Buchner, Eduard

(b. Munich, Germany, 20 May, 1860; d. Focsani, Rumania, 13 August 1917)

chemistry.

Buchner came from an old Bavarian family of scholars. His father, Ernst, was professor of forensic medicine and obstetrics as well as editor of the Ärztliches Intelligenzblatt (later Münchener medizinische Wochenschrift).

Upon graduating from the Realgymnasium in Munich, he served in the field artillery and then studied chemistry at the Technische Hochschule in Munich. After a short while, however, Buchner had to abandon his studies because of financial problems; for four years he worked in canneries in Munich and in Mombach. In 1884, with the assistance of his brother Hans, he was able to resume his chemical studies, this time at the organic section of the chemical laboratory of the Bavarian Academy of Sciences in Munich, under Adolf von Baeyer. Buchner’s first work in organic preparative chemistry resulted from the suggestions of Theodor Curtius, an assistant in the organic section, and were done under his direction; his work with Curtius on the chemistry of diazoacetic ester led to a warm friendship.

While studying chemistry, Buchner also worked at the Institute for Plant Physiology, under Karl von Nägeli. Here he became interested in the problems of alcoholic fermentation, the subject of his first publication (1886). In this paper he arrived at the significant conclusion that, contrary to Pasteur’s contention, the absence of oxygen is not a necessary prerequisite for fermentation.

Buchner obtained his doctorate in 1888 under Baeyer and in 1890 was appointed his teaching assistant. He became Privatdozent the following year. His Habilitationsschrift dealt with research on pyrazole, the five-membered heterocyclic derivative of antipyrine. Baeyer procured the funds for him to set up his own laboratory for fermentation chemistry, but up to 1893 Buchner published only one other paper on the physiology of fermentation, a comparative study of the behavior of fumaric and maleic acids.

In 1893 Buchner succeeded Curtius as head of the Section for Analytical Chemistry at the University of Kiel, and in 1895 he was appointed associate professor there. The following year he became professor of analytical pharmaceutical chemistry in Tübingen and, while there, published his pioneering work, Alkoholische Gärung ohne Hefezellen (1897).

In 1898 Buchner accepted an appointment as full professor of general chemistry at the College of Agriculture in Berlin and simultaneously he became director of the Institute for the Fermentation Industry.

In 1900 he married Lotte Stahl, daughter of a Tübingen mathematician. Two sons and one daughter resulted from this marriage.

Scientifically, Buchner’s Berlin years were his most productive period, especially in the field of the biochemistry of the fermentation process. Nevertheless, he felt that professionally he was not able to develop his knowledge: he missed teaching in a chemical institute of a university. He had to wait a long time before he was invited to teach at a university, however, perhaps because of having insulted the Ministry of Education official in charge of the Prussian academic institutions. After being kept waiting by the official, Buchner rebuked him by pointing to his pocket watch.

After receiving the Nobel Prize in chemistry in 1907 for his work on cell-fre fermentation, Buchner was appointed to the chair of physiological chemistry at the University of Breslau in 1909. Two years later he was invited to Würzburg he accepted with alacrity. In Würzburg he was also able to pursue his hobbies of hunting and mountain climbing.

Politically, Buchner was an admirer of Bismarck and a follower of the National Liberal party. He volunteered for active duty at the outbreak of World War I and in August 1914 was sent to the front as a captain of an ammunition supply unit. He was promoted to major in 1916, but in that same year he was called back to Würzburg to resume teaching. In 1917 he again volunteered for front-line duty and was sent to Rumania, where on 11 August he was wounded by shrapnel and died two days later.

Central to Buchner’s experimental work are three papers published in 1897, which dealt with his sensational discovery of cell-free fermentation, the turning point for the study of enzymes. In the history of enzymology, it is quite proper to differentiate between the pre-Buchner and post-Buchner periods.

The basis of fermentation chemistry or enzyme chemistry is Berzelius’ thesis¹ that all reactions in living organisms are initiated and regulated by catalysts. This of course applies to the processes of fermentation and putrefaction. Originally, the terms “ferment” and “enzyme” designated primarily fermentation, but also putrefaction or a gas-producing agent. Hence, it is understandable that “the history of the conversion of fermentable sugar through yeast overlaps with the history of fermentation processes in general. It was this outstandingly important process in the production of alcoholic beverages that was the prototype of fermentation processes.”²

Between 1830 and 1860, prior to Buchner’s discovery, two theories of fermentation had divided the scientific world into vitalists and mechanists. Liebig was the exponent of the mechanists. According to his theory,³ formulated in 1839, yeast causes fermentation because, as a body in a state of continuous decomposition, it stimulates the sugar molecules to decompose into alcohol and carbon dioxide. Although this appeared to be analogous to the then known fermentative reactions (the decomposition of amygdalin into hydrocyanic acid and sugar by emulsion, the proteolysis of egg albumin by pepsin, the decomposition of starch by diastase), Liebig refused to ascribe the character of a “catalytic force,” as formulated by Berzelius, to the action of yeast.

The mechanical theory of fermentation, regardless of whether it interpreted yeast as an expression of a “catalytic force” or of a body in the process of decomposing, clashed with Pasteur’s vitalistic interpretation of the fermentation process. In 1836 Cagniard de la Tour had reported to the Paris Academy that yeast consisted of living organisms, and the next year Theodor Schwann and Friedrich Kützing were to reach the same conclusion. On the basis of these discoveries and as a result of his own observations and experiments, Pasteur (between 1857 and 1860) formulated the thesis that alcoholic fermentation was an expression of the vital action of the yeast fungi and inseparably bound to this physiological action.⁴ Fermentation was therefore not a catalytic but a vital process. Then Pasteur differentiated between soluble enzymes, which can be separated from the vital processes and therefore are also effective outside the organism, and ferments, which are inseparably bound to a living organism and its vitality. Although such researchers as Berthelot, Traube, and Hoppe-Seyler subsequently defended the view that there were active enzymes in living cells, comparable to those acting outside the cell, Pasteur’s view of the unalterable connection between vitality and fermentation nevertheless found acceptance among the majority of scientists.

Efforts to isolate the fermentation-producing agent from yeast cells remained unsuccessful. This was the problem Buchner attacked anew in 1893 at the suggestion of his brother Hans, who was engaged in the extraction of his brother Hans, who was engaged in the extraction of powerful pathogenic substances from bacteria. The problem was how to obtain cell fluid, in as pure a state as possible, for therapeutic research. Buchner’s approach was an attempt to destroy yeast cells in order to extract their fluid. At the suggestion of Martin Hahn, an assistant of his brother’s, Buchner pulverized yeast in a mortar with one part quartz sand and one-fifth part diatomaceous earth; this became a thick paste within a few minutes. This paste was then wrapped in canvas and subjected to a pressure of ninety kilograms per square centimeter, yielding 500 milliliters of fluid from 1,000 grams yeast.

At first, hardly and thought was given to the idea of producing fermentation with the fluid expressed from yeast. Rather, Buchner and Hahn concentrated on preserving the easily decomposed fluid by adding concentrated sucrose solution. In 1896 Buchner discovered that this mixture soon exhibited lively gas formation. In 1897 he published three papers on the results of these first experiments with cell-free alcoholic fermentation, and by the end of 1902 he had published fifteen more papers on the same subject. In 1903 the first comprehensive presentation of his achievements was published by the two Buchners and Martin Hahn as Die Zymase-Gārung.

Buchner called the active, fermentation-producing agent of the expressed fluid “zymase.” This eliminated the previously valid distinction between the soluble enzymes, effective outside the cell, and the ferments, whose effectiveness is linked to cell structure and cell activity. Accordingly, life and fermentation are not unalterably bound to each other. Instead, fermentation is a chemical, enzymatically catalyzed process.

Through painstaking experimentation, Buchner defended this basic fact against various objections, particularly those of the physiologist Max Rubner, the biochemist Hans von Euler-Chelpin, and the botanist Wilhelm Ruhland. He was able to prove that neither the few intact yeast cells present in the expressed fluid nor any “living plasma particles” cause the sugar conversion that occurs in the fermentation process. Addition of a mixture of alcohol and ether to the fluid yielded a precipitate that could be preserved as a powder without the zymase losing its effectiveness. He also obtained a fully fermentative dry substance by killing the yeast cells through addition of alcohol or acetone to a yeast suspension. He gave the name “zymin” to the substance after it had been washed and dried with ether. It cannot grow but is fully effective in fermentation experiments.

Further test series concerned the chemical properties of the expressed fluid, a yellow-brown opalescent liquid which becomes ineffective after prolonged storage because a proteolytic enzyme, endotryptase, destroys the active principle. The fluid also loses its effectiveness through heating, which causes precipitation of its proteins. In addition to zymase, the fluid contains a series of other enzymes: catalase (diluted fluid decomposes hydrogen peroxide into water and oxygen) as well as enzymes resulting from the spliting of disaccharides and polysaccharides. From the latter, Buchner deduced that not only the simple sugars, glucose and fructose, but also complex sugars, maltose and saccharose (disaccharides), as well as the polysaccharide glycogen, are fermentable. Attempts to separate these enzymes from the zymase were almost always unsuccessful.

In the chemistry of alcoholic fermentation, Buchner and his assistants were confronted by three questions between 1904 and 1917: (1) Is zymase a homogeneous enzyme? (2) In order to be active, does it require the presence of additional substances, especially the presence of a coenzyme? (3) What is the chemical nature of the intermediate products in the decomposition of sugar into alcohol and carbon dioxide? In the experimental treatment of these questions, however, Buchner and his assistants were no longer alone. The scientific world had realized that the fluid expressed from yeast could be profitably studied in order to explain the chemistry of fermentation. The English scientists A. Harden and W. J. Young had been working on these problems since 1904, the St. Petersburg botanist L. Ivanov since 1906, and A. von Lebedev since 1910; and if the reaction chain of alcoholic fermentation can be considered fully explained, it is because of their successful initial experiments. In this phase Buchner and his circle of co-workers take second place. True, they kept up with these developments, but they were not the pacesetters.

Buchner suggested that lactic acid, methylglyoxal, glyceraldehyde, and dihydroxyacetone were the intermediate products of the fermentation of alcohol. It has only recently been established that glyceraldehyde and dihydroxyacetone, in the form of the respective phosphates, are indeed intermediate products of the decomposition of sugar by yeast as well as by animal cells.

Buchner was also interested in the fermentation phenomena of other microorganisms. In 1902 he published a paper on the enzymes of Monilia candida and other milk-sugar yeasts. In subsequent years he worked on acetous fermentation (1906), butyrous fermentation (1908), and citrous fermentation (1909). These investigations also served to confirm that characteristic life phenomena can be attributed to the regularities of enzyme-catalyzed chemical reactions.

Buchner’s revolutionary discoveries in biochemistry overshadow his work in preparative organic chemistry. The starting point of these studies was the synthesis of diazoacetic ester, by means of which Curtius discovered a new group of compounds in 1883. This aliphatic diazo compound is highly reactive. Buchner experimented systematically with it, first under the direction of Curtius and later independently. Between 1885 and 1905 he published forty-eight papers treating preparation of nitrogenous compounds, especially pyrazole, as products of the action of diazoacetic ester on unsaturated acid esters, and the synthesis of trimethylene carboxylic acids by adding diazoacetic ester to fumaric acid ester and heating the mixture. With the aid of brucine salts, Buchner separated the resulting racemic mixture into its two enantiomorphic substances. The papers also concerned the products of reaction of diazoacetic ester with aromatic hydrocarbons (benzene, toluene, m-xylene, and p-xylen). The result of this work was the synthesis of cycloheptatriene and cycloheptane–carboxylic acid. Thus a new direction was furnished for a synthesis of compounds in the cycloheptane series.

After 1905 Buchner published only six additional studies in preparative organic chemistry, an indication that biochemical problems fully occupied his time.

NOTES

1.Jahresberichte von Berzelius, 15 (1835), 245.

2. Carl Oppenheimer, Die Fermente und ihre Wirkungen, 2nd ed. (Leipzig, 1903), p. 302.

3.Annalen der Chemie, 30 (1839), 362.

4.Annales de chimie et de physique, 58 (1860), 323.

BIBLIOGRAPHY

I. Original Works. All of Buchner’s writings are listed in Poggendorff, IV, 200, and V, 182; references to his obituaries are in VI, 362. A complete bibliography can also be found in the appendix to C. Harries, in Berichte der Deutscchen chemischen Gesellschaft, 50 (1917), 1843–1876. For a comprehensive presentation of his work on fermentation, see Die Zymase-Gārung (Munich, 1903), written with Hans Buchner and Martin Hahn; “Alkoholische Gārung des Zuckers,” in Bulletin de la Société chimique de France, 7 (1910), 1–22; “Neuere Ansichten über die Zymase,” in Sitzungsberichte der Physikalisch-medizinischen Gesellschaft zu Würzbug (1917), written with S. Skraup; and “Cell-free Fermentation,” in Nobel Lectures Chemistry 1901–1921 (Amsterdam-London-New York, 1966).

II. Secondary Literature. The history of the fermentation problem is discussed in M. Delbrück and A. Schrohe, Hefe, Gārung und Fāulnis (Berlin, 1904); C. Graebe, Geschichte der organischen Chemie (Berlin, 1920); F. F. Nord, in F. F. Nord and R. Weidenhagen, Handbuch der Enzymologie (Leipzig, 1940); and C. Oppenheimer, Die Fermente und ihre Wirkungen, 4th ed. (Leipzig, 1913). For further literature see the works cited in the notes.

On Buchner’s work in organic synthesis, see P. Walden, Geschichte der organischen Chemie seit 1880 (Berlin, 1941). The history of the discovery of cell-free fermentation is discussed in M. von Gruber, in Münchener medizinishce Wochenschrift (1907).

Herbert Schriefers