Pasteur was born in Dôle on December 7, 1822, the son of a tanner, and grew up in the small town of Arbois. In 1847, he earned a doctorate at the École Normale in Paris, with a focus on both physics and chemistry. Becoming an assistant to one of his teachers, he began research that led to a significant discovery. He found that a beam of polarized light (see Optics) was rotated to either the right or the left as it passed through a pure solution of naturally produced organic nutrients, whereas when such a beam was passed through a solution of artificially synthesized organic nutrients, no rotation took place. If, however, bacteria or other micro-organisms were placed in the latter solution, after a while it would also rotate light to the right or left.
Pasteur concluded that organic molecules can exist in one of two forms, called isomers (that is, having the same structure and differing only in being mirror images of each other), which he referred to as “left-handed” and “right-handed” forms. When chemists synthesize an organic compound, these forms are produced in equal proportions, cancelling each other's optical effects. Living systems, however, which have a high degree of chemical specificity, can discriminate between the two forms, metabolizing one and leaving the other untouched and free to rotate light.
Work on Fermentation
After spending several years of research and teaching at Dijon and Strasbourg, Pasteur moved in 1854 to the University of Lille, where he was named Professor of Chemistry and dean of the faculty of sciences.