Industrial Microbiology and Microbial Ecology:-

Although Theodore Schwann and others had proposed in 1837 that yeast cells were responsible for the conversion of sugars to alcohol, a process they called alcoholic fermentation, the leading chemists of the time believed microorganisms were not involved. They were convinced that fermentation was due to a chemical instability that degraded the sugars to alcohol. Pasteur did not agree. It appears that early in his career Pasteur became interested in fermentation because of his research on the stereochemistry of molecules. He believed that fermentations were carried out by living organisms and produced asymmetric products such as amyl alcohol that had optical activity.

There was an intimate connection between molecular asymmetry, optical activity, and life. Then in 1856 M. Bigo, an industrialist in Lille, France, where Pasteur worked, requested Pasteur’s assistance. His business produced ethanol from the fermentation of beet sugars, and the alcohol yields had recently declined and the product had become sour. Pasteur discovered that the fermentation was failing because the yeast normally responsible for alcohol formation had been replaced by microorganisms producing lactic acid rather than ethanol. In solving this practical problem, Pasteur demonstrated that all fermentations were due to the activities of specific yeasts and bacteria, and he published several papers on fermentation between 1857 and 1860.

His success led to a study of wine diseases and the development of pasteurization  to preserve wine during storage. Pasteur’s studies on fermentation continued for almost 20 years. One of his most important discoveries was that some fermentative microorganisms were anaerobic and could live only in the absence of oxygen, whereas others were able to live either aerobically or anaerobically. Fermentation ; The effect of oxygen on microorganisms.

A few of the early microbiologists chose to investigate the ecological role of microorganisms. In particular they studied microbial involvement in the carbon, nitrogen, and sulfur cycles taking place in soil and aquatic habitats. Two of the pioneers in this endeavor were Sergei N. Winogradsky (1856–1953) and Martinus
W. Beijerinck (1851–1931)

The Russian microbiologist Sergei N. Winogradsky made many contributions to soil microbiology. He discovered that soil bacteria could oxidize iron, sulfur, and ammonia to obtain energy, and that many bacteria could incorporate CO2 into organic matter much like photosynthetic organisms do. Winogradsky also
isolated anaerobic nitrogen-fixing soil bacteria and studied the decomposition of cellulose. Martinus W. Beijerinck was one of the great general microbiologists who made fundamental contributions to microbial
ecology and many other fields. He isolated the aerobic nitrogenfixing bacterium Azotobacter; a root nodule bacterium also capable of fixing nitrogen ; and sulfatereducing bacteria. Beijerinck and Winogradsky developed the enrichment-culture technique and the use of selective media , which have been of such great importance in microbiology.