Yeast, division etc...

I need a little lesson in how yeast works. I am concerned that my "saved" yeast isnt enough for a batch i'm about to do. Doesnt yeast just multiply and multiply?

1. If I create a starter, even with a small amount of yeast, wont it at least double in size?

2. How long can I create a starter before I want to brew?

Yeast counts double about every two hours, if there is enough oxygen and nutrients. Oxygen is normally the limiting factor.

so, if I start with 2 yeast cells after 48 hours I should have 16 million cells.

Yeaaauh, get exponential on those fools! I'd make a starter the day before you brew. It depends on how old the yeast is, the storage conditions, how much there is to begin with, etc.

I had a mason jar full of yeast from a local brewpub. I made a starter in a 1-liter growler the morning of my brewday. Went to work, came home, planned to brew...and my spare basement bathroom had a distinct beer-y smell to it. Yes, I had a yeast blowoff. Ugh. I still salvaged enough, made a new starter, and pitched 6 hours later. Fermentation has been vigorous. I also aerated my wort with an aeration kit, FYI. So, yes, to answer your question, you can do it a day ahead, or you can do it 6 hours ahead. But I'd go on the longer side if your starting amount is small, and/or storage is not great.

No you would have about 16000, and 16 million isn't very much just think that a wyeast smack pack has 100 BILLION cells.

sause said:

No you would have about 16000, and 16 million isn't very much just think that a wyeast smack pack has 100 BILLION cells.

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2 yeast cells doubling 24 times over 48 hours = 16 million.....

Sorry, my math is slowly waking up, the thing is still that 16 million is not that much for yeast. It is a tiny for sizes of batchs that most people do. It is still one thousand times too small for a 1 gallon batch.

Where would you find 2 and only 2 yeast cells?

Yeast will reproduce if there is oxygen present. When they run out of oxygen they become bachelars and just piss and fart (alcohol and CO2) till they get tired and go to sleep at the bottom of your carboy. Keep them in oxygenated solution with the proper amounts of sugar and they will reproduce like mad. Thats why aeration is so important in the starter and early primary stages.

chillHayze said:

Where would you find 2 and only 2 yeast cells?

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If you make your starters from slants, you could potentially pitch 2 cells into a small starter and go from there. You'd more likely have at least a few dozen viable cells.

Assuming ideal conditions and only 12 yeast cells present in your starter, it would take 54 hours to get over a billion cells.

Personally, I like to get my starters going at least 48 hours prior to pitching, and I probably start with a few hundred million if not a billion cells each time. If the starter looks like it ferments out, I let it settle, pour a little of the liquid off, and add some fresh wort, usually in increasing amounts each time ("stepping up"). I like to pitch at least 500 mL of actively fermenting starter into a 5 gallon batch. Works like a charm!

Excellent yeast info here:

http://www.mrmalty.com/pitching.php

Yuri_Rage said:

Personally, I like to get my starters going at least 48 hours prior to pitching, and I probably start with a few hundred million if not a billion cells each time. I

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How do you know how much a billion cells is? I mean, are you using tablespoons, mL, what? I'd really like to know so I can save as much yeast from each generation as possible.