Louis Pasteur

1. Louis Pasteur By Jaekyung Song 9G

2. Biography • Born on December 27th, 1822 • Born in Jura • Grew up in Arbois • Jean Pasteur, his father, was a veteran of the Napoleonic Wars • His headmaster suggested that he go to ÉcoleNormaleSupérieure • Married Marie Laurent • Had five children, only two survived to adulthood

3. His First Discovery • “Pasteur's professors and fellow students were heavily involved in the study of crystals (clear, colorless glass) and their effects on light. Pasteur himself quickly focused on the study of crystals suspended in tartaric and racemic acids (both of which are formed in the process of making wine). His doctoral research led him to his first major discovery. While tartaric and racemic acids have identical chemical structure, the crystals in the two have different effects on polarized light. Pasteur was curious about how this could be, given their identical chemical structure. A closer study of both acids led Pasteur to the realization that racemic acid contained two different crystals: one was chemically identical to those in tartaric acid, the other had a chemical structure that was the mirror image of the former. This structural difference accounted for their different effects on light. It was this discovery of mirror-image molecules that first established Pasteur's scientific reputation.”

4. What It Means • Pasteur was curious of acids on crystals and light • Put crystals into two different acids: Tartaric and racemic acid • Even though the two acids had similar chemical structure, the crystal would have different effects on polar light when put in different acids • Closer study revealed that racemic was made of 2 crystals: a crystal similar to Tartaric, and a mirror image of the former • Discovery of mirror image molecules boosted his reputation

5. His Second Discovery • “Because of the notoriety of Pasteur's research on tartaric and racemic acids, he was approached by a local factory owner who hoped that the scientist could help him with the fermentation and preservation of his product, beet juice. The research that Pasteur embarked on for the factory owner led to his second major discovery. Up until that time, scientists had believed that yeast acted as a chemical catalyst during the process of fermentation, causing the breakdown of complex sugar molecules into simpler sugars. Pasteur concluded that yeast was not an inorganic catalyst but a living organism that consumed sugar in beet juice, leaving alcohol as a waste product. Pasteur also concluded that the juice went sour when other microorganisms, bacteria, fermented sugar into lactic acid.”

6. What It Means • Found yeast is not a catalyst • Yeast is alive and eats sugars and leaves behind alcohol through fermentation • Bacteria makes food go sour

7. Some of His Experiment • 1. “First, Pasteur prepared a nutrient broth similar to the broth one would use in soup.” • 2. “Next, he placed equal amounts of the broth into two long-necked flasks. He left one flask with a straight neck. The other he bent to form an "S" shape.”

8. 3. “Then he boiled the broth in each flask to kill any living matter in the liquid. The sterile broths were then left to sit, at room temperature and exposed to the air, in their open-mouthed flasks.”

9. 4. “After several weeks, Pasteur observed that the broth in the straight-neck flask was discolored and cloudy, while the broth in the curved-neck flask had not changed.”

10. 5. “He concluded that germs in the air were able to fall unobstructed down the straight-necked flask and contaminate the broth. The other flask, however, trapped germs in its curved neck,­ preventing them from reaching the broth, which never changed color or became cloudy.”

11. 6. “If spontaneous generation had been a real phenomenon, Pasteur argued, the broth in the curved-neck flask would have eventually become reinfected because the germs would have spontaneously generated. But the curved-neck flask never became infected, indicating that the germs could only come from other germs.”

12. “Pasteur separated the left and right crystal shapes from each other to form two piles of crystals: in solution one form rotated light to the left, the other to the right, while an equal mixture of the two forms canceled each other's rotation. Hence, the mixture does not rotate polarized light.”

13. “…his research into pathology led to vaccinations against two deadly diseases—anthrax and rabies.”

14. Description of His Work • His work is similar to every other scientist; he follows the scientific method

15. Effects on Society • The cure saved many people • Advanced research of microbiology • Won Leeuwenhoek medal • Is a Grand Croix of the Legion of Honor