Yeast and CO2

[superstock]

Do some yeast produce more CO2, or is it a fixed ratio of sugar in = fixed amt CO2 & fixed amt alcohol out?
Reason for asking, was thinking of lagers that had been at low temps for a long time and needed a yeast top up before bottling. To reduce the yeast in the bottom of the bottle.

 

[AntonW]

It's my understanding that the ratio of alcohol to CO2 is fixed:

C6H12O6 + Zymase → 2 C2H5OH + 2 CO2

http://en.wikipedia.org/wiki/Ethanol_fermentation

But that doesn't mean that some yeasts will do better than others for what you want. I'd think that you'd want a yeast which will attentuate slightly more than the first yeast you used.

How long are we talking though? Others have probably had more experience than me, but there's probably enough viable yeast left in the beer that it'll carb up over time even if you add sugar but don't add more yeast.

Let us know how you go.

 

[superstock]

Didn't even think of the chemistry. Duh!
Got a lager that has been at 0' for about 5 mths.

 

[AntonW]

ok, 5 months is quite a while.

You could test a small amount of it by adding some sugar and seeing if it starts to ferment again if you let it warm up.

Or you could just add more yeast.

Good luck!