A strange and rare mold, Penicillium notatum, happened to be floating around in Fleming’s lab because another researcher was studying it. Luckily, Fleming had the untidy habit of keeping his bacterial plates longer than usual, and when he returned from a weeklong vacation in 1928, he discovered the mold growth.

Who discovered mold on food?

Returning from holiday on September 3, 1928, Fleming began to sort through petri dishes containing colonies of Staphylococcus, bacteria that cause boils, sore throats and abscesses. He noticed something unusual on one dish. It was dotted with colonies, save for one area where a blob of mold was growing.

Who discovered mold juice?

“Mould juice” became penicillin. Alexander Fleming first called the bacteria-killing substance that he had discovered in 1928 in moulds for “mould juice”. On 7 March 1929 he formally named it penicillin.