Effect of Rice Bran Extract upon Growth of Organisms from Several Genera

Abstract

Salle and Dunn 1 have shown that 25% aqueous ethyl alcohol extracts of rice bran, from which the alcohol was subsequently removed by evaporation, contain a substance which stimulates the growth of Escherichia coli, but not Alcaligenes fecalis. This substance is related to the carbohydrates, though probably not a hexose, and is possibly identical with the “pantothenic acid” of Williams et al. 2

The action of this extract on E. coli led us to suspect that other organisms would also be stimulated. Forty-one organisms, which could be readily cultured in liquid media, were selected. The preparation of the extract, inoculation, and measurement of growth were the same as in the previous experiments. 1 Experiments performed with those to be reported, but using extract prepared by the method of Williams, i. e., extraction of the bran with 60% methyl alcohol, showed both extracts to have identical stimulating properties. The 25% ethyl alcohol extraction was adopted following a suggestion by Dr. S. Lepkovsky that the extraction of large amounts of rice bran might conveniently and fairly inexpensively be made by using the first steps of the method devised by Evans and himself 3 for the extraction of vitamin B.

In all the tables of results, the 3 columns under growth and under final pH show the average values obtained from duplicate determinations, and represent the results obtained with 0.0 cc., 0.1 cc., and 1.0 cc. of extract respectively. The amount of growth, expressed in cubic centimeters, was determined by centrifuging 10.0 cc. of the culture in Hopkins tubes. Original and final pH's were determined by means of the hydrogen electrode. The value for the original pH is the average of the pH of the 2 dilutions of the extract and the pH of the control.