- Potato: 200 g
- Tap water: 1,000 mL
- Glucose: 20 g, 2 w/v% (2 g in 100 mL)
- Powdered agar: 15 g, 1.5 w/v% (1.5 g in 100 mL)
- Strain cloth or tea pack
- Aluminum foil
- Stove
- Kettle
- Weight scale
- Heat-resistant measuring cup
- Large heat-resistant container
- Peel the potato skin, and cut into 1 cm to 2 cm squares. Weigh them with a scale.
- Put tap water into the kettle and put it on the stove. Add the tea pack containing the potato and boil for about 20 minutes. Or simmer at 60°C for about 1 hour (*1). During this time, cover the kettle opening with two layers of aluminum foil. (Note: that if it boils, the liquid may spill out.)
- Use a heat-resistant measuring cup to measure the amount, then pour it into a large heat-resistant container. To the entire measured amount, add a suitable amount of glucose and powdered agar. Mix well and pour it back into the kettle.
- Allow it to cool naturally to about 60°C-70°C, then pour it into a petri dish using an aseptic method. 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 9cm petri dishes, pour about 30 mL in each dish.
- 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.
- Alternate procedure: Prepare 2.0% glucose, 2.0% agar, 23 mL of potato extract, and 77 mL of distilled water. To make the potato extract, grate 100 g of peeled potatoes in 300 mL of water, and refrigerate overnight. Then use several layers of gauze to filter the liquid, sterilize the filtrate (autoclave), and preserve it (*2).
*1. The Society for Biotechnology, Japan. "Seibutsu Kōgaku Jikken-Sho, Revised Edition", p.131
*2. H.J. Phaff, M.W. Miller, and E.M. Mrakm. "The Life of Yeasts" translated by Susumu Nagai, p.66