PRODUCTION AND PROPERTIES OF 2,3-BUTANEDIOL: X. THE EFFECTS OF SURFACE–VOLUME RATIO AND REDUCED PRESSURE ON THE FERMENTATION OF CARBOHYDRATES BY AEROBACILLUS POLYMYXA AND AEROBACTER AEROGENES

Abstract

The rate of fermentation of wheat mashes by Aerobacillus polymyxa was markedly increased by providing a high surface-area–volume ratio. Exposure to air or oxygen per se was not a controlling factor since an atmosphere of nitrogen gave the same effect. Inhibition of fermentation of shallow layers of mash by exposure to carbon dioxide suggested that escape of fermentation gases (mainly carbon dioxide) might be the major factor affecting the fermentation rate. Support has been given to this hypothesis by the marked increase in rate obtained when wheat mashes were fermented under reduced pressures.Fermentation of 15% wheat mashes, normally requiring 72 to 96 hr., were complete in 48 hr. under 5 in. pressure (absolute). The fermentation rate was accelerated by decreasing pressures but was retarded slightly by increasing depths of mash. The butanediol–ethanol ratio became progressively lower with decreasing pressures, showing that such conditions favour ethanol formation.Fermentation of sugar media by Aerobacter aerogenes was only mildly stimulated by reduced pressures. This treatment compares unfavourably with aeration as a means of increasing the fermentation rate of this organism.