Louis Pasteur

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e father of microbiology and immunology, he actually launched his career as a chemist who studied the shapes of organic crystals. Crystallography was just emerging as a branch of chemistry and his project was to crystalize a number of organic compounds. While working on this project he began to work with tartaric acid and racemic acid. Earlier these two acids had been determined to be identical, however Pasteur found that in solution they had a striking difference which was that tartaric acid rotated a beam of polarized light whereas the racemic acid did not. When looking at them under the microscope he found that the crystals of the tartaric acid were identical while the crystals of the racemic acid were of two types, almost identical but not quite. One type was mirroring the other the way the
right hand mirrors the left hand (Cohn, par. 6-8).
After discovering the different types of crystals, Pasteur then took a dissecting needle and separated the left and right crystals from each other under the microscope. He then showed that in solution one form rotated light to the left and the other to the right. This proved that organic molecules with the same chemical composition can exist in space in unique stereo specific forms. With this discovery Pasteur launched the new science of stereo chemistry. He proposed that asymmetrical molecules were indicative of living processes. Because of this we know today that proteins of higher animals are made up only of the amino acids that exist in the left-hand form. The mirror image right-hand amino acids are not used in human or animal cells. Just like our cells
only burn the right-hand form of sugar, not the left-hand that can be made in a test tube (Cohn, par. 9-10).
In 1856 Pasteur was approached with a problem by a Monsieur Bigo. Monsieur Bigo manufactured alcohol from beets and recently his beet juice had been spoiling instead of producing alcohol. Pasteur chose to look into the problem ...