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How to Make Penicillin with Potatoes

Penicillin is the most widely used antibiotic globally, and you can use it to treat a range of infections caused by bacteria. Learning how to make penicillin with potatoes is a good idea, although you need to learn more than just that if you want to know how to make penicillin safely at home.

If you want to make pharmaceutical-grade penicillin, you’ll need to know how to filter out the penicillin from the other kinds of fungi it grows with. When mold develops, it makes different things to help kill bacteria, and many of these are harmful for human use. Although making your own penicillin is possible, it’s not easy. Many preppers may argue that there are alternative medicines available that you can use besides this. While this is true, mastering the skill or making penicillin at home can be life-saving when SHTF and you or a loved one find yourself in a survival situation where you can’t access any other natural or commercial medicine. 

Making penicillin requires more than just bread or fruit, so you’ll have to gain the knowledge and get your penicillin-making kit together before things go south. In this article, we hope to shed more light on this useful home-grown medicine and equip you with the right knowledge to grow and extract your own penicillin at home.

How to Make Penicillin at Home

To safely grow and extract penicillin, you’ll need the right ingredients and tools. While many preppers wait for bread or fruit peels to turn moldy and simply use this mold to fight infections, it’s not recommended and can, in fact, cause harm. 

Following the right guidance is essential to make penicillin safely, and below, we explain what you’ll need and take you through the steps.


  • Pieces of citrus fruit, a cantaloupe rind, or bread (preferably home-made)
  • Potato
  • Sugar
  • Salt
  • Yeast
  • Milk Powder
  • Citric Acid
  • Agar (or plain gelatin)
  • Hydrochloric Acid
  • Ethyl Acetate
  • Potassium Acetate
  • Aluminum
  • A scale (grams)
  • Glass containers
  • A separator funnel
  • pH testing kit


  • Isolate the Bacteria

Your first step in making penicillin will be to isolate the penicillin bacteria. To isolate it, you need to put pieces of your chosen growth base (fruit or bread) in a container and place them in a dark spot to encourage mold growth. After a few weeks, gray mold will start growing. At this point, your penicillin isn’t ready yet, so leave it set until the gray mold turns bluish-green in color.

  • Re-culture the Penicillin

Start by placing your 1-liter glass container in the oven at 300 degrees F for about an hour to sterilize it. Thinly slice unpeeled potatoes and put them in your sterilized container with distilled water. Screw the lid on tightly and place the entire jar in a pot with boiling water for about 30 minutes. 

After boiling:

  • Let the container cool slightly, and then drain the contents in the jar through a cheesecloth.
  • Add 20g sugar and 20g agar or plain gelatin to the broth you’ve caught through the cheesecloth.
  • Mix these well and add distilled water to it until you reach a volume of 1 liter. After you’ve mixed everything thoroughly, pour it into broad, flat jars with sealable lids to prevent microbes from reaching the broth.


  • Move the Mold

The next step in making penicillin at home is moving the penicillin mold spores that have developed on your chosen growth base to your potato broth. To move the penicillin spores, use a thin wire which you’ve bend into an oval shape. The oval tip should be sterilized using a flame until it’s red hot. 

Next, you should dip the wire tip into your potato broth to cool and then touch the wire to the green-blue mold which has formed on your chosen growth base. Transfer the collected mold to your potato broth by making three lines with it in the broth.

  • Grow Penicillin

While keeping your broth covered, your penicillin will start growing in about a week.

  • Ferment Penicillin

If you want your penicillin spores to produce large numbers, you’ll have to ferment them. 

To ferment it:

  • Sterilize a flask at 315 degrees F for about an hour in the oven.
  • Add one teaspoon of salt, milk powder, sugar, yeast, and citric acid to a graduated cylinder and fill it with water until you reach a volume of 100ml.
  • Mix the contents and pour them into your flask after sterilization.
  • Add your penicillin cultures to the flask and screw an airtight lid on it.
  • Cover the entire flask with sterilized aluminum foil (lid off) to keep unwanted microbes out but still allow for airflow. You should allow the flask to sit out for about seven days.


  • Extract Penicillin

After approximately 7 – 10 days, the penicillin in your flask should be fermented. You’ll now need to separate the penicillin (found in the liquid part of your mixture) from the other ingredients (found in the solid parts of your mixture) by straining the mixture through a sterilized cheesecloth into a sterilized container.

  • Round the Penicillin Off

After you’ve caught the liquid, you need to adjust your penicillin’s pH level by adding a drop of hydrochloric acid to it. Test the pH of your liquid after you’ve done this and keep adding drops until you reach a pH of 2.2.

  • Final Extraction

Although you can use penicillin as is in the previous step, it’s best that you do a round of final extraction first. If you have ethyl acetate on hand, chill it in your freezer. After it has cooled, mix the cold ethyl acetate with your penicillin liquid in a funnel and shake it for 30 seconds until well combined. Leave it to sit, allowing the two liquids to separate again. 

After separation, open the separator funnel, allowing the ethyl acetate to drip into another sterile container. Once it has dripped through, add 1g of potassium acetate to each 100ml of ethyl acetate. Leave this mixture uncovered in a well-ventilated area to allow for evaporation of the ethyl acetate. After evaporation, you’ll be left with penicillin that is ready for use.

Penicillin Side Effects

Using medicines has its risks, and like others, using penicillin can have side effects. If you experience any of the below side effects, you should discard your penicillin use immediately.

  • Hives, itching, or skin rashes
  • Fever
  • Swelling
  • Shortness of breath or wheezing
  • Nausea, abdominal cramps, vomiting, or diarrhea

Other Natural Antibiotics

Knowing how to make penicillin is a valuable skill, but you might not always have the needed ingredients or supplies available to do so. While you can stock these in your prepper pantry to ensure availability, another factor you should consider is time limits. You, or a loved one, can require immediate treatment of an infected wound or other bacterial illness. When this happens, you won’t have enough time to make a batch of penicillin. 

Luckily, you can use other natural antibiotics, and most of them might already be in your pantry!

Honey: Since it contains both sugar and hydrogen peroxide, honey has been used as an antibiotic for centuries. It helps restrict the growth of certain bacteria, and many preppers use it in conjunction with apple cider vinegar – which is another natural antibiotic – to make an effective potion.

Garlic: Known as one of the best natural antibiotics, garlic is packed with many vitamins, minerals, and nutrients, which help it kill bacteria and viruses without causing any harm to your body’s gut flora. When infused with, for example, olive oil, you can use garlic to treat external infections as well. Garlic is easy to grow, so you can start cultivating this in your garden to be prepared when SHTF.

Ginger: Fresh ginger should also be a priority ingredient for any prepper. Besides the relief it offers you from many foodborne illnesses, ginger is also useful as an antibiotic to fight foodborne pathogens like salmonella.

Cloves: If you’re not able to make penicillin at home, you can also stock up on cloves to aid in breaking down bacterial cells and fighting off oral candidiasis.

Turmeric: Curcumin is a powerful antioxidant contained in turmeric. It can help to reduce the growth of disease-causing bacteria and suppress fungal growth and tumor cells.

When used in the right way, natural antibiotics can be highly effective. They’re safe to use, widely available and have little to no side effects.


When SHTF, it’ll put you in survival situations that push you to your limits. Your chances of getting scrapes and cuts will increase, and immediate treatment might not always be possible. If a lack of proper wound care leads to infection, you might find yourself on your deathbed because of this. A simple respiratory infection or toothache can also be the culprit. Without antibiotics, you’re doomed.

One of the primary reasons why we aren’t experiencing everyday plagues is modern medicine. When society collapses and our access to this is limited, plagues could resurface and cause havoc on humanity. Besides stocking your pantry with essential food items and water for survival, you should prepare for circumstances like these too. Even though the process is tedious, having the right tools and knowledge on how to make penicillin can be a lifesaver.

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