As you have already studied that the antibiotics are the secondary microbial metabolites secreted at stationary growth phase of the microorganisms. Penicillin was the first antibiotic which was discovered first by A. Flaming in 1929 to be produced by Penicillium notatum.
P. notation is a mold which forms a colony on surface of medium. Its mycelia produce conidiophores that bear brush like phialides. Phialides give rise to spherical conidia borne in chains.
Thereafter, a large number of antibiotics have been developed. In recent years biotechnological methods have been developed for strain improvement and production of maximum amount of antibiotics. It shows some of the important antibiotics and microorganisms producing them.
1. Selection of Culture:
Flaming’s culture produced less amount of penicillin. During the course of time many cultures were improved to give maximum yield. P. chrysogenum NRRL 1951 was a ‘superior producer’ of penicillin. Furthermore, some other strains could be developed which produced 1200 Oxford units/ ml (1 Oxford unit = 0.6 µg).
In culture P. chryogenum produces mycelia that bear several conidiophores. Each conidiophore terminates into a whorl of phialides, and every philide cuts of a chain of conidia (Fig. 6.14).
Earlier penicillin was produced in medium supplemented with organic materials such as casein digest, yeast extract or meat products which promoted higher yield of penicillin. Sucrose or glucose was replaced lactose.
Similarly higher yield could also be obtained with more complex nitrogen sources such as extracted cotton seeds, peanut meals and soybean meals. Phenylacetate or phenethylamine is used as precursor of penicillin at a rotary shaker at 25°C. After 4 days contents are transferred into 2 litres of medium in 4 litres flask.
The second flask is incubated for 2 days. Then content of this flask is transferred into 500 litres medium in 800 litres stainless steel tank. After 3 days the content is transferred into 1,80,000 litres of fermentation medium in 2,50,000 litres fermentor. Suitable fermentation medium is
3. Applications of Antibiotics :
Since the discovery of antibiotics, its application has been increased in the area of medical science. These are the life-saving drugs. They are very useful during operation of patients to protect from the disease causing infectious microorganisms.
Moreover, life span of humans has increased as various dangerous diseases could be treated by applying antibiotics for example, pneumonia, meningitis, cholera, cellulites, endocarditis, urinary tract infection (UTI), gas gangrene, tetanus, anthrax, typhoid, tuberculosis, etc.