= Cell-free fermentation as a biochemical experiment
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>.<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]{ref}
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>.<Cell-free fermentation by Eduard Buchner>[Printed pp. 112–114: residual-cell objection, biscuit-porcelain filtration, toluene comparison and extract activity]{ref}
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.<Cell-free fermentation by Eduard Buchner>[Printed p. 115: unsuccessful zymase separation; pp. 117–118: gelatine-filter fractions and restored activity on reunion]{ref}
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