Earlier penicilin

Penicillin is quite difficult to grow on a commercial scale. Once Fleming made his initial discovery, there was lots and lots of work to be done to 1) find high producing strains and 2) grow such a strain on an industrial scale.

A decade earlier is surely possible, 2 decades earlier may be pushing it.

The other thing is, the earlier you get penicillin the earlier you get antibiotic-resistance....
Assuming this occurred, I'd have known my maternal grandfather. He died in 1936 just before sulfa drugs came into widespread use, or about five years before penicillin became established.