A Microbiological Assay of Inositol: its Development and Statistical Analysis

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Abstract
SUMICIARY: The assay of inositol has been developed using Kloeckera brevfs B 768 and a strain of Schixosaccharomyces pombe. In the assay of Difco Bacto yeast extract it was necessary to supplement the basal medium with an inositol-free preparation from yeast extract. A new assay design has been proposed and the results treated statistically. A microbiological assay of inositol was described by Woolley (1941) using a strain of Saccharornyces cerevisiae. This was based on the fact that the rate of growth of the organism is stimulated by inositol; but it has the disadvantage that the organism can grow in the absence of an exogenous supply of inositol. A similar method is given by Williams, Stout, Mitchell & McMahon (1941). Burkholder, RfcVeigh & Moyer (1944) described an assay method using KEoeckera byezis, and Emery, McLeod & Robinson (1946) have given standard cur\-es for K. brezis and Schixosaccharom yces yombe. These organisms appeared to be most suitable for further study since they were unable to grow in the absence of inositol even after prolonged incubation. Although the inositol content of Difco Bacto yeast extract (DYE) was in itself of sniall importance it was chosen as suitable test material in the develop- meiit of the assay since it is rich in substances that stimulate the growth of yeast. Hence a reliable method for the assay of yeast extract might also be expected to give reliable results when applied to other complex biological materials. EXPERIMENTAL Tube tests. The usual procedure for microbiological assay was followed, but in place of bacteriological tubes, flat-bottomed tubes (Samco), 4 x $ in., were used. Tubes were selected so that their internal diameter was within the limits 1-66 and 1.72 cm. Test and standard solutions were added to the tubes from a 5 ml. micro- burette, and the volume made up to 3 ml. with water; 3 ml. of basal medium at double strength was added by means of an automatic pipette, similar in construction to that described by Ridyard (1949). The tubes containing 6 ml. of test medium and covered with loosely fitting glass caps were sterilized in the autoclave by heating until 10 lb. pressure was reached, at which point the gas was extinguished and the tubes allowed to cool. After inoculation, they were incubated in a water-bath at 25O+O-2O.

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