How To Make Penicillin

Antibiotic capsules with container

Did you know that penicillin can be grown outside of a lab? This mold-based antibiotic can be grown as a science project using a slice of bread. Please note that these instructions should be used for experimentation only; when there is a medical need for penicillin, it should be obtained through a doctor. Making penicillin does require some scientific equipment, and it is very important to keep the area sterile while you are growing penicillin. Here’s how to make penicillin:


Slice of bread or citrus peel
750ml Erlenmeyer flask
Media (see Step 4)
1000ml (1 L) graduated cylinder
Several clean milk bottles

  1. Prepare a penicillium culture. Expose a slice of bread or a citrus peel to a 70 degree Fahrenheit environment. A blue-green mold should develop.
  2. Sterilize the equipment. Place the flask in the oven at 315 degrees Fahrenheit for one hour, or sterilize in a pressure cooker for at least 15 minutes. Wash the milk bottles.
  3. Fill the Erlenmeyer flask. Cut the bread or citrus peel into small pieces and fill the flask. Allow to incubate in the dark at 70 degrees Fahrenheit for 5 days. After this incubation period, the flask can be stored in the refrigerator for no more than 10-14 days.
  4. Prepare the media. Dissolve the following ingredients, in the order listed, into 500ml of cold tap water: 44.0 grams Lactose Monohydrate, 25.0 grams cornstarch, 3.0 grams sodium nitrate, 0.25 grams magnesium sulfate, 0.50 grams potassium phosphate mono, 2.75 grams glucose monohydrate, 0.044 grams zinc sulfate, 0.044 grams manganese sulfate. Then add enough cold tap water to make one liter. Use hydrochloric acid to adjust the pH to between 5.0 and 5.5.
  5. Fill the bottles with media. Fill the milk bottles with this media. Use only enough so that when the bottle is placed in its side, the media does not reach the plug.
  6. Add the penicillin spores. First sterilize the bottles of media in a pressure cooker or in the stove, as you did the Erlenmeyer flask. When they have cooled, add approximately one tablespoon of the spores from the bread or citrus peel.
  7. Incubate the bottles. Allow the bottles to rest undisturbed on their sides at 70 degrees Fahrenheit for 7 days. If the culture has worked to produce penicillin, it will be in the liquid portion of the media following this incubation period. Finally, filter the media and refrigerate immediately. If you must use it, although this should be avoided, use as soon as possible.

The penicillin made from this experiment should not be used unless it is a survival situation. It is possible for other, toxic molds to grow along with the penicillin, even if you know what you are doing. It is also possible for mold inhibitors to grow, stopping the growth of the penicillin spores.


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