Louis Pasteur (1822-1895). Computer illustration of the French microbiologist and chemist Louis Pasteur with optical isomer molecules. Pasteur's investigations of tartaric acid resulted in the first resolution of what are now known as optical isomers. His work led the way to current understanding of a fundamental principal in the structure of organic compounds. He found that fermentation is caused by micro-organisms, and also proposed the germ theory of disease. He developed a vaccine against rabies, which led to the founding of the Pasteur Institute in 1888. He discovered the anthrax bacterium and developed a vaccine against it. He also discovered that gentle heating of wine and beer preserves them from souring: the process of pasteurisation which is now widely used in the food industry.