Once penicillin had been isolated, the problem of producing the drug on a mass scale remained. 2,000 litres of P. notatum mould culture fluid were needed to produce enough pure penicillin to treat blood poisoning in a single person. It then fell to American drug companies to mass produce penicillin, in time for the USA entering the Second World War. The search for a fungus that would produce more penicillin per litre began.
In another flash of serendipity, Mary Hunt, a laboratory assistant at the US Northern Regional Research Laboratory, came across a cantaloupe melon with a golden mould. This mould turned out to be P. chrysogenum, and yielded 1,000 times more penicillin than Alexander Fleming’s P. notatum.
In 1949, Florey noted “had it not been for [the US drug companies’] efforts there would certainly not have been sufficient penicillin by D-Day in Normandy in 1944 to treat all severe casualties, both British and American”.