I’ve not experimented much with yeast; with the exception of the kits I used when starting homebrewing and the Orange Wheat I made, I’ve pretty much used Fermentis S-04 English Ale yeast.

In my most recent grain order I ordered a variety of different yeasts. I now have: 

  • Safale S-04: A well known English ale strain noted for its fast fermentation and rapid settling.
  • Safale US-05: Ready-to-pitch American ale yeast for well balanced beers with low diacetyl and a very crisp end palate.
  • Safbrew S-33: Robust ale yeast able to tolerate high alcohol conditions, up to 11.5%. Used to produce a wide range of beer styles including Belgian wheat and Trappist beers.
  • Safbrew WB-06: The yeast produces subtle ester and phenol flavor notes typical of wheat beers.
  • Saflager S-23: Originating from the famous VLB institute in Germany, true lager yeast capable of producing continental lagers with a fruity, estery note.

This will give me some yeasts to experiment with – but what I’d like to do is grab some yeast from commercial beers, such as Hoegaarden and Baird Rising Sun Pale Ale. Rather than using a general yeast, those commercial yeasts are matched to the beer styles that I want to make – IPA, pale ale, and wheat. Using commercial yeasts will also give me more variety to play with. Hopefully I’ll find a yeast I like better than S-04 (which I have no particular attachment to).

Turns out it’s surprisingly easy to get yeast from a bottle of beer – as long as it is bottle conditioned and relatively young. From Homebrewtalk:

This is a Pacman yeast starter I harvested from a bottle of Rogues Brutal Bitter. I poured 3/4 of the bottle into a glass and drank it of course. I then made a starter of 16oz of water and 1/2 cup of DME and boiled. I then cooled the wort and sanitized the neck and mouth of the bottle and poured the rest of the Brutal Bitter into the starter and started spinning it. Super easy to do.

Homebrew Korea also has an excellent post on culturing commercial yeasts – though note that DME should be used instead of sugar, and personally I’d pour the 2/3rds of the bottle out before sanitizing.  How to Brew also has a page on using yeast from commercial beers.

Based on those sources, some others I’ve read, and discussions with homebrewers who harvest yeast, this is how to harvest yeast from commercial beers:

Harvesting yeast from commercial beers

  1. Sanitise a plastic 500ml bottle, then cap it.
  2. Boil 200ml of water with about 20g of DME for 15 minutes (10g for 100ml)  in a sanitised pot. This should give a 1.035-1.040 solution. (This amount was recommended to me by homebrewers who regularly harvest, saying that higher gravity worts could “stress out” the yeast.)
  3. Pour into the plastic bottle using a sanitised funnel, cap tightly, and cool to pitching temp.
  4. Pour about two-thirds to three-quarters of a bottle of the source beer into a glass, taking care not to disturb the yeast at the bottom. If you have two bottles of the source beer use both, because you’ll have more yeast to work from.
  5. Sanitise the neck and top of the source beer bottle(s) with spray sanitiser.
  6. Swirl the beer bottle(s) to ensure all the yeast is unstuck.
  7. Pour into the plastic bottle using a sanitised funnel, cap tightly, and shake to aerate. 
  8. Unscrew the cap slightly to ensure CO2 can escape. Label the bottle.
  9. Let it ferment for 3-4 days (longer if necessary – until fermentation stops), swirling a few times a day.
  10. This yeast can be used now with a starter. Alternatively you can make the yeast more healthy by culturing more. To do that, place in the fridge for the yeast to settle to the bottom. Once the yeast has settled to the bottom, prepare some more wort as per step 2, then take the yeast out of the fridge, discard some of the fermented wort (leaving the yeast at the bottom), and top up with new wort. Repeat step 9.
  11. Once fermentation is done, use within about 2 weeks. A yeast starter is recommended (see below).

There’s also a video on You Tube entitled Culturing Yeast from a Bottle Conditioned Beer – method is slightly different but principle is the same.

I also found two excellent sources on reusing yeast after fermentation: Mikebeer.net and a PDF from Point Brew Supply. The difference between these is that the second link covers washing the yeast. Combining these, this is the method to wash and reuse yeast from a fermentation:

Harvesting yeast from the fermenter

  1. Sanitise three 500ml bottles and a large container (about 3-4L, or two 2L bottles). Keep them capped/sealed.
  2. Bottle/keg the beer from the primary.
  3. Pour some preboiled and cooled water into the primary – about 1L.
  4. Swirl (not splash) until everything is in suspension.
  5. Pour the entire contents into the large container and cover with cling film.
  6. Let stand for 15-45 minutes until there’s a well formed layer on the bottom – the yeast will be in suspension above the gunk layer.
  7. Fill each bottle using a sanitised funnel – 1/3rd full first, then top them to 2/3rds, then fully fill – this is because the liquid at the top of the big container is less “yeast rich”. Leave behind the layer of gunk on the bottom.
  8. Label and date the bottles and store in the fridge. The yeast will settle to the bottom once in the fridge. Use within 2 weeks – a yeast starter is recommended if you exceed one week.

Reusing saved yeast

One bottle of the yeast should be enough for a 19L batch upto, say, 1.060. For yeast harvested from a previous fermentation and less than a week old, you can probably just add straight to the new wort – discard some of the top liquid first (because the yeast will have settled to the bottom) then warm it to pitching temp and shake before pitching. For everything else, or if you want to make your yeast really genki, a 1-2L starter is recommended.

To make a yeast starter, use 10g of DME per 100ml of water. Pour out some of the top liquid from the bottle of yeast, warm to pitching temp (by leaving out of the fridge) then swirl and add to the starter.

This video on You Tube covers making a yeast starter.