Émile Duclaux (June 24, 1840 - May 2, 1904) was a French microbiologist and chemist. His work was largely in the fields of chemistry, bacteriology, hygiene and agriculture. In 1862 he began work as an assistant at the Institut Pasteur. For much of his career he was associated with the work of Louis Pasteur. Duclaux initiated the custom of naming enzymes by adding the suffix 'ase' to the enzyme's substrate. With Pasteur, he collaborated in the study of silkworm diseases, and also took part in experiments to debunk the theory of spontaneous generation. He also performed research on the composition of milk, and conducted studies on beer and wine. Kaufmann-Fabry, 1933 (cropped and cleaned).