Yeast on plates inside the fridge will be in a good temperament for a rational duration, however, it will be in need for re-streaking nearly once a month because the plates during this time will start to dry out. Therefor, as the plates begin to smell, then re-streaking them is a necessity

6/6/19

Dear Alexander,

Without knowing the sensitivity of your yeast or what your downstream procedures are, I can only recommend as a simple solution that you incubate the yeast plates for a shorter period of time to prevent formation of large colonies. In the past, I have grown yeast on Sabouraud agar to determine viable counts. I incubated the plates at 30C for ~40-48 hr, after which time the plate had many isolated colonies with diameters of ~2-4 mm. This may work for you.

I hope this information helps you.

Bill Colonna Center for Crops Utilization Research, Dept. Food Science & Human Nutrition, Iowa State University, Ames, IA USA [email protected]

Can apply procedure , otherwise unknown results may be occur

Yeast on plates inside the fridge will be in a good temperament for a rational duration, however, it will be in need for re-streaking nearly once a month because the plates during this time will start to dry out. Therefor, as the plates begin to smell, then re-streaking them is a necessity

I am working with ethanologenic yeast isolates for about 2 years now.According to my experience, yeast are (although they are Eukaryota) behaving like bacteria on plates.When the incubation period is elongated for more than 24-48 hours they will overgrow on plates.Then they will form larger colonies.But I suppose they will not change their genetics due to this. However, after that they will stop their growth and gradually you will observe that the color of the colonies change.This is because the cultures start to dye after a certain period of time.Not like filamentous fungi,yeast plates cannot be maintained under room temperature or 30 C for a long time .If you want to maintain them in plates ,you should allow the cultures to dormant in refrigerator. Later you can subculture them into fresh media and use.Usually I subculture my yeast isolates into fresh plates when they appear to change their colony color.Otherwise the cultures are dying that late sub culturing will not form colonies.Another thing you can do is to grow yeast in yeast extract peptone dextrose broth and cryopreserve it adding glycerol.when you need them you can subculture in fresh plates.by the way repeated sub culturing them into fresh plates at least by 2 weeks time is essential.

Dear Alex,

I would recommend the answers given above. In addition to them, I would suggest preparing fresh plates (from a glycerol stock) prior to an experiment. Incubating for more than 24-30 h, is just going to cause overgrowth. In my personal experience, I observed an isolate of S.cereviseae to turn colour, and prolong fermentation duration, when I happened to pick colonies from an overgrown plate (72 h).