Hi Cecilia,

I do not understand why it is so important to know if the yeast is C + or C- to change the volume of the fermenter. It is sufficient to provide an oxygen supply (which doesn't almost not changes the volume of the fermenter). If Saccharomyces cerevisiae YPH499 is C +, it will produce ethanol in an aerobic environment, otherwise, no.

If I have not really understand your question, please feel free to contact me on [email protected].

Good luck 

Hello Cecilia

If you want to scale up your process, you have the chance to control the Glucose-Feed, so you avoid extendend levels of sugar in the reaction. Jacque's is right, perhaps  the C-classification is not relevant. Usually, your aeration can be adapted in a way that avoids anaerobic phases or Ethanol-formation, if this is your intention.

It is different in yout flasks because you might not be able to regulate the sugar level there, but I am not sure if it is a problem anyway.

You can check different pH-Values, maybe you get a benefit there.

The yeasts PDCs (Pyruvate decarboxylases) work best around a pH of  6,5, if you lower pH too strong, (with unbufferd growth in a flask f.e.), you inactivate the PDCs and your Pyruvate-metabolism

it is often overlooked, many researchers dont control the pH values and suggest, that the acidic pHs below dont matter for the yeast, because they dont inactivate immediately, but the metabolism depend strongly on the slected pH.

Have a look here, this is a paper of a yeast-based scale-up i worked on too:

https://www.thevespiary.org/library/Files_Uploaded_by_Users/no1uno/pdf/Medicinal/Phenethylamines/Phenethanolamines/Ephedrines.and.Cathinones/l.PAC/Rosche.etal.Enhanced.Production.R.PAC.through.Enzymatic.Bioproduction.pdf

Good Luck

Thank you both for your answers, we have adjusted our conditions and you were right, the fact the C+ or C- was not necessary.