Microbiological Assay Methods for Vitamins

Abstract

Vitamins are organic substances of natural origin, required in minute quantities, and their effects are not based on their caloric value, but exclusively on their catalytic nature. Vitamins, especially the water-soluble ones, provide the coenzymes for the most fundamental cellular reactions. Microchemical methods are used for the determination of thiamine, riboflavin, and some fat-soluble vitamins, based on most sensitive colorimetric and fluorometric techniques. Microbiological assays are applicable when a microorganism responds to a metabolite for which physical and chemical determinations are neither sensitive nor specific enough. One must select a microorganism sensitive to the substance under assay—it should be cultivable with ease; the growth response should be easily measurable and the response should be specific; and it should be non-pathogenic. The chapter accounts for the microbiological assay techniques for the determination of vitamins like thiamine, pantothenic acid, nicotinic acid and amide, biotin, inositol, vitamin B6, folic acid, folinic acid, and vitamin B12 in body fluids. The establishment of quantitative methods for the determination of vitamins in body fluids and tissues by microbiological assay techniques should stimulate the search for the significance of vitamins in disease, not only in nutritional deficiency, but also in much wider field of all metabolic disturbances. Functional vitamin deficiencies are produced by malabsorption, by inhibitors of the vitamin function through products of the body, and particularly through drugs and other toxic substances.