First 407 words of the document:
MAKING ANTIBIOTICS USING MICROBES-PENICILLIN
Penicillin is one of the best known medicines in the world.
THE DISCOVERY OF PENICILLIN
In 1928, Alexander Fleming left some plates on which he was culturing bacteria uncovered near an
open window. When he returned to them, he noticed spots of mould, growing around which there
were clear areas of agar, suggesting the bacteria were killed. This mould was called Penicillium
notatum. He tried to extract the penicillin but it was very difficult and unstable and therefore he gave
During the Second World War, there was a desperate need for an effective antibiotic. Florey and
Chain were able to extract enough penicillin to carry out successful animal trials. Then, they tried it on
an ill London policeman who recovered successfully. However, he died when the supply ran out. They
turned to America in order to mass produce it. Fleming's original mould was difficult to grow in large
cultures but grew more easily in deep tanks, making mass production possible. By 1945, enough
penicillin was produced to treat 7 million people each year.
MODERN PENICILLIN PRODUCTION
Nowadays, almost 30 thousand tonnes of penicillin are manufactured per year. Modern strains of the
Penicillium mould are used which give even higher yields. They are grown in a sterilised medium
which contains sugar, amino acids, mineral salts and other nutrients. Huge 10 thousand cubic
decimetre fermenters with strong paddles to keep stirring the broth are used. Sterile air is blown
into the tanks in order to provide the oxygen needed and the temperature is controlled by a cooling
jacket. The mould uses up the nutrients and grows rapidly for about 40 hours. It is only after the
nutrients have been used up that penicillin starts to be produced by the mould. Over a period of 140
hours, the broth is regularly removed and the penicillin is extracted, which is then purified and turned
The Key Points are:
1. The antibiotic penicillin was discovered by Alexander Fleming. The method of mass
production was the work of Howard Florey and Ernst Chain.
2. Penicillin is made by growing the mould Penicillium in a fermenter.
3. The medium contains sugars and other nutrients and has a good supply of oxygen.
4. The mould only starts making penicillin after most of the nutrients are used up.