Microbiological assay of amino acids

Snell, E. E., and Esmond, E., The microbiological assay of amino acids. Advances in Protein Chem. 2, 85-116 (1945). 

Snell, E. E. The Microbiological Assay of Amino Acids. In M. L. Anson... 

In more recent times chemically defined basal media have been elaborated, on which the growth of various lactic acid bacteria is luxuriant and acid production is near-optimal. The proportions of the nutrients in the basal media have been determined which induce maximum sensitivity of the organisms for the test substance and minimize the stimulatory or inhibitory action of other nutrilites introduced with the test sample. Assay conditions have been provided which permit the attainment of satisfactory precision and accuracy in the determination of amino acids. Experimental techniques have been provided which facilitate the microbiological determination of amino acids. On the whole, microbiological procedures now available for the determination of all the amino acids except hydroxy-proline are convenient, reasonably accurate, and applicable to the assay of purified proteins, food, blood, urine, plant products, and other types of biological materials. On the other hand, it is improbable that any microbiological procedure approaches perfection and it is to be expected that old methods will be improved and new ones proposed by the many investigators interested in this problem. 

D3. Dunn, M. S., Determination of amino acids by microbiological assay. Physiol. Revs. 29, 219-259 (1949). 

B26. Barton-Wright, E. C., Microbiological Assay of the Vitamin B-Complex and Amino Acids. Pitman, London, 1952. 

Recent advances have enormously widened the range of applicability of amino acid determinations as a control on fractionation. Not only have colorimetric procedures been revised and increased in accuracy, but the development of microbiological and chromotographic methods of assay now permits the quantitative determination of almost any amino acid residue, using very small amounts of protein of the order of 10 to 100 mg. The results are rapid and, by some at least of tiiese methods, appear to be trustworthy. Since the general principles of all these methods have been reviewed in the previous volume of this series, by Martin and Synge (142) and by Snell (197), no further discussion of them need be given here. 

Recently Bliss (2), Wood (63), and Barton-Wright (1) have made excellent contributions to the treatment of microbiological assays of vitamins and amino acids. 

An aromatic amino acid found in increased levels in the blood and urine in the inborn error of metabolism, phenylketonuria. It can be estimated by microbiological assay (the Guthrie test, q.v.) or by its reaction with ninhydrin to form a fluorescent compound. This fluorescence is enhanced by the addition of the dipeptide, L-leucylalanine. 

Colorimetry and Spectrophotometry Protein and Amino Acid Analyses Biological Analyses Digestibility Trials Nutrient-Deficient Animals Microbiological Assays Microscopic Analyses for Filth and other Adulterants or Contaminants Physical Methods of Analyses Use of Food Composition Data for Planning Menus and Diets... 

The amino acid contents of different preparations of peanut protein (calculated to 16% of nitrogen) are given in Table III. The analyses of the protein isolated by the method of Arthur and others (7,10) were reported by Murphy and Dunn (154). They obtained the values by microbiological assay methods. The analyses of the other preparations were compiled from various literature sources by Guthrie and others (92,100). 

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