These Are Not The Yeast Your Are Looking For
A month ago I got quite excited about some scientific literature I had come across which may have identified the home of wild Brettanomyces. Long story short, a number of papers looking at the rhizosphere (root-associated microorganisms) of several crops found Brettanomyces. This was an exciting finding, as the usual suspects – insects, on the surface of fruits, or in decaying wood, were all a bust.
As you can imagine, I was rather fired up by this finding, and pretty quickly started my own search. Unfortunately, this came at the end of the growing season, so I was only able to sample the roots of some beans, and of some dill – both which were reported in the literature to contain Brettanomyces in their rhizospheres.
Other Parts to this Series:
- Part I: These Are Not The Yeast You Are Looking For (this post)
- Part II: These ARE The Yeast Your Are Looking For
- Part III: Wild Brettanomyces – a Needle in a Haystack
- Part IV: Fermentation characteristics
Isolating Wild Brettanomyces
I used some of my microbiology know-how to give myself the best opportunity to find wild Brettanomyces in my samples. To start I made a custom growth medium, based on the WLN medium often used to identify Brettanomyces. This medium contains all the nutrients needed by Brettanomyces to grow, along with bromocresol green – a dye which Brettanomyces will break down into a yellow-ish product, but which other yeasts cannot metabolize. In addition to the usual medium components, I also added two bacteria-killing antibiotics: chloramphenicol and ampicillin. I also added a third component not often found in WLN to suppress the growth of non-Brettanomyces yeasts and many other fungi. Those “in the know” can guess what that chemical is. For the uninitiated I’m holding that bit of information back, as that particular chemical is insanely poisonous and I don’t want to risk someone trying to repeat this and harming themselves.
If you know what the magic sauce is, you probably know how to work with it safely. If you don’t, please do not attempt this yourself – after all, you can’t read my blog if you’re dead…
The process itself was fairly simple – I shook the loose dirt off of the roots of the plants I had harvested, then vigorously washed the roots in distilled water. The resulting suspension was plated on my modified-WLN agar plates, and grown at ~25C for 8 days.
Results of the Search
As you can guess from the title, I was not successful. To the right is a picture of one of the dozen plates I prepared. I had pretty clean growth – no bacteria or other yeasts to be found. But instead of Brettanomyces I ended up isolating an unusual filamentous fungus.
I cannot be certain what this fungi is. Every colony I isolated looked the same, meaning I’ve suppressed almost everything in these soil samples. So the assay is good…but I don’t know what this fungi is. Based on its colony morphology and appearance under the microscope (sorry, no pictures), it may be a species of Chrysosporium. But, given its a filamentous fungi and not a yeast, and I’m a brewer, I’m not preceding further trying to identify it.
So What’s Next?
I’m going to repeat this process, but first running an enrichment culture in liquid medium to (hopefully) enrich for Brettanomyces. Filamentous fungi shouldn’t grow too well in a non-aerated liquid culture, so hopefully this will help. I can then plate anything that grows in the hopes of isolating some Brettanomyces. I will also sample a broader range of plants to improve my chances.
Of course, it is fall now, so that will have to wait until spring.
Until then, my dreams will be visions of wild Brettanomyces.
Other Parts to this Series:
- Part I: These Are Not The Yeast You Are Looking For (this post)
- Part II: These ARE The Yeast Your Are Looking For
- Part III: Wild Brettanomyces – a Needle in a Haystack
- Part IV: Fermentation characteristics