Which Belgian microbiologist described Penicillium rubens in 1923?

Philibert Biourge described Penicillium rubens in 1923.

Biourge was a Belgian microbiologist whose 1923 work described the species now known as Penicillium rubens. The connection matters because modern genetic analysis identified Fleming’s original penicillin-producing mould as P. rubens.

The organism’s name has changed repeatedly. Fleming’s mould was first identified as Penicillium rubrum, then associated with P. notatum and P. chrysogenum. In 2005, the International Botanical Congress formally conserved P. chrysogenum as a name, but genome sequencing and phylogenetic analysis published in 2011 showed that Fleming’s strain actually belongs to P. rubens.

That taxonomic history can make the quiz question look more confusing than it is. Charles Thom was important in later classification and popularised P. chrysogenum, but he was not the researcher who originally described P. rubens. The modern identification also links Biourge’s 1923 description to Fleming’s 1928 observation and the antibiotic’s later development.