Yeast culture infection

[pluckthechicken]

Hey guys.

This is more of a point of interest for people messing around with yeast and making starters etc.

So I was culturing some yeast from a white labs vial, I inoculated 2.5ml into sterile wort and flask (400ml with 60g DME at ph 5.8; autoclaved). Usually I use 10ml of yeast to start, but I felt like pushing the boundaries a bit!

Anyway, it grew much slower than usual on the stir plate as you might expect. Normally I get flocculation after 1.5-2 days but this was still going at 3-4 days with very little krausen.

Under the microscope, I found that I'd grown a fair bit of yeast (around 88 billion cells) but I also spied a few rod-shaped bacteria that (I guess) could have been lactobacillus. Here is a youtube link to a video if you're interested.

http://youtu.be/rvShZPfN4Ug

I'm playing around trying to treat with amoxicillin at the moment, I thought this could throw up some interesting/useful results. After a bit of research it seems that the levels needed in a volume like this are tiny compared to what you take in a capsule when you've got an infection, so the amount that ends up in the final beer should be insignificant.

Anyway, I thought this perhaps highlights the level of sterility that you really need when culturing from such small amounts. Most of you probably don't worry about this but I thought it might be of interest to someone :-)

 

[Brew2Day]

Cool video. What type of microscope do you use? All the ones I looked at seem really expensive for just checking yeast.

 

[Brewberoza]

Cool video. What type of microscope do you use? All the ones I looked at seem really expensive for just checking yeast.

That was a cool video! Why only 12 people so far?

 

[honeymonster]

I'm playing around trying to treat with amoxicillin at the moment, I thought this could throw up some interesting/useful results. After a bit of research it seems that the levels needed in a volume like this are tiny compared to what you take in a capsule when you've got an infection, so the amount that ends up in the final beer should be insignificant.

Or you end up with a beer that cures infections. That's got to be a good thing, right???

 

[pluckthechicken]

Cool video. What type of microscope do you use? All the ones I looked at seem really expensive for just checking yeast.

Hey, it's a compound light microscope... it goes up to 1000x but it's nearly impossible to focus at that point unfortunately. I think it costs around £500-600; I'm actually borrowing it from University, taking advantage of being a biology student! I can't imagine ever being able to afford my own :hmm:

@honeymonster Haha, that would be the ultimate objective I guess! I've been quite lucky with infections so far, but I have had a couple of batches with off flavours that I couldn't put my finger on. I do wonder whether a small-scale infection could throw up some odd flavours without totally ruining a beer. I guess it runs back to the old mantra of sanitize, sanitize, sanitize. In the lab we use ampicillin when growing cultures of E. coli for gene cloning. The E. coli we use are resistant (like yeast should be, since penicillin comes from fungi) so it stops any unwanted bacterial infections.

 

[clibit]

A mate of mine sent an unopened White Labs yeast vial to Brewlabs for propagation to a microbrewery pitch size, and they told him it was badly infected by airborne bacteria - so your sample might have been infected when you got it.

 

[pluckthechicken]

A mate of mine sent an unopened White Labs yeast vial to Brewlabs for propagation to a microbrewery pitch size, and they told him it was badly infected by airborne bacteria - so your sample might have been infected when you got it.

I did consider this, especially with the opening and closing of the vial that I've got. I diluted down a sample from the vial to check but it seemed clean as far as I could tell! I'm guessing it was either airborne or the StarSan did't sterilize the syringe 100%.