Louis Pasteur is the 19th-century biologist and chemist whose work with germs and microorganisms opened up whole new fields of scientific inquiry, aided industries ranging
from wine to silk, and made him one of the world`s most celebrated scientists. Pasteur became a professor of chemistry at the University of Lille in 1854 , and soon began studying fermentation in wine and beer. He became convinced that, as he put it in an 1878 paper, "the germs of microscopic organisms abound in the surface of all objects, in the air and in water." He determined that such microorganisms could be killed by heating liquid to 55 degrees Celsius (about 130 degrees Fahrenheit) or higher for short periods of time. This simple process became known as pasteurization, a process used today in milk and many other beverages. Pasteur then turned his attention to other aspects of microorganisms. He virtually created the science of immunology, showing that certain diseases (like rabies) could be prevented by what he called vaccination: injecting animals with weakened forms of the disease. So great were Pasteur`s successes that an international fund was raised to create the Louis Pasteur Institute in 1888. Pasteur worked with the institute until his death, and it continues today as a center of microbiology and immunology.
Pasteur was born in Ole and grew up in the nearby town of Arbois, the only son of a poorly educated tanner, Jean Pasteur. Louis was not an outstanding student during his years of elementary education, preferring fishing and drawing to other subjects. In fact, young Louis drawings suggested that he could easily have become a superior portrait Artist. His later drawings of friends done at college were so professional that Pasteur was listed in at least two compendia of XIX C. artists.
The Senior Pasteur, however, did not see his son ending up as an Artist, and Louis, himself, was showing increasing interest in chemistry and other scientific subjects. The highest wish Father Pasteur had for his son was that he complete his education in the local schools and become a professor in the college at Arbois. However the headmaster of the college recognized that Louis could do much better and convinced father and son that Louis should try for the Ecole Normale Sup rieure in Paris. This most prestigious French University was founded specifically to train outstanding students for University careers in science and letters. And it was here that Pasteur entered and began his long journey of scientific discovery.
It may surprise to some to learn that Pasteur, the father of microbiology and immunology, was a chemist who launched his memorable scientific career by studying the shapes of organic crystals. Pasteur was 26 years old, working for his doctorate in chemistry in the laboratory of Antoine Balard. Crystallography was just emerging as a branch of chemistry. His project was to crystallize a number of different compounds. Happily he started working with tartaric acid. Crystals of this organic acid are present in large amounts in the sediments of fermenting wine. Often one also found in the sediments in the wine barrels crystals of a second acid called paratartaric acid or "racemic acid". A few years earlier, the chemical compositions of these two acids, tartaric and paratartaric, had been determined. They were identical. But in solution there was a striking difference. Whereas tartaric acid rotated a beam of polarized light passing through it to the right, paratartaric acid did not rotate the light. This puzzled the young Pasteur. How could this be?
Pasteur refused to accept the notion that two compounds that had the same chemical composition yet acted so differently in respect to rotation of light could be identical. He was convinced that the internal structure of the two compounds must be different and this difference would show itself in the crystal form. The experts in this field had looked examined tartrate and paratartrate crystals but never saw a difference, perhaps because, as Duclaux thought, they believed that no difference could exist. Pasteur believed that there were differences and indeed found them!
Upon intense examination beneath his microscope, he saw that every crystal of pure tartaric acid looked like every other one. When he examined the paratartrate crystals, on the other hand, he saw two types of crystals, nearly identical but not quite! One type was the mirror image the other -- the way the right hand mirrors the left hand. This was the difference he was looking for!
Pasteur then performed one of the simplest and yet most elegant experiments in the annals of chemistry. With a dissecting needle and his microscope, he separated the left and right crystal shapes from each other to form two piles of crystals. He then showed that in solution one form rotated light to the left, the other to the right. This simple experiment proved that the organic molecules with the same chemical composition can exist in space in unique stereospecific forms. And with this work did Pasteur launch the new science of stereochemistry.
Earlier, Lavoisier had shown that chemical combustion in living animals was quantitatively identical to that occurring in a furnace. Lavoisier also showed that sugar, the starting product of fermentation, could be broken down to alcohol, CO2 and H2O by simply dropping a sugar solution on heated platinum. Woehler startled the scientific world by sythesizing the organic compound urea, showing for the first time that organic compounds, believed up to then as capable of synthesis only by living animals could be made in a test tube. And due, in no small part to Pasteur`s work on crystals, internal structure and analysis of complex organic compounds was becoming routine.
Over the next several years Pasteur identified and isolated the specific microorganisms responsible for normal and abnormal fermentations in production of wine, beer, vinegar. He showed that if he heated wine, beer, milk to moderately high temperatures for a few minutes, he could kill living microorganism and thereby sterilize (pasteurize), the batches and prevent their degradation. If pure cultures of microbes and yeasts were added to sterile mashes uniform, predictable fermentations would follow.