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The cell-free extract experiment under yeast asks whether fermentation requires intact living biological cells. In his 1907 lecture, Eduard Buchner described grinding yeast with quartz sand and diatomite in a large mortar using a heavy pestle, wrapping the dough in canvas, then squeezing it in a hydraulic press. Adding concentrated sugar syrup to the expressed liquid produced carbon dioxide bubbles and foam; separate investigations identified ethanol.[ref]
Cell-free fermentation by Eduard Buchner. Cell-free fermentation, Nobel lecture delivered 11 December 1907, printed pp. 110–112, Figures 2–4 and accompanying preparation/readout text
Activity persisted after filtration through cell-removing porcelain candles. Toluene inhibited live yeast fermentation while the cell-free extract retained activity, addressing a different objection from cell removal. These comparisons support extracted chemical machinery as the cause; bubbles alone would not identify alcoholic fermentation.[ref]
Cell-free fermentation by Eduard Buchner. Printed pp. 112–114: residual-cell objection, biscuit-porcelain filtration, toluene comparison and extract activity
The inference is activity outside intact living biological cells, not that biological cells are unnecessary for making or maintaining the machinery. Nor was this a purified single-enzyme mechanism: the lecture acknowledges unsuccessful purification and reports that two separated inactive fractions recovered fermentation when reunited. Such a reconstitution asks which components must work together, extending the initial separation of organism from chemical activity.[ref]
Cell-free fermentation by Eduard Buchner. Printed p. 115: unsuccessful zymase separation; pp. 117–118: gelatine-filter fractions and restored activity on reunion
Cell-free fermentation by Eduard Buchner 2026-10-14
By Eduard Buchner.
Cited passages: Cell-free fermentation, Nobel lecture delivered 11 December 1907, printed pp. 110–112, Figures 2–4 and accompanying preparation/readout text; Printed p. 115: unsuccessful zymase separation; pp. 117–118: gelatine-filter fractions and restored activity on reunion; Printed pp. 112–114: residual-cell objection, biscuit-porcelain filtration, toluene comparison and extract activity.
Eduard Buchner 2026-10-14
Portrait of Eduard Buchner
. Photograph reproduced in Les Prix Nobel (1907), credited to the Nobel Foundation on Wikimedia Commons, which identifies it as public domain. Source.