Blog about capturing wild yeast - help me find it!

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ikyn

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There was this guy that has a blog post, and he was updating frequently in April/May of this year about his capturing of wild yeast project. I'm having a really hard time finding that blog, and I was wondering if this community could help me find it?

I really have nothing to go on, except that it was super-technical with a lot of microbiology facts thrown in, and it was well cited.

I have my petri dishes, DME, and pressure cooker all ready to try my hand at harvesting some wild Saccharomyces cerevisiae.
 
That's my blog. In case you're wondering, I'm on day ~22 of a 30 day capture project. The post is in-progress and should be up on my page in a week or two. At this point I've captured 20 wild strains, but am looking for another 5-10 before moving onto the next stage (characterizing the yeasts). At this point I know I have some Rhodotorula, plus what I think is some hanseniaspora, pichia, and Saccharomyces.

A few teasers:
plate%252010.png

A plate of oxidative yeasts. The red/orange ones are Rhodotorula.

D10Montage.png

Some non-oxidative yeasts; 10-2 is possibly Saccharomyces.

A full list of all my wild-yeast related posts is maintained on this page.

Bryan
 
May I ask where you got the yeast from?

I'm in an area that produces a lot of grapes and stonefruit. I was thinking of smearing my agar plates with the skins of the fruit. I was going to go towards the back of the orchard/vineyard and get about 10 plate rubbings.

From there, I don't have any way of identifying them aside from how they look on a plate (the light/tan slimy button). From there I was going to use old growlers and taste it all until I found something good. I am fortunate that I work in a very small blood-drawing lab, so I have access to a microscope and KOH / sterile saline if I need it. No stains, unfortunately.

If you have any advice or critique, or even a step-by-step guide of some sort I could follow, I'd be much obliged. I very much admire what you're doing right now, and am trying to do something very similar without the fancy equipment.
 
ikyn, I hope you don't mind that I answer your PM and the above question here.

My current run of yeasts has been harvested off of some uncrushed 2-row malt. Basically, I threw them into a tube of 1.040 wort and let them ferment. At days 4, 10, 20 (and soon, 30), I withdraw a small amount of wort and plated it out on beer-agar plates. 2 days later I had colonies, like in my example image above. No dyes were added to the plates - Rhodotorula is naturally pigmented. About the only thing I had in my plates that is unusual was a bit of penicillin and streptomycin, to inhibit the growth of any bacteria (I'm after wild yeasts, not wild anything). The plates themselves are 1.002 gravity wort + enough agar to make them hard.

For fruit, your best bet is to dip uncrushed fruit in sterile wort and ferment whatever comes off of the skins. Even on fruit, the density of yeast tends to be a little low, so simply streaking on an agar plate may not get good returns. By growing in wort first you'll enrich the beer-compatible organisms, which can then be selected for by plating.

As for a step-by-step guide, that is in progress - I'm writing up the current stage of my wild-yeast hunt, and that post will include inoculating, plating and selecting yeast strains. That should be out late next week. Later in the summer I'll have a follow-up post, looking at the fermentation characteristics and identification of the yeasts I've purified. I don't know when this one will be posted - between holidays and preping the lectures for a new course I'm teaching in the fall, I'm not going to have much free time over the summer.

As for identifying yeast strains with dyes and whatnot, that is not easy. There is no singular dye or other compound that allows you to identify in one step what a yeast is. Typically, you need a number of specialized dyes and plates to ID a species; basically, you look for the ability to survive certain antibiotics, grow on specific carbon sources, and incorporate (or degrade) specific dyes. For example, brettanomyces will grow on a plate containing nothing but cellbiose and yeast extract, is resistant to cycloheximide, and will degrade the dye bromocresol green. To be able to ID the ~20 species of yeasts you may find in a wild ferment is prohibitively expensive, requiring a number of selective medias, antibiotics, and dyes. A good resource for this is "Yeasts, A Taxinomic Study". Every species of yeast, what it looks like, what media it grows on, etc, is outlined in this book. Its also a $500+ book; your local library may have a copy, otherwise a partial copy (with most of the brewing yeasts in it) can be found at google books.

A few bloggers out there have come up with some doable-at-home yeast analysis systems; you may not get a specific match, but you will be able to separate brett from sacch, which are the two kinds of yeast we're usually the most interested in. For example:
http://bkyeast.wordpress.com/experiments/
http://eurekabrewing.wordpress.com/projects/microbiology-projects/
http://sciencebrewer.com/wild-yeast-project/

The methods these guys have written up tend to work better for pulling wild yeasts out of labmics (or a completed wild ferment) than they are for pulling out yeast from a wild source. Basically, the 1-3 year ferment of a wild brew acts as a powerful selection process, leaving only a few species of yeasts (brettanomyces and saccharomyces) and bacteria (lactobacillus, pediococcus) alive. If you're looking at a fresh source, there are dozens of species present at any particular time.

In my case, I'm taking a more technological approach (sequencing a small part of the genome) to ID my yeast. I'm not IDing all of them - I'm only IDing the ones which make OK beer or have a unique character that I might want to include in a mixed fermentation. My method of identification is quite a bit cheaper than the classical media/dye/antibiotic approach, if you have access to the equipment (which is expensive). I run a research lab in a uni, so I have access to all the toys. Obviously, this isn't stuff the average guy has in his garage.

My advice would be:
  1. Soak some intact fruit in 1.020 to 1.040 wort (with moderate hopping, if you desire) for 12-24 hours. Remove at that point (as sterilely as possible), and let ferment at least 20 days. This should give you a Saccharomyces-dominated ferment, with most of the oxidative yeasts and nasty bacteria killed off.
  2. At the 20-day mark (and if you want, every 10 days thereafter), plate out a tiny amount of the ferment - a single drop is literally too much. You should end up with single colonies. Pick individual colonies - ignore anything pigmented, as those are usually nasty yeast or nasty bacteria.
  3. Grow each colony up in its own tube of wort (a few ml or wort is all you need). Store in the fridge, or freeze using wort + 20% glycerol, until you're ready-to-roll
  4. Sanitize a bunch of beer or wine bottles, make a bunch of foil caps to cover the bottles, and sanitize those as well. Brew up a batch of mild-tasting/lightly hoped beer and split it into the bottles (100-200ml/bottle for beer bottles, 500ml/bottle for wine bottles). Innoculate each bottle with one of the strains of yeast you purified, cap with your sanitized foil (AKA your airlock), and then let ferment 2 weeks at 20C/70F. Make sure you hold back a little bit of each yeast sample.
  5. Taste them, and decide if they're any good. Throw out the tubes of the nasty ones, bank the good ones as you see fit.
  6. At this point, if you want, you can make some of the media described in the blog posts I linked to, in order to identify the species of yeast you purified.

As for a source of all of these things, I'm not sure - I'm a Canadian, and get it all from BioShop Canada. They do ship to the US, but I imagine a US-side company would be cheaper. I'm also not sure if they (or their US equivalents) will ship to private homes; chemical companies are a little paranoid and liability-adverse. Those blogs I linked to are all US-based; they may mention where they get stuff from.

In all likelihood, the above process will lead mostly to Saccharomyces or Brettanomyces. You can separate the two of these using bromocresol green (Brett eats it, so when grown on a plate with it, bretts are white-to-yellow in colour; sacc turns blue-green). Identifying the specific species of brett or sacc is much harder, and would require more specialized dyes/medias, as described in the book I linked to above.

Hope this long rambling post sheds a little light...

Bryan
 
That's incredibly comprehensive and an absolute joy to have written out, step-by-step. I actually do have access to some common anti-biotics (amoxicillin, etc) since I work in a clinical setting. What commonly perscribed anti-biotic would be best used for the selection process? Sounds like it's time to get my hands on some glycerol.

PS - I love long rambling posts. I have a family member who just graduated from Cornell with a focus in mycology, but they don't enjoy yeasts at all. Too bad.
 
Penicillin and streptomycin are the best - they cover the gram negative and gram positive bacteria, and do not affect yeast. A lot of other antibiotics will kill yeasts as well as bacteria.

Bryan
 
I have a ready supply of powdered amoxicillin, and a ready supply of liquid ceftriaxone. Would those work at all?
 
amoxicillin should be OK - it targets the same thing as penicillin, so shouldn't harm yeast & will kill gram positives. Ceftriaxone kills gram positives and negatives, and not yeast, so it should be OK as well. In fact, ceftriaxone should be sufficient on its own - amoxicillin is totally redundant if you have ceftriaxone.

Bryan
 
I'm sure this is a whole 'nother can of worms, but once I find a few decent strains, can you isolate the yeasts to selectively breed them? Like, if you wanted a higher flocculation trait, you could take some of clumps at the bottom and keep breeding those?

I'm sure I'm oversimplifying the breeding process. I just don't anticipate getting anything very viable for brewing a really good beer, but I'm willing to work with a strain/species that provides decent results, but needs refining. I'm assuming that, in essence, this is what you're doing?
 
I've tried breeding in the past (I have a post here on HBT, from ~2 years ago, where I talk about that). Its not trivial, requires a lot of special stuff, and is unlikely to give you what you want.

You can try and drive evolution of the strain towards what you want; for example, if you continually re-pitch yeast that has settled mid-way through the ferment, you will select for highly sedimenting strains; which are usually quite flocculant as well. Over several batches of beer you should see the strain become ever more sedimentive.

Bryan
 
This is fantastic, and really answers a lot of my procedural questions. I'll be keeping an eye on your blog. I have two questions:

- What is your ultimate goal? To find a strain or two of viable Saccharomyces Cerv. that is a good, viable "American" strain? (Being that all of our brewing strains are derived from Europe)

- If I have plastic petri dishes, is there any way I can make your process work? Or do I need to order glass ones? (The plastic ones I already have, a friend gave them to me).
 
My ultimate goal is to end up with a handful of wild strains with desirable and consistent fermentation characteristics. That way I (and anyone I share them with) can do 'wild' ferments with a better degree of control. I am hoping for something a little more interesting than US strains though.

As for plastic petri dishes, the answer is 'it depends'. If the package is unopened (or opened in a way to preserve the sterility of the plates) you can use them. However, they cannot be autoclaved/pressure cooked, so there is no way to re-use them or to sanitize them if they were opened in a way that the dishes were exposed to contamination (e.g. opened in room air without a flame).

Bryan
 
This thread is fascinating! Thanks for all the info, Bryan!

I want to try and harvest some wild yeast from Concord Grapes that grow wild in my yard. I have no lab equipment and no intentions of getting any. Am I wasting my time?
 
. . .Am I wasting my time?


Not at all. In fact, I'm beginning something similar but using tomatoes. Make up some 1.040 wort, boil it to sterilize (you can also hop it, to provide some degree of anti-bacterial capacity), dip the grapes in (I'd leave them in no more than a few hours), and then let it ferment to completion (likely a few months). In the end you'll have a mix of bacteria and yeast - you can then either use that as a lambic-like blend, or go through an isolation process to pull out the yeast(s) of interest.

Since this thread started I've made a few more posts, which include some methods to purify strains of yeast from a wild ferment:

First Wild Yeast Hunt
Results of the First Wild Yeast Hunt

All of my posts relating to these sorts of wild-ferments can be found here.

Bryan
 
This might be a dumb question, but I'm going to ask anyway: Do you think there is any benefit if I spray the grapes with Star San before I put them in the wort? I heard that Star San does not kill yeast, but will kill most bacteria. Thoughts?

Thanks,
Mike
 
Bad idea. An accurate statement of what star san does is it "kills yeasts more slowly than it kills bacteria".

You don't really need to worry about the bacteria - a while ago I did a blog post on what happens during a wild ferment. Long story made short:

1) Early on you'll get some bacterial growth, including some stuff we'd normally want to avoid,
2) Between days 10 and 30 of the ferment, yeast will come to dominate, as the dropping pH and climbing alcohol levels of the wort kill off most of the bacteria.
3) Over the next few months the culture will mature, ending up with a (hopefully) tasty mix of wild yeasts and some brew-friendly bacteria.

If you're worried about the bacteria you can heavily hop the wort (bittering additions are all that is really needed). Alpha acids have some anti-microbrial effects but are generally harmless to yeast.

Bryan
 
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