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Yeast growth on varying temperature

Success Goal

Demonstrate the effect of temperature on yeast growth. Students may have a prior belief that temperature effects are linear, ex: a culture at 10℃ will grow at half the rate compared to a culture at 20℃, and a third the rate at 30℃. This experiment would show the non-linear effect of temperature on growth (and relate it to how refrigerators halt spoilage for so long). Students and the teacher can pick temperatures to test beforehand.

Requirements:

  • At least two available Pioreactors
  • Dry baker's yeast
  • YPD mix, or any other media mix

Steps:

  1. Prepare a sterile stock of 10g YPD / 1L distilled water. Aim to make 20ml × the number of Pioreactors you are using, as each Pioreactor will require about 15ml of media.
  2. Once stock is cool, inoculate the stock with a very small amount of baker's yeast using best practices to avoid other contamination. Wait for the yeast granules to dissolve, aided by gentle rocking or stirring.
  3. Mix well, and distribute up to 15ml of liquid to clean and sterilized Pioreactor vials.
  4. Visit pioreactor.local and start a new experiment.
  5. On the Pioreactors page, start Stirring activity, and OD reading activity.
  6. Confirm that everything looks normal (ex: receiving optical density signal)
  7. For each Pioreactor in use, start the temperature automation, select Stable and provide the target temperature for that Pioreactor.
  8. Optional: you can change the names of the Pioreactor in the UI to display the target temperature.
  9. Students can watch growth progress on the Overview page.
  10. After 24 or so hours (even sooner in some cases), the students can explore about maximum growth rates achieved, duration of lag phases, and overall yield of the cultures. Plotting these metrics vs temperature give students an intuition about how temperature affects yeast growth.
info

The Pioreactor doesn't cool samples, so it can't achieve temperatures below your ambient temperature. If you want to test low temperatures, you can place the Pioreactor in a frige, or in a cooler with ice packs (making sure the electronics won't get wet).