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A page from a NRRL notebook showing circled penicillin strain, PS46.

 Image Number D4749-1

A notebook page signed by Dorothy Fennell Alexander, an NRRL "penicillin survey" team member who worked to identify Penicillium mold strains that produced high amounts of penicillin under submerged culture conditions used by pharmaceutical companies. The circled strain, PS46 (later known as NRRL 1951), was the top performer and became the "parent" of all strains used commercially.


Photo by USDA.

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