In my last post, I plated the gross lees from naturally fermented wine on agar without and with drugs that will kill non-Brettanomyces species. In one plate in particular, I got several different types of colonies that metabolized the bromocresol dye at different rates, suggesting different species of wild yeast. After picking some colonies to grow in culture, I will link some photos of their morphology in this post.
To refresh everyone’s memory, Garrett Oliver, brewmaster of Brooklyn Brewery, has used the lees from naturally fermented wine for either a primary or secondary fermentation of wort. Some of these beers are described here. His overall goal is to isolate wild yeast from spontaneously fermented wine to eventually brew wild beers. Interestingly, spontaneously fermented wine can have any number of yeast species depending on the grapes used in the must and where they were grown. This includes species such as Saccharomyces, Pichia, Candida, and Brettanomyces.
For these photos, I picked one colony from the TO sample and five colonies from the GL sample. GL stands for Gross Lees and is taken directly from the fermented must. I’m only showing one colony of TO since all of the colonies that I picked from this sample looked exactly the same:
The cells are very different from I expected compared to Brettanomyces bruxellensis. These cells are not long and sausage-shaped, but more ovoid. They do not appear as round as Saccharomyces cerevisae.
GL-1. Although the yeast in the sample was diluted, cells that are clumped together appear slightly elongated while cells alone in suspension are more ovoid. This is very distinct from TO-1
GL-2. This was the only sample that have very long shaped cells, but in very low abundance. Could this be the teleomorph (sexual reproduction) stage of the yeast.
GL-3. Similar to TO-1.
GL-4. A bit more elongated and thicker (see cell in above right corner).
GL-5. Very similar to GL-3.
Hard to say what strains I have. All of these strains have different abilities to metabolize the bromocresol dye suggesting different strains. Some of the colonies look different, but some are the same, as in GL-3 and GL-5. I cannot rule out that I’ve isolated the same strain either. These cells look very different from the Brettanomyces that I have isolated from Lambics. More importantly, I was hoping to get some wild Saccharomyces in these samples but I found none, since all the colonies that I grew all had the classic funky Brett character. I refuse to believe that the gross lees has no Saccharomyces since it must appear during spontaneous fermentation of wine. My growth media might be missing them somehow and I may have to make media selective for only wild Saccharomyces. Importantly, I’m coming to realize that just looking at cell and colony morphology is not enough to ascertain what these strains are. To truly identify these strains from different classes of fungi, PCR genotyping and growth on limited carbon sources might be the way to go.
I will next take these six strains (same or different) and run some basic fermentation trails to test their ability to ferment wort. I may also include coumaric acid as a test for Brett character since it worked well on my previous plates. As an alternate approach, I am going to inoculate the gross lees with sterile wort, stimulating whatever is growing there. Hopefully, any Saccharomyces that is there will grow faster than Brettanomyces.