How do commercial yeast companies propagate their yeast without changing yeas...

[youngdh]

In reading various threads about harvesting your yeast and that one should only harvest for a few generations otherwise yeast begins to mutate got me thinking "how do commercial companies such as White Labs and Wyeast do this generation after generation without altering the yeast's characteristics?"

On a similar thought if one harvest the yeast from your low gravity starter does that minimize the impact of generational mutation and you don't need to worry about using a 20th generation WLP001 given proper sanitation is followed?

 

[z-bob]

Microscopes and quality control?

 

[Brew_Dude41]

Something that i have often wondered about. I am looking forward tot he answers.

 

[DavidJP]

Guessing they will aliquot lots of standard stock solutions of their yeast stocks at low generation time and freeze in liquid nitrogen or -80C. Then keep track of the number of passages or generations they use to get the yeast for production and routinely return to their original aliquot from low generation yeast. Combine that with plating out to grow from original single colonies and perhaps now or in the near future developing DNA fingerprints of their original stocks of yeast to look for any shift away from the original strain.

For the other question I'd guess that a strain would adapt to best propagate in a given solution so many passages in low gravity wort would favour mutations that help the yeast that survive in that environment so over time it might start to look different than one grown in a higher gravity wort. On the other hand I suppose the lower gravity would restrict the number of generations and so limit to some extent the genetic drift or chances for mutations to accumulate that might occur. I wouldn't think that 20 passages might be too much of a problem but I really have no idea of when it might become a problem, I'd guess when you start seeing changes in the yeasts behaviour that might be time to change. Try getting slants of the yeast strain going and you can always go back to low generation time yeast. That would be my guess.

 

[Talgrath]

Well, keep in mind a few things here. First, the reason that yeast changes over time is that beer isn't the ideal environment for it. In fact, the ideal yeast environment is much warmer than we generally like to ferment our beers; that ideal yeast environment just happens to produce flavors we don't like. Ever have a fermentation get too warm and get far too active far too quickly? For us that's a bad sign, the beer will taste too "boozy" and "hot" and will be unpleasant, but from the yeast's perspective this is great. The ideal environment probably also has steady supplies of oxygen and other nutrients, not just sugar and is regularly flushed of yeast waste (aka alcohol). The yeast changes because we put it in a less than ideal environment, as generations change the yeast adapts to the wort/beer environment and that results in changes to the beer that we may not appreciate. Unless someone from the yeast companies comes on and leaks techniques to us, you probably won't get a real break down of everything they do, company secrets and all that.

 

[jbaysurfer]

They can go infinitely more generations then you can at home without mutation because they're infinitely cleaner on the sanitation front. They can also freeze samples virtually indefinitely so when they plate a yeast or otherwise notice genetic mutations, they can pull from the original stock and propagate up again. Many commercial brewers develop their own house yeasts but pay the yeast companies to bank them so they can order future clean samples of their own house yeast.

 

[biertourist]

1. Freezing for long-term storage
Can use laboratory freezers (-20 to -40C range) Single or double stage refrigeration systems
Ultra low freezers (-86C) use "cascade" / double-stage refridgeration systems (2 compressors, evaporators, condensors and 2 different refridgerants the first droping the temp to the -20 to -40C range and the 2nd going from -20 to -40C to -80 to -90C. Very expensive but can maintain the culture in good health at a single generation for several years.
Cryogenic freezers (colder still) using exotic insanely expensive to purchase AND operate freezers often relying upon liquid nitrogen (pretty insane for brewery usage)

All of these require using glycerol media or pre-made "cryotubes" often containing some sort of proprietary storage media to help prevent cellular damage.


2. Once the culture approach their max lifetime in "cryoslumber" -plate them and identify healthy colonies and then prop them up get them all nice and healthy with plenty of glycogen reserves and put them back into cryo slumber

Seems there's lots of different media and associated procedures but this is a high-level overview.

There's plenty of people on HBT who do this for a living / degree program and hopefully some of them will chime in with more details.



Adam

P.S. There's no mutation with cryopreservation methods as there's no generations. You're taking those individual cells and just slowing down time for them in the deep freeze.

 

[Yooper]

The bigger breweries I've been to, like Summit, have a full time microbiologist on staff, and a big sealed lab. The lab was quite large from what I could see through the glass!

 

[Alt]

Single cell propagation: http://www.pivarstvo.info/forum/files/yeast_propagation_and_maintenance_607.pdf