Grow lager yeast for 60L batch

[ODI3]

I just bought a 60L fermzilla and looking to start doing some 60 L 1.040 pressure fermented Lager batches for my thirsty hockey buddies.

What method do you recommend I use to get yeast for these batches?
buying it is kinda expensive. I assume i need 1200 cells for a pressure lager at 15 psi at 50 deg f?

Buying these packets would be like $8.99x6=53.94 +tax = $62.00 i think?

Or would this work better?
use 1 packet of 34/70 fermentis yeast, make a 20L batch, ferment at 68F at 15 psi. would this give me 1200 cells?

I have some 8L pop bottles i can use for some sort of shake method and a 4L Erlymeyer flask and stir plate availabe.

I am hoping to just use my fermzilla as a uni tank then bring a couple 8L bottles to each game.
Maybe even just repitch on the slurry after the beer runs out.

Maybe my math is all screwed up? Any ideas is appreciated!

 

[Kickass]

use 1 packet of 34/70 fermentis yeast, make a 20L batch, ferment at 68F at 15 psi. would this give me 1200 cells?

Without running numbers, I’d go this route. If you brew frequently and/or have the means to store yeast, it’s really easy to keep an active colony. I’m a miser so I’m always trying to stretch my yeast bank.

34/70 does really well at warmer temps, even without pressure so you can easily ferment it in the low 60’s.

 

[IslandLizard]

Or would this work better?
use 1 packet of 34/70 fermentis yeast, make a 20L batch, ferment at 68F at 15 psi. would this give me 1200 cells?

I'd do that!^
Otherwise you'll need to make 3 or 4 rounds of starters, from one 11.5 gram pack, for your 60L batch.

From Fermentis:

Dosage / Temperature​

80 to 120 g/hl at ideally 12°C – 18°C (53.6-64.4°F).​

That equates to 8-12 grams of dry yeast per 10 liter of wort. There's no indication of wort gravity, let's presume 1.044-1.052.

Viable yeast > 6.0 *10^9 cfu/g​

cfu/g is colony-forming units per gram
So that's 6 billion "active cells" per gram, or 69 (or 70) billion per 11.5 gr package.

A standard yeast pitch of 200 billion cells in 20 liters of medium gravity wort typically quadruples or even quintuples her cell count. Similarly here, expect to have 250-300 billion cells (4x 70 billion = 280 cells) after the first 20 liter fermentation.

If you were to pitch 2 packs you may have 1.5 times (450 B) to double that (600 B), depending on growth rate. At best, halfway there... But you'll have 20 liters of good beer.

They also sell 100 gram and 500 gram packs of that yeast.
A 500g brick is $225 at Morebeer, or around $5.18 per 11.5 gram (the weight of a homebrew sachet). No crazy big savings there either.

 

[Malticulous]

I have a 60L allrounder. I think the best way to get yeast is a five gallon batch.
With ale temp pressure fermenting and a low gravity you can get away with much less.

 

[Rich1234]

I'd consider just buying 3 packs and don't look back. I (warm) pressure ferment 15 gal batches in a spike conical with 3 packs of 34/70 all the time. My target ABV is usually 5-5.5%. I do them in my basement which is currently 68 deg F, without issue. 8 psi on the beer if that helps. I've seen as high as 76 deg on the active ferment and still made high quality beer. You can get good deals on that yeast on amazon. My target price is 5 packs for just under $30.

Not to hijack, but if anyone has a good, peer reviewed solid link to a video on a good yeast harvesting process from a spike conical, it would be much appreciated. That's the next step in my evolution.