Florey and Heatley visited the United States in June 1941 to seek large-scale penicillin production. Their Oxford team had shown that penicillin could cure serious infections, but its laboratory methods produced far too little for sustained human treatment.
The Rockefeller Foundation helped arrange the trip, and the researchers traveled to American laboratories with penicillin samples and production expertise. Heatley worked at the Northern Regional Research Laboratory in Peoria, Illinois, while Florey contacted government and industrial partners. The laboratory’s agricultural expertise proved crucial because fermentation was the central manufacturing problem.
Andrew J. Moyer improved yields by replacing sucrose with lactose and adding corn steep liquor, a by-product of corn processing. The nutrient-rich mixture increased production dramatically. American companies then refined large-scale fermentation, including Pfizer’s deep-tank process, allowing penicillin to be produced in quantities suitable for wartime use.
This visit did not mean the United States had discovered penicillin. Fleming had identified it in Britain in 1928; the American contribution was essential to turning an unstable laboratory extract into a mass-produced drug.