae – that is, it can survive in saltier, sugarier, etc conditions than it’s fungal relative. This can be tested (in an admittedly quick-and-dirty way) using the solid media osmotolerance testing methodology described by Hernandez-Lopez et. al, and while it couldn’t conclusively demonstrate which species WLP300 is, it might provide some useful preliminary information. So that’s where the next step lies – growing some WLP300 up and comparing it’s osmotolerance to a reference strain. Stay tuned!

Have any information regarding these strain’s species? I’d love to hear it!

Footnotes

¹As another caveat, not all T. delbrueckii strains robustly produce 4VG (they can be POF-, meaning that they lack the enzyme to produce 4VG). In other words, both S. cerevisae and T. delbrueckii can generate 4VG, but either species may also lack the capacity to do so. Therefore, ability or lack thereof to produce 4VG probably doesn’t help us much in determining what species a yeast strain is.

²I didn’t know about the Eureka Brewing yeast science blog until I googled around a bit on this subject. If you haven’t read the linked article or others on the blog, I’d highly recommend it! Very interesting information.

³And if this strain is indeed not S. cerevisae, is it really an ale yeast (as labeled by White Labs – “Hefeweizen Ale Yeast”)? It seems that most definitions of “ale yeast” specify that the strain is S. cerevisae. Sure, this is being a little pedantic, but I still think it’s an important question to ask!

Edit: I did a bit of reading and it actually might not be cost prohibitive to ID this strain via sequencing, so I may try that as well.

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16 thoughts on “The Weihenstephan Strain (WLP300/WY3068) – Saccharomyces or Torulaspora? Part 1

  1. Nice research, I hope you keep going down this rabbit hole (even if it does end up being “just” sacc). Between “Brett” Trois not being brett and WLP300 (maybe) not being sacc there’s been a lot of shakeup in fermentation world. I guess that’s a good thing, lots of serious amateur homebrewers are doing experiments that formerly only professional brewers/labs would share amongst themselves.

    I predict that in the new few years we’ll start seeing the flow of info generally going from homebrewer -> pro and not the other way around.

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    1. That’s an interesting thought! I think that you might be right – especially regarding novel techniques and cost cutting measures.

      I imagine that the big yeast labs have the resources to positively ID these strains, but it just hasn’t been done yet (perhaps because if a yeast strain makes good beer, why bother?). I can imagine it’s hard for these companies to justify the costs surrounding these experiments, although as I understand it White Labs and Illumina are collaborating to build a better taxonomy/genomic understanding of the brewing strains.

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  2. Fascinating read! This is a strain I rarely use, primarily because of the 4VG, among other compounds, it imparts. I’m curious if the commercial labs’ vagueness is intentional or not?

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    1. Interesting – that’s one of the things that I love about it! Different strokes, of course.

      One interesting thing I learned while reading is that 4VG is considered an off flavor in some contexts (as it should be) – and the strains that produce it are called POF+ (for phenolic off flavor).

      I suspect that it probably is intentional. I was thinking about emailing them to find out for sure!

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      1. They certainly have access to the tools to properly ID this yeast strain (and they make a mighty fine hefeweiss). I’ll follow up with them to see what kind of analyses they do. I wonder, then, where the claim that is Torulaspora delbrueckii originated?

        Thanks for the tip!

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      2. I don’t know where the claim came from but I wish it would die. It is not like this strain is some random find from some yeast reseller. It is a commercial strain used by one of the worlds oldest most respected breweries that happens to be hand in hand with probably the most respected brewing school on earth. I bet there has been a ton of research on the strain between the university and brewery.

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      3. I’m sure has been a ton of research on this particular strain. I’ve shot an email over to someone at the university – hope to get a response! I’d be interested to see any data they have.

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  3. Thanks for the post – very interesting. Much like the recent hullabaloo about Brett trois; there is a point that you can claim victory in nomenclature based on DNA relatedness and there is simply the consideration of the strain as a tool to get the right job accomplished without regard for its family tree. I think most commercial brewers (especially big ones) will fall into the second camp. However, still fascinating for homebrewers and people who never really got to use their Bachelor’s in microbi (like me) for anything else.
    Cheers.

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    1. Glad you found it interesting! I think you’re right – if it makes good beer (and doesn’t kill you in the process) there’s no reason for a large brewer to dive into the nitty gritty of what species it really is (and, of course, the species itself is something of an artifact of humans’ unrelenting need to categorize everything)! At the very least, it makes for some interesting discussion.

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  4. Awesome write up, I just got a pure culture of this THIS week and i am going to do the 100% fermentation next month. I’ll let you know what the result is.

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