13,591
edits
Changes
m
no edit summary
# Start with 75 mL of 6° Plato wort with yeast nutrient in a 250 mL flask. Add the sample (fruit, flower, bee, etc). If it's fruit, squish it up. Set the flask on a shaker or stirplate at 80-90F with a foam stopper (aerobic; aluminum foil should work too) for 12-48 hours. Look for frothing and as soon as that happens put an airlock on the flask, but keep on stirplate to assist fermentation.
# After the 24-48 hours, decant the liquid and leave the biomass at the bottom. Add new starter media 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 the liquid and leave the biomass at the bottom of the flask. Purge with CO2, and add 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 Plato or so. # After the 20° Plato wort has finished fermenting, samples from the liquid (the liquid can be decanted, and contains the more active yeast versus the biomass can be at the bottom of the flask) are streaked onto media to isolate the strains that have survived.
Agar that David uses (see also [[Laboratory_Techniques#Growth_Media|Growth Media]] on the wiki for other media types that might also be useful):
* Wallenstein labs nutrient: serves as a catch -all.
* HLP: isolate ''Lactobacillus'' and ''Pediococcus''.
* LMDA: color indicators for acid production (then do a gram stain to see if it is positive or negative; ''Lactobacillus'' versus ''Acetobacter'').
Other notes:
* Measure pH to make sure it gets down to under 4.65; this helps monitor for fermentation activity.
* Generally this method selects for 1-3 strains of yeast with usually a lactic acid bacteria strain.
* The anaerobic nature of this method selects against mold growth.