Why was Fleming unable to purify penicillin for medical use?

Although Alexander Fleming identified the antibacterial properties of penicillin in 1928, he was unable to purify the substance for medical use because the necessary scientific techniques for its isolation in sufficient quantities or in a sufficiently pure form had not yet been developed.12

While Fleming recognized the clinical potential of the substance, his efforts to stabilize and purify it—even with the assistance of two young researchers—were unsuccessful. The successful isolation and purification of penicillin were eventually achieved nearly a decade later by a team of scientists at the University of Oxford, led by Howard Florey and Ernst Boris Chain. Their work, combined with the development of commercial production techniques in the United States during World War II, finally allowed for the widespread therapeutic use of the drug.123