Dadux/Ryan, thanks for the responses--definitely some technical stuff.
OK that makes sense, that several scars do not necessarily correlate with a mother cell being very old. I must have incorrectly assumed that while reading the article. I will say that I would be surprised if the s. cerevisiae cells in our meads reproduce every 100 minutes though, for the reason you pointed out below in your first post: suppose once the bio mass has reached 1.024 KG (a little over 2.2 pounds, on the 9th replication; Stasis's math below), it hits stationary phase. Assuming it does 1 - 2 replications during lag phase, that leaves either 7 or 8 replications to do during exponential growth before it hits stationary phase and most growth comes to a stop. If the yeast are replicating every 100 min, then this leaves between 7 x 100 and 8 x 100 minutes for exponential growth phase, which comes out to between ~11.5 and 13.3 hours. I was always under the impression exponential growth lasted for several days, not about half a day. This means that replication would have to take far longer than 100 minutes. So in theory I agree, it just seems unreasonable that cells could still be relatively "young" and have gone through tons of replications.
[/QUOTE] I dont understand this " If yeast are capable of living for a long time, what causes there to be so much either dead or inactive yeast to be piling up already (prior to the "signal" that starts stationary phase)?"
Maybe you refer to the lees but i dont see that much lees early on. Sometimes also yeast fall to the bottom but that does not necessarily mean that they are not fermenting. But as i said i dont see much/any until at least 5-7 days have passed since pitch, and thats already stationary phase. [/QUOTE]
Thats correct, I was referring to all the lees and how much cloudier the mead gets when I stir, even after only a couple days go by. I was just wondering why they seem to be going inactive, or going dormant and falling to the bottom when the article indicates that they are capable of doing so many replications.
Yeah, similar to the comment above, I'm kind of getting at what causes a healthy colony of yeast that are capable of doing many many more cycles of replications to suddenly slow down. I assumed alcohol might be one factor. Dadux mentioned that they might start to secrete "short chain lipids" to start to "inactivate" growth. I'd be curious to read more up on these signal substances, and if there was a way to repress them to extend the exponential growth stage?
So I'm not sure if my questions will be able to help our techniques for our mead or make it better, they were just things that popped up in my mind as I was reading the article Thanks again for your inputs gents!
What if it does not matter the number of scars the mother has? what if these people just measured the ammount of times they reproduced but the important thing is actual time lived. According to this study, a cell that grows on a rich medium and reproduces every 100 minutes, at her lets say 12th reproduction will give a daughter cell with less lifespan.
OK that makes sense, that several scars do not necessarily correlate with a mother cell being very old. I must have incorrectly assumed that while reading the article. I will say that I would be surprised if the s. cerevisiae cells in our meads reproduce every 100 minutes though, for the reason you pointed out below in your first post: suppose once the bio mass has reached 1.024 KG (a little over 2.2 pounds, on the 9th replication; Stasis's math below), it hits stationary phase. Assuming it does 1 - 2 replications during lag phase, that leaves either 7 or 8 replications to do during exponential growth before it hits stationary phase and most growth comes to a stop. If the yeast are replicating every 100 min, then this leaves between 7 x 100 and 8 x 100 minutes for exponential growth phase, which comes out to between ~11.5 and 13.3 hours. I was always under the impression exponential growth lasted for several days, not about half a day. This means that replication would have to take far longer than 100 minutes. So in theory I agree, it just seems unreasonable that cells could still be relatively "young" and have gone through tons of replications.
[/QUOTE] I dont understand this " If yeast are capable of living for a long time, what causes there to be so much either dead or inactive yeast to be piling up already (prior to the "signal" that starts stationary phase)?"
Maybe you refer to the lees but i dont see that much lees early on. Sometimes also yeast fall to the bottom but that does not necessarily mean that they are not fermenting. But as i said i dont see much/any until at least 5-7 days have passed since pitch, and thats already stationary phase. [/QUOTE]
Thats correct, I was referring to all the lees and how much cloudier the mead gets when I stir, even after only a couple days go by. I was just wondering why they seem to be going inactive, or going dormant and falling to the bottom when the article indicates that they are capable of doing so many replications.
I think that the ABV limit somehow stops their ability to assimilate sugar.
Yeah, similar to the comment above, I'm kind of getting at what causes a healthy colony of yeast that are capable of doing many many more cycles of replications to suddenly slow down. I assumed alcohol might be one factor. Dadux mentioned that they might start to secrete "short chain lipids" to start to "inactivate" growth. I'd be curious to read more up on these signal substances, and if there was a way to repress them to extend the exponential growth stage?
So I'm not sure if my questions will be able to help our techniques for our mead or make it better, they were just things that popped up in my mind as I was reading the article Thanks again for your inputs gents!