What's rotting in your kitchen right now? How about we grab it, and make life-saving antibiotics with it? We'll take you through the steps, and you'll be prepared if the world ends by Sunday.


Penicillin, the most famous antibiotic of all time, has saved millions of lives. And it's quietly lurking in your kitchen right now. If you have that moldy piece of bread in a bag at the back of the fridge, or a rotting cantaloupe or orange in the crisper, you're most likely growing penicillin by accident. In fact, penicillin's whole discovery hinged on the fact that it was easy to grow accidentally.

The Accidental History of Penicillin

Infection has always been a killer, and while soap and water could prevent it externally, when it went internal humans were often helpless. Any anti-bacterial agent injected into the body would kill a person more quickly than the infection would. Then Alexander Fleming had the nasal drip felt round the world. He was working with a plate of bacteria when his nose dripped into them. The bacteria around the dripping died off, and he was encouraged by the idea that the body could tolerate internally a substance that could fight off bacteria.


Fleming's next stroke of luck came when he lost his assistant. When dishes of bacteria were no longer useful, they were put in a sort of tub of bleach. Without his assistant, Fleming's dirty dishes formed towers in the tub. The highest dishes sat well above bleach, and remained filthy. They grew even filthier when mold which had floated up from the lab downstairs started growing on them. And then they stopped being as filthy, when the mold, one of the many types of penicillium fungi, killed off the bacteria.

That was all the luck Fleming got. It took years to find a way to cultivate the right strain of penicillium, and to extract the right parts of it to make penicillin.

How to Make Your Own Penicillin

The strains that we have are from the mold grown on a cantaloupe in the 1940s, so you can grab some cantaloupe if you're feeling like a traditionalist. Otherwise, a leftover crust of bread or the peel of some citrus fruit will do fine. The mold will start out gray, but as it develops will turn a bright blue-green. Once it gets started, cut the bread up into pieces and put it in a sterilized flask. (You can sterilize a flask by putting it in an oven at 315 degrees for an hour.) Incubate it in the flask for about a week at around seventy degrees.


Some people just stop there. Folk recipes for "penicillin tea" or "penicillin soup" abound, with people just boiling up the molded bread or adding the citrus to tea with honey, and serving it to sick people. (Note: Do not do this.)


If you want to get more involved, you can extract the penicillin by sterilizing yet another jar and, according to the experts, adding the following:

Into 500ml of cold tap water put 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.


Then you add the spores from the moldy bread. Another seven days incubation will leave the penicillin floating in the liquid portion of the results. A quick filter and you have penicillin.

Urgent Medical Disclaimer!

In theory, at least, you have penicillin. I must stress at this point that you should not use this homemade penicillin on any limb that you want to keep. Although you did probably get a lot of penicillium mold growing on the bread, you also got other molds. Even with the right kind of fungi growing, filtering out everything but the penicillin is difficult, and best left to the professionals. Molds make a lot of different things to kill bacteria, and many of them are harmful to humans. While there are plenty of survivalist websites that recommend clapping whatever grows on bread or citrus to your wound, and while that might even be an option sometimes after the world ends, there are better options right now, and you should take advantage of them. If you want to see how well you've done making penicillin, try growing a tray of bacteria and using the penicillin on that.


Moldy Lemon Image: Tuválkin

[Via How to Do Things, University of Oxford.]