Extraction Process

Part of Antibiotics

Once you have cultivated Penicillium mold and grown it in nutrient broth, the raw penicillin must be separated from the liquid, concentrated, and prepared for medical use. This extraction process transforms a murky yellow broth into a usable antibiotic.

Why Extraction Is Necessary

You cannot simply feed someone moldy bread or raw culture broth and expect it to cure an infection. The penicillin concentration in raw broth is far too low for therapeutic effect, and the broth also contains mold debris, waste products, and potentially harmful substances. Extraction and concentration increase the potency by 50-100 fold while removing contaminants.

The original wartime penicillin extraction process in 1943 used industrial equipment, but the underlying chemistry is straightforward: penicillin is an organic acid that dissolves preferentially in certain solvents depending on the pH of the solution. By manipulating acidity and using common solvents, you can pull penicillin out of the broth and concentrate it.

Step 1: Filtration

Removing the Mold

The first step is separating the mold itself from the liquid broth where penicillin has accumulated.

Method	Materials	Effectiveness
Cloth filtration	Multiple layers of tightly woven linen or cotton	Good — removes mold chunks
Gravity sand filter	Sand layered over gravel in a funnel	Better — removes finer particles
Charcoal filtration	Crushed charcoal over sand	Best available — also removes some impurities

Procedure:

1. Let the culture flask sit undisturbed for 1-2 hours so the mold mat settles.
2. Carefully pour the liquid through your filter, leaving the thick mold mat behind.
3. Filter again through a finer medium — ideally two passes through progressively finer cloth.
4. The resulting liquid should be translucent yellow to amber. It contains dissolved penicillin along with sugars, amino acids, and other byproducts.

Save the Mold Mat

The filtered mold mat still contains active mold. You can transfer it to fresh nutrient broth to start another production cycle, saving you the time of growing a new culture from spores.

Cooling the Filtrate

Penicillin degrades rapidly at temperatures above 30 degrees C and especially above 40 degrees C. From this point forward, keep the liquid cool — below 20 degrees C ideally. Work in a cellar, use cold water baths, or work during the coolest part of the day.

Step 2: Acidification

Penicillin behaves differently at different pH levels. This is the key to extraction.

At neutral pH (around 7), penicillin is dissolved in water and will not transfer to an organic solvent. At acidic pH (2.0-2.5), penicillin becomes much more soluble in organic solvents than in water.

Adjusting the pH

1. Measure pH if possible — litmus paper, pH strips, or red cabbage juice indicator.
2. Add acid slowly to bring the pH to 2.0-2.5:
   • Vinegar (acetic acid) — add gradually, testing frequently
   • Citric acid (from citrus juice) — effective but dilute
   • Hydrochloric acid if available — use with extreme caution, very small amounts
   • Sulfuric acid (dilute battery acid) — a few drops at a time

Speed Is Critical

Penicillin degrades rapidly in acid conditions. Once you acidify the broth, you must complete the solvent extraction within 15-30 minutes. Have everything prepared before you add the acid. Work fast and work cold.

pH Indicator	Acid (pH ~2)	Neutral (pH ~7)	Alkaline (pH ~8+)
Red cabbage juice	Red/pink	Purple/violet	Blue/green
Litmus paper	Red	—	Blue
Turmeric solution	Yellow	Yellow	Red/brown

Step 3: Solvent Extraction

This is the heart of the process. You use an organic solvent to pull penicillin out of the acidified water.

Suitable Solvents

Solvent	Source	Effectiveness
Diethyl ether	Produced from ethanol + sulfuric acid	Excellent — traditional choice
Ethyl acetate	Produced from ethanol + acetic acid + sulfuric acid catalyst	Excellent — less flammable than ether
Amyl acetate (banana oil)	From fusel oils in distillation	Good
Butanol	From fermentation of starch by Clostridium	Good

Extraction Procedure

1. Pour the acidified broth into a tall, narrow container (a bottle or separatory vessel).
2. Add solvent — approximately one-third the volume of broth (e.g., 300 ml solvent for 1 liter of broth).
3. Mix vigorously by shaking, stirring, or swirling for 2-3 minutes. Penicillin transfers from the water into the solvent.
4. Let layers separate — the organic solvent layer floats on top (ether, ethyl acetate) or sinks to the bottom (chloroform). Wait 5-10 minutes for clean separation.
5. Carefully remove the solvent layer — pour off the top layer, or drain the bottom layer through a spigot if your vessel has one. A turkey baster or syringe can also work for precise separation.
6. Repeat — extract the broth a second time with fresh solvent to capture remaining penicillin.

Improvised Separatory Funnel

If you lack laboratory glassware, use a tall wine bottle with a narrow neck. After shaking, let it settle. Insert a thin tube to the interface between layers and siphon off the lower water layer, leaving the solvent behind. Alternatively, use a plastic bottle with a small hole punched in the bottom — let the lower layer drain out, then stop when the interface reaches the hole.

Step 4: Back-Extraction into Water

The penicillin is now dissolved in the organic solvent. To make it medically usable, transfer it back into water at neutral pH, which also concentrates it.

1. Add a small volume of water to the solvent — use about one-tenth the original broth volume (e.g., 100 ml water for 1 liter of original broth). This is where the concentration happens.
2. Make the water alkaline — add a small amount of sodium bicarbonate (baking soda) to raise pH to 7.0-7.5. At this pH, penicillin prefers water over the organic solvent.
3. Mix gently for 2-3 minutes.
4. Separate layers again. The penicillin is now in the water layer, which is much smaller than the original broth — hence concentration.
5. Discard the solvent layer (or recover the solvent by distillation for reuse).

The resulting aqueous solution contains penicillin at 10-100 times the concentration of the original broth.

Step 5: Concentration and Preservation

Evaporative Concentration

To further concentrate the penicillin solution:

1. Pour into a wide, shallow dish.
2. Place in a cool, dry area with good airflow — a gentle breeze accelerates evaporation.
3. Do NOT heat — temperatures above 40 degrees C destroy penicillin. Use only ambient temperature or slightly cooled air evaporation.
4. Reduce volume to roughly one-quarter while monitoring that no crystals form on the edges (those are penicillin — scrape them back in).

Freeze Concentration

If nighttime temperatures drop below freezing:

1. Leave the solution outside overnight.
2. In the morning, remove ice that forms — this is mostly pure water.
3. The remaining liquid is more concentrated penicillin.
4. Repeat over several nights for progressive concentration.

Preservation

Method	Shelf Life	Notes
Refrigerated liquid (below 10 degrees C)	1-2 weeks	Best for immediate use
Frozen	1-3 months	Thaw just before use
Dried powder (evaporated at room temperature)	3-6 months	Store in dark, airtight container
Dissolved in 50% glycerin	2-4 weeks	Good for topical application

Potency Testing

Before each use, test your penicillin extract. Apply a drop to a plate where you have spread bacteria. If a clear zone forms after 24 hours, the extract is still active. No zone means degradation has occurred — discard and prepare fresh.

Dosing Crude Penicillin

Without standardized units, dosing is inherently imprecise. This is the most dangerous part of the process.

Topical Application

The safest use — apply directly to infected wounds:

1. Soak a clean cloth in penicillin solution.
2. Apply to the wound and cover loosely.
3. Reapply every 4-6 hours.
4. Continue for 5-7 days minimum.

Oral Administration

Less effective than injection because stomach acid destroys much of the penicillin, but still useful:

1. Dissolve concentrated extract in a cup of water.
2. Drink on an empty stomach (food reduces absorption).
3. Repeat every 4-6 hours around the clock.
4. Continue for a minimum of 7 days — stopping early breeds resistant bacteria.

Allergic Reactions

Approximately 1-10% of people are allergic to penicillin. Before full dosing, apply a small drop of solution to a scratch on the inner forearm. Wait 30 minutes. If redness, swelling, or itching develops, do NOT give penicillin — the patient is allergic. Severe allergic reactions (anaphylaxis) can be fatal.

Quality Control

Consistency Between Batches

Every production run will vary in potency. Track these variables:

1. Mold strain — always use the same tested strain
2. Growth period — harvest at the same day (10-14 days)
3. Temperature during growth — record daily
4. Broth recipe — use exact same proportions
5. Extraction timing — minimize acid exposure time

Contamination Signs

Discard the batch if you observe:

• Foul or putrid smell (bacterial contamination)
• Black or red mold growth (wrong species)
• Cloudy solution after filtration (incomplete separation)
• No zone of inhibition in testing (no active penicillin)

Common Mistakes

1. Overheating during extraction — penicillin denatures above 40 degrees C. Work cold, fast, and never apply direct heat to the extract.
2. Leaving penicillin in acid too long — acidification starts a degradation clock. Complete solvent extraction within 30 minutes of adding acid.
3. Inadequate filtration — mold debris in the final product causes severe injection-site reactions and abscesses. Filter meticulously.
4. Stopping treatment early — partial antibiotic courses select for resistant bacteria. Always complete the full 7-10 day course.
5. Skipping the allergy test — penicillin allergy can cause anaphylaxis. A 30-second forearm scratch test can save a life.

Summary

Extraction Process — At a Glance

• Filter the culture broth through progressively finer media to remove all mold solids
• Acidify to pH 2.0-2.5, then immediately extract with an organic solvent (ether or ethyl acetate)
• Back-extract into a small volume of alkaline water (pH 7.0-7.5) to concentrate the penicillin
• Further concentrate by cool evaporation or freeze concentration — never heat above 40 degrees C
• Test every batch for antibiotic activity before use
• Always perform an allergy scratch test before first administration to any patient
• Complete the full treatment course to prevent breeding resistant bacteria
• Store dried powder in dark, airtight containers for longest shelf life (3-6 months)