Calling All Yeast Platers!

[dreamboat]

I have just commenced my first foray into yeast plating in order to resurrect a wheat yeast which I obtained a small sample of over a year ago. The yeast paste had gone somewhat brown, so i figured that plating was the best way to go to check viability, and to get get a nice healthy population.

I made a pair of agar / dme plates in the steamer at home, and generally followed the instructions available around the web to streak the plates. Now, 60 hours later, I have some life showing on the plates, with some distinctive white blobs, and nothing else to be seen... hopefully a good indication for both my sanitation methods and the viability of the yeasties.

The question is - how big should I let the blobs get before collecting them (one?)and pitching to a small starter? pictures attached.

 

[Gulf Brewery]

The question is - how big should I let the blobs get before collecting them (one?)and pitching to a small starter? pictures attached.

[post="54571"][/post]​

Dreamboat

I normally get the equivalent of 2 match heads in size and put that in 50ml of starter, then step it up to 100ml, 500ml, then starter size. You can do it from less, but more is better.

Cheers
Pedro

 

[Steve Lacey]

Yes, you could probably do it now if you were in a hurry, using say three colonies. But you can let them go a bit longer if you like. I put my plates in a ziplock placky bag and then inside a biscuit tin. They last for ages like this and the colonies can get quite big.

steve

 

[dreamboat]

Thanks Steve/Pedro.
I am in no rush at all - really a couple of weeks before I need a pitchable quantity. My concern is as to whether I need to prevent the colony growing to the size where the individual colonies start to merge, or whether I am better of to take a smaller quantity of yeast, but from a single colony.
Since I have two plate to play with, I might look at making a starter from one colony from one plate this weekend, and let the other go until maybe next weekend.... by which time I will know how the first has performed. I will post a picture of my setup - but I can run a nice sporadic aeration of my starter, so should be able to get up to big numbers in pretty quick time.




dreamboat

 

[Kai]

I would say that you can collect the blobs when they're big enough to tell whether they're yeast colonies or not. Or, leave longer if that floats your boat.

 

[pint of lager]

Welcome dreamboat, to the wonderful world of petri dishes.

have just commenced my first foray into yeast plating in order to resurrect a wheat yeast which I obtained a small sample of over a year ago.

Plating is definitely the way to go from a small sample.

Because the sample is old, try and make sure that you select your colonies to make your starter for uniform size and appearance. After a year in less than ideal conditions, the chances are that there will be more mutations in your sample.

Let the plate grow for at least a week at about 20 deg C, so the overall macro appearance of a colony is obvious to the naked eye.

The colonies will self limit in size, they are not going to grow and take over the whole plate.

I also tried steaming plates, but found that 3 out of 10 plates were infected. Then I went to using a pressure cooker.

I collect about 2 matchheads worth of yeast and pitch to 50ml of sterilized wort, then when that is active continue stepping up.

 

[Steve Lacey]

I also tried steaming plates, but found that 3 out of 10 plates were infected. Then I went to using a pressure cooker.

[post="54668"][/post]​

I now have a pressure cooker too. BUT, I never got an infection using steaming. However, I added the step of doing the initial boil-up of the media in a tough glass wide-mouth bottle (fruit juice) in the microwave. You have to watch it carefully or it tries to boil right over the top. I wouldn't boil this for long, only a couple of minutes, and it is very on/off because of said boilover problems. Sitting the bottle in a shallow water bath reduces the boilover effect but takes a bit longer. Anyway, I then poured that into a triple cleaned petri dish (soaked in bleach, then boiled). Then I would give that a blast for 20 minutes or so in the steamer. A lot of frigging around that is mostly eliminated by a pressure cooker, but it has always worked for me.

One tip: The media in the juice bottle can be made up to more than you need, say 100 mL. The excess is just stored in the fridge and you zap it with the microwave whenever you need some more. Works a treat.

Steve

 

[sluggerdog]

I have no idea what this is all about.

Is this growing yeast from scratch or something?

 

[Gulf Brewery]

Sluggerdog

What we are talking about is a way of storing yeast on plates. Have a read on this article on Craftbrewers that may help explain it.

Cheers
Pedro

 

[Kai]

I don't think any method short of a pressure cooker is fully sufficient for sterilising plates, but if it works then it works.

Do you platers use selective media for your yeasties?

Because the sample is old, try and make sure that you select your colonies to make your starter for uniform size and appearance. After a year in less than ideal conditions, the chances are that there will be more mutations in your sample.

That's a better way of putting it... big enough so you can see what the colonies look like too.

Look at the pattern on the edge, the colour, the sheen and the three-dimensional shape (is it a bubble? flat? a crater? a nipple(i forget the technical term)?). Then make sure you choose several colonies, as you can't pick up any metabolic mutations with the naked eye. Choosing several kind of averages this out.

 

[sluggerdog]

Sluggerdog

What we are talking about is a way of storing yeast on plates. Have a read on this article on Craftbrewers that may help explain it.

Cheers
Pedro

[post="54684"][/post]​

Thanks GB/ Pedro, Will read up on it.

Cheers!

 

[pint of lager]

Dreamboat, you may want to streak some yeast from a more recent sample, this is more likely to grow into an easier plate to work with.

For a first yeast petri dish project, using a fresh source of yeast will give you an easier introduction to the world of streaking.

 

[kungy]

I don't think any method short of a pressure cooker is fully sufficient for sterilising plates, but if it works then it works.

By sterilising plate, are you referring to both the yeast growing media and petri dish? Or are you referring just to the petri dish?

Cheers

Will

 

[Gout]

where does everyone get their agar? i have looked around and found it very expencive

mind you in 500g or 5Kg (got upto $1800) I gather i only need about 50-100g to last a long time

 

[pint of lager]

Have purchased it from both Asian foodstores and a health food store.

You want the fine powder, not the stuff that resembles noodles.

And yes, 25 gms will last you a long time. My recipe is 100ml water, 12 gms DME, 1.5 gms agar.

Boil the water in a beaker, remove from stove, add DME and agar, stir, reboil till agar is dissolved, pour into glass plates and pressure cook.

If you don't dissolve the agar, some plates end up with not enough and do not set.

 

[Airgead]

where does everyone get their agar? i have looked around and found it very expencive

mind you in 500g or 5Kg (got upto $1800) I gather i only need about 50-100g to last a long time

[post="55057"][/post]​

Local chinese supermarket. Food grade agar agar powder. About $2 for a 25g packet. Its used a lot in asian deserts and things.

 

[bradmcm]

I've got a 25g packet here of "Best Quality Agar-Agar Powder" (must be good then )
that set me back all of $1.55 from a grocer in Adelaide's Central Market.
Seeing Gout is in Melbourne, there are no shortage of Asian groceries
for him to choose from!

 

[Steve Lacey]

By sterilising plate, are you referring to both the yeast growing media and petri dish? Or are you referring just to the petri dish?

[post="55047"][/post]​

He was talking about sterilising the plate with media already poured into it.

 

[Gout]

thanks people i wll try to find some then, i didnot know the supadupa markets would have it, thought it was more a science supply thing and hence the huge quantities and price i was finding

 

[kungy]

In this talk of sterlisation, Does anyone sterilise there plates via tyndallisation?

Will