Essential Growth Factors for Propionic Acid Bacteria

Abstract

1.[long dash]Potato extract, orange juice and yeast water stimulate the fermentation of glucose and the production of acid by Propionibacterium pentosaceum No. 11. The potato extract was active only in the presence of another factor which was supplied by corn or corn extracts. The effect of potato extract was probably due to true essential growth factors and not primarily to its available N or buffering capacity. Potato extract was separated into 2 fractions both of which must be present to cause stimulation. One fraction was precipitated by Neuberg''s reagent and was probably composed of amino acids or similar compounds; the other was contained in the Neuberg filtrate and apparently was neither carbohydrate nor amino acid in character.[long dash]2.[long dash]The stimulatory effect of the Neuberg precipitate fraction of potato extract was found to be due primarily to the ammonium N and the asparagine which it contains. Urea, glutamic acid and peptone also replaced this fraction, but a number of amino acids were less effective. All strains tested responded to the stimulant. Vigorous growth was obtained on a medium containing corn extract, (NH4)2SO4, glucose and Neuberg filtrate of potato. The propionic acid bacteria are able to utilize ammonium N in the presence of necessary growth factors.