I have yeast on a petri-dish... now what?

[Thedillestpickle]

I happened to find some agar agar at an Asian food store and decided to pour myself some agar plates... cool right?

Now I also managed to culture up yeast from a batch of kombucha and brew some really tasty beer with it. See here: https://www.homebrewtalk.com/showthread.php?t=569170

I wanted to test to see if there was any discernible amount of non-yeast organisms present in the final product, so I streaked an agar plate with some dregs from a bottle of that beer. As far as I can tell there is nothing other than yeast growing on that agar.

I've had really good results with this yeast, so is there any way I can improve/preserve/maintain this culture?

What are my options with this plate? Right now I am storing it in the fridge to stall growth.

 

[CA_Mouse]

Two options...

Slant it and prop it up every 2 months.

Prop it up to 100 million cells and freeze with Glycerin and prop it back up every 3 to 4 months.

 

[Thedillestpickle]

Yes I was thinking a slant was somehow involved so I actually have 4 slants made and ready to transfer to.

But what I'm not sure about is how I select the right colony to transfer? Is it as obvious as simply taking the biggest most uniform looking one? If you look at the picture of the plate I would say I have a few obvious candidates in that case.

Or should I be using a microscope to look for something?

I just don't fully understand how it would be more effective at preserving my yeast strain than saving the dregs from a bottle.

Let's say hypothetically that I was a large successful brewing that has been preserving my house strain for 50 years... what would I be doing with this plate?

I have more plates, I also have slants, I also have access to a microscope but I'm not sure if it will go up to 400x or not

Or maybe a link to something that explains this because I'm generally uneducated about this whole process.

 

[ajdelange]

I don't know much about this but i can make a couple of general remarks. You want to select isolated colonies that grew from a single cell. These are in the lower right (4 - 6 o'clock) part of your plate. Also do a search on how to get single cell colonies. It's similar to what you did. Select as many single cell colonies as you are willing to deal with and stab, them into slant and let them grow up. Now you have a series of stabs with cultures based on single cells some of which mutated from what you started with in favorable directions, some of which mutated in unfavorable directions and some of which didn't mutate at all. Grow up a reasonable number of cells from each stab and brew with them. Propagate the stab that gave you the best beer into other stabs and throw the others away.

NTCC found years ago that yeast can be kept for long periods under plain old sterile distilled water. I don't remember the details but I think a year was OK. Every time I set out to experiment with this I forgot about it and found the tubes in a closet three years later but apparently it works.

 

[Thedillestpickle]

I see.... So if I wanted to do this correctly I would want to obtain as many single cell colonies as possible. It looks like I have at least 3 that I could choose from on the plate. I could re-streak from some of the denser areas of the plate and obtain as many as 40 or so.

So I could brew 40 small batches from single cell colonies, taste each one and decide which I liked the best and keep. Or pitch to a high gravity and keep the one that doesn't stall. Or test the FG and keep the one that has the highest attenuation, or the one with the best flocculation... etc, etc.

I suppose a brewery could do something like this on an ongoing basis and select for a different favourable trait each time, so that over a number of years they would obtain an all around ideal yeast.

Cool. I might actually try something like that. I have an idea:

I could obtain 40 unique colonies on slants, and then simply pour wort into each slant to create hopefully enough of a starter to ferment a 500ml bottle of beer. Then I could fill 40 500ml fermenters(beer bottles) with one 5 gallon batch, pitch the unique yeasts into each bottle and place an air-lock. After primary completes I could simply add priming sugar to each, allow to carbonate, cellar for a month, then refrigerate. The yeast cake should compress enough to simply pour each "batch" out from the bottle and test.

The test tubes I have access to are quite large so it is possible that it would be enough cells to ferment one bottle of beer. The only problem is aerating the wort in the slants... I would need a multi-tube-vortexer.

To be honest this doesn't seem like all that much extra work. It wouldn't be that hard to do, except the vortexer which would be an expensive item.

 

[danthebugman]

Nice looking plate! I just got done inoculating slants with Wyeast 3711 and a strain I cultured from a commercial Farmhouse Ale this evening. What I have been doing for the last year and a half or so is this:

I maintain 3 slants of each strain in my bank. Before brew day, I pull out whatever slant I need and start stepping up a starter. When I am on the last tube I make more slants or if it's approaching 6 months on any strain I'll plate it out and make more slants. I currently maintain 6 strains in my bank.

You can also inoculate a starter with yeast taken directly from the plate, but the benefit of a slant is that it doesn't dry out as fast so is viable longer. Happy yeast wrangling and good luck!

 

[EarlyAmateurZymurgist]

I have been plating and slanting brewers yeast for over twenty years. What I do when isolating yeast on a plate is to select two well-isolated colonies for propagation to two different slants, one colony per slant. You want to use a loop, not a needle to inoculate the slants.

Assuming that one is using a nichrome loop, place the loop in the hottest part of the flame until it is cherry red. The hottest part of the flame is the tip of the inner cone. One wants to flame the portion of the loop that will enter the culture tube. Working with the plate within the sterile area around the flame, lift one side of the dish cover high enough to cool the red hot loop on a sacrificial spot on the solidified agar before scraping one of the well-isolated colonies from the plate. Now, remove the cap on the blank slant culture tube with the pinky of the hand in which one is holding the loop, quickly pass the mouth of the culture tube through the flame a couple of times before inserting the loop and inoculating the surface of the slant by drawing squiggly lines across the surface of the slant with the loop. The loop is then removed and the mouth of the culture tube is quickly passed quickly through the flame a couple of times before capping the tube loosely for incubation. The tubes should be incubated at between 22C/70F and 25C/77F until most, if not all of the surface is covered. The caps should remain loose during the entire incubation period after which they should be tightened and sealed with a strip of Parafilm before being stored at 3 to 4C/ 38 to 40F.

What you will have at this point are two isolates. Isolates can have slightly different fermentation characteristics, which is why you should pick one and discard the other when it comes time to propagate a slant for use in fermentation, or at least maintain the cultures as separate isolates. There are several cultures there that are isolates of the same strain. Two that come readily to mind are W-34/70 and W-34/78. These strains are the 70th and 78th isolates from culture number 34.

I always pick the healthiest looking slant to propagate and maintain when maintaining a yeast culture. I propagate two new slants and start a culture from the healthiest looking slant. The lesser of the two slants is always discarded when it comes time to subculture a slant to two new slants. I have maintained cultures for up to a decade using this technique and periodic sub-culturing. One should remember that going back to slant should be how one grows a new culture for day-to-day brewing using cropped yeast.