I am preparing to start my own small yeast bank and I was wondering what is the optimal method for scaling up to a starter from a single colony.

  • What step sizes should I use?
  • What strength of wort should I use?
  • How long should it take for each step?

For the sake of an example, what would be the optimal path to get from a single colony on a plate to a starter suitable for pitching into 100l of 1050 wort?

Edit for clarity: By optimal I mean giving me the smallest pitchable starter, for the required number of cells, and having cells at the highest viability and vitality when pitching.

2 Answers 2


You want to grow the slant up to about 100b cells by a mini starter, I start with 500ml 1.040 with nutrients.

Then treat that as I would a new pack of yeast.

Each step up of a starter takes 12-24 hours generally. Stirplate will help a lot to give more growth in shorter times.


What I have pieced together so far: (as I dig up more I will expand this)

For 100l at 1050 I would require ~800 Billion cells +/- 10%. [http://homebrewacademy.com/stepping-up-a-yeast-starter/ ]

To grow cells from a slant would require me to scale the starter up first into a 10-15ml starter and from there scale around 1:6 times each step, so 10ml -> 50ml -> 250ml -> 1.25l -> 5l.

Each step should be allowed to ferment for 12-18 hours at 22C +- 2C with 8 hours to sit in the fridge (overnight) to force floccuation. Then pour off the bad tasting starter beer. Re-pitch the slurry into the next sized vessel and top up with fresh DME/nutrient solution. [http://www.mrmalty.com/starter_faq.php ]

The solution for the starter should be between 1030 and 1040 with the addition of yeast nutrients, and oxygen if you have it. If not a stir plate will force off CO2 and help dissolve more oxygen, failing these shaking every hour or so will work but be a bit slower and stress the yeast more. Pushing you more towards the 18 hour mark for each step.

So for a healthy pitch into a 100l batch it would optimally take 5 days to scale up ready for pitching.

  • Yeast will continue to multiply as long as thier is food & nutrients or until it's ABV tollerence is reached. So we can estimate cell count on a starter step by the OG and volume. That being said a multi step starter for a large pitch is really just to prevent infection in the starter because the same can be accomplished by a single yeast cell in a large starter volume over a long time. So ideally you want your steps to ferment out in 24 hours the max volume of the starter step is determinded by the cell count available. Commented Mar 29, 2016 at 3:12
  • You are correct, they will continue to multiply as long as there are nutrients, but I am looking for an optimal path. I should have defined my exact definition of optimal, which I will do now. Also, I am looking at multi step as multi step appears to be to reduce the total size of starter required to pitch in, and you can get more efficient growth with lower stress levels on the yeast.
    – Mr_road
    Commented Mar 29, 2016 at 9:01
  • for a pitch this big 100l / 26.5g your last step would be bigger than 5000ml, this is about the biggest size of flask homebrewers keep around. Though some use carboys on stirplates. So most will to split into a couple starters midway. There's really no reason not to start with 200-500ml from the slant, any less you can't use a stirplate to areate. I just did an 8 step 1200bil cell starter for a dopplebock it took a week to grow the pitch. Commented Mar 29, 2016 at 11:35

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