Yeast identification

[sam04]

Hi all,

I recently cultured some yeast from an IPA and grew up a small aerobic starter. When I looked at it under a microscope I can see S. cerevisiae, but also lots of smaller cells that I can't identify.

I actually emailed the brewery (photos included) and the QA/QC guy said it was likely mold. But, the sub-sample I took smells and tastes good (very fruity), and the small cells were dominant from the get go, and clearly budding. Also, the starter doesn't look gross.

Ideas on what this is? Or was the guy from the brewery right and its just mold...

Thanks!

 

[Vale71]

I'd be more worried about what appear to be nice specimen of L. brevis in the second picture. Mold won't grow during anaerobic fermentation, L. brevis might.

 

[RPh_Guy]

What's the pH of the starter?

 

[sam04]

What's the pH of the starter?

Pulled another sample this morning. PH is about 4. Its definitely producing CO2, so there will be carbonic acid in solution. Don't taste lactic acid.

The off chance that there are lactobacillus in the starter is less interesting to me than the identity of these smaller "yeast?" cells. Anybody have ideas based off morphology?

So far, S. Cerevisiae are out competing the smaller "yeast" by a long shot, so whatever they are they don't seem brew worthy.

 

[Vale71]

You misunderstood my post. I wasn't worried that your starter might "theoretically" be infected with L. brevis, I was providing you with an actual (tentative) identification of these smaller cells. In other words, your starter is infected with lactobacillus.

 

[sam04]

You misunderstood my post. I wasn't worried that your starter might "theoretically" be infected with L. brevis, I was providing you with an actual (tentative) identification of these smaller cells. In other words, your starter is infected with lactobacillus.

Got it, sorry I misunderstood. But, don't those cells seem a little large for bacteria, they are comparable in length to the yeast?

 

[Vale71]

Lactos can reach up to 10um in lenght depending on the actual type. Brevis is one of the largest. 10um is comparable to a yeast cell's diameter. They are however much thinner than a yeast cell.

 

[bleme]

I don't know if it was you or the guy who posted about larvae in his wine, but one of you is responsible for my nightmares last night!

 

[Dland]

Slightly off topic, but what magnification is needed to get slides like one in post #4?

 

[sam04]

Slightly off topic, but what magnification is needed to get slides like one in post #4?

Its 1000x on a phase contrast microscope... and a cellphone camera...

 

[sam04]

Lactos can reach up to 10um in lenght depending on the actual type. Brevis is one of the largest. 10um is comparable to a yeast cell's diameter. They are however much thinner than a yeast cell.

Cool. Thanks again for you help. I'm pretty new to microscopy, so its nice to have others input. Down the drain it goes...

 

[sam04]

I don't know if it was you or the guy who posted about larvae in his wine, but one of you is responsible for my nightmares last night!

Not me, but that sounds so gross.

 

[RPh_Guy]

Not me, but that sounds so gross.

I make beverages from insect vomit mixed with a little fungus.