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As an experiment, I brewed a gallon-sized batch last weekend using some wild yeast I had captured. Fermentation looks to have proceeded pretty normally, except that the yeast has a somewhat strange appearance. In particular, it seems to be very gummy. Big chunks of it keep traveling in both directions -- from the sediment at the bottom to the kräusen at the top, and vice versa -- and it's starting to stick to pretty much every part of the glass fermenter.

Is this unusual? Is it a sign of lactobacillus or some other non-yeast activity?

EDIT

The history behind the yeast: last summer, I used unwashed organic grapes with white flour and water to create a bread starter. I've been keeping the starter alive since then; at first, by feeding it every day, three times a day. More recently, it spends six days out of seven in the refrigerator and gets three feedings on its day out. The starter has a rather floral bouquet and does not taste very sour at all.

I took about two tablespoons of this starter and put it into a DME soup. As I was able to observe the expected yeast activity, I concluded that my "bread yeast" was capable of doing duty as "brewers yeast". When I pitched, I avoided including the original blobs of dough -- though of course, some flour is likely to have dissolved into the larger quantity of liquid.

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With this captured yeast, do you know its yeast, and did you purify a culture of it so you know you pitched one colonal organism? –  brewchez Feb 25 '12 at 21:27
    
More details added. I definitely did not purify a culture of it; it did not occur to me to do so. I assume this is a kind of "spray a few drops on agar and look for distinct patches" culturing? I haven't done that since grade school... could be fun! –  Curt Hagenlocher Feb 26 '12 at 2:07
    
You've almost certainly got a grab bag of yeasts and bacteria at work. Some small percentage of the yeast will be S. Cervisiae. See here for some info about making wine with indigenous yeast. –  Tobias Patton Feb 26 '12 at 15:39
    
Your wild yeast could be highly flocculent and the chunks you see are groups of yeast cells. How does it smell/taste? –  Mattress Mar 2 '12 at 15:53
    
I've now siphoned the beer out of its original one-gallon container and into a new one. I took the opportunity to smell and taste, and it seemed unremarkable -- a little oddly bitter, a little too much ester, but neither sour nor unpleasant. A few globlets of yeast did get sucked into the siphon, and they continue their odd up-and-down travel in their new home. What was left behind in the fermenter looked a little chunky but otherwise unremarkable. It had none of the glossy sheen of the yeast suspended in the beer. I'll probably try a bottle in two weeks and report back. –  Curt Hagenlocher Mar 4 '12 at 15:42
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1 Answer 1

As Tobias notes, you likely have a mix of yeast and bacteria. You might have primarily had yeast from the grapes but as you have advanced your starter using flour, you likely picked up lactobacteria.

Sourdough starter, which is basically what it sounds like you made, is a mix of bacteria and yeast.

The wikipedia page has a touch of info on sourdough culturing. http://en.wikipedia.org/wiki/Sourdough

I'd be guessing at what the activity you are observing is.

Have you sampled the fermenting beer? Sour? Not sour? Very curious...

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