- Yeast extract: 0.3%
- Polypeptone: 0.5%
- Malt extract: 0.3%
- Glucose: 1%
- Agar (powdered): 1.5%-2%, *For plate media.
- Pure water
*Concentrations are all weight/volume percentages w/v% (number of grams dissolved in 100 mL).
- Chloramphenicol: 100 μg/mL. *Suppresses bacteria.
- Sodium propionate: 2 mg/mL (0.2%). *Suppresses mold.
- Lactic acid: 20 mL/L. *Suppresses bacteria.
- Weighing paper or weighing dish
- Autoclave seal
- Aluminum foil
- Pipette and tip. *If using liquids such as lactic acid.
- Dispensing spoon. *The lab might not allow it due to the chemical reaction.
- Erlenmeyer flask
- Graduated cylinder
- Magnetic stirrer or stirrer
- Clean bench
- Weighing scale
- Have enough 500 mL Erlenmeyer flasks for the amount of YM media to be made.
- Weigh each reagent and put it into an Erlenmeyer flask.
- Measure about 250 mL of pure water in a graduated cylinder, then pour it into the Erlenmeyer flask. Shake to mix, but avoid bubbling or foaming.
- Transfer the entire liquid into a graduated cylinder. While washing the inside of the Erlenmeyer flask with pure water, fill it up with 400 mL.
- Make sure that there is no undissolved residue in the graduated cylinder. Transfer the entire amount to the Erlenmeyer flask (or kettle).
- Use a double layer of aluminum foil to cover the opening of the Erlenmeyer flask (or kettle).
- Autoclave (2 atm, 121°C, 15 min.).
- After the autoclave, wait until the pressure goes down to almost zero, then remove the contents.
- Allow it to cool naturally to about 60°C-70°C, then pour it into a petri dish using an aseptic method. For plate media: Stack about 10 petri dishes, and start with the bottom one by holding up the cover and pouring into the dish. In the case of 9 cm petri dishes, pour about 30 mL in each dish. For liquid media: On a tube stand, place 50 mL tubes upright, and pour about 20 mL to 25 mL into each tube.
- Sprinkle the growth medium and leave it on a clean bench or table until it dries somewhat. This is to prevent water vapor and droplets from forming on the cover after a few days.
- When it is dry, use a permanent marker to write relevant information on the back of the petri dish and store it with the lid on.
- For the reagents used for the yeast separation, “Sakura Kōbo no Bunri” Table 1 by Takanori Yoshiura et al. was used as reference. Only the amount of sodium propionate was changed to 0.2%.
- Other methods to separate the yeast: Add alcohol, lower the pH (yeast supposed to be more acid resistant than bacteria), use SD growth media having low nutritional value, or set the glucose in the YPD growth media to 10%-20% (other things can hardly survive other than the yeast).