Streaking Yeast

In this video, we streak different yeast strains on plates and slants in which wort agar has been poured. We show the yeast growth on the plates and describe how to isolate a single yeast colony.

Category:

Education

Tags:

• beer
• brewing
• yeast
• culture
• plate
• slant

[luisbaltazar1]

hi John, thanks for all your videos on brewing, they are much appreciated.

i have a few questions: what's the lowest temperature these cultures can take? i mean is that fine if i simply put them in a freezer and let it do its normal job? do you know how many generations of yeast you have cultured and successfully using this method? and once you have your culture ready to use, how do you start it and get it ready to pour in your wort? do you plan to make a video about that?

thanks again.

[subasavage]

@luisbaltazar1 With this method, you don't want to freeze the cultures, just put them in the fridge. To freeze, you would need glycerol to prevent rupturing the cells (too much trouble, in my opinion though it will last longer). Each time I streak to a new plate, I get a pure sample, so the "generation" term doesn't mean what it does when one repitches yeast. In those cases, each generation carries with it some contamination. In this case, you can go forever (with some mutations likely).

[lumbardh]

I can't get this one video of yours to play. Everything else works fine. Great info so far!

[subasavage]

Huh, it seems to come up for me. Anyone else having trouble viewing this video?

Thanks!

[funkmasterchilly]

First off thank for the great vid's. This is the first video I've found on youtube laying out step by step instructions on making agar plates and cultivating yeast. I've been looking for one of these for a wile now B/C I think I'm going to try doing this soon. With that said one thing I've read is after making up the agar plates some ppl leave the plates untouched for a week or two to make sure the plates are uncontaminated before streaking. do you do this?

[subasavage]

I much appreciate the feedback...glad to be of help. As for leaving the plates untouched, you have heard correctly that this is a good practice. You'll want to leave these at room temp so any possible contaminants can grow. I have found that a fair fraction do become contaminated (~10%) somehow (perhaps not a surprise without a laminar hood). Recently to save time, I have begun streaking right away and if the plate is contaminated, I'll streak again (either way, you lose the first plate).

[dvdfrnzwbr]

It works! Haven't purchased the lab equipment yet. I use baby food jars, a paper clip wire, and my gas kitchen stove. The jars have autoclaving lids and what works good is that I mix the ingredients for the agar in each jar, pressure cook, and they autoclave shut. Agar forms well after cooling. To streak a new yeast, just take a jar out of storage and "pop" one open. Sterilized inside and no contaminated jars yet. Give streaking yeast a try. Looks hard but easy. Thanks Subasavage for your help!

[funkmasterchilly]

i have just watched Yeast Starter, Yeast Propogation, & Bottle Culturing Part 2 and had seen the infected plate and was like "oh I just asked a question about that" so I came back here to comment on my comment and seen you had already answered my question. that was quick. Your good

[crazyboy0602]

Yeast vials can keep for about 1 year probably more. One vial can be cultured about four generations. After that the yeast will mutate.

[subasavage]

Well, I'm too new to this to provide a definitive answer. I think that the yeast labs (i.e., White & Wyeast) essentially do the same thing we're doing here (though they don't keep slants for a year, they restreak more frequently). After a period of several years, they re-evaluate the strain to see that it still has the intended characteristics. So in effect, you should be able to re-streak a significant number of times without worry. Not the same as repitching yeast (i.e., generation +1).