Index >> Pasteur Contribution to Microbiology

From these experiments be concluded that the air contained microbes and the number of microorganisms in the atmosphere varied from place to place Pasteur's entry into the area of fermentation was a necessity of that time. It is said that for patriotic reasons Pasteur, who was a chemist by profession, turned his attention to the phenomenon of fermentation, which was until then believed to be a chemical process.
He made an intensive study of the beer and wine manufacturing processes and causes of souring and spoilage of beer and wines. He found that wine spoilage was caused by the growth of undesirable contaminating microbes which produced the so called "disease". The solution to this problem lay in preventing the growth of undesirable organisms. After considerable experimentation Pasteur showed that wine did not undergo spoilage if it was held for a few minutes at 50 to 60°C. In the same way, he found that beer could also escape the disease by heating to 50-55° C. This gave rise to the new process of preserving wine, fruit juices, milk etc., and was called "Pasteurization".

While examining samples from a butyric acid fermentation microscopically, he found that the motile butyric acid bacteria at the margin of a flattened drop became immotile when they came in contact with the air. while those at the centre remained motile. He reasoned that oxygen was inhibitory to the growth of butyric acid bacteria. To establish this, he passed a current of air through the butyric fermentation fluid and found that this resulted incomplete arrest of the fermentation. He thus concluded that some microorganisms could live only in the absence of oxygen, an element previously considered essential for life. He designated life in the presence of oxygen as "aerobic" and in the absence of oxygen as "anaerobic". Pasteur also found that many other microorganisms, including, yeast could grow either In the presence or in the absence of oxygen. These he termed as facultative anaerobes.