Artturi Ilmari Virtanen was a Finnish biochemist who discovered many of the nutritionally important components of plants, including vitamins and amino acids. His most important discovery, a method of preserving green fodder and silage, led to an improved understanding of the mechanism of plant decay . For his biochemical investigations in agriculture and nutrition he received the 1945 Nobel Prize in chemistry.
Virtanen was born January 15, 1895, in Helsinki, Finland, to Serafina (Isotalo) and Kaarlo Virtanen. He began his education at the Classical Lyceum in Viipuri (now Vyborg, Russia). Upon graduation, he entered the University of Helsinki to study biology, chemistry, and physics. Virtanen received his master of science degree in 1916 and worked briefly as an assistant chemist in the Central Industrial Laboratory of Helsinki. That same year he returned to the University to continue his studies and in 1919 he received his doctorate. Interested in a broad range of scientific subjects, Virtanen traveled extensively to pursue his studies. In 1920 he left for Zurich, Switzerland, to undertake postgraduate work in physical chemistry. The next year he had moved to Stockholm, Sweden, to study bacteriology, and in 1923 he worked on enzymology with Hans von Euler-Chelpin. At this time Virtanen discovered the subject that would become his life work, biochemistry.
In 1921 Virtanen was appointed Laboratory Director of the Finnish Cooperative Dairies Association in Valio, where he was responsible for controlling the manufacture of dairy products such as cheese and butter. A decade later, in 1931, he was appointed the Director of the Biochemical Research Institute in Helsinki. In that same year, he began teaching as professor of biochemistry at the Finland Institute of Technology. Late in 1939 he became professor of biochemistry at the University of Helsinki.
Virtanen was interested in both the theoretical and practical aspects of biochemistry. His first important study was an investigation of the fermentation reactions of some biologically important acids. His research showed how enzymes were necessary for bacterial fermentation. Enzymes, the complex organic catalysts of living cells, were thought to speed up chemical reactions without being chemically changed. Virtanen, who believed that enzymes were composed of proteins, began an exhaustive study of the protein content and enzyme activity of plants.
Proteins are rich in nitrogen, an essential element in both human and animal nutrition. Virtanen realized that nitrogen was plentiful in the atmosphere but almost completely unavailable to most plants and animals. He began to study legumes (peas, clover, and soybeans), which are able to convert atmospheric nitrogen into nitrogen compounds suitable for plant growth. Virtanen became interested in what happened to plants after they were cut and stored for cattle fodder. It was found that fodder stored as silage could lose one quarter to one half of its nutrients to bacterial decay. Animals consuming this silage produced poor quality butter, milk, and cheese. After study and experimentation, Virtanen discovered that the addition of a simple mixture of dilute hydrochloric and sulfuric acids to stored silage could slow down bacterial decay and prevent the destruction of nutritionally important vitamins and proteins.
Virtanen fed his acid-treated silage to dairy cows and tested the milk to determine the safety and effectiveness of his method. He discovered that milk remained rich in protein, carotene, and vitamin C, and that the milk cows remained healthy and strong. The method Virtanen devised for treating silage--called the Artturi Ilmari Virtanen (AIV) method --was first used in Finland in 1929.
Although most of Virtanen's scientific investigations had practical agricultural applications, his later work was more theoretical. He studied how bacteria in the root nodules of legumes synthesize nitrogen compounds, and how plant cells assimilate simple molecules into large complex vitamins. He discovered a red pigment in plant cells similar in structure and function to hemoglobin, the molecule that transports life-giving oxygen in human blood. He also studied the composition of plants, discovering many important amino acids --the building blocks of proteins. For his work on the AIV method of silage preservation and for his research in agricultural chemistry Virtanen received the 1945 Nobel Prize in chemistry.
After winning the Nobel Prize, Virtanen remained actively engaged in research. He published a book on animal and human nutrition and served on the editorial boards of several leading biochemical journals. He represented Finland on a United Nations Commission on Nutrition, and in 1948 he was elected president of Finland's State Academy of Science and Arts. Virtanen, remembered as one of Finland's leading scientists, died November 11, 1973, in the city of his birth, Helsinki.
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