Growth Factors for Bacteria

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Abstract
An ether soluble factor has been obtained from yeast extract which is indispensable for growth of all tested cultures of propionic acid bacteria on a synthetic (NH4)2SO4 medium. Addition of hydrolyzed casein greatly improves growth and makes repeated transfer possible in the supplemented synthetic medium. The factor has been found in corn steep, potato extract, corn extract, and liver extract. It is a non-volatile acid which is soluble in chloroform, ether, benzene and xylene, but almost insoluble in petroleum ether. The Ba salt is soluble in 95% alcohol but sparingly so in acetone. The factor is absorbed on Norite and may be eluted with acid-alcohol. It can not be replaced by hepatoflavine, vitamin B1, Sporogenes vitamin, pantothenic acid, indolacetic acid, inositol or nicotinic acid amide.