[on4now4]

Hello,

I am not sure if this is the correct place to post this so please move it if somewhere else better fits. 

When generating CO2 from a yeast and sugar mixture is there a maximum pressure that it can generate before it will stop?  If so what is that pressure and once it drops below the given pressure will is start back up?

To be honest this makes little sense to me.  But I read from a fairly unreliable source randomly found through google that when creating CO2 in this manner it will max out around 100PSI.  But it seems to me there should be no limit...  Wont the yeast just keep working until all the sugar is gone or the solution becomes to alcoholic for the yeast to live anymore? 

If the latter is the case,  Is there a simple formula I can use to calculate the amount of yeast to sugar ratio given a volume that will tell me the resulting PSI?

[Borek]

No idea what is the limit, but it must be definitely there. No matter how the yeast produce the CO₂ thermodynamics is not different from every other reaction - this is an equilibrium process, increasing pressure of gaseous reactants shifts the equilibrium.

Actually, in this case presence of CO₂ will most likely shut down the process much earlier than in the case of in vitro chemistry, by acidifying the solution, slowing (or even shutting down) cellular respiration and killing the yeast.

[Darryl1]

I was going to say Le Châtelier's principle should still be valid even in biological systems.  I think Borek is correct in that the CO2 is going to start dissolving in the liquid to the point that the acidity inactivates the yeast.
100 PSI seems about right though.  I recall reading somewhere that Champagne bottles are roughly 90 PSI, so it seems reasonable.

-d

[Arkcon]

Also remember that living cells also have pressure constraints outside of simple chemical equilibrium.  Even if the gas is reasonably inert, like nitrogen, hundreds of psi, if the vessel can hold it, will begin to disrupt cell structures and inhibit or kill yeast.

If the latter is the case,  Is there a simple formula I can use to calculate the amount of yeast to sugar ratio given a volume that will tell me the resulting PSI?

This is deceptively easy, but unfortunately, likely very incomplete.  We can determine how what quantity of gas we get from any reaction, but with side reaction of the sort found in living things, and with the non-ideal behavior of gasses -- both under pressure and because CO₂ reacts with water, calculations are likely to go nowhere fast.

[curiouscat]

Also remember that living cells also have pressure constraints outside of simple chemical equilibrium.

It'd be interesting to know how much. Do cells stop functioning at 10 atm? 100 atm? I'm assuming the partial pressure of O2 is maintained.

[Darryl1]

I'm not sure about cells under pressure, but I do know when there is a sudden release of pressure, the cells burst and die.  This is the basis for how some of the fancy retail guacamoles are preserved.  They put the guac under extreme pressure, then release it.
It kills the pathogens and significantly reduces the microload to get a longer shelf life without heating.

-d

[Borek]

It'd be interesting to know how much. Do cells stop functioning at 10 atm? 100 atm? I'm assuming the partial pressure of O2 is maintained.

I don't think there is a simple answer to that. I remember reading bacteria taken from the Marianas Trench survived the trip, but were not interested in metabolism - till they were put in a cold water at 1000 atm

[Babcock_Hall]

Biochemistry, 4th edition, by Geoffrey Zubay (p. 373) gives the equilibrium constant for forming glucose from CO₂ and water at 27 °C as 10^-496 in the absence of light.

[on4now4]

I cant say I fully follow everything that has been said but it is enough to point me in the right direction.  I will keep reading. 

Thank you for all the *delete me*  It is a very interesting topic for reasons I did not even know when I was posing the question...

[Babcock_Hall]

My point was that the equilibrium constant for forming carbon dioxide and water from glucose and oxygen is extremely large.  I have not done the calculations, but it is difficult to see how that particular reaction could come to equilibrium.  However, as I am writing this, I am beginning to see an important caveat.  In a yeast cell, this oxidation is coupled to the synthesis of ATP.  One should consider instead the oxidation coupled to the synthesis of ATP and ask what the equilibrium constant is for that process.

[Yggdrasil]

My point was that the equilibrium constant for forming carbon dioxide and water from glucose and oxygen is extremely large.  I have not done the calculations, but it is difficult to see how that particular reaction could come to equilibrium.  However, as I am writing this, I am beginning to see an important caveat.  In a yeast cell, this oxidation is coupled to the synthesis of ATP.  One should consider instead the oxidation coupled to the synthesis of ATP and ask what the equilibrium constant is for that process.

The only cells at equilibrium are dead cells.

[Darryl1]

In addition to ATP, there have got to be other intermediates that could affect equilibrium.
I like Yggdrasil's response.  It's very true.

-d

[Babcock_Hall]

My point was that the equilibrium constant for forming carbon dioxide and water from glucose and oxygen is extremely large.  I have not done the calculations, but it is difficult to see how that particular reaction could come to equilibrium.  However, as I am writing this, I am beginning to see an important caveat.  In a yeast cell, this oxidation is coupled to the synthesis of ATP.  One should consider instead the oxidation coupled to the synthesis of ATP and ask what the equilibrium constant is for that process.

The only cells at equilibrium are dead cells.

Yes I agree, but one question that was posed (if I understand it correctly) was whether there would be a level of carbon dioxide that was so high that the reaction would stop solely because it had come to equilibrium.

[Borek]

I have mentioned the equilibrium, not the OP.

I agree with Ygg's comment about the dead cells, but I still believe argument about the reaction not being able to get to the end for thermodynamic reasons is valid. I suppose OP thinks in terms of "reactions always go to the end, so all glucose should convert to CO₂" - that is clearly incorrect and calls for introducing the equilibrium as a counterargument.

[on4now4]

I have mentioned the equilibrium, not the OP.

I agree with Ygg's comment about the dead cells, but I still believe argument about the reaction not being able to get to the end for thermodynamic reasons is valid. I suppose OP thinks in terms of "reactions always go to the end, so all glucose should convert to CO₂" - that is clearly incorrect and calls for introducing the equilibrium as a counterargument.

I think that is a fair statement to make.  I study electrical engineering and have very little knowladge about this stuff.  Of course I am realizing that there is much more to this than I first realized.  However when I made the first post yeah I was thinking it would just continue reacting until everything is gone.