Abstract
Rice bran has been implicated by various investigators to contain growth-stimulants. Williams and his associates 1 claimed that pantothenic acid present in the rice-bran extract is chiefly responsible for the growth stimulation of certain strains of yeast. Salle and Dunn 2 working with Escherichia coli found that the extent of growth was related directly to the concentration of rice-bran extract added to meat-infusion broth. Alcaligenes fecalis did not behave in the same manner. They concluded that the enhancement of growth in the case of E. coli was due to the presence of a growth-promoting substance. The presence of vitamin B in rice bran has long been recognized. West and Cruz 3 found that in addition to vitamin B, vitamin E is also present. While the existence of such growth-stimulating substances may well be admitted, it is of interest to determine whether rice-bran extract by itself will serve as an efficient nutrient for cultivating microörganisms.
In our present study it was found that the best extract was prepared by macerating 200 gm. of rice bran with one liter of 12.5,% alcohol and incubating at 37°C. for 48 hours with occasional shaking. After centrifugation about 800 cc. of extract was recovered. This was concentrated to about 50 cc. either by vacuum-distillation or by evaporation in a steam bath. After cooling, the extract was centrifuged to remove coagulated material, adjusted to pH 7.0 with sodium hydroxide, allowed to stand in the keenest for at least half an hour, centrifuged, made up to 85 cc. and sterilized either by filtering through a Seitz filter or by autoclaving at 10 pounds pressure for 30 minutes. In the latter process of sterilization the extract was adjusted to pH 7.4 before autoclaving.
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