Who discovered dry yeast?

Yeast Today

It was not until the invention of the microscope, followed by the pioneering scientific work of Louis Pasteur in the late 1860's, that yeast was identified as a living organism and the agent responsible for alcoholic fermentation and dough leavening.

Where does yeast come from originally?

Baker's yeast, brewer's yeast, yeast that lives in infected toenails—they all descended from a common ancestor. When scientists in France set out to sequence 1,000 yeast genomes, they looked at strains from all the places you might expect: beer, bread, wine.