History of penicillin History of penicillin The history of penicillin follows a number of observations and discoveries of apparent evidence of antibiotic activity in molds before the modern isolation of the chemical penicillin in 1928. There are anecdotes about ancient societies using molds to treat infections, and in the following centuries many people observed the inhibition of bacterial growth by various molds. However, it is unknown if the species involved were "Penicillium" species or if the antimicrobial substances produced were penicillin. The Scottish physician Alexander Fleming was the first to suggest that a "Penicillium" mold must secrete an antibacterial substance, and the first
Penicillin is a secondary metabolite of certain species of "Penicillium" and is produced when growth of the fungus is inhibited by stress. It is not produced during active growth. Production is also limited by feedback in the synthesis pathway of penicillin. The by-product, -lysine, inhibits the production of homocitrate, so the presence of exogenous lysine should be avoided in penicillin production. The "Penicillium" cells are grown using a technique called fed-batch culture, in which the cells are constantly subject to stress, which is required for induction of penicillin production. The available carbon sources are also important: glucose inhibits penicillin production, whereas