[Kaiser]

Also posted here

Ever wondered what would happen if you let a yeast culture on agar grow? The result is called giant yeast colonies which in the past have been used to distinguish yeast strain. Differences in metabolism, flocculation characteristics and genetic stability lead to differences in the appearance of the giant colonies.

So I wanted to give it a try myself. Brewing Techniques featured a nice article on that topic which pointed out that the growth medium needs to be much thicker than the thin agar medium that is commonly used for Petri dishes. Not having deep mycological Petri dishes I used 4 oz canning jars. The growth medium was regular strength brewing wort solidified with agar. The BT article suggests using gelatin but that didn’t work for me, likely because I forgot about the advice not to autoclave the gelatin.



The agar surface was inoculated with very small amount WLP 002 (English Ale) yeast and allowed to grow for a few weeks at about 15-20 C (60-68 F). The result is shown below.



Apparent are “growth rings” which are considered typical for highly flocculent yeast. Another interesting feature is the wedge shaped change in yeast appearance. This is likely caused by a mutation that happened to a cell at the tip of the wedge which caused it and the cells originating from it to grow differently than the other cells in the colony.

While growing giant yeast cells has little application in practical brewing it is one of those fun things that can be done with supplies that I have in the brewery anyway and I also plan to gow and document the giant colonies of other strains in my yeast collection.

Kai

[euge]

I think it's cool. Surely there is a way to utilize this approach to grow up enough yeast to inoculate a starter from very few yeast cells. 

[jaybeerman]

Nice pics, thanks for sharing.  I've always been curious, how many other homebrewers read Brewing Techniques.  I'm sure I've learned more from various articles of theirs than from any other source.  Cheers, j

[tschmidlin]

I've grown some pretty big colonies from a single cell, it is a pretty cool to check the genetic stability of the yeast.  I've always just done macro colonies on a regular plate though, I wonder why they say it needs to be thicker?  It's probably an issue of the plate drying out or depletion of nutrients, I can believe both would be an issue if you are growing them big enough. 

That's a pretty big colony there Kai, I don't think I ever got one that big

[Kaiser]

I think it's cool. Surely there is a way to utilize this approach to grow up enough yeast to inoculate a starter from very few yeast cells. 

While there are lots of cells in this colony it is not the most practical; way of growing yeast for a batch of beer. For that growth in a liquid culture is much more productive and feasible because in a liquid culture each yeast cell has equal access to the nutrients. In a colony the nutrients to the cells that are not touching the agar has to be transported through capillary action. As a result they grow slower and there will also be a difference in the yeast health of cells within the same colony.
 

Nice pics, thanks for sharing.  I've always been curious, how many other homebrewers read Brewing Techniques.  I'm sure I've learned more from various articles of theirs than from any other source.  Cheers, j

BT was before my time as a home brewer. I’d love to have a more technically oriented publication for home brewing but the reality might be that there is not enough demand to support a print edition and there may also not be enough interest to have a well edited on-line edition.

I've always just done macro colonies on a regular plate though, I wonder why they say it needs to be thicker?  It's probably an issue of the plate drying out or depletion of nutrients, I can believe both would be an issue if you are growing them big enough. 

On a regular plate I never got my colonies larger than 2 mm in diameter. They’d already show some interesting ridges and other features, though. But growing them on a thicker medium gives them much more nutrients to support their growth.

Kai

[mabrungard]

My hat's off.  Kai, you truely are an imperial brewing geek.  Good work!

[jaybeerman]

1. BT was before my time as a home brewer.
2. I’d love to have a more technically oriented publication for home brewing but the reality might be that there is not enough demand to support a print edition and there may also not be enough interest to have a well edited on-line edition.

1. Same here, many of my online searches have led to a surprise archive article from BT.  
2. Agreed but it sure would make a few of us (all 5 of us) happy.  It could be just semi-well edited; the editing standards of most magazines and websites have fallen to the point that you wouldn't stick out even if someone like me did the editing.

[1vertical]

That is interesting Kai, I did not know that about yeast and their propensity to grow super colonies.
But in that reguard they show their kinship to fungi. Which are unique in their forms as well.