Yeast, can too much O2 be toxic?

[killroy]

We've got a new yeast prop going. 1BBL -10BBL -100BBL.

We are at the 10BBL stage. Our temp sensor stopped working and the wort was at 47 this morning with no activity. Through pumping hot water through the jacket and gentle recirculating it is now at 70.

I am not at work anymore, but the idea was to re-oxygenate with a stone. I was told that we were going to "Oxygenate the hell out of it".

I was told some time ago that too much O2 can be toxic to yeast. Since we don't have a meeter we can't tell how much we are putting in. Also, does O2 "Oxidize" yeasts cellular membrane if put in direct contact? Like Hydrogen Peroxide? Seems like a very small ammount of wort with a lot of cells at this point.

Thanks,

Killroy

[TL Services]

I'm not sure that too much O2 can be toxic to yeast, but it will certainly cause problems with controlling the rate of yeast multiplication.

Excessively fast growth may also result in weak, abnormal cells and resulting difficulties further down the line when you are using it, eg. high levels of dead cells, off-flavours, etc.

I would be inclined to oxygenate to help reinvigorate multiplication, but not to go overboard in that for the above reasons.

[BonedaleBeer]

You can most definitely over O2 your yeast. Similar to Hydrogen peroxide and ozone, it can be a sterileant. Sounds like you just had them go dormant for a short period if at all. Check your viability and count and add o2 in a normal proportion for your yeast for the next step-up.

[killroy]

Thanks for the replys.

I went to find the Methelyne Blue, but turns out it is lost...

They took it from 1.040 to 1.021 overnight and seemed to still be going strong yesterday morning. Without any added 02 I am told. I would really like to check the viability though.

Killroy