The famous controversy between Pasteur and Liebig over the nature of alcoholic fermentation was uncovered by Eduard Büchner, a German chemist and zymologist.  Influenced by his brother Hans, who became the famous bacteriologist, Büchner developed an interest in the fermentation process in which yeast breaks down sugar into alcohol and carbon dioxide. He published his first paper in 1885 which revealed that fermentation could occur in the presence of oxygen, a conclusion contrary to the view held by Louis Pasteur.
By 1893, Büchner was fully involved in seeking the active agent of fermentation. He obtained pure samples of the inner fluid of yeast cells by pulverizing yeast within a mixture of sand and diatomaceous earth, then squeezing the mixture through a canvas filter. This process avoided using solvents and high temperatures which had foiled previous investigations. He assumed that the collected fluid was incapable of producing fermentation because the yeast cells were dead. However, when he attempted to preserve the fluid in concentrated sugar, he was startled to observe carbon dioxide being released, a sign that fermentation was taking place. Büchner hypothesized that the fermentation was caused by an enzyme which he named zymase. His findings that fermentation was the result of chemical process both inside and outside cells, were published in 1897.