Final answer:
Alexander Fleming and his colleagues discovered and identified penicillin. The isolation and mass production of penicillin were accomplished by a team of researchers at Oxford University under the direction of Howard Florey and Ernst Chain. Their work was recognized with the Nobel Prize in Physiology and Medicine in 1945.
Step-by-step explanation:
Fleming and his colleagues were credited with discovering and identifying penicillin, but its isolation and mass production were accomplished by a team of researchers at Oxford University under the direction of Howard Florey and Ernst Chain. In 1940, the research team purified penicillin and reported its success as an antimicrobial agent against streptococcal infections in mice. Their subsequent work with human subjects also showed penicillin to be very effective. Because of their important work, Fleming, Florey, and Chain were awarded the Nobel Prize in Physiology and Medicine in 1945.