(1822-95) a French scientist who established the study of microbiology (=the study of very small living things such as bacteria), and proved that disease can be caused by germs. He also studied fermentation (=the process by which substances change chemically and become filled with gas by the action of bacteria), and invented the process of pasteurization. He also developed somevaccines (=substances that are put into people's bodies to protect them from diseases).
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.
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