He disproved the widely accepted myth of spontaneous generation. He demonstrated that both fermentation and putrefaction were initiated by air borne microbes.

He described the scientific basis for fermentation, winemaking, and the brewing of beer.

His discovery that most infectious diseases are caused by germs, known as the "germ theory of disease", is one of the most important in medical history.

He discovered the method for the attenuation of virulent microorganisms that is the basis of vaccination. He developed vaccines against rabies, chicken cholera, anthrax, swine erysipelas and silkworm diseases.

He introduced the methods of sterilization, namely the steam sterilizer, autoclave and the hot air oven. 

He proved the importance of cotton wool as stoppers for protecting media in flasks or tubes.

He had realized the importance of the constituents of the nutrients contained in a culture media, the pH and the oxygen.

Pasteur developed "pasteurization", a technique by which harmful microbes in perishable food products are destroyed using heat, without destroying the food.

He discovered the existence of life without oxygen. That is, discovered that bacteria can survive in anaerobic conditions. 

 Coined the term "vaccine" to commemorate the first successful vaccination against smallpox by Jenner.