Culturing yeast?

[bernardsmith]

I am not a chemist but I wonder how practical and easy it might be to be able to culture yeast on slants or petri dishes -not to bank or harvest them but to be able to see if my sanitation protocols are weak. I make meads and wines but occasionally I brew beers and I find that these beers tend to have far more CO2 in them than I would anticipate. My concern is that there is some bacterial infection coming from my bottling. Would I be able to identify visually without a microscope a culture of bacteria or yeast that I was able to grow on agar over two or three days? Can you identify different strains of yeast by sight? Would a culture of bacteria be large enough to observe as something other than yeast or would I need a 400 X lens on a microscope? Thoughts? Thanks.

 

[Sourz4life]

Well first, that's a microbiologist, not a chemist =P. So if you pre bought the poured plates then you could streak out any slurry. But you do need to do this in a sterile environment (under a flame such as a bunsen burner or alcohol lamp). You can't identify microbes from just looking at them, but if your streaking out a pure culture then all the cell morphology should look the same once it has grown, if it doesn't then you know something else is growing in there. But what it is, is impossible to figure out by the morphology. Most yeast strains look similar on a plate, where bacteria/molds etc look different. Even throwing under a microscope won't tell you what anything is, that takes isolating and then sequencing its DNA. You can use things like gram strains, and basic morphology under a scope to narrow it down a bit, and you can use certain lab medias to narrow it down further(more advanced) but that still won't tell you what your dealing with. My suggestion would be to pick up the book Yeast by Chris White and Jamil and give that a read before dipping into it. Its a good starting point.

 

[IslandLizard]

In your carbonation calculation, do you include the estimated amount of CO2 dissolved in the beer just from fermentation alone? That could be the cause of the discrepancy you're noticing.

Sanitation of chilled wort, pitching yeast, fermentation, and packaging on homebrew scale are hardly sterile procedures. We try to keep the invasions at bay by giving one or a few microorganisms the overhand and providing for a beneficial environment.

When I think of our pitching procedures and lag times we experience, it's quite a miracle our beers come out as nice as they do. I'm convinced all our homebrew is infected to some degree.

Don't sweat it, enjoy the beer for what it is!

 

[Oginme]

There is a good tutorial at http://suigenerisbrewing.blogspot.ca/. He runs through making plates and plating yeast step by step. You are correct that it is not hard, but you do need to have good sanitary practices to make sure you don't contaminate your plates either as you make them or as you streak them. It does take some practice to get the technique down when streaking.

 

[passedpawn]

This plate was sterile until I opened it for 5 seconds to see that bubble in the agar agar better. Something got in there during that time. A week or two later this appeared.

 

[bernardsmith]

Thanks for your thoughts and comments. I think I will simply soak my bottles in - rather than fill them with K-meta and forget about culturing the beasties to see what I have in my wine making/beer brewing area

 

[TexasWine]

Thanks for your thoughts and comments. I think I will simply soak my bottles in - rather than fill them with K-meta and forget about culturing the beasties to see what I have in my wine making/beer brewing area

Might I recommend StarSan instead of kmeta? I'm a wine maker as well, but then got into beer and that is where I found StarSan. I use it for all my wine making now.

 

[bernardsmith]

Might I recommend StarSan instead of kmeta? I'm a wine maker as well, but then got into beer and that is where I found StarSan. I use it for all my wine making now.

You could recommend StarSan (I have some) but presumably that does not inhibit oxidation, does it?

 

[TexasWine]

You could recommend StarSan (I have some) but presumably that does not inhibit oxidation, does it?

It does not. I meant to only recommend it for sanitizing purposes 😀

 

[Sourz4life]

This plate was sterile until I opened it for 5 seconds to see that bubble in the agar agar better. Something got in there during that time. A week or two later this appeared.

I don't open my plates unless its under a flame or in my laminar flow hood. Almost always get mold without it.