1897

Zymase Fermentation

Hans Ernst August Buchner (1850–1902), Eduard Buchner (1860–1917)

Fermentation has been practiced since prehistory—bread, wine, yogurt, and pickles are older than any written language—although it wasn’t until 1857 that French chemist Louis Pasteur determined that it was tied to the microorganisms identified as yeast and bacteria. Clearly, fermentation, the breaking down of sugars to small acids and carbon dioxide, happened only in living cells.

That explanation endured until 1897, when German chemist Eduard Buchner—with the help of his older brother, Hans—startled the scientific world by fermenting sugars without any living organisms at all. He broke up the cells of dry yeast to release their contents and pressed the results through fine filtering material, a suggestion of his brother’s assistant, Martin Hahn. When Eduard added simple sugars to the pressed extract, the mixture consumed the sugars and evolved carbon dioxide. No yeast cells were present (they definitely would have been noticeable through a microscope, since the yeast would have grown rapidly). Not only had he discovered active proteins (enzymes, in particular the complex named zymase), but he demonstrated that they could be freed from their native environments and remain functional. It was another blow to vitalism. Rather than being full of some vital essence that disappeared upon death, the insides of living cells were apparently full of machinery that could be removed.

Others had actually tried this before, but with no success. One of the reasons for previous failures, it was found, was the use of ground glass to break up the cells, which apparently inactivated the cell contents through a reaction with the glass surface. The success of this process also varied greatly depending on the strain of yeast used. Hans Buchner was interested in preparing bacterial extracts, and he and Martin Hahn worked out the pressing technique that made the difference.

Cell-free enzyme chemistry is now a huge field, with applications in everything from detergents to therapy for rare genetic diseases. Even today, it can be a tricky business to keep things working correctly, so the amount of work the pioneers put into it is worth remembering.

Yeast of the genus Candida growing on a laboratory plate. Brewing and baking yeasts are so vigorous that anyone working in a cell-culture facility must be extremely careful not to contaminate the lab cultures if they do any baking or home brewing as an after-work activity!