Production of Antibiotics

Many antibiotics are naturally produced by microbes.

Penicillin, one of the most widely used antibiotics, is produced by the fungus Penicillium chrysogenum.

For industrial production, high-yield fungal strains are first cultivated in seed cultures and then scaled up in large bioreactors.

The fermentation medium contains lactose as the carbon source, with added nitrogen and sulfur sources.

Glucose is added in minimal quantities to support fungal growth, as higher glucose concentrations can suppress penicillin synthesis, a process known as carbon catabolite repression.

The culture is maintained at 25 to 27 °C and within a pH range of 6.8 to 7.4.

Initially, the fungal cells multiply exponentially, building up the biomass with minimal penicillin production.

As carbon sources become depleted, the culture enters the stationary phase and begins producing penicillin.

At this stage, phenylacetic acid is added as a precursor to direct the synthesis of a specific variant, penicillin G.

After about a week of fermentation, the broth is filtered and purified to collect the penicillin.