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# After the 24-48 hours, decant and discard the liquid and leave the biomass at the bottom. Add 75 mL of new starter media to the flask (with the biomass still at the bottom of the flask) that is 8-10* Plato with yeast nutrient, and purge the flask with CO2. Put an airlock on it on a stirplate and grow until the sugars have fermented.
# Again, decant and discard the liquid and leave the biomass at the bottom of the flask. Purge the flask (with the biomass still at the bottom) with CO2, and add 75 mL of 20° Plato wort with yeast nutrient and an airlock, and place on a stirplate or shaker. Look for the wort to ferment down to around 2 Plato or so.
# After the 20° Plato wort has finished fermenting, samples from the liquid (the liquid contains the more active yeast versus the biomass at the bottom of the flask) are streaked onto media to isolate the strains that have survived. If agar plating is not an option, a less advanced approach can be taken by [[Wild_Yeast_Isolation#Growing_and_Testing_Without_Plating|growing and testing without plating]].
Agar that David uses (see also [[Laboratory_Techniques#Growth_Media|Growth Media]] on the wiki for other media types that might also be useful):