Penicillin was discovered in 1928 by Scottish scientist Alexander Fleming. People began using it to treat infections in 1942. There are several enhanced penicillin families which are effective against additional bacteria; these include the antistaphylococcal penicillins, aminopenicillins and the antipseudomonal penicillins. They are derived from "Penicillium" fungi. The term "penicillin" is often used generically to refer to benzylpenicillin (penicillin G, the original penicillin found in 1928), procaine benzylpenicillin (procaine penicillin), benzathine benzylpenicillin (benzathine penicillin), and phenoxymethylpenicillin (penicillin V). Procaine penicillin and benzathine penicillin have the same antibacterial activity as benzylpenicillin but act for a longer period of time. Phenoxymethylpenicillin is less
Penicillin lactose does not. The pH and the levels of nitrogen, lysine, phosphate, and oxygen of the batches must also be carefully controlled. The biotechnological method of directed evolution has been applied to produce by mutation a large number of "Penicillium" strains. These techniques include error-prone PCR, DNA shuffling, , and strand-overlap PCR. Semisynthetic penicillins are prepared starting from the penicillin nucleus 6-APA. Overall, there are three main and important steps to the biosynthesis of penicillin G (benzylpenicillin). Penicillin Penicillin (PCN or pen) is a group of antibiotics which include penicillin G (intravenous use), penicillin V (use by mouth), procaine penicillin,