yeast ranching for the Junior Scientist in all of us

Yeast culturing is cool because it's where you get to pretend to be a microbiologist, use neat gear, and save about a ton of money on liquid yeast.

Yeast cultures can be done in slants (ie, test tubes leaned so the media congeals at an angle or "slant"), in petri dishes, or frozen in specially prepared anti-icing media. I use the slant method.

Yeast culturing is not particularly difficult but it does require a bit of time, some extra pieces of hardware and sterilization (not sanitation) that you don't often use in homebrewing. Planning ahead can greatly reduce the time factor. Basically you make some media for the yeast to live on, inoculate the media with the yeast, then later on you inoculate your starter with the cultured yeast and pitch when ready.

gear

bulk lot of 100 borosilicate test tubes off eBay - $10. You probably don't need that many but they were cheap.
bulk #2 stoppers for the tubes -$4
alcohol lamp - $3
inoculating loop - $2
agar from the asian food store - $1
dust mask from my workshop - $0
safety glasses - $5. You will be flaming glass and things can shatter or blow up on you.
DME thieved from my brewing supply - $0
stirplate made from a PC fan, HD magnet, and a piece of tupperware. - $0
pressure cooker - $0 (already owned)
grease pencil or sharpie to mark the tubes.
some mason jars and lids if you want to sterilize water or wort for later use.

I buy much of my lab gear from Basic Science Supplies.

cultural history

Culture-al history, hahaha!

culture[9a]: 20081221 - Storage of batch[9] sample in 6 vials of sterile water (3 distilled, 3 filtered)SITCap method.
culture[1a]: 20081221 - Replated batch[1] store of 1275 Thames Valley Ale yeast. 1 plate, 3 slants., SITCap method.
culture[9]: 20081206 - inoculation of 2 plates, 7 slants from Wyeast 1084 Irish Ale, SITCap method.
culture[8]: 20081115 - streaking of plates from expired White Labs WLP011 European Ale. Plates cultures streaked into 8 slants, SITC method.
culture[7a]: 20080928 - inoculation of slants from culture[7]. 5 slants, SITC method.
culture[4a]: 20080928 - inoculation of slants from culture[4]. 5 slants, SITC method.
culture[7]: 20080803 - inoculation of slants from Wyeast Labs 3726 Farmhouse 'private collection' yeast. 5 slants, SITC method.
culture[6]: 20080705 - inoculation of slants from White Labs WLP005 British Ale yeast. 5 slants, SITC method.
culture[5]: 20080606 - inoculation of slants from Wyeast 1056 American ale yeast. 10 slants, SITC method.
culture[4]: 20080515 - inoculation of slants from a buddy's White Labs WLP720 Sweet mead yeast. 1 slant, SITC method.
culture[3]: 20080504 - inoculation of slants from Wyeast 3068 Weihenstephan Weizen yeast. 10 slants, SIT method.
culture[2]: 20080501 - inoculation of slants from Wyeast 1098 British Ale yeast. 10 slants, HAP method.
culture[1]: 200870425 - inoculation of slants from Wyeast 1275 Thames Valley Ale yeast. 12 slants, SIT method. Taped and refrigerated after 4 days growth.
~~culture[0]: failed attempt to culture yeast from a Sierra Nevada bottle.~~

some methods I am testing

The main problem I am experiencing is water condensation (presumably from the agar) in the tubes. From best to worse so far:

DW=5ml of Distilled Water pressure cooked 15psi/15min and cooled. Blob dropped in from a loop, close cap, shake vigorously. Store at room temperature. This method requires plating before building back up into a starter. Based on an archive in the March/April 1997 Brewing Techniques magazine article A Simple, Practical Method for Long_Term Storage of Yeast, by Michael D. Graham.
SITCap=Sterilized In Tube, cap in place: agar poured into tubes, caps screwed on but not tight.. Pressure cooked 15psi/15min cooled in closed cooker overnight. Close caps when condensation is gone.
SITC=Sterilized In Tube: agar poured into tubes, tops stuffed with cotton ball. Pressure cooked 15psi/15min with "canned" stoppers, cooled in closed cooker overnight. Note: pulling the cotton out results in wispy attachments. Twisting the cotton before removal greatly reduces this problem.
HAP=Hot Agar Pour: agar and tubes sterilized 15psi/15min, agar cooled somewhat, poured into tubes and cooled.
SIT=Sterilized In Tube: agar poured into tubes, loosely capped. Pressure cooked 15psi/15min, cooled in closed cooker overnight..
SIOT=Sterilized In Open Tube: agar poured into open tubes, caps separate in pressure cooker. Pressure cooked 15psi/15min, cooled closed cooker overnight. Caps placed on when cool.

yeast ranching for the Junior Scientist in all of us

gear

cultural history

some methods I am testing

further reading