Motility of yeast

[jeff.k...@gmail.com]

I'm going to pull out this question from the other thread.

Do we know why some yeast remain in suspension and some falls to the bottom of the fermentation vessel?  Can living yeast keep themselves suspended in solution somehow?  If the vector of suspension is fluid movement in the cider caused by the release of CO2, then the yeast in suspension should be a mix of both living and dead yeast.  

Have any studies looked at viability of yeast both in suspension and at the bottom of the fermentation vessel?

/J

[Taylog1]

Jeff,

there's quite a lot online re yeast flocculation, such as this paper, which discusses different reasons why Saccharomyces cerevisiae yeast cells clump together; they consider inorganic ions, ethanol, Ph, temperature and more (p430). it also discusses different reasons why flocculated cells fall to the bottom (p428).   

And I like how they shoehorned a pun into the abstract.  

Gareth

[Love Lindholm]

Jeff,

I liked your thread, much because I have had the same idea: the yeast ought to live in a bad microcosm at the bottom of the tank.

Regarding why and how yeast is kept in suspension, AW provided two articles that deal with that in the previous thread. The second article, especially, builds a full mathematical model of that problem. It seems as if yeast cells move around both because of convection caused by the overall fermentation and from floating with their own, proper bubbles, but that the adhesion to self produced bubbles differs between species. So yes, it sounds as if some dead yeast could be in suspension, and mostly so when the fermentation is strong. Here is the paper again:

https://royalsocietypublishing.org/doi/10.1098/rsif.2020.0735

/L

[Miguel Pereda]

In real cellar conditions and in cider, it is also easy to see many yeasts adhering to small particles in suspension probably mostly pectinic in nature, during and after fermentation. 

Miguel A. Pereda .