where does yeast come from? I know we use it in fermentation and baking and many things, but where do they harvest it from?

To deal with men by force is as impractical as to deal with nature by persuasion.

Yeast is all over the place. When the medium it is living in dries up, the yeast forms spores that can float around for years before it finds another damp dark place to propagate.
The yeast strains we use for baking and brewing have been domesticated. Great effort is put into keeping the growth vats from being infested by wild yeast strains. In winemaking, the yeast species that are useful for fermentation also live very nicely on the moist skins of the grapes. For home wine making, purified cultures of these yeasts are available, which takes a lot of the guesswork out of the craft.
IIRC, the yeast strains used in pilsner brewing (which ferments at a cooler temperature than ales) have been bred so far from their wild progenitors that we cannot be sure what type of yeast they were originally.
To grow a pure culture of a yeast variety all you need is one cell. But, it is very difficult to culture yeast out of commercial beer, as the pasteurization process kills the yeast. Makes the product more stable, but takes away all the personality. (I have told The Wife that all the vitamins are in the yeast. And a few weeks ago I discovered that my last batch of wine was rather, um, unstable in extreme weather conditions. Messy.)

Dr. Fidelius, Charlatan
Associate Curator Anomalous Paleontology, Miskatonic University
“You cannot reason a man out of a position that he did not reach through reason.”

I’m assuming that the reason we use yeast in bread now is because at one point it was airborne and landed in someones bread. But who was the one who left their dough out and came back later to find that it was bigger and still decided to cook and eat it?

Formerly known as Nec3f on the AOL SDMB


When food is scarce, you will eat anything, no matter how spoiled it may look. Of course, peoople did take note when Uncle Murray keeled over after eating the botulism special…

Any word yet on whether it’s a plant or an animal? Last I heard, it’s “both.”


I’d have to go with “Other” as it seems to be a simple fungus.

Where the hell is Lynn when ya’ really need her?


Or, if Ranger Jeff were here, “When a Mommy yeast and a Daddy yeast love each other very much…”

I was refering to the similarities between yeasts and animals. They are true fungi, yes, but for years the yeast S. cerevisiae has been the model system for much of molecular genetic research because the basic cellular mechanics of replication, recombination, cell division and metabolism are generally conserved between yeast and larger eukaryotes, including mammals.

Yeah Nick, yeast is neat. You haven’t lived until you’ve read a paper that starts "The genetic and physical maps of the sixteen chromosomes of Saccharomyces cerevisiae are based on data presented in Mortimer et al. in preparation (1995) as well as on data presented in earlier reviews (Mortimer and Schild, Microbiol. Rev. 44:519-571 (1980), Microbiol. Rev. 49:181-213 (1985), Mortimer et al., Yeast 5:321-404 (1989), and Mortimer et al., Yeast 8:817-902 (1992). "

The fungi and the animals are much closer to each other, biochemistry-wise, than either is to plants, protists, or monera. Many many moons ago, fungi decided to live off already dead things, while animals decided to hunt down their food while it was still twitching…

Dr. Fidelius, Charlatan
Associate Curator Anomalous Paleontology, Miskatonic University
“You cannot reason a man out of a position that he did not reach through reason.”

Someone call me?

Lynn the Packrat