I posted a similar post in the ‘Milk The Funk’ Facebook group recently, and thought I’d copy it over to the blog as well. This post will be about White Labs’ WLP099, which I’ve been using recently for some fermentations. What are people’s experiences with it? Reading around on various homebrew forums etc. you get the impression that this yeast is a monster that will eat through everything you throw at it. Some people are even reporting that it ferments worts down to specific gravities closer to 1.000 (just do a search for “WLP099” on Homebrewtalk). This is very much in contrast to my own experiences with. Using single cell isolates of it in test fermentations, I’ve noticed that it is unable to use maltotriose, and usually ends up with attenuations of around 70% in wort. The only other similar experience I found after googling around was (apparently with input from Mr. White himself):
This of course very much goes against the fact that this yeast could ‘super-attenuate’ plain wort (which would at least require the use of maltotriose, and possibly even longer sugars). So I guess these high attenuations can only be achieved in worts supplemented with simple sugars? Another possibility is that the yeast is actually a blend (either intentional or unintentional; more on this later below).
I did some more digging, and came across this recent study by Borneman et al.:
In it they’ve sequenced a set of mostly wine strains, but they’ve included some White Labs strains as well: one of which is WLP099. Interestingly, it was found to belong to the wine yeast clade. So the fact that it actually seems to be a wine strain, would explain the lack of maltotriose use (and would fit with it having good ethanol tolerance). This paper unfortunately doesn’t go into physiology.
Another study that probably included this strain and does go into physiology is of course the recent Gallone et al. paper:
The strain names are unfortunately encoded, but I did some more digging. Going by the fact that WLP099 is POF-, I looked at the SNPs in the sequences of its PAD1 and FDC1 genes using the reads from the Borneman et al. paper:
Cross-referencing with all the sequences from the Gallone et al. paper, I was able to find only 7 strains containing the same SNPs (Beer024, Beer033, Beer088, Spirits002, Wine001, Wine009 and Wine013); all seven of which belong to the wine clade! Of these strains one, Beer033, seems to have a familiar origin and description (from Table S1): England, Beer (Strong Ale). I think we’ve found WLP099. Anyways, looking at Figure 3 and Table S5 we see that this strain doesn’t use maltotriose! Five of the other six strains which it could be also don’t use maltotriose. Beer088 is the only strain with the same SNPs which uses maltotriose, but its origin is Germany so it’s unlikely that strain would be WLP099.
So, looking at the different independent evidence (my own ferments, the forum post with the apparent input from Chris White, and the Borneman et al. and Gallone et al. papers) it looks like WLP099 is actually a wine strain and I think we can say for sure that it doesn’t use maltotriose and thus won’t super-attenuate in wort, unless it has been supplemented with simple sugars. So regarding finishing off high-gravity ferments with this yeast, it looks like it is only useful for worts to which you add sugar. In worts made only from malt, WLP099 would likely have little to no effect when adding it as a secondary yeast (i.e. when all of the monosaccharides and most of the maltose has been consumed).
So how are peopling still getting 80+% attentuations with WLP099 as the only yeast in all-malt worts? There was some speculation in the ‘Milk The Funk’ Facebook group, that WLP099 might actually (either intentionally or unintentionally) contain two yeast strains (two independent observations were given). If the other yeast strain was a dextrin-degrading one, such as S. cerevisiae var. diastaticus, it could explain how people are seeing ‘super-attenuation’ with WLP099. These strains produce extracellular glucoamylase enzymes which break down dextrin to glucose molecules, which WLP099 could then easily ferment. But this is of course only speculation!