Streaked Pacman on plate: most colonies light brown

[RJS]

Usually i get off white colonies, this time most colonies on 3 plates were light brown. I think the plates in general looked great though, also smelled normal. The plates were slightly older than my normal timeline. Instead of stepping up a two day old plate, these are about 4-5 days, not ridiculous.

I stepped up anyway into a 5ml vile. View attachment ImageUploadedByHome Brew1433219725.697357.jpgView attachment ImageUploadedByHome Brew1433219759.410174.jpg

 

[RJS]

no one with experience to clarify the color as a possible issue???

 

[SnakeRidge]

I'm a microbiologist by trade, but I don't plate yeast. Having said that, assuming you trust your starter culture (what you streaked on the plate), those colonies are yeast colonies. Contaminants would be obvious and not more numerous than what you streaked. Unless you licked the plate.

I would pick several that look 'normal' to you and grow up from there. After the first couple steps, check to make sure everything looks and smells normal.

 

[RJS]

Cool, thanks Snake

 

[b-boy]

Looks fine to me. Could the Agar color be effecting how you see the colonies?

 

[RJS]

b-boy that was my first thought, also the light i was using was in question. I was thinking also the break material in the agar/dme medium was causing off colors, but not really thinking thats the case.

Im positive that the pac yeast streaked clean, without contamination, but the light brown color made me think of maybe a respiratory or nutrient issue, in the cell itself, Petit mutant.

I also used more agar than normal, so that i didnt cut into the plate as i streaked, i hate doing that. I like using more agar than normal, the plate dries super fast and you can turn it upside down in two minutes.

 

[PoppinCaps]

Hard to tell any issues from color, I've seen varying shades of white to brown with different strains. As said above, contaminants will be easy to see, bacteria usually shiny and growing at a different rate than the yeast, mold will develop hyphae, etc. only way to tell is grow it up and taste.

Plates look great to me!

 

[RJS]

alrighty, i feel better about it, thanks everyone.

 

[SnakeRidge]

A thought that I had: You said these were older, and you used more Agar. Did you notice a similar amount of condensation on the plate tops? I'm thinking the humidity might be the reason for darker color, if it were not as humid as usual.

 

[RJS]

Everything was drier, much less condensation. Would that effect cell health?

They seem to be doing nicely in their 5 ml wort bath

 

[SnakeRidge]

Everything was drier, much less condensation. Would that effect cell health?

They seem to be doing nicely in their 5 ml wort bath

Won't effect health. Yeast have a lot of protective mechanisms. Drying out some might cause them to adapt their cell walls And change the color a bit. If they're growing now I'm positive they're fine.

How many colonies do you pitch to 5 mL?

 

[RJS]

Usually two per plate, for diversity. So 6 colonies per 5 mil

 

[SnakeRidge]

Thanks. I've kept out of a lot of yeast stuff so as to not "bring my work home" but it's pretty cool. I repitch slurry from batch to batch but the most I've done is to bring a sample of a weird starter to work to look at on a hemacytometer.

 

[RJS]

I understand completely. Your knowledge is helpful and i appreciate it.

I figured most HBers were doing plates and slants these days.

 

[PoppinCaps]

I started doing plates when I got into harvesting to keep a ton of Gen1 stock, but I quickly got into freezing instead, plates just don't last that long. And replating 20 strains is a pain!

But for bottle harvesting, I still think it's the best way to ensure a healthy phenotype.

 

[RJS]

Ya i don't even like storing available plates, i like to make everything fresh based on when i need to do a streak.

Right now im keeping 4 strains in slants and i streak to plate when im brewing, so each batch starts from a pure colony, ideally.

I live on an island so yeast has to be shipped in, so i figured why not just get my own yeast bank. Our fermenter house is sealed and air/hunidity controlled, so its now a lab too.

So far its been a blast. Probably couldn't do it if i wasn't a monk.

 

[PoppinCaps]

Sounds like you've got a perfect setup!

 

[RJS]

Good growth and normal color/aroma.View attachment ImageUploadedByHome Brew1433364445.570468.jpg

 

[SnakeRidge]

I understand completely. Your knowledge is helpful and i appreciate it.

I figured most HBers were doing plates and slants these days.

I don't really have a good space to keep or work with plates and slants at home. Since I work in a lab, I have access to 10mL vials of sterile saline (0.9%) which is isotonic. So whenever I get a new strain of yeast, I pull about a mL of thick slurry with a syringe and inject it into the saline vial. The vial has a rubber diaphragm so the chance of contaminating my 'P-Zero' culture is very low. Using a sterile syringe, I can pull 500uL or so and pitch to 5mL of wort. It takes a few steps to get up to pitching volumes, but I've had zero problems with this method. I don't think I've bought liquid yeast in 3-4 years, aside from maybe one vial here and there to try out.

 

[RJS]

nice. Sounds like you have a perfect setup. Low overhead.

 

[RJS]

One of my favorite aspects of the slant/plate/vile process is the incredible health of the yeast and not having to get super concerned about pitching rates.

If you have grown clean and almost 100% viable/vital yeast, you can cut the pitching rate in half. Thats almost a direct quote from Jamil Z. and Chris White

 

[RJS]

And look at the mini flasks, fun to just look at. View attachment ImageUploadedByHome Brew1433444587.756270.jpg