Hansen, Emil Christian

(b. Ribe, Denmark, 8 May 1842; d. Hornbaek, Denmark, 27 August 1909)

botany, physiology.

Hansen’s father, Joseph Christian Hansen, was a house painter who settled in the small provincial town of Ribe, Jutland, where he married Ane Dyhre. Their large family and poor circumstances often made it necessary for Emil Hansen to help his father. In 1850 he entered school and showed himself to be a diligent pupil and an avid reader. He wished to become an actor, but his father would not allow it. In 1860 he became a journeyman house painter; he also sought to become an artist, but the Academy of Fine Arts refused his application for admission.

Hansen became a private tutor in 1862 at the estate of Holsteinborg, where he prepared to become a teacher. During his stay at Holsteinborg the botanist Peder Nielsen, at that time schoolmaster in Ørslev, aroused Hansen’s interest in botany and gave him emotional and financial support. In spite of illness Hansen completed a three-year teaching course at Copenhagen Polytechnical High School in 1869, earning money by publishing novels. The following two years he tutored in natural science, and in 1871 he became private assistant to the zoologist Japetus Steenstrup.

In 1873 Hansen discovered beech leaves in the deeper peat stratum of a moor in Femsølyng and concluded that the beech had existed in Denmark longer than Steenstrup believed. Hansen boasted of his discovery, then resigned from his job in the belief that he had made an enemy of Steenstrup. In the following years he prepared for the M.Sc. but did not achieve it. Nor did he make the further investigations of the moor regions for which he had obtained government support.

In 1876, however, Hansen received a gold medal from Copenhagen University for his essay on fungi growing on mammal dung, the subject of the 1874 competition. Hansen gave a detailed morphological and anatomical description of the fungi he had found and mentioned several new species (for example, Peziza ripensis) as a result of his culture experiments. His prize-winning work was published as De danske Gjødningssvampe (1876), and he spent the following years studying the biology and variation of species of fungi. He cultured Coprinus stercorarius, Coprinus niveus, and Coprinus restrupianus and demonstrated the phototropism of Coprinus stercorarius: the stalk turns toward the light while the spores are thrown away from it. He also described a new family of Ascomycetes, Anixiopsis, from the species Eurotium stercorarium (1878). These studies were published in French and German (both in 1880).

Inspired by the physiologist P. L. Panum, Hansen next studied fermentation in the zoophysiological laboratory of Copenhagen University. Despite some opposition from Steenstrup he was allowed to prepare and publicly defend a thesis for a Ph.D. On 1 July 1878 he obtained a job in the laboratory of the Carlsberg breweries—through Steenstrup’s recommendation—and here Hansen began his microscopic studies of beer. From 1879 until his death Hansen was superintendent of the laboratories. In his thesis, “Om Organismer i Øl og Ølurt” (1879), he tried to demonstrate which organisms (yeast fungi, molds, bacteria) could be found free in nature and how they could be cultured on sterile nutrient liquids. By chemical reactions, when morphology failed, he could prove which organisms occurred in beer, which occurred in its foam, and which occurred in other organic liquids when they were exposed to air. He was able to demonstrate that there are two forms of Pasteur’s bacterium: Mycoderma aceti and Mycoderma pasteurianum. These discoveries led him to assume that the common types of beer yeast are physiologically different.

Between 1881 and 1908 Hansen published thirteen papers under the general title “Undersøgelser over Alkoholgjaersvampenes Fysiologi og Morfologi,” which provided many essential contributions to the knowledge of saccharomycetes. He chose the easily recognizable Saccharomyces apiculatus and demonstrated its life cycle in nature, its relation to sugar, its hibernation in the earth, and its presence on juicy fruits in summer. He demonstrated that it could neither invert saccharoses nor produce alcoholic fermentation (1881).

In order to follow the development of the microorganisms under the microscope Hansen constructed a special “moist chamber” (1881). Through further experiments he subsequently succeeded in proving the life cycle of other saccharomycete species. (Their morphologies and their spore formation were being investigated at that time not only in Copenhagen but also in Germany and Italy [1902].) In addition Hansen demonstrated that Torula, Mucor, and other bacteria react like yeasts. Finding that beer often acquired a bad taste from “wild” yeast types, which involved the breweries in heavy economic losses, Hansen was inspired to follow up his studies on various yeast types. A common airborne saccharomycete, which he named Saccaromyces pastorianus Riess, produced a beer with bitter taste and heavy sedimentation.

Hansen then took up the methods for pure cultivation developed by Pasteur, Robert Koch, and the Danish bacteriologist C. J. Salomonsen and succeeded in developing cultures from one cell. These cultures could be kept alive for years in a glass flask that he had made. He also proved that there were several different varieties and races of saccharomycete species, and through fermentation experiments he found that their effect on beer was very different. The common yeast of the old Carlsberg brewery, “Carlsberg bottom yeast I,” which J. C. Jacobsen had obtained at Munich in 1845, produced excellent beer, but the admixture of “wild” yeast types had spoiled it. Although skeptical, Jacobsen allowed Hansen to use his cultured pure strains of yeast to brew experimentally on a large scale—and 12 November 1883 became a red-letter day in the history of brewing. The new beer was excellent, as Hansen had expected, and Jacobsen continued to use the cultivated yeast. Following the policy he had proclaimed for the Carlsberg laboratory, Jacobsen refused to have the method patented, and in a short time it was used all over the world. Hansen published his investigations and results in seven papers with the title “Undersøgelser fra Gjaeringsindustriens Praxis” (1888–1892), which were translated into French (1888), German (1888, 1890, 1893), and English (1896).

During the following years Hansen took up problems concerning acetic-acid bacteria—their film formation, variation, and life-span—and continued investigations on the life cycle, spore formation, variation, genetics, and systematics of saccharomycetes (1904). He had seen that pure yeast cultured through several generations in beer wort at a certain temperature lost its ability to form spores and never regained it even if the most favorable temperatures for spore formation were obtained. Hansen acknowledged here an environmentally produced genetic characteristic, a conclusion that caused a great stir—but his discovery was probably the result of a mutation (1899).

From 1900 Hansen studied the relationship between top yeast and bottom yeast and found that the changes in the nature of yeast were caused by mutation (1905, 1907). For years he had considered most of the yeast types differentiated by him as physiological races, but now he considered them as species and in 1904 published “Grundlinien zur Systematik der Saccharomyceten,” which also appeared in Danish, French, and English journals.

Hansen was made a member of the Royal Danish Society for Sciences in 1890 and obtained large donations from the Carlsberg Foundation and the Brewers’ Association. He left a large fortune for a foundation to bear his name, the income to be used for prizes for biological papers; the prizes were to be awarded by an international committee. He also left a fine library on art and the history of the natural sciences. Hansen was an honorary member of learned societies all over the world and held honorary doctorates from the universities of Uppsala (1907) and Geneva (1909) and the Technische Hochschule of Vienna (1908).

In 1879 Hansen married Mathilde Melchior. His difficult childhood had made him somewhat harsh and devoid of humor; he compelled strict respect from his co-workers but in later years was kind to the poor.

BIBLIOGRAPHY

I. Original Works. A full catalog of Hansen’s works is in Carl Christensen, Den danske Botaniks Historie, II (Copenhagen, 1926), 441–457. Many of his scientific papers were reprinted in Albert Kløcker, ed., Gesammelte theoretische Abhandlungen über Gärungsorganismen von Emil Chr. Hansen (Jena, 1911).

II. Secondary Literature. See Carl Christensen, Den danske Botaniks Historie, I (Copenhagen, 1924), 718–731; E. Gotfredsen, Medicinens Historie (Copenhagen, 1964), p. 447; A. Kløcker, in Meddelelser fra Carlsberg Laboratoriet, 2 (1911), i–xxxvi; C. Nyrop, J. C. Jacobsen (Copenhagen, 1911), pp. 55–58; and Johannes Pedersen, The Carlsberg Foundation, XII (Copenhagen, 1956), 46–48.

E. Snorrason